v1.10.0

FIXED:
* Windows logging

ADDED:
* netx (and netx/inetcksum), the latter of which implements the Internet
  Checksum as a hash.Hash.

.encoding.TODO/bit/docs.go

@@ -0,0 +1,19 @@
+/*
+Package bit aims to provide feature parity with stdlib's [encoding/hex].
+
+It's a ludicrous tragedy that hex/base16, base32, base64 all have libraries for converting
+to/from string representations... but there's nothing for binary ('01010001' etc.) whatsoever.
+
+This package also provides some extra convenience functions and types in an attempt to provide
+an abstracted bit-level fidelity in Go. A [Bit] is a bool type, in which that underlying bool
+being false represents a 0 and that underlying bool being true represents a 1.
+
+Note that a [Bit] or arbitrary-length or non-octal-aligned [][Bit] may take up more bytes in memory
+than expected; a [Bit] will actually always occupy a single byte -- thus representing
+`00000000 00000000` as a [][Bit] or [16][Bit] will actually occupy *sixteen bytes* in memory,
+NOT 2 bytes (nor, obviously, [2][Byte])!
+It is recommended instead to use a [Bits] instead of a [Bit] slice or array, as it will try to properly align to the
+smallest memory allocation possible (at the cost of a few extra CPU cycles on adding/removing one or more [Bit]).
+It will properly retain any appended, prepended, leading, or trailing bits that do not currently align to a byte.
+*/
+package bit

.encoding.TODO/bit/funcs.go

@@ -0,0 +1,14 @@
+package bit
+
+// TODO: Provide analogues of encoding/hex, encoding/base64, etc. functions etc.
+
+/*
+	TODO: Also provide interfaces for the following:
+
+	* https://pkg.go.dev/encoding#BinaryAppender
+	* https://pkg.go.dev/encoding#BinaryMarshaler
+	* https://pkg.go.dev/encoding#BinaryUnmarshaler
+	* https://pkg.go.dev/encoding#TextAppender
+	* https://pkg.go.dev/encoding#TextMarshaler
+	* https://pkg.go.dev/encoding#TextUnmarshaler
+*/

.encoding.TODO/bit/types.go

@@ -0,0 +1,34 @@
+package bit
+
+type (
+	// Bit aims to provide a native-like type for a single bit (Golang operates on the smallest fidelity level of *byte*/uint8).
+	Bit bool
+
+	// Bits is an arbitrary length of bits.
+	Bits struct {
+		/*
+			leading is a series of Bit that do not cleanly align to the beginning of Bits.b.
+			They will always be the bits at the *beginning* of the sequence.
+			len(Bits.leading) will *never* be more than 7;
+			it's converted into a byte, prepended to Bits.b, and cleared if it reaches that point.
+		*/
+		leading []Bit
+		// b is the condensed/memory-aligned alternative to an [][8]Bit (or []Bit, or [][]Bit, etc.).
+		b []byte
+		/*
+			remaining is a series of Bit that do not cleanly align to the end of Bits.b.
+			They will always be the bits at the *end* of the sequence.
+			len(Bits.remaining) will *never* be more than 7;
+			it's converted into a byte, appended to Bits.b, and cleared if it reaches that point.
+		*/
+		remaining []Bit
+		// fixedLen, if 0, represents a "slice". If >= 1, it represents an "array".
+		fixedLen uint
+	}
+
+	// Byte is this package's representation of a byte. It's primarily for convenience.
+	Byte byte
+
+	// Bytes is defined as a type for convenience single-call functions.
+	Bytes []Byte
+)

.gitignore

@@ -28,6 +28,11 @@
 
 # Test binary, built with `go test -c`
 *.test
+# But DO include the actual tests.
+!_test.go
+!*_test.go
+!*_test_*.go
+!*_test/
 
 # Output of the go coverage tool, specifically when used with LiteIDE
 *.out

bitmask/bitmask.go

@@ -0,0 +1,171 @@
+package bitmask
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"math/bits"
+)
+
+// MaskBit is a flag container.
+type MaskBit uint
+
+/*
+	NewMaskBit is a convenience function.
+	It will return a MaskBit with a (referenced) value of 0, so set your consts up accordingly.
+
+	It is highly recommended to set this default as a "None" flag (separate from your iotas!)
+	as shown in the example.
+*/
+func NewMaskBit() (m *MaskBit) {
+
+	m = new(MaskBit)
+
+	return
+}
+
+// NewMaskBitExplicit is like NewMaskBit, but allows you to specify a non-zero (0x0) value.
+func NewMaskBitExplicit(value uint) (m *MaskBit) {
+
+	var v MaskBit = MaskBit(value)
+
+	m = &v
+
+	return
+}
+
+/*
+	HasFlag is true if m has MaskBit flag set/enabled.
+
+	THIS WILL RETURN FALSE FOR OR'd FLAGS.
+
+	For example:
+
+		flagA MaskBit = 0x01
+		flagB MaskBit = 0x02
+		flagComposite = flagA | flagB
+
+		m *MaskBit = NewMaskBitExplicit(uint(flagA))
+
+	m.HasFlag(flagComposite) will return false even though flagComposite is an OR
+	that contains flagA.
+	Use [MaskBit.IsOneOf] instead if you do not desire this behavior,
+	and instead want to test composite flag *membership*.
+	(MaskBit.IsOneOf will also return true for non-composite equality.)
+
+	To be more clear, if MaskBit flag is a composite MaskBit (e.g. flagComposite above),
+	HasFlag will only return true of ALL bits in flag are also set in MaskBit m.
+*/
+func (m *MaskBit) HasFlag(flag MaskBit) (r bool) {
+
+	var b MaskBit = *m
+
+	if b&flag == flag {
+		r = true
+	}
+	return
+}
+
+/*
+	IsOneOf is like a "looser" form of [MaskBit.HasFlag]
+	in that it allows for testing composite membership.
+
+	See [MaskBit.HasFlag] for more information.
+
+	If composite is *not* an OR'd MaskBit (i.e.
+	it falls directly on a boundary -- 0, 1, 2, 4, 8, 16, etc.),
+	then IsOneOf will behave exactly like HasFlag.
+
+	If m is a composite MaskBit (it usually is) and composite is ALSO a composite MaskBit,
+	IsOneOf will return true if ANY of the flags set in m is set in composite.
+*/
+func (m *MaskBit) IsOneOf(composite MaskBit) (r bool) {
+
+	var b MaskBit = *m
+
+	if b&composite != 0 {
+		r = true
+	}
+	return
+}
+
+// AddFlag adds MaskBit flag to m.
+func (m *MaskBit) AddFlag(flag MaskBit) {
+
+	*m |= flag
+
+	return
+}
+
+// ClearFlag removes MaskBit flag from m.
+func (m *MaskBit) ClearFlag(flag MaskBit) {
+
+	*m &^= flag
+
+	return
+}
+
+// ToggleFlag switches MaskBit flag in m to its inverse; if true, it is now false and vice versa.
+func (m *MaskBit) ToggleFlag(flag MaskBit) {
+
+	*m ^= flag
+
+	return
+}
+
+/*
+	Bytes returns the current value of a MasBit as a byte slice (big-endian).
+
+	If trim is false, b will (probably) be 4 bytes long if you're on a 32-bit size system,
+	and b will (probably) be 8 bytes long if you're on a 64-bit size system. You can determine
+	the size of the resulting slice via (math/)bits.UintSize / 8.
+
+	If trim is true, it will trim leading null bytes (if any). This will lead to an unpredictable
+	byte slice length in b, but is most likely preferred for byte operations.
+
+*/
+func (m *MaskBit) Bytes(trim bool) (b []byte) {
+
+	var b2 []byte
+	var size int = bits.UintSize / 8
+	var err error
+
+	b2 = make([]byte, size)
+
+	switch s := bits.UintSize; s {
+	case 32:
+		binary.BigEndian.PutUint32(b2[:], uint32(*m))
+	case 64:
+		binary.BigEndian.PutUint64(b2[:], uint64(*m))
+	default:
+		err = errors.New("unsupported Uint/system bit size")
+		panic(err)
+	}
+
+	if trim {
+		b = bytes.TrimLeft(b2, "\x00")
+		return
+	} else {
+		b = b2
+		return
+	}
+
+	return
+}
+
+// Copy returns a pointer to a (new) copy of a MaskBit.
+func (m *MaskBit) Copy() (newM *MaskBit) {
+
+	newM = new(MaskBit)
+	*newM = *m
+
+	return
+}
+
+// Value returns the current raw uint value of a MaskBit.
+func (m *MaskBit) Value() (v uint) {
+
+	v = uint(*m)
+
+	return
+}

bitmask/bitmasks.go

@@ -1,46 +0,0 @@
-package bitmask
-
-// MaskBit is a flag container.
-type MaskBit uint8
-
-/*
-	NewMaskBit is a convenience function.
-	It will return a MaskBit with a (referenced) value of 0, so set your consts up accordingly.
-	It is highly recommended to set this default as a "None" flag (separate from your iotas!)
-	as shown in the example.
-*/
-func NewMaskBit() (m *MaskBit) {
-
-	m = new(MaskBit)
-
-	return
-}
-
-// HasFlag is true if m has MaskBit flag set/enabled.
-func (m *MaskBit) HasFlag(flag MaskBit) (r bool) {
-
-	var b MaskBit = *m
-
-	if b&flag != 0 {
-		r = true
-	}
-	return
-}
-
-// AddFlag adds MaskBit flag to m.
-func (m *MaskBit) AddFlag(flag MaskBit) {
-	*m |= flag
-	return
-}
-
-// ClearFlag removes MaskBit flag from m.
-func (m *MaskBit) ClearFlag(flag MaskBit) {
-	*m &= flag
-	return
-}
-
-// ToggleFlag switches MaskBit flag in m to its inverse; if true, it is now false and vice versa.
-func (m *MaskBit) ToggleFlag(flag MaskBit) {
-	*m ^= flag
-	return
-}

bitmask/doc.go

@@ -1,9 +1,35 @@
 /*
 Package bitmask handles a flag-like opt/bitmask system.
 
-See https://yourbasic.org/golang/bitmask-flag-set-clear/ for more information.
+See https://yourbasic.org/golang/bitmask-flag-set-clear/ for basic information on what bitmasks are and why they're useful.
 
-To use this, set constants like thus:
+Specifically, in the case of Go, they allow you to essentially manage many, many, many "booleans" as part of a single value.
+
+A single bool value in Go takes up 8 bits/1 byte, unavoidably.
+
+However, a [bitmask.MaskBit] is backed by a uint which (depending on your platform) is either 32 bits/4 bytes or 64 bits/8 bytes.
+
+"But wait, that takes up more memory though!"
+
+Yep, but bitmasking lets you store a "boolean" AT EACH BIT - it operates on
+whether a bit in a byte/set of bytes at a given position is 0 or 1.
+
+Which means on 32-bit platforms, a [MaskBit] can have up to 4294967295 "booleans" in a single value (0 to (2^32)-1).
+
+On 64-bit platforms, a [MaskBit] can have up to 18446744073709551615 "booleans" in a single value (0 to (2^64)-1).
+
+If you tried to do that with Go bool values, that'd take up 4294967295 bytes (4 GiB)
+or 18446744073709551615 bytes (16 EiB - yes, that's [exbibytes]) of RAM for 32-bit/64-bit platforms respectively.
+
+"But that has to be so slow to unpack that!"
+
+Nope. It's not using compression or anything, the CPU is just comparing bit "A" vs. bit "B" 32/64 times. That's super easy work for a CPU.
+
+There's a reason Doom used bitmasking for the "dmflags" value in its server configs.
+
+# Usage
+
+To use this library, set constants like thus:
 
 	package main
 
@@ -11,18 +37,18 @@ To use this, set constants like thus:
 		"r00t2.io/goutils/bitmask"
 	)
 
-	const OPTNONE types.MaskBit = 0
+	const OPTNONE bitmask.MaskBit = 0
 	const (
-		OPT1 types.MaskBit = 1 << iota
+		OPT1 bitmask.MaskBit = 1 << iota
 		OPT2
 		OPT3
 		// ...
 	)
 
-	var MyMask *MaskBit
+	var MyMask *bitmask.MaskBit
 
 	func main() {
-		MyMask = types.NewMaskBit
+		MyMask = bitmask.NewMaskBit()
 
 		MyMask.AddFlag(OPT1)
 		MyMask.AddFlag(OPT3)
@@ -41,5 +67,96 @@ As would this:
 But this would return false:
 
 	MyMask.HasFlag(OPT2)
+
+# Technical Caveats
+
+TARGETING
+
+When implementing, you should always set MyMask (from Usage section above) as the actual value.
+For example, if you are checking a permissions set for a user that has the value, say, 6
+
+	var userPerms uint = 6 // 0x0000000000000006
+
+and your library has the following permission bits defined:
+
+	const PermsNone bitmask.MaskBit = 0
+	const (
+		PermsList bitmask.MaskBit = 1 << iota // 1
+		PermsRead                             // 2
+		PermsWrite                            // 4
+		PermsExec                             // 8
+		PermsAdmin                            // 16
+	)
+
+And you want to see if the user has the PermsRead flag set, you would do:
+
+	userPermMask = bitmask.NewMaskBitExplicit(userPerms)
+	if userPermMask.HasFlag(PermsRead) {
+		// ...
+	}
+
+NOT:
+
+	userPermMask = bitmask.NewMaskBitExplicit(PermsRead)
+	// Nor:
+	// userPermMask = PermsRead
+	if userPermMask.HasFlag(userPerms) {
+		// ...
+	}
+
+This will be terribly, horribly wrong, cause incredibly unexpected results,
+and quite possibly cause massive security issues. Don't do it.
+
+COMPOSITES
+
+If you want to define a set of flags that are a combination of other flags,
+your inclination would be to bitwise-OR them together:
+
+	const (
+		flagA bitmask.MaskBit = 1 << iota // 1
+		flagB                             // 2
+	)
+
+	const (
+		flagAB bitmask.MaskBit = flagA | flagB // 3
+	)
+
+Which is fine and dandy. But if you then have:
+
+	var myMask *bitmask.MaskBit = bitmask.NewMaskBit()
+
+	myMask.AddFlag(flagA)
+
+You may expect this call to [MaskBit.HasFlag]:
+
+	myMask.HasFlag(flagAB)
+
+to be true, since flagA is "in" flagAB.
+It will return false - HasFlag does strict comparisons.
+It will only return true if you then ALSO do:
+
+	// This would require setting flagA first.
+	// The order of setting flagA/flagB doesn't matter,
+	// but you must have both set for HasFlag(flagAB) to return true.
+	myMask.AddFlag(flagB)
+
+or if you do:
+
+	// This can be done with or without additionally setting flagA.
+	myMask.AddFlag(flagAB)
+
+Instead, if you want to see if a mask has membership within a composite flag,
+you can use [MaskBit.IsOneOf].
+
+# Other Options
+
+If you need something with more flexibility (as always, at the cost of complexity),
+you may be interested in one of the following libraries:
+
+	* [github.com/alvaroloes/enumer]
+	* [github.com/abice/go-enum]
+	* [github.com/jeffreyrichter/enum/enum]
+
+[exbibytes]: https://simple.wikipedia.org/wiki/Exbibyte
 */
 package bitmask

go.mod

@@ -1,8 +1,15 @@
 module r00t2.io/goutils
 
-go 1.16
+go 1.24.5
 
 require (
-	github.com/coreos/go-systemd v0.0.0-20191104093116-d3cd4ed1dbcf
-	r00t2.io/sysutils v0.0.0-20210224054841-55ac47c86928
+	github.com/coreos/go-systemd/v22 v22.5.0
+	github.com/google/uuid v1.6.0
+	golang.org/x/sys v0.34.0
+	r00t2.io/sysutils v1.14.0
+)
+
+require (
+	github.com/djherbis/times v1.6.0 // indirect
+	golang.org/x/sync v0.16.0 // indirect
 )

go.sum

@@ -1,5 +1,13 @@
-github.com/coreos/go-systemd v0.0.0-20191104093116-d3cd4ed1dbcf h1:iW4rZ826su+pqaw19uhpSCzhj44qo35pNgKFGqzDKkU=
-github.com/coreos/go-systemd v0.0.0-20191104093116-d3cd4ed1dbcf/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
-github.com/jszwec/csvutil v1.5.0/go.mod h1:Rpu7Uu9giO9subDyMCIQfHVDuLrcaC36UA4YcJjGBkg=
-r00t2.io/sysutils v0.0.0-20210224054841-55ac47c86928 h1:aYEn20eguqsmqT3J9VjkzdhyPwmOVDGzzffcEfV18a4=
-r00t2.io/sysutils v0.0.0-20210224054841-55ac47c86928/go.mod h1:XzJkBF6SHAODEszJlOcjtGoTHwYnZZNmseA6PyOujes=
+github.com/coreos/go-systemd/v22 v22.5.0 h1:RrqgGjYQKalulkV8NGVIfkXQf6YYmOyiJKk8iXXhfZs=
+github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
+github.com/djherbis/times v1.6.0 h1:w2ctJ92J8fBvWPxugmXIv7Nz7Q3iDMKNx9v5ocVH20c=
+github.com/djherbis/times v1.6.0/go.mod h1:gOHeRAz2h+VJNZ5Gmc/o7iD9k4wW7NMVqieYCY99oc0=
+github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+golang.org/x/sync v0.16.0 h1:ycBJEhp9p4vXvUZNszeOq0kGTPghopOL8q0fq3vstxw=
+golang.org/x/sync v0.16.0/go.mod h1:1dzgHSNfp02xaA81J2MS99Qcpr2w7fw1gpm99rleRqA=
+golang.org/x/sys v0.0.0-20220615213510-4f61da869c0c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.34.0 h1:H5Y5sJ2L2JRdyv7ROF1he/lPdvFsd0mJHFw2ThKHxLA=
+golang.org/x/sys v0.34.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
+r00t2.io/sysutils v1.14.0/go.mod h1:ZJ7gZxFVQ7QIokQ5fPZr7wl0XO5Iu+LqtE8j3ciRINw=

iox/docs.go

@@ -0,0 +1,4 @@
+/*
+Package iox includes extensions to the stdlib `io` module.
+*/
+package iox

iox/errs.go

@@ -0,0 +1,9 @@
+package iox
+
+import (
+	`errors`
+)
+
+var (
+	ErrBufTooSmall error = errors.New("buffer too small; buffer size must be > 0")
+)

iox/funcs.go

@@ -0,0 +1,41 @@
+package iox
+
+import (
+	`io`
+)
+
+/*
+CopyBufN is a mix between io.CopyN and io.CopyBuffer.
+
+Despite what the docs may suggest, io.CopyN does NOT *read* n bytes from src AND write n bytes to dst.
+Instead, it always reads 32 KiB from src, and writes n bytes to dst.
+
+There are, of course, cases where this is deadfully undesired.
+
+One can, of course, use io.CopyBuffer, but this is a bit annoying since you then have to provide a buffer yourself.
+
+This convenience-wraps io.CopyBuffer to have a similar signature to io.CopyN but properly uses n for both reading and writing.
+*/
+func CopyBufN(dst io.Writer, src io.Reader, n int64) (written int64, err error) {
+
+	var b []byte
+
+	if n <= 0 {
+		err = ErrBufTooSmall
+		return
+	}
+
+	b = make([]byte, n)
+
+	written, err = io.CopyBuffer(dst, src, b)
+
+	return
+}
+
+// CopyBufWith allows for specifying a buffer allocator function, otherwise acts as CopyBufN.
+func CopyBufWith(dst io.Writer, src io.Reader, bufFunc func() (b []byte)) (written int64, err error) {
+
+	written, err = io.CopyBuffer(dst, src, bufFunc())
+
+	return
+}

iox/types.go

@@ -0,0 +1,8 @@
+package iox
+
+type (
+	// RuneWriter matches the behavior of *(bytes.Buffer).WriteRune and *(bufio.Writer).WriteRune
+	RuneWriter interface {
+		WriteRune(r rune) (n int, err error)
+	}
+)

logging/TODO

@@ -1,11 +1,25 @@
+- macOS support beyond the legacy NIX stuff. it apparently uses something called "ULS", "Unified Logging System".
+-- https://developer.apple.com/documentation/os/logging
+-- https://developer.apple.com/documentation/os/generating-log-messages-from-your-code
+-- no native Go support (yet)?
+--- https://developer.apple.com/forums/thread/773369
+
+- The log destinations for e.g. consts_nix.go et. al. probably should be unexported types.
+
+- add a `log/slog` logging.Logger?
+
 - Implement code line/func/etc. (only for debug?):
   https://stackoverflow.com/a/24809646
   https://golang.org/pkg/runtime/#Caller
+  -- log.LlongFile and log.Lshortfile flags don't currently work properly for StdLogger/FileLogger; they refer to the file in logging package rather than the caller.
+  -- ZeroLog seems to be able to do it, take a peek there.
 
-- Support simultaneous writing to multiple Loggers.
+- StdLogger2; where stdout and stderr are both logged to depending on severity level.
+  - make configurable via OR bitmask
 
-- Suport remote loggers? (eventlog, syslog, systemd)
+- Suport remote loggers? (eventlog, syslog, journald)
+
+- JSON logger? YAML logger? XML logger?
 
 - DOCS.
-
-- Unit/Integration tests.
+-- Done, but flesh out.

logging/consts.go

@@ -5,7 +5,23 @@ import (
 )
 
 const (
+	// logPerm is the octal mode to use for testing the file.
 	logPerm os.FileMode = 0600
+	// logPrefix is the default log prefix.
 	logPrefix string = "GOLANG PROGRAM"
+	// appendFlags are the flags used for testing the file (and opening/writing).
 	appendFlags int = os.O_APPEND | os.O_CREATE | os.O_WRONLY
 )
+
+const PriorityNone logPrio = 0
+const (
+	PriorityEmergency logPrio = 1 << iota
+	PriorityAlert
+	PriorityCritical
+	PriorityError
+	PriorityWarning
+	PriorityNotice
+	PriorityInformational
+	PriorityDebug
+)
+const PriorityAll logPrio = PriorityEmergency | PriorityAlert | PriorityCritical | PriorityError | PriorityWarning | PriorityNotice | PriorityInformational | PriorityDebug

logging/consts_darwin.go

@@ -0,0 +1,9 @@
+package logging
+
+var (
+	// defLogPaths indicates default log paths.
+	defLogPaths = []string{
+		"/var/log/golang/program.log",
+		"~/Library/Logs/Golang/program.log",
+	}
+)

logging/consts_linux.go

@@ -1,26 +1,7 @@
 package logging
 
-import (
-	`log/syslog`
-
-	`r00t2.io/goutils/bitmask`
-)
-
-const (
-	devlog         string          = "/dev/log"
-	syslogFacility syslog.Priority = syslog.LOG_USER
-)
-
-// Flags for logger configuration
-const (
-	LogUndefined bitmask.MaskBit = 1 << iota
-	LogJournald
-	LogSyslog
-	LogFile
-	LogStdout
-)
-
 var (
+	// defLogPaths indicates default log paths.
 	defLogPaths = []string{
 		"/var/log/golang/program.log",
 		"~/.local/log/golang/program.log",

logging/consts_nix.go

@@ -0,0 +1,34 @@
+//go:build !(windows || plan9 || wasip1 || js || ios)
+// +build !windows,!plan9,!wasip1,!js,!ios
+
+// I mean maybe it works for plan9 and ios, I don't know.
+
+package logging
+
+import (
+	"log/syslog"
+
+	"r00t2.io/goutils/bitmask"
+)
+
+const (
+	// devlog is the path to the syslog char device.
+	devlog string = "/dev/log"
+	// syslogFacility is the facility to use; it's a little like a context or scope if you think of it in those terms.
+	syslogFacility syslog.Priority = syslog.LOG_USER
+)
+
+// Flags for logger configuration. These are used internally.
+
+// LogUndefined indicates an undefined Logger type.
+const LogUndefined bitmask.MaskBit = iota
+const (
+	// LogJournald flags a SystemDLogger Logger type. This will, for hopefully obvious reasons, only work on Linux systemd systems.
+	LogJournald bitmask.MaskBit = 1 << iota
+	// LogSyslog flags a SyslogLogger Logger type.
+	LogSyslog
+	// LogFile flags a FileLogger Logger type.
+	LogFile
+	// LogStdout flags a StdLogger Logger type.
+	LogStdout
+)

logging/consts_test.go

@@ -0,0 +1,39 @@
+package logging
+
+import (
+	`log`
+)
+
+/*
+	The following are strings written to the Logger in the various tests.
+	The %v is populated with the name of the type of Logger.
+*/
+const (
+	testAlert   string = "This is a test ALERT-priority log message for logger %v."
+	testCrit    string = "This is a test CRITICAL-priority (CRIT) log message for logger %v."
+	testDebug   string = "This is a test DEBUG-priority log message for logger %v."
+	testEmerg   string = "This is a test EMERGENCY-priority (EMERG) log message for logger %v."
+	testErr     string = "This is a test ERROR-priority (ERR) log message for logger %v."
+	testInfo    string = "This is a test INFO-priority log message for logger %v."
+	testNotice  string = "This is a test NOTICE-priority log message for logger %v."
+	testWarning string = "This is a test WARNING-priority log message for logger %v."
+)
+
+// Prefixes to use for tests.
+const (
+	// TestLogPrefix is used as the initial prefix.
+	TestLogPrefix string = "LOGGING_TESTRUN"
+	// TestLogAltPrefix is used as the alternative prefix to Logger.SetPrefix.
+	TestLogAltPrefix string = "LOGGING_TESTRUN_ALT"
+)
+
+const (
+	// EnvVarKeepLog is the env var key/var name to use to suppress removal of FileLogger.Path after tests complete.
+	EnvVarKeepLog string = "LOGGING_KEEP_TEMPLOG"
+)
+
+const (
+	// logFlags are used to set the log flags for StdLogger (and FileLogger.StdLogger).
+	// logFlags int = log.Ldate | log.Lmicroseconds | log.Llongfile | log.LUTC
+	logFlags int = log.Ldate | log.Lmicroseconds | log.Lshortfile | log.LUTC
+)

logging/consts_windows.go

@@ -3,27 +3,45 @@ package logging
 import (
 	`os`
 	`path/filepath`
-	`regexp`
 )
 
-// Flags for logger configuration
+// Flags for logger configuration. These are used internally.
+// LogUndefined indicates an undefined Logger type.
+const LogUndefined bitmask.MaskBit = 0
 const (
-	LogUndefined types.MaskBit = 1 << iota
-	LogWinLogger
+	// LogWinLogger indicates a WinLogger Logger type (Event Log).
+	LogWinLogger bitmask.MaskBit = 1 << iota
+	// LogFile flags a FileLogger Logger type.
 	LogFile
+	// LogStdout flags a StdLogger Logger type.
 	LogStdout
 )
 
 var (
+	// defLogPaths indicates default log paths.
 	defLogPaths = []string{
 		filepath.Join(os.Getenv("ALLUSERSPROFILE"), "golang", "program.log"),     // C:\ProgramData\log\golang\program.log
 		filepath.Join(os.Getenv("LOCALAPPDATA"), "log", "golang", "program.log"), // C:\Users\<username>\AppData\Local\log\golang\program.log
 	}
 )
 
-var ptrnSourceExists *regexp.Regexp = regexp.MustCompile(`registry\skey\salready\sexists$`)
+/*
+	ptrnSourceExists is a regex pattern to check for a registry entry (Event Log entry) already existing.
 
-// Default WinEventID
+	Deprecated: this is handled differently now.
+*/
+// var ptrnSourceExists *regexp.Regexp = regexp.MustCompile(`registry\skey\salready\sexists$`)
+
+const (
+	EIDMin uint32 = 1
+	EIDMax uint32 = 1000
+)
+
+const (
+	eventLogRegistryKey string = "SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application"
+)
+
+// Default WinEventID, (can be) used in GetLogger and MultiLogger.AddWinLogger.
 var DefaultEventID *WinEventID = &WinEventID{
 	Alert:   EventAlert,
 	Crit:    EventCrit,
@@ -35,7 +53,7 @@ var DefaultEventID *WinEventID = &WinEventID{
 	Warning: EventWarning,
 }
 
-// Default Event IDs for WinEventID.
+// Default Event IDs for WinEventID (DefaultEventID, specifically).
 const (
 	EventAlert uint32 = 1 << iota
 	EventCrit

logging/doc.go

@@ -0,0 +1,64 @@
+/*
+Package logging implements and presents various loggers under a unified interface, making them completely swappable.
+
+These particular loggers (logging.Logger) available are:
+
+	NullLogger
+	StdLogger
+	FileLogger
+	SystemDLogger (Linux only)
+	SyslogLogger (Linux/macOS/other *NIX-like only)
+	WinLogger (Windows only)
+
+There is a seventh type of logging.Logger, MultiLogger, that allows for multiple loggers to be written to with a single call.
+(This is similar to stdlib's io.MultiWriter()'s return value, but with priority awareness and fmt string support).
+
+As you may have guessed, NullLogger doesn't actually log anything but is fully "functional" as a logging.Logger (similar to io.discard/io.Discard()'s return).
+
+Note that for some Loggers, the prefix may be modified after the Logger has already initialized.
+"Literal" loggers (StdLogger and FileLogger) will append a space to the end of the prefix by default.
+If this is undesired (unlikely), you will need to modify (Logger).Prefix and run (Logger).Logger.SetPrefix(yourPrefixHere) for the respective logger.
+
+Every logging.Logger type has the following methods that correspond to certain "levels".
+
+	Alert(s string, v ...interface{}) (err error)
+	Crit(s string, v ...interface{}) (err error)
+	Debug(s string, v ...interface{}) (err error)
+	Emerg(s string, v ...interface{}) (err error)
+	Err(s string, v ...interface{}) (err error)
+	Info(s string, v ...interface{}) (err error)
+	Notice(s string, v ...interface{}) (err error)
+	Warning(s string, v ...interface{}) (err error)
+
+Not all loggers implement the concept of levels, so approximations are made when/where possible.
+
+In each of the above methods, s is the message that is optionally in a fmt.Sprintf-compatible format.
+If it is, the values to fmt.Sprintf can be passed as v.
+
+Note that in the case of a MultiLogger, err (if not nil) will be a (r00t2.io/goutils/)multierr.MultiError.
+
+logging.Logger types also have the following methods:
+
+	DoDebug(d bool) (err error)
+	GetDebug() (d bool)
+	SetPrefix(p string) (err error)
+	GetPrefix() (p string, err error)
+	Setup() (err error)
+	Shutdown() (err error)
+
+In some cases, Logger.Setup and Logger.Shutdown are no-ops. In other cases, they perform necessary initialization/cleanup and closing of the logger.
+It is recommended to *always* run Setup and Shutdown before and after using, respectively, regardless of the actual logging.Logger type.
+
+Lastly, all logging.Loggers have a ToLogger() method. This returns a *log.Logger (from stdlib log), which also conforms to io.Writer inherently.
+In addition. all have a ToRaw() method, which extends a Logger even further and returns an unexported type (*logging.logWriter) compatible with:
+
+  - io.ByteWriter
+  - io.Writer
+  - io.WriteCloser (Shutdown() on the Logger backend is called during Close(), rendering the underlying Logger unsafe to use afterwards)
+  - io.StringWriter
+
+and, if stdlib io ever defines an e.g. RuneWriter (WriteRune(r rune) (n int, err error)), it will conform to that too (see (r00t2.io/goutils/iox).RuneWriter).
+Obviously this and io.ByteWriter are fairly silly, as they're intended to be high-speed throughput-optimized methods, but if you wanted to e.g.
+log every single byte on a wire as a separate log message, go ahead; I'm not your dad.
+*/
+package logging

logging/errs.go

@@ -0,0 +1,19 @@
+package logging
+
+import (
+	"errors"
+)
+
+var (
+	// ErrExistingLogger indicates that the user attempted to add a Logger to a MultiLogger using an already-existing identifier.
+	ErrExistingLogger error = errors.New("a Logger with that identifier already exists; please remove it first")
+	/*
+		ErrInvalidFile indicates that the user attempted to add a FileLogger to a MultiLogger but the file doesn't exist,
+		exists with too restrictive perms to write/append to, and/or could not be created.
+	*/
+	ErrInvalidFile error = errors.New("a FileLogger was requested but the file does not exist and cannot be created")
+	// ErrInvalidRune is returned if a rune was expected but it is not a valid UTF-8 codepoint.
+	ErrInvalidRune error = errors.New("specified rune is not valid UTF-8 codepoint")
+	// ErrNoEntry indicates that the user attempted to MultiLogger.RemoveLogger a Logger but one by that identifier does not exist.
+	ErrNoEntry error = errors.New("the Logger specified to be removed does not exist")
+)

logging/errs_linux.go

@@ -0,0 +1,10 @@
+package logging
+
+import (
+	"errors"
+)
+
+var (
+	// ErrNoSysD indicates that the user attempted to add a SystemDLogger to a MultiLogger but systemd is unavailable.
+	ErrNoSysD error = errors.New("a systemd (journald) Logger was requested but systemd is unavailable on this system")
+)

logging/errs_nix.go

@@ -0,0 +1,19 @@
+//go:build !(windows || plan9 || wasip1 || js || ios)
+// +build !windows,!plan9,!wasip1,!js,!ios
+
+package logging
+
+import (
+	"errors"
+	"fmt"
+)
+
+var (
+	// ErrNoSyslog indicates that the user attempted to add a SyslogLogger to a MultiLogger but syslog's logger device is unavailable.
+	ErrNoSyslog error = errors.New("a Syslog Logger was requested but Syslog is unavailable on this system")
+	/*
+		ErrInvalidDevLog indicates that the user attempted to add a SyslogLogger to a MultiLogger but
+		the Syslog char device file is... not actually a char device file.
+	*/
+	ErrInvalidDevLog error = errors.New(fmt.Sprintf("a Syslog Logger was requested but %v is not a valid logger handle", devlog))
+)

logging/errs_windows.go

@@ -0,0 +1,15 @@
+package logging
+
+import (
+	`errors`
+	`fmt`
+)
+
+var (
+	// ErrBadBinPath is returned if installing a binary-registered Event Log source instead of using EventCreate.exe.
+	ErrBadBinPath error = errors.New("evaluated binary path does not actually exist")
+	// ErrBadPerms is returned if an access denied error is received when attempting to register, write to, close, etc. a source without proper perms.
+	ErrBadPerms error = errors.New("access denied when attempting to register Event Log source")
+	// ErrBadEid is returned if an event ID is within an invalid range.
+	ErrBadEid error = errors.New(fmt.Sprintf("event IDs must be between %v and %v inclusive", EIDMin, EIDMax))
+)

logging/funcs.go

@@ -1,17 +1,45 @@
 package logging
 
 import (
+	"log"
 	"os"
 )
 
+/*
+ToLog returns a stdlib *log.Logger from a logging.Logger. It simply wraps the (logging.Logger).ToLogger() methods.
+
+prio is an OR'd logPrio of the Priority* constants.
+*/
+func ToLog(l Logger, prio logPrio) (stdLibLog *log.Logger) {
+
+	stdLibLog = l.ToLogger(prio)
+
+	return
+}
+
+// ToRaw returns a *logWriter from a logging.Logger. It is an alternative to the (logging.Logger).ToRaw() methods.
+func ToRaw(l Logger, prio logPrio) (raw *logWriter) {
+
+	raw = &logWriter{
+		backend: l,
+		prio:    prio,
+	}
+
+	return
+}
+
+// testOpen attempts to open a file for writing to test for suitability as a LogFile path.
 func testOpen(path string) (success bool, err error) {
+
 	var f *os.File
 
 	// Example #2, https://golang.org/pkg/os/#OpenFile
 	if f, err = os.OpenFile(path, appendFlags, logPerm); err != nil {
 		return
 	}
-	defer f.Close()
+	if err = f.Close(); err != nil {
+		return
+	}
 
 	success = true
 

logging/funcs_file.go

@@ -1,49 +1,94 @@
 package logging
 
 import (
+	"errors"
 	"fmt"
-	"io"
+	"io/fs"
 	"log"
 	"os"
+	"strings"
 )
 
-func (l *FileLogger) Setup() {
+// Setup sets up/configures a FileLogger and prepares it for use.
+func (l *FileLogger) Setup() (err error) {
 
-	var err error
-
-	l.Logger = log.Default()
-	l.Logger.SetPrefix(l.Prefix)
+	// This uses a shared handle across the import. We don't want that.
+	// l.Logger = log.Default()
+	if l.Prefix != "" {
+		l.Prefix = strings.TrimRight(l.Prefix, " ") + " "
+		// l.Logger.SetPrefix(l.Prefix)
+	}
 	if l.writer, err = os.OpenFile(l.Path, appendFlags, logPerm); err != nil {
-		log.Panicf("could not open log file \"%v\" for writing: %v\n", l.Path, err)
-	}
-	// https://stackoverflow.com/a/36719588/733214
-	multi := io.MultiWriter(os.Stdout, l.writer)
-	l.Logger.SetOutput(multi)
+		return
 	}
 
-func (l *FileLogger) Shutdown() {
+	l.Logger = log.New(l.writer, l.Prefix, l.LogFlags)
+	// l.Logger.SetOutput(multi)
 
-	var err error
+	return
+}
+
+// Shutdown cleanly shuts down a FileLogger.
+func (l *FileLogger) Shutdown() (err error) {
 
 	if err = l.writer.Close(); err != nil {
-		log.Panicf("could not close log file \"%v\": %v\n", l.Path, err)
+		if !errors.Is(err, fs.ErrClosed) {
+			return
+		}
+		err = nil
+		return err
 	}
 
+	return
 }
 
-func (l *FileLogger) GetPrefix() string {
-	return l.Prefix
+/*
+GetPrefix returns the prefix used by this FileLogger.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *FileLogger) GetPrefix() (prefix string, err error) {
+
+	prefix = l.Prefix
+
+	return
 }
 
-func (l *FileLogger) DoDebug(d bool) {
+/*
+DoDebug sets the debug state of this FileLogger.
+Note that this merely acts as a *safety filter* for debug messages to avoid sensitive information being written to the log.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *FileLogger) DoDebug(d bool) (err error) {
+
 	l.EnableDebug = d
+
+	return
 }
 
-func (l *FileLogger) SetPrefix(prefix string) {
+// GetDebug returns the debug status of this FileLogger.
+func (l *FileLogger) GetDebug() (d bool) {
+
+	d = l.EnableDebug
+
+	return
+}
+
+/*
+SetPrefix sets the prefix for this FileLogger.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *FileLogger) SetPrefix(prefix string) (err error) {
+
 	l.Prefix = prefix
-	l.Logger.SetPrefix(prefix)
+	if prefix != "" {
+		l.Prefix = strings.TrimRight(l.Prefix, " ") + " "
+	}
+	l.Logger.SetPrefix(l.Prefix)
+
+	return
 }
 
+// Alert writes an ALERT-level message to this FileLogger.
 func (l *FileLogger) Alert(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -59,6 +104,7 @@ func (l *FileLogger) Alert(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Crit writes an CRITICAL-level message to this FileLogger.
 func (l *FileLogger) Crit(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -74,6 +120,7 @@ func (l *FileLogger) Crit(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Debug writes a DEBUG-level message to this FileLogger.
 func (l *FileLogger) Debug(s string, v ...interface{}) (err error) {
 
 	if !l.EnableDebug {
@@ -93,6 +140,7 @@ func (l *FileLogger) Debug(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Emerg writes an EMERGENCY-level message to this FileLogger.
 func (l *FileLogger) Emerg(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -108,6 +156,7 @@ func (l *FileLogger) Emerg(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Err writes an ERROR-level message to this FileLogger.
 func (l *FileLogger) Err(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -123,6 +172,7 @@ func (l *FileLogger) Err(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Info writes an INFO-level message to this FileLogger.
 func (l *FileLogger) Info(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -138,6 +188,7 @@ func (l *FileLogger) Info(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Notice writes a NOTICE-level message to this FileLogger.
 func (l *FileLogger) Notice(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -153,6 +204,7 @@ func (l *FileLogger) Notice(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Warning writes a WARNING/WARN-level message to this FileLogger.
 func (l *FileLogger) Warning(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -168,6 +220,23 @@ func (l *FileLogger) Warning(s string, v ...interface{}) (err error) {
 	return
 }
 
+// ToLogger returns a stdlib log.Logger.
+func (l *FileLogger) ToLogger(prio logPrio) (stdLibLog *log.Logger) {
+
+	stdLibLog = log.New(l.ToRaw(prio), "", 0)
+
+	return
+}
+
+// ToRaw returns a *logWriter.
+func (l *FileLogger) ToRaw(prio logPrio) (raw *logWriter) {
+
+	raw = &logWriter{backend: l, prio: prio}
+
+	return
+}
+
+// renderWrite prepares/formats a log message to be written to this FileLogger.
 func (l *FileLogger) renderWrite(msg, prio string) {
 
 	s := fmt.Sprintf("[%v] %v", prio, msg)

logging/funcs_linux.go

@@ -5,7 +5,8 @@ import (
 	`os`
 	`path`
 
-	sysd `github.com/coreos/go-systemd/journal`
+	sysd `github.com/coreos/go-systemd/v22/journal`
+	`r00t2.io/goutils/bitmask`
 	`r00t2.io/sysutils/paths`
 )
 
@@ -17,16 +18,28 @@ var (
 
 /*
 	GetLogger returns an instance of Logger that best suits your system's capabilities.
+
 	If enableDebug is true, debug messages (which according to your program may or may not contain sensitive data) are rendered and written.
+
 	If prefix is "\x00" (a null byte), then the default logging prefix will be used. If anything else, even an empty string,
 	is specified then that will be used instead for the prefix.
+
+	logConfigFlags is the corresponding flag(s) OR'd for StdLogger.LogFlags / FileLogger.StdLogger.LogFlags if either is selected. See StdLogger.LogFlags and
+	https://pkg.go.dev/log#pkg-constants for details.
+
 	logPaths is an (optional) list of strings to use as paths to test for writing. If the file can be created/written to,
 	it will be used (assuming you have no higher-level loggers available). Only the first logPaths entry that "works" will be used, later entries will be ignored.
+	If you want to log to multiple files simultaneously, use a MultiLogger instead.
+
+	If you call GetLogger, you will only get a single ("best") logger your system supports.
+	If you want to log to multiple Logger destinations at once (or want to log to an explicit Logger type),
+	use GetMultiLogger.
 */
-func GetLogger(enableDebug bool, prefix string, logPaths ...string) (logger Logger, err error) {
+func GetLogger(enableDebug bool, prefix string, logConfigFlags int, logPaths ...string) (logger Logger, err error) {
 
 	var logPath string
-	var logFlags types.MaskBit
+	var logFlags bitmask.MaskBit
+	var currentPrefix string
 
 	// Configure system-supported logger(s).
 	if sysd.Enabled() {
@@ -67,7 +80,7 @@ func GetLogger(enableDebug bool, prefix string, logPaths ...string) (logger Logg
 					break
 				} else {
 					dirPath := path.Dir(p)
-					if err = paths.MakeDirIfNotExist(&dirPath); err != nil {
+					if err = paths.MakeDirIfNotExist(dirPath); err != nil {
 						continue
 					}
 					if success, err = testOpen(p); err != nil {
@@ -100,6 +113,7 @@ func GetLogger(enableDebug bool, prefix string, logPaths ...string) (logger Logg
 					StdLogger: StdLogger{
 						Prefix:      logPrefix,
 						EnableDebug: enableDebug,
+						LogFlags:    logConfigFlags,
 					},
 					Path: logPath,
 				}
@@ -107,17 +121,26 @@ func GetLogger(enableDebug bool, prefix string, logPaths ...string) (logger Logg
 				logger = &StdLogger{
 					Prefix:      logPrefix,
 					EnableDebug: enableDebug,
+					LogFlags:    logConfigFlags,
 				}
 			}
 		}
 	}
 
-	logger.Setup()
 	if prefix != "\x00" {
-		logger.SetPrefix(prefix)
+		if err = logger.SetPrefix(prefix); err != nil {
+			return
+		}
+	}
+	if err = logger.Setup(); err != nil {
+		return
 	}
 
-	logger.Info("logger initialized of type %T with prefix %v", logger, logger.GetPrefix())
+	if currentPrefix, err = logger.GetPrefix(); err != nil {
+		return
+	}
+
+	logger.Debug("logger initialized of type %T with prefix %v", logger, currentPrefix)
 
 	return
 }

logging/funcs_linux_test.go

@@ -0,0 +1,270 @@
+package logging
+
+import (
+	`fmt`
+	`os`
+	`testing`
+)
+
+/*
+	TestSysDLogger tests functionality for SystemDLogger.
+*/
+func TestSysDLogger(t *testing.T) {
+
+	var l *SystemDLogger
+	var ltype string = "SystemDLogger"
+	var prefix string
+	var err error
+
+	l = &SystemDLogger{
+		EnableDebug: true,
+		Prefix:      TestLogPrefix,
+	}
+
+	if err = l.Setup(); err != nil {
+		t.Fatalf("error when running Setup: %v", err.Error())
+	}
+
+	t.Logf("Logger %v passed Setup. Logger: %#v", ltype, l)
+
+	if err = l.Alert(testAlert, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Crit(testCrit, ltype); err != nil {
+		t.Fatalf("error for Crit: %v", err.Error())
+	}
+
+	if err = l.Debug(testDebug, ltype); err != nil {
+		t.Fatalf("error for Debug: %v", err.Error())
+	}
+
+	if err = l.Emerg(testEmerg, ltype); err != nil {
+		t.Fatalf("error for Emerg: %v", err.Error())
+	}
+
+	if err = l.Err(testErr, ltype); err != nil {
+		t.Fatalf("error for Err: %v", err.Error())
+	}
+
+	if err = l.Info(testInfo, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Notice(testNotice, ltype); err != nil {
+		t.Fatalf("error for Notice: %v", err.Error())
+	}
+
+	if err = l.Warning(testWarning, ltype); err != nil {
+		t.Fatalf("error for Warning: %v", err.Error())
+	}
+
+	if prefix, err = l.GetPrefix(); err != nil {
+		t.Fatalf("error when fetching prefix: %v", err.Error())
+	}
+
+	if prefix != TestLogPrefix {
+		t.Fatalf("true prefix ('%v') does not match TestLogPrefix ('%v')", prefix, TestLogPrefix)
+	}
+	if err = l.SetPrefix(TestLogAltPrefix); err != nil {
+		t.Fatalf("error when setting prefix to %v: %v", TestLogAltPrefix, err.Error())
+	} else {
+		_ = l.SetPrefix(TestLogPrefix)
+	}
+
+	if err = l.DoDebug(false); err != nil {
+		t.Fatalf("error when changing debug to false: %v", err.Error())
+	} else if l.EnableDebug {
+		t.Fatalf("did not properly set Debug filter state")
+	} else {
+		_ = l.DoDebug(true)
+	}
+
+	if err = l.Shutdown(); err != nil {
+		t.Fatalf("Error when running Shutdown: %v", err.Error())
+	}
+
+	t.Logf("Logger %v passed all logging targets.", ltype)
+}
+
+/*
+	TestSyslogLogger tests functionality for SyslogLogger.
+*/
+func TestSyslogLogger(t *testing.T) {
+
+	var l *SyslogLogger
+	var ltype string = "SyslogLogger"
+	var prefix string
+	var err error
+
+	l = &SyslogLogger{
+		EnableDebug: true,
+		Prefix:      TestLogPrefix,
+	}
+
+	if err = l.Setup(); err != nil {
+		t.Fatalf("error when running Setup: %v", err.Error())
+	}
+
+	t.Logf("Logger %v passed Setup. Logger: %#v", ltype, l)
+
+	if err = l.Alert(testAlert, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Crit(testCrit, ltype); err != nil {
+		t.Fatalf("error for Crit: %v", err.Error())
+	}
+
+	if err = l.Debug(testDebug, ltype); err != nil {
+		t.Fatalf("error for Debug: %v", err.Error())
+	}
+
+	if err = l.Emerg(testEmerg, ltype); err != nil {
+		t.Fatalf("error for Emerg: %v", err.Error())
+	}
+
+	if err = l.Err(testErr, ltype); err != nil {
+		t.Fatalf("error for Err: %v", err.Error())
+	}
+
+	if err = l.Info(testInfo, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Notice(testNotice, ltype); err != nil {
+		t.Fatalf("error for Notice: %v", err.Error())
+	}
+
+	if err = l.Warning(testWarning, ltype); err != nil {
+		t.Fatalf("error for Warning: %v", err.Error())
+	}
+
+	if prefix, err = l.GetPrefix(); err != nil {
+		t.Fatalf("error when fetching prefix: %v", err.Error())
+	}
+
+	if prefix != TestLogPrefix {
+		t.Fatalf("true prefix ('%v') does not match TestLogPrefix ('%v')", prefix, TestLogPrefix)
+	}
+	if err = l.SetPrefix(TestLogAltPrefix); err != nil {
+		t.Fatalf("error when setting prefix to %v: %v", TestLogAltPrefix, err.Error())
+	} else {
+		_ = l.SetPrefix(TestLogPrefix)
+	}
+
+	if err = l.DoDebug(false); err != nil {
+		t.Fatalf("error when changing debug to false: %v", err.Error())
+	} else if l.EnableDebug {
+		t.Fatalf("did not properly set Debug filter state")
+	} else {
+		_ = l.DoDebug(true)
+	}
+
+	if err = l.Shutdown(); err != nil {
+		t.Fatalf("Error when running Shutdown: %v", err.Error())
+	}
+
+	t.Logf("Logger %v passed all logging targets.", ltype)
+}
+
+// TestDefaultLogger tests GetLogger.
+func TestDefaultLogger(t *testing.T) {
+
+	var l Logger
+	var tempfile *os.File
+	var tempfilePath string
+	var keepLog bool
+	var ltype string
+	var prefix string
+	var testPrefix string
+	var err error
+
+	if tempfile, err = os.CreateTemp("", ".LOGGINGTEST_*"); err != nil {
+		t.Fatalf("error when creating temporary log file '%v': %v", tempfile.Name(), err.Error())
+	}
+	tempfilePath = tempfile.Name()
+	// We can close the handler immediately; we don't need it since the FileLogger opens its own.
+	if err = tempfile.Close(); err != nil {
+		t.Fatalf("error when closing handler for temporary log file '%v': %v", tempfile.Name(), err.Error())
+	}
+
+	if l, err = GetLogger(true, TestLogPrefix, logFlags, tempfilePath); err != nil {
+		t.Fatalf("error when spawning default Linux logger via GetLogger: %v", err.Error())
+	}
+
+	ltype = fmt.Sprintf("%T", l)
+
+	t.Logf("Logger %v passed Setup. Logger: %#v", ltype, l)
+
+	if err = l.Alert(testAlert, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Crit(testCrit, ltype); err != nil {
+		t.Fatalf("error for Crit: %v", err.Error())
+	}
+
+	if err = l.Debug(testDebug, ltype); err != nil {
+		t.Fatalf("error for Debug: %v", err.Error())
+	}
+
+	if err = l.Emerg(testEmerg, ltype); err != nil {
+		t.Fatalf("error for Emerg: %v", err.Error())
+	}
+
+	if err = l.Err(testErr, ltype); err != nil {
+		t.Fatalf("error for Err: %v", err.Error())
+	}
+
+	if err = l.Info(testInfo, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Notice(testNotice, ltype); err != nil {
+		t.Fatalf("error for Notice: %v", err.Error())
+	}
+
+	if err = l.Warning(testWarning, ltype); err != nil {
+		t.Fatalf("error for Warning: %v", err.Error())
+	}
+
+	if prefix, err = l.GetPrefix(); err != nil {
+		t.Fatalf("error when fetching prefix: %v", err.Error())
+	}
+
+	if ltype == "StdLogger" || ltype == "FileLogger" { // StdLogger (and thus FileLogger) adds a space at the end.
+		testPrefix = TestLogPrefix + " "
+	} else {
+		testPrefix = TestLogPrefix
+	}
+
+	if prefix != testPrefix {
+		t.Fatalf("true prefix ('%v') does not match TestLogPrefix ('%v')", prefix, TestLogPrefix)
+	}
+	if err = l.SetPrefix(TestLogAltPrefix); err != nil {
+		t.Fatalf("error when setting prefix to %v: %v", TestLogAltPrefix, err.Error())
+	} else {
+		_ = l.SetPrefix(TestLogPrefix)
+	}
+
+	if err = l.DoDebug(false); err != nil {
+		t.Fatalf("error when changing debug to false: %v", err.Error())
+	} else {
+		_ = l.DoDebug(true)
+	}
+
+	if err = l.Shutdown(); err != nil {
+		t.Fatalf("Error when running Shutdown: %v", err.Error())
+	}
+
+	_, keepLog = os.LookupEnv(EnvVarKeepLog)
+
+	if !keepLog {
+		if err = os.Remove(tempfilePath); err != nil {
+			t.Fatalf("error when removing temporary log file '%v': %v", tempfilePath, err.Error())
+		}
+	}
+
+	t.Logf("Logger %v passed all logging targets.", ltype)
+}

logging/funcs_logprio.go

@@ -0,0 +1,25 @@
+package logging
+
+import (
+	`r00t2.io/goutils/bitmask`
+)
+
+// HasFlag provides a wrapper for functionality to the underlying bitmask.MaskBit.
+func (l *logPrio) HasFlag(prio logPrio) (hasFlag bool) {
+
+	var m *bitmask.MaskBit
+	var p *bitmask.MaskBit
+
+	if l == nil {
+		return
+	}
+
+	m = bitmask.NewMaskBitExplicit(uint(*l))
+	p = bitmask.NewMaskBitExplicit(uint(prio))
+
+	// Use IsOneOf instead in case PriorityAll is passed for prio.
+	// hasFlag = m.HasFlag(*p)
+	hasFlag = m.IsOneOf(*p)
+
+	return
+}

logging/funcs_logwriter.go

@@ -0,0 +1,211 @@
+package logging
+
+import (
+	"unicode/utf8"
+
+	"r00t2.io/goutils/multierr"
+)
+
+/*
+Close calls Logger.Shutdown() on the underlying Logger.
+The Logger *must not be used* after this; it will need to be re-initialized with Logger.Setup()
+or a new Logger (and thuse new logWriter) must be created to replace it.
+
+It (along with logWriter.Write()) conforms to WriteCloser().
+*/
+func (l *logWriter) Close() (err error) {
+
+	if err = l.backend.Shutdown(); err != nil {
+		return
+	}
+
+	return
+}
+
+/*
+Write writes bytes b to the underlying Logger's priority level if the logWriter's priority level(s) match.
+It conforms to io.Writer. n will *always* == len(b) on success, because otherwise n would technically be >= len(b)
+(if multiple priorities are enabled), which is undefined behavior per io.Writer.
+
+b is converted to a string to normalize to the underlying Logger.
+*/
+func (l *logWriter) Write(b []byte) (n int, err error) {
+
+	var s string
+	var mErr *multierr.MultiError = multierr.NewMultiError(nil)
+
+	if b == nil {
+		return
+	}
+
+	s = string(b)
+
+	// Since this explicitly checks each priority level, there's no need for IsOneOf in case of PriorityAll.
+
+	if l.prio.HasFlag(PriorityEmergency) {
+		if err = l.backend.Emerg(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityAlert) {
+		if err = l.backend.Alert(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityCritical) {
+		if err = l.backend.Crit(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityError) {
+		if err = l.backend.Err(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityWarning) {
+		if err = l.backend.Warning(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityNotice) {
+		if err = l.backend.Notice(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityInformational) {
+		if err = l.backend.Info(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityDebug) {
+		if err = l.backend.Debug(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+
+	if !mErr.IsEmpty() {
+		err = mErr
+		return
+	}
+
+	n = len(b)
+
+	return
+}
+
+/*
+WriteByte conforms a logWriter to an io.ByteWriter. (It just wraps logWriter.Write().)
+You should probably never use this; the logging overhead/prefix is going to be more data than the single byte itself.
+
+c is converted to a string to normalize to the underlying Logger.
+*/
+func (l *logWriter) WriteByte(c byte) (err error) {
+
+	if _, err = l.Write([]byte{c}); err != nil {
+		return
+	}
+
+	return
+}
+
+/*
+WriteRune follows the same signature of (bytes.Buffer).WriteRune() and (bufio.Writer).WriteRune(); thus if `io` ever defines an io.RuneWriter interface, here ya go.
+
+n will *always* be equal to (unicode/utf8).RuneLen(r), unless r is an "invalid rune" -- in which case n will be 0 and err will be ErrInvalidRune..
+*/
+func (l *logWriter) WriteRune(r rune) (n int, err error) {
+
+	var b []byte
+
+	n = utf8.RuneLen(r)
+	if n < 0 {
+		err = ErrInvalidRune
+		n = 0
+		return
+	}
+
+	b = make([]byte, n)
+	utf8.EncodeRune(b, r)
+
+	if n, err = l.Write(b); err != nil {
+		return
+	}
+
+	return
+}
+
+/*
+WriteString writes string s to the underlying Logger's priority level if the logWriter's priority level(s) match.
+It conforms to io.StringWriter. n will *always* == len(s) on success, because otherwise n would technically be >= len(s)
+(if multiple priorities are enabled), which is undefined behavior per io.StringWriter.
+*/
+func (l *logWriter) WriteString(s string) (n int, err error) {
+
+	var mErr *multierr.MultiError = multierr.NewMultiError(nil)
+
+	if l.prio.HasFlag(PriorityEmergency) {
+		if err = l.backend.Emerg(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityAlert) {
+		if err = l.backend.Alert(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityCritical) {
+		if err = l.backend.Crit(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityError) {
+		if err = l.backend.Err(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityWarning) {
+		if err = l.backend.Warning(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityNotice) {
+		if err = l.backend.Notice(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityInformational) {
+		if err = l.backend.Info(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+	if l.prio.HasFlag(PriorityDebug) {
+		if err = l.backend.Debug(s); err != nil {
+			mErr.AddError(err)
+			err = nil
+		}
+	}
+
+	if !mErr.IsEmpty() {
+		err = mErr
+		return
+	}
+
+	n = len(s)
+
+	return
+}

logging/funcs_multilogger.go

@@ -0,0 +1,389 @@
+package logging
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"sync"
+
+	"r00t2.io/goutils/multierr"
+)
+
+// Setup sets up/configures a MultiLogger (and all its MultiLogger.Loggers) and prepares it for use.
+func (m *MultiLogger) Setup() (err error) {
+
+	var wg sync.WaitGroup
+	var errs *multierr.MultiError = multierr.NewMultiError(nil)
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logger Logger, lName string) {
+			var err2 error
+			defer wg.Done()
+			if err2 = logger.Setup(); err2 != nil {
+				errs.AddError(errors.New(fmt.Sprintf("error on Setup for logger %v; follows (may be out of order):", lName)))
+				errs.AddError(err2)
+				err2 = nil
+			}
+		}(l, logName)
+	}
+
+	wg.Wait()
+
+	if errs.Count() > 0 {
+		err = errs
+		return
+	}
+
+	return
+}
+
+// Shutdown cleanly shuts down a MultiLogger (and all its MultiLogger.Loggers).
+func (m *MultiLogger) Shutdown() (err error) {
+
+	var wg sync.WaitGroup
+	var errs *multierr.MultiError = multierr.NewMultiError(nil)
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logger Logger, lName string) {
+			var err2 error
+			defer wg.Done()
+			if err2 = logger.Shutdown(); err2 != nil {
+				errs.AddError(errors.New(fmt.Sprintf("error on Shutdown for logger %v; follows (may be out of order):", lName)))
+				errs.AddError(err2)
+				err2 = nil
+			}
+		}(l, logName)
+	}
+
+	wg.Wait()
+
+	if errs.Count() > 0 {
+		err = errs
+		return
+	}
+
+	return
+}
+
+/*
+GetPrefix returns the prefix used by this MultiLogger (and all its MultiLogger.Loggers).
+err will always be nil; it's there for interface-compat.
+*/
+func (m *MultiLogger) GetPrefix() (prefix string, err error) {
+
+	prefix = m.Prefix
+
+	return
+
+}
+
+/*
+DoDebug sets the debug state of this MultiLogger (and all its MultiLogger.Loggers).
+Note that this merely acts as a *safety filter* for debug messages to avoid sensitive information being written to the log.
+
+If you had a logger-specific EnableDebug set, you will need to re-set it to your desired state after running this method.
+*/
+func (m *MultiLogger) DoDebug(d bool) (err error) {
+
+	var wg sync.WaitGroup
+	var errs *multierr.MultiError = multierr.NewMultiError(nil)
+
+	m.EnableDebug = d
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logger Logger, lName string) {
+			var err2 error
+			defer wg.Done()
+			if err2 = l.DoDebug(d); err2 != nil {
+				errs.AddError(errors.New(fmt.Sprintf("error on DoDebug for logger %v; follows (may be out of order):", lName)))
+				errs.AddError(err2)
+				err2 = nil
+			}
+		}(l, logName)
+	}
+
+	wg.Wait()
+
+	if errs.Count() > 0 {
+		err = errs
+		return
+	}
+
+	return
+}
+
+// GetDebug returns the debug status of this MultiLogger.
+func (m *MultiLogger) GetDebug() (d bool) {
+
+	d = m.EnableDebug
+
+	return
+}
+
+/*
+SetPrefix sets the prefix for this MultiLogger (and all its MultiLogger.Loggers).
+
+If you had a logger-specific Prefix set, you will need to re-set it to your desired prefix after running this method.
+*/
+func (m *MultiLogger) SetPrefix(prefix string) (err error) {
+
+	var wg sync.WaitGroup
+	var errs *multierr.MultiError = multierr.NewMultiError(nil)
+
+	m.Prefix = prefix
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logger Logger, lName string) {
+			var err2 error
+			defer wg.Done()
+			if err2 = l.SetPrefix(prefix); err != nil {
+				errs.AddError(errors.New(fmt.Sprintf("error on SetPrefix for logger %v; follows (may be out of order):", lName)))
+				errs.AddError(err2)
+				err2 = nil
+			}
+		}(l, logName)
+	}
+
+	wg.Wait()
+
+	if errs.Count() > 0 {
+		err = errs
+		return
+	}
+
+	return
+}
+
+// Alert writes an ALERT-level message to this MultiLogger (and all its MultiLogger.Loggers).
+func (m *MultiLogger) Alert(s string, v ...interface{}) (err error) {
+
+	var wg sync.WaitGroup
+	var e *multierr.MultiError = multierr.NewMultiError(nil)
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logObj Logger, msg, lName string, rplc ...interface{}) {
+			defer wg.Done()
+			if err = logObj.Alert(msg, rplc...); err != nil {
+				e.AddError(errors.New(fmt.Sprintf("error on Alert for logger %v; follows (may be out of order):", lName)))
+				e.AddError(err)
+				err = nil
+			}
+		}(l, s, logName, v...)
+	}
+
+	wg.Wait()
+
+	if !e.IsEmpty() {
+		err = e
+	}
+
+	return
+}
+
+// Crit writes an CRITICAL-level message to this MultiLogger (and all its MultiLogger.Loggers).
+func (m *MultiLogger) Crit(s string, v ...interface{}) (err error) {
+
+	var wg sync.WaitGroup
+	var e *multierr.MultiError = multierr.NewMultiError(nil)
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logObj Logger, msg, lName string, rplc ...interface{}) {
+			defer wg.Done()
+			if err = logObj.Crit(msg, rplc...); err != nil {
+				e.AddError(errors.New(fmt.Sprintf("error on Crit for logger %v; follows (may be out of order):", lName)))
+				e.AddError(err)
+				err = nil
+			}
+		}(l, s, logName, v...)
+	}
+
+	wg.Wait()
+
+	if !e.IsEmpty() {
+		err = e
+	}
+
+	return
+}
+
+// Debug writes a DEBUG-level message to this MultiLogger (and all its MultiLogger.Loggers).
+func (m *MultiLogger) Debug(s string, v ...interface{}) (err error) {
+
+	var wg sync.WaitGroup
+	var e *multierr.MultiError = multierr.NewMultiError(nil)
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logObj Logger, msg, lName string, rplc ...interface{}) {
+			defer wg.Done()
+			if err = logObj.Debug(msg, rplc...); err != nil {
+				e.AddError(errors.New(fmt.Sprintf("error on Debug for logger %v; follows (may be out of order):", lName)))
+				e.AddError(err)
+				err = nil
+			}
+		}(l, s, logName, v...)
+	}
+
+	wg.Wait()
+
+	if !e.IsEmpty() {
+		err = e
+	}
+	return
+}
+
+// Emerg writes an EMERGENCY-level message to this MultiLogger (and all its MultiLogger.Loggers).
+func (m *MultiLogger) Emerg(s string, v ...interface{}) (err error) {
+
+	var wg sync.WaitGroup
+	var e *multierr.MultiError = multierr.NewMultiError(nil)
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logObj Logger, msg, lName string, rplc ...interface{}) {
+			defer wg.Done()
+			if err = logObj.Emerg(msg, rplc...); err != nil {
+				e.AddError(errors.New(fmt.Sprintf("error on Emerg for logger %v; follows (may be out of order):", lName)))
+				e.AddError(err)
+				err = nil
+			}
+		}(l, s, logName, v...)
+	}
+
+	wg.Wait()
+
+	if !e.IsEmpty() {
+		err = e
+	}
+	return
+}
+
+// Err writes an ERROR-level message to this MultiLogger (and all its MultiLogger.Loggers).
+func (m *MultiLogger) Err(s string, v ...interface{}) (err error) {
+
+	var wg sync.WaitGroup
+	var e *multierr.MultiError = multierr.NewMultiError(nil)
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logObj Logger, msg, lName string, rplc ...interface{}) {
+			defer wg.Done()
+			if err = logObj.Err(msg, rplc...); err != nil {
+				e.AddError(errors.New(fmt.Sprintf("error on Err for logger %v; follows (may be out of order):", lName)))
+				e.AddError(err)
+				err = nil
+			}
+		}(l, s, logName, v...)
+	}
+
+	wg.Wait()
+
+	if !e.IsEmpty() {
+		err = e
+	}
+
+	return
+}
+
+// Info writes an INFO-level message to this MultiLogger (and all its MultiLogger.Loggers).
+func (m *MultiLogger) Info(s string, v ...interface{}) (err error) {
+
+	var wg sync.WaitGroup
+	var e *multierr.MultiError = multierr.NewMultiError(nil)
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logObj Logger, msg, lName string, rplc ...interface{}) {
+			defer wg.Done()
+			if err = logObj.Info(msg, rplc...); err != nil {
+				e.AddError(errors.New(fmt.Sprintf("error on Info for logger %v; follows (may be out of order):", lName)))
+				e.AddError(err)
+				err = nil
+			}
+		}(l, s, logName, v...)
+	}
+
+	wg.Wait()
+
+	if !e.IsEmpty() {
+		err = e
+	}
+
+	return
+}
+
+// Notice writes a NOTICE-level message to this MultiLogger (and all its MultiLogger.Loggers).
+func (m *MultiLogger) Notice(s string, v ...interface{}) (err error) {
+
+	var wg sync.WaitGroup
+	var e *multierr.MultiError = multierr.NewMultiError(nil)
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logObj Logger, msg, lName string, rplc ...interface{}) {
+			defer wg.Done()
+			if err = logObj.Notice(msg, rplc...); err != nil {
+				e.AddError(errors.New(fmt.Sprintf("error on Notice for logger %v; follows (may be out of order):", lName)))
+				e.AddError(err)
+				err = nil
+			}
+		}(l, s, logName, v...)
+	}
+
+	wg.Wait()
+
+	if !e.IsEmpty() {
+		err = e
+	}
+
+	return
+}
+
+// Warning writes a WARNING/WARN-level message to this MultiLogger (and all its MultiLogger.Loggers).
+func (m *MultiLogger) Warning(s string, v ...interface{}) (err error) {
+
+	var wg sync.WaitGroup
+	var e *multierr.MultiError = multierr.NewMultiError(nil)
+
+	for logName, l := range m.Loggers {
+		wg.Add(1)
+		go func(logObj Logger, msg, lName string, rplc ...interface{}) {
+			defer wg.Done()
+			if err = logObj.Warning(msg, rplc...); err != nil {
+				e.AddError(errors.New(fmt.Sprintf("error on Warning for logger %v; follows (may be out of order):", lName)))
+				e.AddError(err)
+				err = nil
+			}
+		}(l, s, logName, v...)
+	}
+
+	wg.Wait()
+
+	if !e.IsEmpty() {
+		err = e
+	}
+
+	return
+}
+
+// ToLogger returns a stdlib log.Logger.
+func (m *MultiLogger) ToLogger(prio logPrio) (stdLibLog *log.Logger) {
+
+	stdLibLog = log.New(m.ToRaw(prio), "", 0)
+
+	return
+}
+
+// ToRaw returns a *logWriter.
+func (m *MultiLogger) ToRaw(prio logPrio) (raw *logWriter) {
+
+	raw = &logWriter{backend: m, prio: prio}
+
+	return
+}

logging/funcs_multilogger_mgr.go

@@ -0,0 +1,195 @@
+package logging
+
+import (
+	"path"
+
+	"github.com/google/uuid"
+	"r00t2.io/sysutils/paths"
+)
+
+/*
+	GetMultiLogger returns a MultiLogger.
+	If you call GetLogger, you will only get a single ("best") logger your system supports.
+	If you want to log to multiple Logger destinations at once (or want to log to an explicit Logger type),
+	use GetMultiLogger.
+
+	Remember to add at least one Logger (e.g. MultiLogger.AddStdLogger), otherwise no entries will actually be logged.
+
+	If you want to modify e.g. if debug is enabled for a specific Logger, reference the Logger directly (e.g. MultiLogger.Loggers[identifier].SetDebug(false)).
+*/
+func GetMultiLogger(enableDebug bool, prefix string) (m *MultiLogger) {
+
+	m = &MultiLogger{
+		EnableDebug: enableDebug,
+		Prefix:      logPrefix,
+		Loggers:     make(map[string]Logger),
+	}
+	if prefix != "\x00" {
+		m.Prefix = prefix
+	}
+
+	return
+}
+
+/*
+	AddStdLogger adds a StdLogger to a MultiLogger.
+
+	identifier is a string to use to identify the added StdLogger in MultiLogger.Loggers.
+	If empty, one will be automatically generated.
+
+	enableStdOut indicates that messages should be logged to STDOUT;
+	it is *strongly encouraged* to set at least one of enableStdOut or enableStdErr to true.
+
+	enableStdErr indicates that messages should be logged to STDERR;
+	it is *strongly encouraged* to set at least one of enableStdErr or enableStdOut to true.
+
+	See GetLogger's logConfigFlags argument and StdLogger.LogFlags for details on logFlags.
+*/
+func (m *MultiLogger) AddStdLogger(identifier string, enableStdOut, enableStdErr bool, logFlags int) (err error) {
+
+	var exists bool
+	var prefix string
+
+	if identifier == "" {
+		identifier = uuid.New().String()
+	}
+
+	if _, exists = m.Loggers[identifier]; exists {
+		err = ErrExistingLogger
+		return
+	}
+
+	m.Loggers[identifier] = &StdLogger{
+		Logger:       nil,
+		EnableDebug:  m.EnableDebug,
+		Prefix:       m.Prefix,
+		LogFlags:     logFlags,
+		EnableStdOut: enableStdOut,
+		EnableStdErr: enableStdErr,
+	}
+	if err = m.Loggers[identifier].Setup(); err != nil {
+		return
+	}
+
+	if prefix, err = m.Loggers[identifier].GetPrefix(); err != nil {
+		return
+	}
+
+	m.Loggers[identifier].Debug("logger initialized of type %T with prefix %v", m.Loggers[identifier], prefix)
+
+	return
+}
+
+/*
+	AddFileLogger adds a FileLogger to a MultiLogger.
+
+	identifier is a string to use to identify the added FileLogger in MultiLogger.Loggers.
+	If empty, one will be automatically generated.
+
+	logfilePath is a string for the path to the desired logfile.
+*/
+func (m *MultiLogger) AddFileLogger(identifier string, logFlags int, logfilePath string) (err error) {
+
+	var exists bool
+	var success bool
+	var dirPath string
+	var prefix string
+
+	if identifier == "" {
+		identifier = uuid.New().String()
+	}
+
+	if _, exists = m.Loggers[identifier]; exists {
+		err = ErrExistingLogger
+		return
+	}
+
+	if exists, err = paths.RealPathExists(&logfilePath); err != nil {
+		return
+	} else if !exists {
+		if success, err = testOpen(logfilePath); err != nil {
+			return
+		} else if !success {
+			dirPath = path.Dir(logfilePath)
+			if err = paths.MakeDirIfNotExist(dirPath); err != nil {
+				return
+			}
+			if success, err = testOpen(dirPath); err != nil {
+				return
+			} else if !success {
+				err = ErrInvalidFile
+				return
+			}
+		}
+	}
+
+	m.Loggers[identifier] = &FileLogger{
+		StdLogger: StdLogger{
+			Logger:      nil,
+			EnableDebug: m.EnableDebug,
+			Prefix:      m.Prefix,
+			LogFlags:    logFlags,
+		},
+		Path: logfilePath,
+	}
+	if err = m.Loggers[identifier].Setup(); err != nil {
+		return
+	}
+
+	if prefix, err = m.Loggers[identifier].GetPrefix(); err != nil {
+		return
+	}
+
+	m.Loggers[identifier].Debug("logger initialized of type %T with prefix %v", m.Loggers[identifier], prefix)
+
+	return
+}
+
+/*
+	AddNullLogger adds a NullLogger to a MultiLogger.
+
+	identifier is a string to use to identify the added NullLogger in MultiLogger.Loggers.
+	If empty, one will be automatically generated.
+*/
+func (m *MultiLogger) AddNullLogger(identifier string) (err error) {
+
+	var exists bool
+	var prefix string
+
+	if identifier == "" {
+		identifier = uuid.New().String()
+	}
+
+	if _, exists = m.Loggers[identifier]; exists {
+		err = ErrExistingLogger
+		return
+	}
+
+	m.Loggers[identifier] = &NullLogger{}
+	if err = m.Loggers[identifier].Setup(); err != nil {
+		return
+	}
+
+	if prefix, err = m.Loggers[identifier].GetPrefix(); err != nil {
+		return
+	}
+
+	m.Loggers[identifier].Debug("logger initialized of type %T with prefix %v", m.Loggers[identifier], prefix)
+
+	return
+}
+
+// RemoveLogger will let you remove a Logger from MultiLogger.Loggers.
+func (m *MultiLogger) RemoveLogger(identifier string) (err error) {
+
+	var exists bool
+
+	if _, exists = m.Loggers[identifier]; !exists {
+		err = ErrNoEntry
+		return
+	}
+
+	delete(m.Loggers, identifier)
+
+	return
+}

logging/funcs_multilogger_mgr_linux.go

@@ -0,0 +1,79 @@
+package logging
+
+import (
+	sysd "github.com/coreos/go-systemd/v22/journal"
+	"github.com/google/uuid"
+)
+
+/*
+AddDefaultLogger adds a default Logger (as would be determined by GetLogger) to a MultiLogger.
+
+identifier is a string to use to identify the added Logger in MultiLogger.Loggers.
+If empty, one will be automatically generated.
+
+See the documentation for GetLogger for details on other arguments.
+*/
+func (m *MultiLogger) AddDefaultLogger(identifier string, logFlags int, logPaths ...string) (err error) {
+
+	var l Logger
+	var exists bool
+
+	if identifier == "" {
+		identifier = uuid.New().String()
+	}
+
+	if _, exists = m.Loggers[identifier]; exists {
+		err = ErrExistingLogger
+		return
+	}
+
+	if l, err = GetLogger(m.EnableDebug, m.Prefix, logFlags, logPaths...); err != nil {
+		return
+	}
+
+	m.Loggers[identifier] = l
+
+	return
+}
+
+/*
+AddSysdLogger adds a SystemDLogger to a MultiLogger.
+
+identifier is a string to use to identify the added SystemDLogger in MultiLogger.Loggers.
+If empty, one will be automatically generated.
+*/
+func (m *MultiLogger) AddSysdLogger(identifier string) (err error) {
+
+	var exists bool
+	var prefix string
+
+	if identifier == "" {
+		identifier = uuid.New().String()
+	}
+
+	if _, exists = m.Loggers[identifier]; exists {
+		err = ErrExistingLogger
+		return
+	}
+
+	if !sysd.Enabled() {
+		err = ErrNoSysD
+		return
+	}
+
+	m.Loggers[identifier] = &SystemDLogger{
+		EnableDebug: m.EnableDebug,
+		Prefix:      m.Prefix,
+	}
+	if err = m.Loggers[identifier].Setup(); err != nil {
+		return
+	}
+
+	if prefix, err = m.Loggers[identifier].GetPrefix(); err != nil {
+		return
+	}
+
+	m.Loggers[identifier].Debug("logger initialized of type %T with prefix %v", m.Loggers[identifier], prefix)
+
+	return
+}

logging/funcs_multilogger_mgr_nix.go

@@ -0,0 +1,63 @@
+//go:build !(windows || plan9 || wasip1 || js || ios)
+// +build !windows,!plan9,!wasip1,!js,!ios
+
+package logging
+
+import (
+	"os"
+
+	"github.com/google/uuid"
+	"r00t2.io/sysutils/paths"
+)
+
+/*
+AddSyslogLogger adds a SyslogLogger to a MultiLogger.
+
+identifier is a string to use to identify the added SyslogLogger in MultiLogger.Loggers.
+If empty, one will be automatically generated.
+*/
+func (m *MultiLogger) AddSyslogLogger(identifier string) (err error) {
+
+	var exists bool
+	var hasSyslog bool
+	var stat os.FileInfo
+	var devlogPath string = devlog
+	var prefix string
+
+	if identifier == "" {
+		identifier = uuid.New().String()
+	}
+
+	if _, exists = m.Loggers[identifier]; exists {
+		err = ErrExistingLogger
+		return
+	}
+
+	if hasSyslog, stat, err = paths.RealPathExistsStat(&devlogPath); hasSyslog && err != nil {
+		return
+	} else if !hasSyslog {
+		err = ErrNoSyslog
+		return
+	}
+
+	if stat.Mode().IsRegular() {
+		err = ErrInvalidDevLog
+		return
+	}
+
+	m.Loggers[identifier] = &SyslogLogger{
+		EnableDebug: m.EnableDebug,
+		Prefix:      m.Prefix,
+	}
+	if err = m.Loggers[identifier].Setup(); err != nil {
+		return
+	}
+
+	if prefix, err = m.Loggers[identifier].GetPrefix(); err != nil {
+		return
+	}
+
+	m.Loggers[identifier].Debug("logger initialized of type %T with prefix %v", m.Loggers[identifier], prefix)
+
+	return
+}

logging/funcs_multilogger_mgr_oldnix.go

@@ -0,0 +1,41 @@
+//go:build !(windows || plan9 || wasip1 || js || ios || linux)
+// +build !windows,!plan9,!wasip1,!js,!ios,!linux
+
+// Linux is excluded because it has its own.
+
+package logging
+
+import (
+	"github.com/google/uuid"
+)
+
+/*
+AddDefaultLogger adds a default Logger (as would be determined by GetLogger) to a MultiLogger.
+
+identifier is a string to use to identify the added Logger in MultiLogger.Loggers.
+If empty, one will be automatically generated.
+
+See the documentation for GetLogger for details on other arguments.
+*/
+func (m *MultiLogger) AddDefaultLogger(identifier string, logFlags int, logPaths ...string) (err error) {
+
+	var l Logger
+	var exists bool
+
+	if identifier == "" {
+		identifier = uuid.New().String()
+	}
+
+	if _, exists = m.Loggers[identifier]; exists {
+		err = ErrExistingLogger
+		return
+	}
+
+	if l, err = GetLogger(m.EnableDebug, m.Prefix, logFlags, logPaths...); err != nil {
+		return
+	}
+
+	m.Loggers[identifier] = l
+
+	return
+}

logging/funcs_multilogger_mgr_windows.go

@@ -0,0 +1,102 @@
+package logging
+
+import (
+	`github.com/google/uuid`
+)
+
+/*
+	AddDefaultLogger adds a default Logger (as would be determined by GetLogger) to a MultiLogger.
+
+	identifier is a string to use to identify the added Logger in MultiLogger.Loggers.
+	If empty, one will be automatically generated.
+
+	A pointer to a WinEventID struct may be specified for eventIDs to map extended logging levels (as Windows only supports three levels natively).
+	If it is nil, a default one (DefaultEventID) will be used.
+
+	logPaths is an (optional) list of strings to use as paths to test for writing. If the file can be created/written to,
+	it will be used (assuming you have no higher-level loggers available).
+
+	See the documentation for GetLogger for details on other arguments.
+
+	Only the first logPaths entry that "works" will be used, later entries will be ignored.
+	Currently this will almost always return a WinLogger.
+*/
+func (m *MultiLogger) AddDefaultLogger(identifier string, eventIDs *WinEventID, logFlags int, logPaths ...string) (err error) {
+
+	var l Logger
+	var exists bool
+
+	if identifier == "" {
+		identifier = uuid.New().String()
+	}
+
+	if _, exists = m.Loggers[identifier]; exists {
+		err = ErrExistingLogger
+		return
+	}
+
+	if logPaths != nil {
+		l, err = GetLogger(m.EnableDebug, m.Prefix, eventIDs, logFlags, logPaths...)
+	} else {
+		l, err = GetLogger(m.EnableDebug, m.Prefix, eventIDs, logFlags)
+	}
+	if err != nil {
+		return
+	}
+
+	m.Loggers[identifier] = l
+
+	return
+}
+
+/*
+	AddWinLogger adds a WinLogger to a MultiLogger. Note that this is a VERY generalized interface to the Windows Event Log.
+
+	If you require more robust logging capabilities (e.g. custom event IDs per uniquely identifiable event),
+	you will want to set up your own logger (golang.org/x/sys/windows/svc/eventlog).
+
+	identifier is a string to use to identify the added WinLogger in MultiLogger.Loggers.
+	If empty, one will be automatically generated.
+
+	A blank source will return an error as it's used as the source name. Other functions, struct fields, etc. will refer to this as the "prefix".
+
+	A pointer to a WinEventID struct may be specified for eventIDs to map extended logging levels (as Windows only supports three levels natively).
+	If it is nil, a default one (DefaultEventID) will be used.
+
+	See GetLogger for details.
+*/
+func (m *MultiLogger) AddWinLogger(identifier string, eventIDs *WinEventID) (err error) {
+
+	var exists bool
+	var prefix string
+
+	if identifier == "" {
+		identifier = uuid.New().String()
+	}
+
+	if _, exists = m.Loggers[identifier]; exists {
+		err = ErrExistingLogger
+		return
+	}
+
+	if eventIDs == nil {
+		eventIDs = DefaultEventID
+	}
+
+	m.Loggers[identifier] = &WinLogger{
+		Prefix:      m.Prefix,
+		EnableDebug: m.EnableDebug,
+		EIDs:        eventIDs,
+	}
+	if err = m.Loggers[identifier].Setup(); err != nil {
+		return
+	}
+
+	if prefix, err = m.Loggers[identifier].GetPrefix(); err != nil {
+		return
+	}
+
+	m.Loggers[identifier].Info("logger initialized of type %T with prefix %v", m.Loggers[identifier], prefix)
+
+	return
+}

logging/funcs_nulllogger.go

@@ -0,0 +1,94 @@
+package logging
+
+import (
+	"log"
+)
+
+// Setup does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) Setup() (err error) {
+	return
+}
+
+// DoDebug does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) DoDebug(d bool) (err error) {
+	return
+}
+
+// GetDebug returns the debug status of this NullLogger. It will always return true. 🙃
+func (n *NullLogger) GetDebug() (d bool) {
+
+	d = true
+
+	return
+}
+
+// SetPrefix does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) SetPrefix(p string) (err error) {
+	return
+}
+
+// GetPrefix does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) GetPrefix() (p string, err error) {
+	return
+}
+
+// Shutdown does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) Shutdown() (err error) {
+	return
+}
+
+// Alert does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) Alert(s string, v ...interface{}) (err error) {
+	return
+}
+
+// Crit does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) Crit(s string, v ...interface{}) (err error) {
+	return
+}
+
+// Debug does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) Debug(s string, v ...interface{}) (err error) {
+	return
+}
+
+// Emerg does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) Emerg(s string, v ...interface{}) (err error) {
+	return
+}
+
+// Err does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) Err(s string, v ...interface{}) (err error) {
+	return
+}
+
+// Info does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) Info(s string, v ...interface{}) (err error) {
+	return
+}
+
+// Notice does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) Notice(s string, v ...interface{}) (err error) {
+	return
+}
+
+// Warning does nothing at all; it's here for interface compat. 🙃
+func (l *NullLogger) Warning(s string, v ...interface{}) (err error) {
+	return
+}
+
+// ToLogger returns a stdlib log.Logger (that doesn't actually write to anything).
+func (l *NullLogger) ToLogger(prio logPrio) (stdLibLog *log.Logger) {
+
+	stdLibLog = log.New(&nullWriter{}, "", 0)
+
+	return
+}
+
+// ToRaw returns a *logWriter. (This is a little less efficient than using ToLogger's log.Logger as an io.Writer if that's all you need.)
+func (l *NullLogger) ToRaw(prio logPrio) (raw *logWriter) {
+
+	raw = &logWriter{backend: l, prio: prio}
+
+	return
+}

logging/funcs_nullwriter.go

@@ -0,0 +1,58 @@
+package logging
+
+import (
+	"unicode/utf8"
+)
+
+// Close conforms a nullWriter to an io.WriteCloser. It obviously does nothing, and will always return with err == nil.
+func (nw *nullWriter) Close() (err error) {
+
+	// NO-OP
+
+	return
+}
+
+// Write conforms a nullWriter to an io.Writer, but it writes... nothing. To avoid errors, however, in downstream code it pretends it does (n will *always* == len(b)).
+func (nw *nullWriter) Write(b []byte) (n int, err error) {
+
+	if b == nil {
+		return
+	}
+	n = len(b)
+
+	return
+}
+
+// WriteByte conforms to an io.ByteWriter but again... nothing is actually written anywhere.
+func (nw *nullWriter) WriteByte(c byte) (err error) {
+
+	// NO-OP
+
+	_ = c
+
+	return
+}
+
+/*
+WriteRune conforms to the other Loggers. It WILL return the proper value for n (matching (bytes.Buffer).WriteRune() and (bufio.Writer).WriteRune() signatures,
+and it WILL return an ErrInvalidRune if r is not a valid rune, but otherwise it will no-op.
+*/
+func (nw *nullWriter) WriteRune(r rune) (n int, err error) {
+
+	n = utf8.RuneLen(r)
+	if n < 0 {
+		err = ErrInvalidRune
+		n = 0
+		return
+	}
+
+	return
+}
+
+// WriteString conforms to an io.StringWriter but nothing is actually written. (n will *always* == len(s))
+func (nw *nullWriter) WriteString(s string) (n int, err error) {
+
+	n = len(s)
+
+	return
+}

logging/funcs_oldnix.go

@@ -0,0 +1,138 @@
+//go:build !(windows || plan9 || wasip1 || js || ios || linux)
+// +build !windows,!plan9,!wasip1,!js,!ios,!linux
+
+// Linux is excluded because it has its own.
+
+package logging
+
+import (
+	native "log"
+	"os"
+	"path"
+
+	"r00t2.io/goutils/bitmask"
+	"r00t2.io/sysutils/paths"
+)
+
+var (
+	_ = native.Logger{}
+	_ = os.Interrupt
+)
+
+/*
+GetLogger returns an instance of Logger that best suits your system's capabilities.
+
+If enableDebug is true, debug messages (which according to your program may or may not contain sensitive data) are rendered and written.
+
+If prefix is "\x00" (a null byte), then the default logging prefix will be used. If anything else, even an empty string,
+is specified then that will be used instead for the prefix.
+
+logConfigFlags is the corresponding flag(s) OR'd for StdLogger.LogFlags / FileLogger.StdLogger.LogFlags if either is selected. See StdLogger.LogFlags and
+https://pkg.go.dev/log#pkg-constants for details.
+
+logPaths is an (optional) list of strings to use as paths to test for writing. If the file can be created/written to,
+it will be used (assuming you have no higher-level loggers available). Only the first logPaths entry that "works" will be used, later entries will be ignored.
+If you want to log to multiple files simultaneously, use a MultiLogger instead.
+
+If you call GetLogger, you will only get a single ("best") logger your system supports.
+If you want to log to multiple Logger destinations at once (or want to log to an explicit Logger type),
+use GetMultiLogger.
+*/
+func GetLogger(enableDebug bool, prefix string, logConfigFlags int, logPaths ...string) (logger Logger, err error) {
+
+	var logPath string
+	var logFlags bitmask.MaskBit
+	var currentPrefix string
+
+	// Configure system-supported logger(s).
+
+	// If we can detect syslog, use that. If not, try to use a file logger (+ stdout).
+	// Last ditch, stdout.
+	var hasSyslog bool
+	var stat os.FileInfo
+	var devlogPath string = devlog
+
+	if hasSyslog, stat, err = paths.RealPathExistsStat(&devlogPath); hasSyslog && err != nil {
+		return
+	}
+
+	if hasSyslog && !stat.Mode().IsRegular() {
+		logFlags.AddFlag(LogSyslog)
+	} else {
+		var exists bool
+		var success bool
+		var ckLogPaths []string
+
+		logFlags.AddFlag(LogStdout)
+		ckLogPaths = defLogPaths
+		if logPaths != nil {
+			ckLogPaths = logPaths
+		}
+		for _, p := range ckLogPaths {
+			if exists, _ = paths.RealPathExists(&p); exists {
+				if success, err = testOpen(p); err != nil {
+					continue
+				} else if !success {
+					continue
+				}
+				logFlags.AddFlag(LogFile)
+				logPath = p
+				break
+			} else {
+				dirPath := path.Dir(p)
+				if err = paths.MakeDirIfNotExist(dirPath); err != nil {
+					continue
+				}
+				if success, err = testOpen(p); err != nil {
+					continue
+				} else if !success {
+					continue
+				}
+				logFlags.AddFlag(LogFile)
+				logPath = p
+				break
+			}
+		}
+	}
+
+	if logFlags.HasFlag(LogSyslog) {
+		logger = &SyslogLogger{
+			Prefix:      logPrefix,
+			EnableDebug: enableDebug,
+		}
+	} else {
+		if logFlags.HasFlag(LogFile) {
+			logger = &FileLogger{
+				StdLogger: StdLogger{
+					Prefix:      logPrefix,
+					EnableDebug: enableDebug,
+					LogFlags:    logConfigFlags,
+				},
+				Path: logPath,
+			}
+		} else {
+			logger = &StdLogger{
+				Prefix:      logPrefix,
+				EnableDebug: enableDebug,
+				LogFlags:    logConfigFlags,
+			}
+		}
+	}
+
+	if prefix != "\x00" {
+		if err = logger.SetPrefix(prefix); err != nil {
+			return
+		}
+	}
+	if err = logger.Setup(); err != nil {
+		return
+	}
+
+	if currentPrefix, err = logger.GetPrefix(); err != nil {
+		return
+	}
+
+	logger.Debug("logger initialized of type %T with prefix %v", logger, currentPrefix)
+
+	return
+}

logging/funcs_std.go

@@ -2,38 +2,108 @@ package logging
 
 import (
 	"fmt"
+	"io"
 	"log"
+	"os"
+	"strings"
 )
 
-func (l *StdLogger) Setup() {
+/*
+Setup sets up/configures a StdLogger and prepares it for use.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *StdLogger) Setup() (err error) {
 
-	l.Logger = log.Default()
+	var multi io.Writer
+
+	// This uses a shared handle across the import. We don't want that.
+	// l.Logger = log.Default()
+	if l.Prefix != "" {
+		l.Prefix = strings.TrimRight(l.Prefix, " ") + " "
+		// l.Logger.SetPrefix(l.Prefix)
+	}
+	// (stdlib).log.std is returned by log.Default(), which uses os.Stderr but we have flags for that.
+	// https://stackoverflow.com/a/36719588/733214
+	switch {
+	case l.EnableStdErr && l.EnableStdOut:
+		multi = io.MultiWriter(os.Stdout, os.Stderr)
+	case l.EnableStdErr:
+		multi = os.Stderr
+	case l.EnableStdOut:
+		multi = os.Stdout
+	default:
+		multi = nil
+	}
+	if multi != nil {
+		l.Logger = log.New(multi, l.Prefix, l.LogFlags)
+	} else {
+		// This honestly should throw an error.
+		l.Logger = &log.Logger{}
 		l.Logger.SetPrefix(l.Prefix)
+		l.Logger.SetFlags(l.LogFlags)
 	}
 
-func (l *StdLogger) Shutdown() {
+	return
+}
+
+/*
+Shutdown cleanly shuts down a StdLogger.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *StdLogger) Shutdown() (err error) {
 
 	// NOOP
-	_ = ""
 
+	return
 }
 
-func (l *StdLogger) DoDebug(d bool) {
-	l.EnableDebug = d
-}
-
-func (l *StdLogger) SetPrefix(prefix string) {
-	l.Prefix = prefix
-	l.Logger.SetPrefix(prefix)
-}
-
-func (l *StdLogger) GetPrefix() (prefix string) {
+/*
+GetPrefix returns the prefix used by this StdLogger.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *StdLogger) GetPrefix() (prefix string, err error) {
 
 	prefix = l.Prefix
 
 	return
 }
 
+/*
+DoDebug sets the debug state of this StdLogger.
+Note that this merely acts as a *safety filter* for debug messages to avoid sensitive information being written to the log.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *StdLogger) DoDebug(d bool) (err error) {
+
+	l.EnableDebug = d
+
+	return
+}
+
+// GetDebug returns the debug status of this StdLogger.
+func (l *StdLogger) GetDebug() (d bool) {
+
+	d = l.EnableDebug
+
+	return
+}
+
+/*
+SetPrefix sets the prefix for this StdLogger.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *StdLogger) SetPrefix(prefix string) (err error) {
+
+	l.Prefix = prefix
+	if prefix != "" {
+		l.Prefix = strings.TrimRight(l.Prefix, " ") + " "
+	}
+	l.Logger.SetPrefix(l.Prefix)
+
+	return
+}
+
+// Alert writes an ALERT-level message to this StdLogger.
 func (l *StdLogger) Alert(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -49,6 +119,7 @@ func (l *StdLogger) Alert(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Crit writes an CRITICAL-level message to this StdLogger.
 func (l *StdLogger) Crit(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -64,6 +135,7 @@ func (l *StdLogger) Crit(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Debug writes a DEBUG-level message to this StdLogger.
 func (l *StdLogger) Debug(s string, v ...interface{}) (err error) {
 
 	if !l.EnableDebug {
@@ -83,6 +155,7 @@ func (l *StdLogger) Debug(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Emerg writes an EMERGENCY-level message to this StdLogger.
 func (l *StdLogger) Emerg(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -98,6 +171,7 @@ func (l *StdLogger) Emerg(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Err writes an ERROR-level message to this StdLogger.
 func (l *StdLogger) Err(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -113,6 +187,7 @@ func (l *StdLogger) Err(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Info writes an INFO-level message to this StdLogger.
 func (l *StdLogger) Info(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -128,6 +203,7 @@ func (l *StdLogger) Info(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Notice writes a NOTICE-level message to this StdLogger.
 func (l *StdLogger) Notice(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -143,6 +219,7 @@ func (l *StdLogger) Notice(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Warning writes a WARNING/WARN-level message to this StdLogger.
 func (l *StdLogger) Warning(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -158,6 +235,23 @@ func (l *StdLogger) Warning(s string, v ...interface{}) (err error) {
 	return
 }
 
+// ToLogger returns a stdlib log.Logger.
+func (l *StdLogger) ToLogger(prio logPrio) (stdLibLog *log.Logger) {
+
+	stdLibLog = log.New(l.ToRaw(prio), "", 0)
+
+	return
+}
+
+// ToRaw returns a *logWriter.
+func (l *StdLogger) ToRaw(prio logPrio) (raw *logWriter) {
+
+	raw = &logWriter{backend: l, prio: prio}
+
+	return
+}
+
+// renderWrite prepares/formats a log message to be written to this StdLogger.
 func (l *StdLogger) renderWrite(msg, prio string) {
 
 	s := fmt.Sprintf("[%v] %v", prio, msg)

logging/funcs_sysd_linux.go

@@ -4,38 +4,74 @@ import (
 	"fmt"
 	"log"
 
-	"github.com/coreos/go-systemd/journal"
+	"github.com/coreos/go-systemd/v22/journal"
 )
 
-func (l *SystemDLogger) Setup() {
+/*
+Setup sets up/configures a SystemDLogger and prepares it for use.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *SystemDLogger) Setup() (err error) {
 
 	// NOOP
-	_ = ""
 
+	return
 }
 
-func (l *SystemDLogger) Shutdown() {
+/*
+Shutdown cleanly shuts down a SystemDLogger.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *SystemDLogger) Shutdown() (err error) {
 
 	// NOOP
-	_ = ""
 
+	return
 }
 
-func (l *SystemDLogger) DoDebug(d bool) {
-	l.EnableDebug = d
-}
-
-func (l *SystemDLogger) SetPrefix(prefix string) {
-	l.Prefix = prefix
-}
-
-func (l *SystemDLogger) GetPrefix() (prefix string) {
+/*
+GetPrefix returns the prefix used by this SystemDLogger.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *SystemDLogger) GetPrefix() (prefix string, err error) {
 
 	prefix = l.Prefix
 
 	return
 }
 
+/*
+DoDebug sets the debug state of this SystemDLogger.
+Note that this merely acts as a *safety filter* for debug messages to avoid sensitive information being written to the log.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *SystemDLogger) DoDebug(d bool) (err error) {
+
+	l.EnableDebug = d
+
+	return
+}
+
+// GetDebug returns the debug status of this SystemDLogger.
+func (l *SystemDLogger) GetDebug() (d bool) {
+
+	d = l.EnableDebug
+
+	return
+}
+
+/*
+SetPrefix sets the prefix for this SystemDLogger.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *SystemDLogger) SetPrefix(prefix string) (err error) {
+
+	l.Prefix = prefix
+
+	return
+}
+
+// Alert writes an ALERT-level message to this SystemDLogger.
 func (l *SystemDLogger) Alert(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -51,6 +87,7 @@ func (l *SystemDLogger) Alert(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Crit writes an CRITICAL-level message to this SystemDLogger.
 func (l *SystemDLogger) Crit(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -66,6 +103,7 @@ func (l *SystemDLogger) Crit(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Debug writes a DEBUG-level message to this SystemDLogger.
 func (l *SystemDLogger) Debug(s string, v ...interface{}) (err error) {
 
 	if !l.EnableDebug {
@@ -85,6 +123,7 @@ func (l *SystemDLogger) Debug(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Emerg writes an EMERGENCY-level message to this SystemDLogger.
 func (l *SystemDLogger) Emerg(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -100,6 +139,7 @@ func (l *SystemDLogger) Emerg(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Err writes an ERROR-level message to this SystemDLogger.
 func (l *SystemDLogger) Err(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -115,6 +155,7 @@ func (l *SystemDLogger) Err(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Info writes an INFO-level message to this SystemDLogger.
 func (l *SystemDLogger) Info(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -130,6 +171,7 @@ func (l *SystemDLogger) Info(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Notice writes a NOTICE-level message to this SystemDLogger.
 func (l *SystemDLogger) Notice(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -145,6 +187,7 @@ func (l *SystemDLogger) Notice(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Warning writes a WARNING/WARN-level message to this SystemDLogger.
 func (l *SystemDLogger) Warning(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -160,6 +203,7 @@ func (l *SystemDLogger) Warning(s string, v ...interface{}) (err error) {
 	return
 }
 
+// renderWrite prepares/formats a log message to be written to this SystemDLogger.
 func (l *SystemDLogger) renderWrite(msg string, prio journal.Priority) {
 
 	// TODO: implement code line, etc.
@@ -179,3 +223,19 @@ func (l *SystemDLogger) renderWrite(msg string, prio journal.Priority) {
 
 	return
 }
+
+// ToLogger returns a stdlib log.Logger.
+func (l *SystemDLogger) ToLogger(prio logPrio) (stdLibLog *log.Logger) {
+
+	stdLibLog = log.New(l.ToRaw(prio), "", 0)
+
+	return
+}
+
+// ToRaw returns a *logWriter.
+func (l *SystemDLogger) ToRaw(prio logPrio) (raw *logWriter) {
+
+	raw = &logWriter{backend: l, prio: prio}
+
+	return
+}

logging/funcs_syslog_nix.go

@@ -1,70 +1,129 @@
+//go:build !(windows || plan9 || wasip1 || js || ios)
+// +build !windows,!plan9,!wasip1,!js,!ios
+
 package logging
 
 import (
 	"fmt"
 	"log"
 	"log/syslog"
+
+	"r00t2.io/goutils/multierr"
 )
 
-func (l *SyslogLogger) Setup() {
+// Setup sets up/configures a SyslogLogger and prepares it for use.
+func (l *SyslogLogger) Setup() (err error) {
 
-	var err error
+	var errs *multierr.MultiError = multierr.NewMultiError(nil)
 
 	if l.alert, err = syslog.New(syslog.LOG_ALERT|syslogFacility, l.Prefix); err != nil {
-		log.Panicln("could not open log for Alert")
+		errs.AddError(err)
+		err = nil
 	}
 	if l.crit, err = syslog.New(syslog.LOG_CRIT|syslogFacility, l.Prefix); err != nil {
-		log.Panicln("could not open log for Crit")
+		errs.AddError(err)
+		err = nil
 	}
 	if l.debug, err = syslog.New(syslog.LOG_DEBUG|syslogFacility, l.Prefix); err != nil {
-		log.Panicln("could not open log for Debug")
+		errs.AddError(err)
+		err = nil
 	}
 	if l.emerg, err = syslog.New(syslog.LOG_EMERG|syslogFacility, l.Prefix); err != nil {
-		log.Panicln("could not open log for Emerg")
+		errs.AddError(err)
+		err = nil
 	}
 	if l.err, err = syslog.New(syslog.LOG_ERR|syslogFacility, l.Prefix); err != nil {
-		log.Panicln("could not open log for Err")
+		errs.AddError(err)
+		err = nil
 	}
 	if l.info, err = syslog.New(syslog.LOG_INFO|syslogFacility, l.Prefix); err != nil {
-		log.Panicln("could not open log for Info")
+		errs.AddError(err)
+		err = nil
 	}
 	if l.notice, err = syslog.New(syslog.LOG_NOTICE|syslogFacility, l.Prefix); err != nil {
-		log.Panicln("could not open log for Notice")
+		errs.AddError(err)
+		err = nil
 	}
 	if l.warning, err = syslog.New(syslog.LOG_WARNING|syslogFacility, l.Prefix); err != nil {
-		log.Panicln("could not open log for Warning")
+		errs.AddError(err)
+		err = nil
 	}
 
+	if errs.Count() > 0 {
+		err = errs
 	}
 
-func (l *SyslogLogger) Shutdown() {
+	return
+}
 
-	var err error
+// Shutdown cleanly shuts down a SyslogLogger.
+func (l *SyslogLogger) Shutdown() (err error) {
+
+	var errs *multierr.MultiError = multierr.NewMultiError(nil)
 
 	for _, i := range []*syslog.Writer{l.alert, l.crit, l.debug, l.emerg, l.err, l.info, l.notice, l.warning} {
 		if err = i.Close(); err != nil {
-			log.Panicf("could not close log %#v\n", i)
+			errs.AddError(err)
+			err = nil
 		}
 	}
 
+	if errs.Count() > 0 {
+		err = errs
 	}
 
-func (l *SyslogLogger) DoDebug(d bool) {
-	l.EnableDebug = d
+	return
 }
 
-func (l *SyslogLogger) SetPrefix(prefix string) {
-	l.Prefix = prefix
-	l.Setup()
-}
-
-func (l *SyslogLogger) GetPrefix() (prefix string) {
+/*
+GetPrefix returns the prefix used by this SyslogLogger.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *SyslogLogger) GetPrefix() (prefix string, err error) {
 
 	prefix = l.Prefix
 
 	return
 }
 
+/*
+DoDebug sets the debug state of this SyslogLogger.
+Note that this merely acts as a *safety filter* for debug messages to avoid sensitive information being written to the log.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *SyslogLogger) DoDebug(d bool) (err error) {
+
+	l.EnableDebug = d
+
+	return
+}
+
+// GetDebug returns the debug status of this SyslogLogger.
+func (l *SyslogLogger) GetDebug() (d bool) {
+
+	d = l.EnableDebug
+
+	return
+}
+
+// SetPrefix sets the prefix for this SyslogLogger.
+func (l *SyslogLogger) SetPrefix(prefix string) (err error) {
+
+	l.Prefix = prefix
+
+	// We need to close the current loggers first.
+	if err = l.Shutdown(); err != nil {
+		return
+	}
+
+	if err = l.Setup(); err != nil {
+		return
+	}
+
+	return
+}
+
+// Alert writes an ALERT-level message to this SyslogLogger.
 func (l *SyslogLogger) Alert(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -82,6 +141,7 @@ func (l *SyslogLogger) Alert(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Crit writes an CRITICAL-level message to this SyslogLogger.
 func (l *SyslogLogger) Crit(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -99,6 +159,7 @@ func (l *SyslogLogger) Crit(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Debug writes a DEBUG-level message to this SyslogLogger.
 func (l *SyslogLogger) Debug(s string, v ...interface{}) (err error) {
 
 	if !l.EnableDebug {
@@ -120,6 +181,7 @@ func (l *SyslogLogger) Debug(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Emerg writes an EMERGENCY-level message to this SyslogLogger.
 func (l *SyslogLogger) Emerg(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -137,6 +199,7 @@ func (l *SyslogLogger) Emerg(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Err writes an ERROR-level message to this SyslogLogger.
 func (l *SyslogLogger) Err(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -154,6 +217,7 @@ func (l *SyslogLogger) Err(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Info writes an INFO-level message to this SyslogLogger.
 func (l *SyslogLogger) Info(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -171,6 +235,7 @@ func (l *SyslogLogger) Info(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Notice writes a NOTICE-level message to this SyslogLogger.
 func (l *SyslogLogger) Notice(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -188,6 +253,7 @@ func (l *SyslogLogger) Notice(s string, v ...interface{}) (err error) {
 	return
 }
 
+// Warning writes a WARNING/WARN-level message to this SyslogLogger.
 func (l *SyslogLogger) Warning(s string, v ...interface{}) (err error) {
 	var msg string
 
@@ -203,3 +269,19 @@ func (l *SyslogLogger) Warning(s string, v ...interface{}) (err error) {
 
 	return
 }
+
+// ToLogger returns a stdlib log.Logger.
+func (l *SyslogLogger) ToLogger(prio logPrio) (stdLibLog *log.Logger) {
+
+	stdLibLog = log.New(l.ToRaw(prio), "", 0)
+
+	return
+}
+
+// ToRaw returns a *logWriter.
+func (l *SyslogLogger) ToRaw(prio logPrio) (raw *logWriter) {
+
+	raw = &logWriter{backend: l, prio: prio}
+
+	return
+}

logging/funcs_test.go

@@ -0,0 +1,196 @@
+package logging
+
+import (
+	`os`
+	`testing`
+)
+
+/*
+	TestStdLogger tests functionality for StdLogger.
+*/
+func TestStdLogger(t *testing.T) {
+
+	var l *StdLogger
+	var ltype string = "StdLogger"
+	var prefix string
+	var err error
+
+	l = &StdLogger{
+		EnableDebug:  true,
+		Prefix:       TestLogPrefix,
+		LogFlags:     logFlags,
+		EnableStdOut: false,
+		EnableStdErr: true,
+	}
+
+	if err = l.Setup(); err != nil {
+		t.Fatalf("error when running Setup: %v", err.Error())
+	}
+
+	t.Logf("Logger %v passed Setup. Logger: %#v", ltype, l)
+
+	if err = l.Alert(testAlert, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Crit(testCrit, ltype); err != nil {
+		t.Fatalf("error for Crit: %v", err.Error())
+	}
+
+	if err = l.Debug(testDebug, ltype); err != nil {
+		t.Fatalf("error for Debug: %v", err.Error())
+	}
+
+	if err = l.Emerg(testEmerg, ltype); err != nil {
+		t.Fatalf("error for Emerg: %v", err.Error())
+	}
+
+	if err = l.Err(testErr, ltype); err != nil {
+		t.Fatalf("error for Err: %v", err.Error())
+	}
+
+	if err = l.Info(testInfo, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Notice(testNotice, ltype); err != nil {
+		t.Fatalf("error for Notice: %v", err.Error())
+	}
+
+	if err = l.Warning(testWarning, ltype); err != nil {
+		t.Fatalf("error for Warning: %v", err.Error())
+	}
+
+	if prefix, err = l.GetPrefix(); err != nil {
+		t.Fatalf("error when fetching prefix: %v", err.Error())
+	}
+
+	if prefix != (TestLogPrefix + " ") { // StdLogger adds a space at the end.
+		t.Fatalf("true prefix ('%v') does not match TestLogPrefix ('%v')", prefix, TestLogPrefix)
+	}
+	if err = l.SetPrefix(TestLogAltPrefix); err != nil {
+		t.Fatalf("error when setting prefix to %v: %v", TestLogAltPrefix, err.Error())
+	} else {
+		_ = l.SetPrefix(TestLogPrefix)
+	}
+
+	if err = l.DoDebug(false); err != nil {
+		t.Fatalf("error when changing debug to false: %v", err.Error())
+	} else if l.EnableDebug {
+		t.Fatalf("did not properly set Debug filter state")
+	} else {
+		_ = l.DoDebug(true)
+	}
+
+	if err = l.Shutdown(); err != nil {
+		t.Fatalf("Error when running Shutdown: %v", err.Error())
+	}
+
+	t.Logf("Logger %v passed all logging targets.", ltype)
+}
+
+/*
+	TestFileLogger tests functionality for FileLogger.
+	If the appropriate env var is set (see the EnvVarKeepLog constant), the temporary log file that is created will not be cleaned up.
+*/
+func TestFileLogger(t *testing.T) {
+
+	var l *FileLogger
+	var ltype string = "FileLogger"
+	var prefix string
+	var tempfile *os.File
+	var tempfilePath string
+	var keepLog bool
+	var err error
+
+	if tempfile, err = os.CreateTemp("", ".LOGGINGTEST_*"); err != nil {
+		t.Fatalf("error when creating temporary log file '%v': %v", tempfile.Name(), err.Error())
+	}
+	tempfilePath = tempfile.Name()
+	// We can close the handler immediately; we don't need it since the FileLogger opens its own.
+	if err = tempfile.Close(); err != nil {
+		t.Fatalf("error when closing handler for temporary log file '%v': %v", tempfile.Name(), err.Error())
+	}
+
+	l = &FileLogger{
+		StdLogger: StdLogger{
+			EnableDebug: true,
+			Prefix:      TestLogPrefix,
+			LogFlags:    logFlags,
+		},
+		Path: tempfilePath,
+	}
+
+	if err = l.Setup(); err != nil {
+		t.Fatalf("error when running Setup: %v", err.Error())
+	}
+
+	t.Logf("Logger %v passed Setup. Logger: %#v", ltype, l)
+
+	if err = l.Alert(testAlert, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Crit(testCrit, ltype); err != nil {
+		t.Fatalf("error for Crit: %v", err.Error())
+	}
+
+	if err = l.Debug(testDebug, ltype); err != nil {
+		t.Fatalf("error for Debug: %v", err.Error())
+	}
+
+	if err = l.Emerg(testEmerg, ltype); err != nil {
+		t.Fatalf("error for Emerg: %v", err.Error())
+	}
+
+	if err = l.Err(testErr, ltype); err != nil {
+		t.Fatalf("error for Err: %v", err.Error())
+	}
+
+	if err = l.Info(testInfo, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Notice(testNotice, ltype); err != nil {
+		t.Fatalf("error for Notice: %v", err.Error())
+	}
+
+	if err = l.Warning(testWarning, ltype); err != nil {
+		t.Fatalf("error for Warning: %v", err.Error())
+	}
+
+	if prefix, err = l.GetPrefix(); err != nil {
+		t.Fatalf("error when fetching prefix: %v", err.Error())
+	}
+
+	if prefix != (TestLogPrefix + " ") { // StdLogger (and thus FileLogger) adds a space at the end.
+		t.Fatalf("true prefix ('%v') does not match TestLogPrefix ('%v')", prefix, TestLogPrefix)
+	}
+	if err = l.SetPrefix(TestLogAltPrefix); err != nil {
+		t.Fatalf("error when setting prefix to %v: %v", TestLogAltPrefix, err.Error())
+	} else {
+		_ = l.SetPrefix(TestLogPrefix)
+	}
+
+	if err = l.DoDebug(false); err != nil {
+		t.Fatalf("error when changing debug to false: %v", err.Error())
+	} else if l.EnableDebug {
+		t.Fatalf("did not properly set Debug filter state")
+	} else {
+		_ = l.DoDebug(true)
+	}
+
+	if err = l.Shutdown(); err != nil {
+		t.Fatalf("Error when running Shutdown: %v", err.Error())
+	}
+
+	_, keepLog = os.LookupEnv(EnvVarKeepLog)
+
+	if !keepLog {
+		if err = os.Remove(tempfilePath); err != nil {
+			t.Fatalf("error when removing temporary log file '%v': %v", tempfilePath, err.Error())
+		}
+	}
+
+	t.Logf("Logger %v passed all logging targets.", ltype)
+}

logging/funcs_windows.go

@@ -2,29 +2,47 @@ package logging
 
 import (
 	`errors`
+	`path`
 	`strings`
+
+	`r00t2.io/goutils/bitmask`
+	`r00t2.io/sysutils/paths`
 )
 
 /*
 	GetLogger returns an instance of Logger that best suits your system's capabilities. Note that this is a VERY generalized interface to the Windows Event Log.
+
 	If you require more robust logging capabilities (e.g. custom event IDs per uniquely identifiable event),
 	you will want to set up your own logger (golang.org/x/sys/windows/svc/eventlog).
+
 	If enableDebug is true, debug messages (which according to your program may or may not contain sensitive data) are rendered and written (otherwise they are ignored).
+
 	A blank source will return an error as it's used as the source name. Other functions, struct fields, etc. will refer to this as the "prefix".
+
 	A pointer to a WinEventID struct may be specified for eventIDs to map extended logging levels (as Windows only supports three levels natively).
 	If it is nil, a default one (DefaultEventID) will be used.
+
+	logConfigFlags is the corresponding flag(s) OR'd for StdLogger.LogFlags / FileLogger.StdLogger.LogFlags if either is selected. See StdLogger.LogFlags and
+	https://pkg.go.dev/log#pkg-constants for details.
+
 	logPaths is an (optional) list of strings to use as paths to test for writing. If the file can be created/written to,
 	it will be used (assuming you have no higher-level loggers available).
+
 	Only the first logPaths entry that "works" will be used, later entries will be ignored.
-	Currently this will almost always return a WinLogger until multiple logging destination support is added.
+	Currently this will almost always return a WinLogger.
+
+	If you call GetLogger, you will only get a single ("best") logger your system supports.
+	If you want to log to multiple Logger destinations at once (or want to log to an explicit Logger type),
+	use GetMultiLogger.
 */
-func GetLogger(enableDebug bool, source string, eventIDs *WinEventID, logPaths ...string) (logger Logger, err error) {
+func GetLogger(enableDebug bool, source string, eventIDs *WinEventID, logConfigFlags int, logPaths ...string) (logger Logger, err error) {
 
 	var logPath string
-	var logFlags types.MaskBit
+	var logFlags bitmask.MaskBit
 	var exists bool
 	var success bool
 	var ckLogPaths []string
+	var prefix string
 
 	if strings.TrimSpace(source) == "" {
 		err = errors.New("invalid source for Windows logging")
@@ -53,7 +71,7 @@ func GetLogger(enableDebug bool, source string, eventIDs *WinEventID, logPaths .
 				break
 			} else {
 				dirPath := path.Dir(p)
-				if err = paths.MakeDirIfNotExist(&dirPath); err != nil {
+				if err = paths.MakeDirIfNotExist(dirPath); err != nil {
 					continue
 				}
 				if success, err = testOpen(p); err != nil {
@@ -72,7 +90,7 @@ func GetLogger(enableDebug bool, source string, eventIDs *WinEventID, logPaths .
 		logger = &WinLogger{
 			Prefix:      source,
 			EnableDebug: enableDebug,
-			eids:        eventIDs,
+			EIDs:        eventIDs,
 		}
 	} else {
 		if logFlags.HasFlag(LogFile) {
@@ -80,6 +98,7 @@ func GetLogger(enableDebug bool, source string, eventIDs *WinEventID, logPaths .
 				StdLogger: StdLogger{
 					Prefix:      source,
 					EnableDebug: enableDebug,
+					LogFlags:    logConfigFlags,
 				},
 				Path: logPath,
 			}
@@ -87,13 +106,25 @@ func GetLogger(enableDebug bool, source string, eventIDs *WinEventID, logPaths .
 			logger = &StdLogger{
 				Prefix:      source,
 				EnableDebug: enableDebug,
+				LogFlags:    logConfigFlags,
 			}
 		}
 	}
 
-	logger.Setup()
+	if err = logger.Setup(); err != nil {
+		return
+	}
+	if source != "\x00" {
+		if err = logger.SetPrefix(source); err != nil {
+			return
+		}
+	}
 
-	logger.Info("logger initialized of type %T with source %v", logger, logger.GetPrefix())
+	if prefix, err = logger.GetPrefix(); err != nil {
+		return
+	}
+
+	logger.Debug("logger initialized of type %T with source %v", logger, prefix)
 
 	return
 

logging/funcs_windows_test.go

@@ -0,0 +1,205 @@
+package logging
+
+import (
+	`fmt`
+	`os`
+	`testing`
+)
+
+/*
+	TestWinLogger tests functionality for WinLogger.
+	You will probably need to run it with an Administrator shell.
+*/
+func TestWinLogger(t *testing.T) {
+
+	var l *WinLogger
+	var ltype string = "WinLogger"
+	var prefix string
+	var exists bool
+	var err error
+
+	l = &WinLogger{
+		EnableDebug:   true,
+		Prefix:        TestLogPrefix,
+		RemoveOnClose: true,
+		EIDs:          DefaultEventID,
+	}
+
+	if exists, err = l.Exists(); err != nil {
+		t.Fatalf("error when checking for existence of registered Event Log source '%v': %v", TestLogPrefix, err.Error())
+	} else {
+		t.Logf("Prefix (source) '%v' exists before setup: %v", TestLogPrefix, exists)
+	}
+
+	if err = l.Setup(); err != nil {
+		t.Fatalf("error when running Setup: %v", err.Error())
+	}
+
+	if exists, err = l.Exists(); err != nil {
+		t.Fatalf("error when checking for existence of registered Event Log source '%v': %v", TestLogPrefix, err.Error())
+	} else {
+		t.Logf("Prefix (source) '%v' exists after setup: %v", TestLogPrefix, exists)
+	}
+
+	t.Logf("Logger %v passed Setup. Logger: %#v", ltype, l)
+
+	if err = l.Alert(testAlert, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Crit(testCrit, ltype); err != nil {
+		t.Fatalf("error for Crit: %v", err.Error())
+	}
+
+	if err = l.Debug(testDebug, ltype); err != nil {
+		t.Fatalf("error for Debug: %v", err.Error())
+	}
+
+	if err = l.Emerg(testEmerg, ltype); err != nil {
+		t.Fatalf("error for Emerg: %v", err.Error())
+	}
+
+	if err = l.Err(testErr, ltype); err != nil {
+		t.Fatalf("error for Err: %v", err.Error())
+	}
+
+	if err = l.Info(testInfo, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Notice(testNotice, ltype); err != nil {
+		t.Fatalf("error for Notice: %v", err.Error())
+	}
+
+	if err = l.Warning(testWarning, ltype); err != nil {
+		t.Fatalf("error for Warning: %v", err.Error())
+	}
+
+	if prefix, err = l.GetPrefix(); err != nil {
+		t.Fatalf("error when fetching prefix: %v", err.Error())
+	}
+
+	if prefix != TestLogPrefix {
+		t.Fatalf("true prefix ('%v') does not match TestLogPrefix ('%v')", prefix, TestLogPrefix)
+	}
+	if err = l.SetPrefix(TestLogAltPrefix); err != nil {
+		t.Fatalf("error when setting prefix to %v: %v", TestLogAltPrefix, err.Error())
+	} else {
+		_ = l.SetPrefix(TestLogPrefix)
+	}
+
+	if err = l.DoDebug(false); err != nil {
+		t.Fatalf("error when changing debug to false: %v", err.Error())
+	} else if l.EnableDebug {
+		t.Fatalf("did not properly set Debug filter state")
+	} else {
+		_ = l.DoDebug(true)
+	}
+
+	if err = l.Shutdown(); err != nil {
+		t.Fatalf("Error when running Shutdown: %v", err.Error())
+	}
+
+	t.Logf("Logger %v passed all logging targets.", ltype)
+}
+
+// TestDefaultLogger tests GetLogger.
+func TestDefaultLogger(t *testing.T) {
+
+	var l Logger
+	var tempfile *os.File
+	var tempfilePath string
+	var keepLog bool
+	var ltype string
+	var prefix string
+	var testPrefix string
+	var err error
+
+	if tempfile, err = os.CreateTemp("", ".LOGGINGTEST_*"); err != nil {
+		t.Fatalf("error when creating temporary log file '%v': %v", tempfile.Name(), err.Error())
+	}
+	tempfilePath = tempfile.Name()
+	// We can close the handler immediately; we don't need it since the FileLogger opens its own.
+	if err = tempfile.Close(); err != nil {
+		t.Fatalf("error when closing handler for temporary log file '%v': %v", tempfile.Name(), err.Error())
+	}
+
+	if l, err = GetLogger(true, TestLogPrefix, DefaultEventID, logFlags, tempfilePath); err != nil {
+		t.Fatalf("error when spawning default Windows logger via GetLogger: %v", err.Error())
+	}
+
+	ltype = fmt.Sprintf("%T", l)
+
+	t.Logf("Logger %v passed Setup. Logger: %#v", ltype, l)
+
+	if err = l.Alert(testAlert, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Crit(testCrit, ltype); err != nil {
+		t.Fatalf("error for Crit: %v", err.Error())
+	}
+
+	if err = l.Debug(testDebug, ltype); err != nil {
+		t.Fatalf("error for Debug: %v", err.Error())
+	}
+
+	if err = l.Emerg(testEmerg, ltype); err != nil {
+		t.Fatalf("error for Emerg: %v", err.Error())
+	}
+
+	if err = l.Err(testErr, ltype); err != nil {
+		t.Fatalf("error for Err: %v", err.Error())
+	}
+
+	if err = l.Info(testInfo, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Notice(testNotice, ltype); err != nil {
+		t.Fatalf("error for Notice: %v", err.Error())
+	}
+
+	if err = l.Warning(testWarning, ltype); err != nil {
+		t.Fatalf("error for Warning: %v", err.Error())
+	}
+
+	if prefix, err = l.GetPrefix(); err != nil {
+		t.Fatalf("error when fetching prefix: %v", err.Error())
+	}
+
+	if ltype == "StdLogger" || ltype == "FileLogger" { // StdLogger (and thus FileLogger) adds a space at the end.
+		testPrefix = TestLogPrefix + " "
+	} else {
+		testPrefix = TestLogPrefix
+	}
+
+	if prefix != testPrefix {
+		t.Fatalf("true prefix ('%v') does not match TestLogPrefix ('%v')", prefix, TestLogPrefix)
+	}
+	if err = l.SetPrefix(TestLogAltPrefix); err != nil {
+		t.Fatalf("error when setting prefix to %v: %v", TestLogAltPrefix, err.Error())
+	} else {
+		_ = l.SetPrefix(TestLogPrefix)
+	}
+
+	if err = l.DoDebug(false); err != nil {
+		t.Fatalf("error when changing debug to false: %v", err.Error())
+	} else {
+		_ = l.DoDebug(true)
+	}
+
+	if err = l.Shutdown(); err != nil {
+		t.Fatalf("Error when running Shutdown: %v", err.Error())
+	}
+
+	_, keepLog = os.LookupEnv(EnvVarKeepLog)
+
+	if !keepLog {
+		if err = os.Remove(tempfilePath); err != nil {
+			t.Fatalf("error when removing temporary log file '%v': %v", tempfilePath, err.Error())
+		}
+	}
+
+	t.Logf("Logger %v passed all logging targets.", ltype)
+}

logging/funcs_winlogger_windows.go

@@ -1,107 +1,207 @@
 package logging
 
 import (
-	`errors`
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"syscall"
+
+	"golang.org/x/sys/windows/registry"
+	"golang.org/x/sys/windows/svc/eventlog"
+	"r00t2.io/sysutils/paths"
 )
 
-func (l *WinLogger) Setup() {
+/*
+Setup sets up/configures a WinLogger and prepares it for use.
+This will fail with an Access Denied (the first time, at least) unless running with elevated permissions unless WinLogger.Prefix is
+a registered Event Log source.
 
-	var err error
+If a failure occurs while trying to open the log with the given WinLogger.Prefix ("source"), a new Event Log source will be registered.
+If WinLogger.Executable is not empty at the time of calling WinLogger.Setup (or WinLogger.ForceService is true),
+eventlog.Install will be used (with the WinLogger.ExpandKey field).
+Otherwise eventlog.InstallAsEventCreate will be used.
+*/
+func (l *WinLogger) Setup() (err error) {
 
 	/*
-		First a sanity check on the EventIDs.
+		A sanity check on the EventIDs.
 		Since we use eventcreate, all Event IDs must be 1 <= eid <= 1000.
 	*/
 	for _, eid := range []uint32{
-		l.eids.Alert,
-		l.eids.Crit,
-		l.eids.Debug,
-		l.eids.Emerg,
-		l.eids.Err,
-		l.eids.Info,
-		l.eids.Notice,
-		l.eids.Warning,
+		l.EIDs.Alert,
+		l.EIDs.Crit,
+		l.EIDs.Debug,
+		l.EIDs.Emerg,
+		l.EIDs.Err,
+		l.EIDs.Info,
+		l.EIDs.Notice,
+		l.EIDs.Warning,
 	} {
-		if !(1 <= eid <= 1000) {
-			err = errors.New("event IDs must be between 1 and 1000 inclusive")
-			panic(err)
+		if !((eid <= EIDMax) && (EIDMin <= eid)) {
+			err = ErrBadEid
+			return
 		}
 	}
 
-	if err = eventlog.InstallAsEventCreate(l.Prefix, eventlog.Error|eventlog.Warning|eventlog.Info); err != nil {
-		if idx := ptrnSourceExists.FindStringIndex(err.Error()); idx == nil {
-			// It's an error we want to panic on.
-			panic(err)
-		} else {
-			// It already exists, so ignore the error.
-			err = nil
-		}
+	if err = l.Install(); err != nil {
+		return
 	}
 
 	if l.elog, err = eventlog.Open(l.Prefix); err != nil {
-		panic(err)
+		return
 	}
 
+	return
 }
 
-func (l *WinLogger) Shutdown() {
+// Install installs/registers the WinLogger Event Log interface. You most likely do not need to run this directly.
+func (l *WinLogger) Install() (err error) {
 
-	var err error
+	var exists bool
+	var doNotCreate bool
+	var useEventCreate bool = true
 
-	if err = l.elog.Close(); err != nil {
-		panic(err)
+	if doNotCreate, err = l.Exists(); err != nil {
+		return
+	} else if !doNotCreate {
+		if l.Executable != "" {
+			if l.Executable, err = exec.LookPath(l.Executable); err != nil {
+				return
 			}
-
-	if err = eventlog.Remove(l.Prefix); err != nil {
-		panic(err)
+			useEventCreate = false
+		} else if l.ForceService {
+			if l.Executable, err = exec.LookPath(os.Args[0]); err != nil {
+				return
 			}
-
+			useEventCreate = false
 		}
-
-func (l *WinLogger) DoDebug(d bool) {
-
-	l.EnableDebug = d
-
+		if !useEventCreate {
+			if exists, err = paths.RealPathExists(&l.Executable); err != nil {
+				return
+			} else if !exists {
+				err = ErrBadBinPath
+				return
 			}
-
-func (l *WinLogger) SetPrefix(prefix string) {
-
-	var err error
-
-	l.Prefix = prefix
-
-	// To properly change the prefix, we need to tear down the old event log and create a new one.
-	if err = l.elog.Close(); err != nil {
-		panic(err)
+			if err = eventlog.Install(l.Prefix, l.Executable, l.ExpandKey, eventlog.Error|eventlog.Warning|eventlog.Info); err != nil {
+				return
 			}
-
-	if err = eventlog.Remove(l.Prefix); err != nil {
-		panic(err)
-	}
-
-	if err = eventlog.InstallAsEventCreate(l.Prefix, eventlog.Error|eventlog.Warning|eventlog.Info); err != nil {
-		if idx := ptrnSourceExists.FindStringIndex(err.Error()); idx == nil {
-			// It's an error we want to panic on.
-			panic(err)
 		} else {
-			// It already exists, so ignore the error.
-			err = nil
+			if err = eventlog.InstallAsEventCreate(l.Prefix, eventlog.Error|eventlog.Warning|eventlog.Info); err != nil {
+				return
+			}
 		}
 	}
 
-	if l.elog, err = eventlog.Open(l.Prefix); err != nil {
-		panic(err)
-	}
+	return
 
 }
 
-func (l *WinLogger) GetPrefix() (prefix string) {
+// Remove uninstalls a registered WinLogger source.
+func (l *WinLogger) Remove() (err error) {
+
+	if err = eventlog.Remove(l.Prefix); err != nil {
+		return
+	}
+
+	return
+}
+
+/*
+Shutdown cleanly shuts down a WinLogger but keep the source registered. Use WinLogger.Remove
+(or set WinLogger.RemoveOnClose to true before calling WinLogger.Shutdown) to remove the registered source.
+*/
+func (l *WinLogger) Shutdown() (err error) {
+
+	if err = l.elog.Close(); err != nil {
+		// TODO: check for no access or file not exists syscall errors?
+		return
+	}
+
+	if l.RemoveOnClose {
+		if err = l.Remove(); err != nil {
+			return
+		}
+	}
+
+	return
+}
+
+/*
+GetPrefix returns the prefix used by this WinLogger.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *WinLogger) GetPrefix() (prefix string, err error) {
 
 	prefix = l.Prefix
 
 	return
 }
 
+/*
+DoDebug sets the debug state of this WinLogger.
+Note that this merely acts as a *safety filter* for debug messages to avoid sensitive information being written to the log.
+err will always be nil; it's there for interface-compat.
+*/
+func (l *WinLogger) DoDebug(d bool) (err error) {
+
+	l.EnableDebug = d
+
+	return
+}
+
+// GetDebug returns the debug status of this WinLogger.
+func (l *WinLogger) GetDebug() (d bool) {
+
+	d = l.EnableDebug
+
+	return
+}
+
+// SetPrefix sets the prefix for this WinLogger.
+func (l *WinLogger) SetPrefix(prefix string) (err error) {
+
+	// To properly change the prefix, we need to tear down the old event log and create a new one.
+	if err = l.Shutdown(); err != nil {
+		return
+	}
+
+	l.Prefix = prefix
+
+	if err = l.Setup(); err != nil {
+		return
+	}
+
+	return
+}
+
+// Exists indicates if the WinLogger.Prefix is a registered source or not.
+func (l *WinLogger) Exists() (e bool, err error) {
+
+	var regKey registry.Key
+	var subKey registry.Key
+
+	if regKey, err = registry.OpenKey(registry.LOCAL_MACHINE, eventLogRegistryKey, registry.READ); err != nil {
+		return
+	}
+	defer regKey.Close()
+
+	if subKey, err = registry.OpenKey(regKey, l.Prefix, registry.READ); err != nil {
+		if errors.Is(err, syscall.ERROR_FILE_NOT_FOUND) {
+			e = false
+			err = nil
+		}
+		return
+	}
+	defer subKey.Close()
+
+	e = true
+
+	return
+}
+
+// Alert writes an ALERT-level message to this WinLogger.
 func (l *WinLogger) Alert(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -113,11 +213,12 @@ func (l *WinLogger) Alert(s string, v ...interface{}) (err error) {
 	}
 
 	// Treat ALERT as Warning
-	err = l.elog.Warning(l.eids.Alert, msg)
+	err = l.elog.Warning(l.EIDs.Alert, msg)
 
 	return
 }
 
+// Crit writes an CRITICAL-level message to this WinLogger.
 func (l *WinLogger) Crit(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -129,11 +230,12 @@ func (l *WinLogger) Crit(s string, v ...interface{}) (err error) {
 	}
 
 	// Treat CRIT as Error
-	err = l.elog.Error(l.eids.Crit, msg)
+	err = l.elog.Error(l.EIDs.Crit, msg)
 
 	return
 }
 
+// Debug writes a DEBUG-level message to this WinLogger.
 func (l *WinLogger) Debug(s string, v ...interface{}) (err error) {
 
 	if !l.EnableDebug {
@@ -149,12 +251,13 @@ func (l *WinLogger) Debug(s string, v ...interface{}) (err error) {
 	}
 
 	// Treat DEBUG as Info
-	err = l.elog.Info(l.eids.Debug, msg)
+	err = l.elog.Info(l.EIDs.Debug, msg)
 
 	return
 
 }
 
+// Emerg writes an EMERGENCY-level message to this WinLogger.
 func (l *WinLogger) Emerg(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -166,12 +269,13 @@ func (l *WinLogger) Emerg(s string, v ...interface{}) (err error) {
 	}
 
 	// Treat EMERG as Error
-	err = l.elog.Error(l.eids.Emerg, msg)
+	err = l.elog.Error(l.EIDs.Emerg, msg)
 
 	return
 
 }
 
+// Err writes an ERROR-level message to this WinLogger.
 func (l *WinLogger) Err(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -182,12 +286,13 @@ func (l *WinLogger) Err(s string, v ...interface{}) (err error) {
 		msg = s
 	}
 
-	err = l.elog.Error(l.eids.Error, msg)
+	err = l.elog.Error(l.EIDs.Err, msg)
 
 	return
 
 }
 
+// Info writes an INFO-level message to this WinLogger.
 func (l *WinLogger) Info(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -198,12 +303,13 @@ func (l *WinLogger) Info(s string, v ...interface{}) (err error) {
 		msg = s
 	}
 
-	err = l.elog.Info(l.eids.Info, msg)
+	err = l.elog.Info(l.EIDs.Info, msg)
 
 	return
 
 }
 
+// Notice writes a NOTICE-level message to this WinLogger.
 func (l *WinLogger) Notice(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -215,12 +321,13 @@ func (l *WinLogger) Notice(s string, v ...interface{}) (err error) {
 	}
 
 	// Treat NOTICE as Info
-	err = l.elog.Info(l.eids.Notice, msg)
+	err = l.elog.Info(l.EIDs.Notice, msg)
 
 	return
 
 }
 
+// Warning writes a WARNING/WARN-level message to this WinLogger.
 func (l *WinLogger) Warning(s string, v ...interface{}) (err error) {
 
 	var msg string
@@ -231,8 +338,24 @@ func (l *WinLogger) Warning(s string, v ...interface{}) (err error) {
 		msg = s
 	}
 
-	err = l.elog.Warning(l.eids.Warning, msg)
+	err = l.elog.Warning(l.EIDs.Warning, msg)
 
 	return
 
 }
+
+// ToLogger returns a stdlib log.Logger.
+func (l *WinLogger) ToLogger(prio logPrio) (stdLibLog *log.Logger) {
+
+	stdLibLog = log.New(l.ToRaw(prio), "", 0)
+
+	return
+}
+
+// ToRaw returns a *logWriter.
+func (l *WinLogger) ToRaw(prio logPrio) (raw *logWriter) {
+
+	raw = &logWriter{backend: l, prio: prio}
+
+	return
+}

logging/muiltilogger_linux_test.go

@@ -0,0 +1,121 @@
+package logging
+
+import (
+	`os`
+	`testing`
+)
+
+// TestMultiLogger tests GetMultiLogger and MultiLogger methods.
+func TestMultiLogger(t *testing.T) {
+
+	var l *MultiLogger
+	var tempfile *os.File
+	var tempfilePath string
+	var keepLog bool
+	var ltype string = "MultiLogger"
+	var prefix string
+	var testPrefix string
+	var err error
+
+	if tempfile, err = os.CreateTemp("", ".LOGGINGTEST_*"); err != nil {
+		t.Fatalf("error when creating temporary log file '%v': %v", tempfile.Name(), err.Error())
+	}
+	tempfilePath = tempfile.Name()
+	// We can close the handler immediately; we don't need it since the FileLogger opens its own.
+	if err = tempfile.Close(); err != nil {
+		t.Fatalf("error when closing handler for temporary log file '%v': %v", tempfile.Name(), err.Error())
+	}
+
+	l = GetMultiLogger(true, TestLogPrefix)
+
+	if err = l.AddStdLogger("StdLogger", false, true, logFlags); err != nil {
+		t.Fatalf("error when adding StdLogger to MultiLogger: %v", err.Error())
+	}
+	if err = l.AddFileLogger("FileLogger", logFlags, tempfilePath); err != nil {
+		t.Fatalf("error when adding FileLogger to MultiLogger: %v", err.Error())
+	}
+
+	if err = l.AddDefaultLogger("DefaultLogger", logFlags, tempfilePath); err != nil {
+		t.Fatalf("error when adding default logger to MultiLogger: %v", err.Error())
+	}
+
+	if err = l.AddSysdLogger("SystemDLogger"); err != nil {
+		t.Fatalf("error when adding SystemDLogger to MultiLogger: %v", err.Error())
+	}
+	if err = l.AddSyslogLogger("SyslogLogger"); err != nil {
+		t.Fatalf("error when adding SyslogLogger to MultiLogger: %v", err.Error())
+	}
+
+	t.Logf("Logger %v passed Setup. Logger: %#v", ltype, l)
+
+	if err = l.Alert(testAlert, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Crit(testCrit, ltype); err != nil {
+		t.Fatalf("error for Crit: %v", err.Error())
+	}
+
+	if err = l.Debug(testDebug, ltype); err != nil {
+		t.Fatalf("error for Debug: %v", err.Error())
+	}
+
+	if err = l.Emerg(testEmerg, ltype); err != nil {
+		t.Fatalf("error for Emerg: %v", err.Error())
+	}
+
+	if err = l.Err(testErr, ltype); err != nil {
+		t.Fatalf("error for Err: %v", err.Error())
+	}
+
+	if err = l.Info(testInfo, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Notice(testNotice, ltype); err != nil {
+		t.Fatalf("error for Notice: %v", err.Error())
+	}
+
+	if err = l.Warning(testWarning, ltype); err != nil {
+		t.Fatalf("error for Warning: %v", err.Error())
+	}
+
+	if prefix, err = l.GetPrefix(); err != nil {
+		t.Fatalf("error when fetching prefix: %v", err.Error())
+	}
+
+	if ltype == "StdLogger" || ltype == "FileLogger" { // StdLogger (and thus FileLogger) adds a space at the end.
+		testPrefix = TestLogPrefix + " "
+	} else {
+		testPrefix = TestLogPrefix
+	}
+
+	if prefix != testPrefix {
+		t.Fatalf("true prefix ('%v') does not match TestLogPrefix ('%v')", prefix, TestLogPrefix)
+	}
+	if err = l.SetPrefix(TestLogAltPrefix); err != nil {
+		t.Fatalf("error when setting prefix to %v: %v", TestLogAltPrefix, err.Error())
+	} else {
+		_ = l.SetPrefix(TestLogPrefix)
+	}
+
+	if err = l.DoDebug(false); err != nil {
+		t.Fatalf("error when changing debug to false: %v", err.Error())
+	} else {
+		_ = l.DoDebug(true)
+	}
+
+	if err = l.Shutdown(); err != nil {
+		t.Fatalf("Error when running Shutdown: %v", err.Error())
+	}
+
+	_, keepLog = os.LookupEnv(EnvVarKeepLog)
+
+	if !keepLog {
+		if err = os.Remove(tempfilePath); err != nil {
+			t.Fatalf("error when removing temporary log file '%v': %v", tempfilePath, err.Error())
+		}
+	}
+
+	t.Logf("Logger %v passed all logging targets.", ltype)
+}

logging/multilogger_windows_test.go

@@ -0,0 +1,118 @@
+package logging
+
+import (
+	`os`
+	`testing`
+)
+
+// TestMultiLogger tests GetMultiLogger and MultiLogger methods.
+func TestMultiLogger(t *testing.T) {
+
+	var l *MultiLogger
+	var tempfile *os.File
+	var tempfilePath string
+	var keepLog bool
+	var ltype string = "MultiLogger"
+	var prefix string
+	var testPrefix string
+	var err error
+
+	if tempfile, err = os.CreateTemp("", ".LOGGINGTEST_*"); err != nil {
+		t.Fatalf("error when creating temporary log file '%v': %v", tempfile.Name(), err.Error())
+	}
+	tempfilePath = tempfile.Name()
+	// We can close the handler immediately; we don't need it since the FileLogger opens its own.
+	if err = tempfile.Close(); err != nil {
+		t.Fatalf("error when closing handler for temporary log file '%v': %v", tempfile.Name(), err.Error())
+	}
+
+	l = GetMultiLogger(true, TestLogPrefix)
+
+	if err = l.AddStdLogger("StdLogger", false, true, logFlags); err != nil {
+		t.Fatalf("error when adding StdLogger to MultiLogger: %v", err.Error())
+	}
+	if err = l.AddFileLogger("FileLogger", logFlags, tempfilePath); err != nil {
+		t.Fatalf("error when adding FileLogger to MultiLogger: %v", err.Error())
+	}
+
+	if err = l.AddDefaultLogger("DefaultLogger", DefaultEventID, logFlags, tempfilePath); err != nil {
+		t.Fatalf("error when adding default logger to MultiLogger: %v", err.Error())
+	}
+
+	if err = l.AddWinLogger("WinLogger", DefaultEventID); err != nil {
+		t.Fatalf("error when adding WinLogger to MultiLogger: %v", err.Error())
+	}
+
+	t.Logf("Logger %v passed Setup. Logger: %#v", ltype, l)
+
+	if err = l.Alert(testAlert, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Crit(testCrit, ltype); err != nil {
+		t.Fatalf("error for Crit: %v", err.Error())
+	}
+
+	if err = l.Debug(testDebug, ltype); err != nil {
+		t.Fatalf("error for Debug: %v", err.Error())
+	}
+
+	if err = l.Emerg(testEmerg, ltype); err != nil {
+		t.Fatalf("error for Emerg: %v", err.Error())
+	}
+
+	if err = l.Err(testErr, ltype); err != nil {
+		t.Fatalf("error for Err: %v", err.Error())
+	}
+
+	if err = l.Info(testInfo, ltype); err != nil {
+		t.Fatalf("error for Alert: %v", err.Error())
+	}
+
+	if err = l.Notice(testNotice, ltype); err != nil {
+		t.Fatalf("error for Notice: %v", err.Error())
+	}
+
+	if err = l.Warning(testWarning, ltype); err != nil {
+		t.Fatalf("error for Warning: %v", err.Error())
+	}
+
+	if prefix, err = l.GetPrefix(); err != nil {
+		t.Fatalf("error when fetching prefix: %v", err.Error())
+	}
+
+	if ltype == "StdLogger" || ltype == "FileLogger" { // StdLogger (and thus FileLogger) adds a space at the end.
+		testPrefix = TestLogPrefix + " "
+	} else {
+		testPrefix = TestLogPrefix
+	}
+
+	if prefix != testPrefix {
+		t.Fatalf("true prefix ('%v') does not match TestLogPrefix ('%v')", prefix, TestLogPrefix)
+	}
+	if err = l.SetPrefix(TestLogAltPrefix); err != nil {
+		t.Fatalf("error when setting prefix to %v: %v", TestLogAltPrefix, err.Error())
+	} else {
+		_ = l.SetPrefix(TestLogPrefix)
+	}
+
+	if err = l.DoDebug(false); err != nil {
+		t.Fatalf("error when changing debug to false: %v", err.Error())
+	} else {
+		_ = l.DoDebug(true)
+	}
+
+	if err = l.Shutdown(); err != nil {
+		t.Fatalf("Error when running Shutdown: %v", err.Error())
+	}
+
+	_, keepLog = os.LookupEnv(EnvVarKeepLog)
+
+	if !keepLog {
+		if err = os.Remove(tempfilePath); err != nil {
+			t.Fatalf("error when removing temporary log file '%v': %v", tempfilePath, err.Error())
+		}
+	}
+
+	t.Logf("Logger %v passed all logging targets.", ltype)
+}

logging/types.go

@@ -3,32 +3,120 @@ package logging
 import (
 	"log"
 	"os"
+
+	"r00t2.io/goutils/bitmask"
 )
 
+type logPrio bitmask.MaskBit
+
+/*
+Logger is one of the various loggers offered by this module.
+*/
 type Logger interface {
-	Alert(string, ...interface{}) error
-	Crit(string, ...interface{}) error
-	Debug(string, ...interface{}) error
-	Emerg(string, ...interface{}) error
-	Err(string, ...interface{}) error
-	Info(string, ...interface{}) error
-	Notice(string, ...interface{}) error
-	Warning(string, ...interface{}) error
-	DoDebug(bool)
-	SetPrefix(string)
-	GetPrefix() string
-	Setup()
-	Shutdown()
+	Alert(s string, v ...interface{}) (err error)
+	Crit(s string, v ...interface{}) (err error)
+	Debug(s string, v ...interface{}) (err error)
+	Emerg(s string, v ...interface{}) (err error)
+	Err(s string, v ...interface{}) (err error)
+	Info(s string, v ...interface{}) (err error)
+	Notice(s string, v ...interface{}) (err error)
+	Warning(s string, v ...interface{}) (err error)
+	DoDebug(d bool) (err error)
+	GetDebug() (d bool)
+	SetPrefix(p string) (err error)
+	GetPrefix() (p string, err error)
+	Setup() (err error)
+	Shutdown() (err error)
+	ToLogger(prio logPrio) (stdLibLog *log.Logger)
+	ToRaw(prio logPrio) (raw *logWriter)
 }
 
+/*
+StdLogger uses the log package in stdlib to perform all logging. The default is to write to STDOUT.
+If you wish to modify the underling log.Logger object, you can access it directly via StdLogger.Logger.
+*/
 type StdLogger struct {
+	// All log.Logger fields/methods are exposed.
 	*log.Logger
+	/*
+		EnableDebug indicates if the debug filter should be disabled (true) or if the filter should be enabled (false).
+		This prevents potential data leak of sensitive information, as some loggers (e.g. FileLogger) will otherwise write all messages.
+	*/
 	EnableDebug bool
+	// Prefix indicates the prefix for log entries; in shared logs, this helps differentiate the source.
 	Prefix string
+	/*
+		LogFlags control some of the formatting options presented as an OR'd value.
+		See https://pkg.go.dev/log#pkg-constants for flag details.
+		e.g.:
+			*StdLogger.LogFlags = log.Ldate | log.Lmicroseconds | log.Llongfile | log.LUTC // a very detailed log output
+			*StdLogger.LogFlags = log.Ldate | log.Ltime // the flags used by log.Default() (also available as simply log.LstdFlags)
+		The default is 0; no flags (no output except prefix if non-empty and message).
+		You will need to run *StdLogger.Shutdown and then *StdLogger.Setup again if you wish to change this.
+	*/
+	LogFlags int
+	/*
+		EnableStdOut is true if the log will send to STDOUT.
+		If false (default), no output will be written to STDOUT.
+		You will need to run StdLogger.Shutdown and then StdLogger.Setup again if you wish to change this.
+
+		If EnableStdOut is false and EnableStdErr is false, no logging output will occur by default
+		and StdLogger.Logger will be largely useless.
+		It will be up to you to modify the underlying log.Logger to behave as you want.
+	*/
+	EnableStdOut bool
+	/*
+		EnableStdErr is true if the log will send to STDERR.
+		If false (default), no output will be written to STDERR.
+		You will need to run StdLogger.Shutdown and then StdLogger.Setup again if you wish to change this.
+
+		If EnableStdErr is false and EnableStdOut is false, no logging output will occur by default
+		and StdLogger.Logger will be largely useless.
+		It will be up to you to modify the underlying log.Logger to behave as you want.
+	*/
+	EnableStdErr bool
 }
 
+/*
+FileLogger uses a StdLogger with a file handle writer to write to the file given at Path.
+
+NOTE: If you wish to change the FileLogger.StdLogger.LogFlags, do *not* run FileLogger.StdLogger.Setup after doing so as this
+will instead create a logger detached from the file handler. Instead, be sure to call FileLogger.Setup.
+(Alternatively, run FileLogger.Shutdown and replace your logger with a new FileLogger.)
+*/
 type FileLogger struct {
+	// StdLogger is used for the log formation and handling. See StdLogger for more details.
 	StdLogger
+	// Path is the path to the logfile.
 	Path string
+	// writer is used for the writing out of the log file.
 	writer *os.File
 }
+
+// NullLogger is used mainly for test implementations, mockup code, etc. It does absolutely nothing with all messages sent to it.
+type NullLogger struct{}
+
+// MultiLogger is used to contain one or more Loggers and present them all as a single Logger.
+type MultiLogger struct {
+	/*
+		EnableDebug indicates if the debug filter should be disabled (true) or if the filter should be enabled (false).
+		This prevents potential data leak of sensitive information, as some loggers (e.g. FileLogger) will otherwise write all messages.
+	*/
+	EnableDebug bool
+	// Prefix indicates the prefix for log entries; in shared logs, this helps differentiate the source.
+	Prefix string
+	/*
+		Loggers contains a map of map[logname]Logger. It can be used to set log-specific options, or replace a Logger
+		with one of a different type or options.
+	*/
+	Loggers map[string]Logger
+}
+
+// logWriter is used as a log.Logger and is returned by <Logger>.ToLogger.
+type logWriter struct {
+	backend Logger
+	prio    logPrio
+}
+
+// nullWriter is used as a shortcut by NullLogger.ToLogger.
+type nullWriter struct{}

logging/types_linux.go

@@ -1,23 +1,9 @@
 package logging
 
-import (
-	`log/syslog`
-)
-
+/*
+SystemDLogger (yes, I'm aware it's actually written as "systemd") writes to journald on systemd-enabled systems.
+*/
 type SystemDLogger struct {
 	EnableDebug bool
 	Prefix      string
 }
-
-type SyslogLogger struct {
-	EnableDebug bool
-	Prefix      string
-	alert,
-	crit,
-	debug,
-	emerg,
-	err,
-	info,
-	notice,
-	warning *syslog.Writer
-}

logging/types_nix.go

@@ -0,0 +1,22 @@
+//go:build !(windows || plan9 || wasip1 || js || ios)
+// +build !windows,!plan9,!wasip1,!js,!ios
+
+package logging
+
+import (
+	"log/syslog"
+)
+
+// SyslogLogger writes to syslog on syslog-enabled systems.
+type SyslogLogger struct {
+	EnableDebug bool
+	Prefix      string
+	alert,
+	crit,
+	debug,
+	emerg,
+	err,
+	info,
+	notice,
+	warning *syslog.Writer
+}

logging/types_windows.go

@@ -4,13 +4,60 @@ import (
 	`golang.org/x/sys/windows/svc/eventlog`
 )
 
+// WinLogger is used for logging to the Windows Event Log. These entries are viewable in the Event Viewer application, under "Windows Logs > Application".
 type WinLogger struct {
+	/*
+		EnableDebug indicates if the debug filter should be disabled (true) or if the filter should be enabled (false).
+		This prevents potential data leak of sensitive information, as some loggers (e.g. FileLogger) will otherwise write all messages.
+	*/
 	EnableDebug bool
+	/*
+		Prefix is used as the Event Log "Source". It's named as Prefix to retain compatability with methods in the Logger interface.
+	*/
 	Prefix string
+	/*
+		Executable is used as the path for the executable implementing this logger.
+		If non-empty, it enables the "service" mode of Event Log (intended for "installed" software that's expected
+		to exist as a specific path reliably).
+		It can be a file within the PATHs or an absolute/relative path; an attempt to resolve the actual path will be made. If this fails or the file
+		does not exist, an error will be raised.
+	*/
+	Executable string
+	/*
+		ExpandKey is only used if Executable is non-empty and valid and/or ForceService is true.
+		If true, the WinLogger will be installed/registered with the REG_EXPAND_SZ mode - otherwise it will be installed as REG_SZ.
+		See the definition for the two at https://docs.microsoft.com/en-us/windows/win32/sysinfo/registry-value-types for further details.
+		If you're unsure which you want, it's probably REG_SZ (WinLogger.ExpandKey == false), which is the default.
+	*/
+	ExpandKey bool
+	/*
+		ForceService, if true, will enforce WinLogger to be used as if Executable is populated and valid (it will use os.Args[0] as the Executable path).
+		If Executable is empty but ForceService is true and os.Args[0] is empty or invalid (not a real path, etc.), an error will be raised.
+	*/
+	ForceService bool
+	// RemoveOnClose should be true if the logger should be removed/unregistered from the Registry upon calling WinLogger.Shutdown.
+	RemoveOnClose bool
+	// elog is the actual writer to the Event Log.
 	elog *eventlog.Log
-	eids        *WinEventID
+	// EIDs is used to look up what event ID to use when writing to a WinLogger.elog.
+	EIDs *WinEventID
 }
 
+/*
+	WinEventID is a collection of Event IDs to use for a WinLogger.
+	Because Event Log only supports three entry types (informational, warning, or error),
+	these event IDs allow you to filter the messages in a slightly more granular way. They map to their corresponding method name/Logger level.
+	However, this means that a WinLogger does not support custom event IDs (and thus you cannot assign individual event IDs to specific errors).
+	This is the price of convenience.
+
+	An additional method set may be added in the future to support this, but this is currently an unplanned feature.
+
+	Event IDs *must* be between the constants EIDMin and EIDMax (inclusive) unless the WinLogger is used in "service" mode
+	(see WinLogger.Executable and WinLogger.ForceService).
+
+	If you need recommended defaults, you may want to use the Event* constants (e.g. EventAlert, EventDebug, etc.)
+	or even use the pre-populated DefaultEventID (which is assigned the above Event* constants).
+*/
 type WinEventID struct {
 	Alert,
 	Crit,

multierr/doc.go

@@ -0,0 +1,63 @@
+/*
+Package multierr provides a simple way of handling multiple errors and consolidating them into a single error.
+
+Example:
+
+	package main
+
+	import (
+		`r00t2.io/goutils/multierr`
+	)
+
+	func main() {
+
+		var err error
+		var errs []error
+
+		errs = make([]error, 0)
+
+		for _, i := range someSlice {
+			go func() {
+				if err = i.DoSomething(); err != nil {
+					errs = append(errs, err)
+				}
+			}()
+		}
+
+		if errs != nil && len(errs) != 0 {
+			// err now contains multiple errors presented as a single error interface.
+			err = multierr.NewErrors(errs...)
+		}
+	}
+
+MultiError also has a shorthand, making the above much less verbose:
+
+	package main
+
+	import (
+		`r00t2.io/goutils/multierr`
+	)
+
+	func main() {
+
+		var err error
+		var multierror *multierr.MultiError = multierr.NewMultiError(nil)
+
+		for _, i := range someSlice {
+			go func() {
+				if err = i.DoSomething(); err != nil {
+					multierror.AddError(err)
+				}
+			}()
+		}
+
+		// multierror now contains any/all errors above. If calling in a function, you'll probably want to do:
+		// if !multierror.IsEmpty() {
+		//		err = multierror
+		// }
+
+	}
+
+In the above, the multierror assignment can still be used as an error.
+*/
+package multierr

multierr/funcs.go

@@ -0,0 +1,116 @@
+package multierr
+
+import (
+	`fmt`
+)
+
+/*
+	NewErrors returns a new MultiError (as an error) based on/initialized with a slice of error.Error (errs).
+	Any nil errors are trimmed.
+	If there are no actual errors after trimming, err will be nil.
+*/
+func NewErrors(errs ...error) (err error) {
+
+	if errs == nil || len(errs) == 0 {
+		return
+	}
+
+	var realErrs []error = make([]error, 0)
+
+	for _, e := range errs {
+		if e == nil {
+			continue
+		}
+		realErrs = append(realErrs, e)
+	}
+
+	if len(realErrs) == 0 {
+		return
+	}
+
+	err = &MultiError{
+		Errors:   realErrs,
+		ErrorSep: "\n",
+	}
+
+	return
+}
+
+// NewMultiError will provide a MultiError (true type), optionally initialized with errors.
+func NewMultiError(errs ...error) (m *MultiError) {
+
+	var realErrs []error = make([]error, 0)
+
+	if errs != nil {
+		for _, e := range errs {
+			if e == nil {
+				continue
+			}
+			realErrs = append(realErrs, e)
+		}
+	}
+
+	m = &MultiError{
+		Errors:   realErrs,
+		ErrorSep: "\n",
+	}
+
+	return
+}
+
+// Error returns a string representation of a MultiError (to conform with the error interface).
+func (e *MultiError) Error() (errStr string) {
+
+	var numErrs int
+
+	if e == nil || len(e.Errors) == 0 {
+		return
+	} else {
+		numErrs = len(e.Errors)
+	}
+
+	e.lock.Lock()
+	defer e.lock.Unlock()
+
+	for idx, err := range e.Errors {
+		if (idx + 1) < numErrs {
+			errStr += fmt.Sprintf("%v%v", err.Error(), e.ErrorSep)
+		} else {
+			errStr += err.Error()
+		}
+	}
+
+	return
+}
+
+// AddError is a shorthand way of adding an error to a MultiError.
+func (e *MultiError) AddError(err error) {
+
+	if err == nil {
+		return
+	}
+
+	e.lock.Lock()
+	defer e.lock.Unlock()
+
+	e.Errors = append(e.Errors, err)
+
+}
+
+// Count returns the number of errors in a MultiError.
+func (e *MultiError) Count() (n int) {
+
+	n = len(e.Errors)
+
+	return
+}
+
+// IsEmpty is a shorthand for testing if e.Errors is empty.
+func (e *MultiError) IsEmpty() (empty bool) {
+
+	if e.Count() == 0 {
+		empty = true
+	}
+
+	return
+}

multierr/types.go

@@ -0,0 +1,14 @@
+package multierr
+
+import (
+	`sync`
+)
+
+// MultiError is a type of error.Error that can contain multiple errors.
+type MultiError struct {
+	// Errors is a slice of errors to combine/concatenate when .Error() is called.
+	Errors []error `json:"errors"`
+	// ErrorSep is a string to use to separate errors for .Error(). The default is "\n".
+	ErrorSep string `json:"separator"`
+	lock sync.Mutex
+}

netx/docs.go

@@ -0,0 +1,4 @@
+/*
+Package netx includes extensions to the stdlib `net` module.
+*/
+package netx

netx/inetcksum/consts.go

@@ -0,0 +1,24 @@
+package inetcksum
+
+import (
+	`encoding/binary`
+)
+
+const (
+	// EmptyCksum is returned for checksums of 0-length byte slices/buffers.
+	EmptyCksum uint16 = 0xffff
+)
+
+const (
+	// cksumMask is AND'd with a checksum to get the "carried ones".
+	cksumMask uint32 = 0x0000ffff
+	// cksumShift is used in the "carried-ones folding".
+	cksumShift uint32 = 0x00000010
+	// padShift is used to "pad out" a checksum for odd-length buffers by left-shifting.
+	padShift uint32 = 0x00000008
+)
+
+var (
+	// ord is the byte order used by the Internet Checksum.
+	ord binary.ByteOrder = binary.BigEndian
+)

netx/inetcksum/docs.go

@@ -0,0 +1,26 @@
+/*
+Package inetcksum applies the "Internet Checksum" algorithm as specified/described in:
+
+	* [RFC 1071]
+	* [RFC 1141]
+	* [RFC 1624]
+
+It provides [InetChecksum], which can be used as a:
+
+	* [hash.Hash]
+	* [io.ByteWriter]
+	* [io.StringWriter]
+	* [io.Writer]
+	* [io.WriterTo]
+
+and is concurrency-safe.
+
+There is also an [InetChecksumSimple] provided, which is more
+tailored for performance/resource usage at the cost of concurrency
+safety and data retention.
+
+[RFC 1071]: https://datatracker.ietf.org/doc/html/rfc1071
+[RFC 1141]: https://datatracker.ietf.org/doc/html/rfc1141
+[RFC 1624]: https://datatracker.ietf.org/doc/html/rfc1624
+*/
+package inetcksum

netx/inetcksum/funcs.go

@@ -0,0 +1,62 @@
+package inetcksum
+
+import (
+	`io`
+)
+
+// New returns a new initialized [InetChecksum]. It will never panic.
+func New() (i *InetChecksum) {
+
+	i = &InetChecksum{}
+	_ = i.Aligned()
+
+	return
+}
+
+/*
+NewFromBytes returns a new [InetChecksum] initialized with explicit bytes.
+
+b may be nil or 0-length; this will not cause an error.
+*/
+func NewFromBytes(b []byte) (i *InetChecksum, copied int, err error) {
+
+	var cksum InetChecksum
+
+	if b != nil && len(b) > 0 {
+		if copied, err = cksum.Write(b); err != nil {
+			return
+		}
+		_ = i.Aligned()
+	} else {
+		i = New()
+		return
+	}
+
+	i = &cksum
+
+	return
+}
+
+/*
+NewFromBuf returns an [InetChecksum] from a specified [io.Reader].
+
+buf may be nil. If it isn't, NewFromBuf will call [io.Copy] on buf.
+Note that this may exhaust your passed buf or advance its current seek position/offset,
+depending on its type.
+*/
+func NewFromBuf(buf io.Reader) (i *InetChecksum, copied int64, err error) {
+
+	var cksum InetChecksum
+
+	_ = i.Aligned()
+
+	if buf != nil {
+		if copied, err = io.Copy(&cksum, buf); err != nil {
+			return
+		}
+	}
+
+	i = &cksum
+
+	return
+}

netx/inetcksum/funcs_inetchecksum.go

@@ -0,0 +1,351 @@
+package inetcksum
+
+import (
+	`io`
+)
+
+/*
+Aligned returns true if the current underlying buffer in an InetChecksum is
+aligned to the algorithm's requirement for an even number of bytes.
+
+Note that if Aligned returns false, a single null pad byte will be applied
+to the underlying data buffer at time of a Sum* call, but will not be written
+to the persistent underlying storage.
+
+If aligned's underlying buffer/storage is empty or nil, aligned will be true.
+
+Aligned will also force-set the internal state's aligned status.
+*/
+func (i *InetChecksum) Aligned() (aligned bool) {
+
+	i.alignLock.Lock()
+	defer i.alignLock.Unlock()
+
+	i.bufLock.RLock()
+	aligned = i.buf.Len()&2 == 0
+	i.bufLock.RUnlock()
+
+	i.aligned = aligned
+
+	return
+}
+
+// BlockSize returns the number of bytes at a time that InetChecksum operates on. (It will always return 1.)
+func (i *InetChecksum) BlockSize() (blockSize int) {
+
+	blockSize = 1
+
+	return
+}
+
+/*
+Bytes returns teh bytes currently in the internal storage.
+
+curBuf will be nil if the internal storage has not yet been initialized.
+*/
+func (i *InetChecksum) Bytes() (curBuf []byte) {
+
+	i.bufLock.RLock()
+	defer i.bufLock.RUnlock()
+
+	if i.buf.Len() != 0 {
+		curBuf = i.buf.Bytes()
+	}
+
+	return
+}
+
+// Clear empties the internal buffer (but does not affect the checksum state).
+func (i *InetChecksum) Clear() {
+
+	i.bufLock.Lock()
+	defer i.bufLock.Unlock()
+
+	i.buf.Reset()
+}
+
+/*
+DisablePersist disables the internal persistence of an InetChecksum.
+
+This is recommended for integrations that desire the concurrency safety
+of an InetChecksum but want a smaller memory footprint and do not need a copy
+of data that was hashed.
+
+Any data existing in the buffer will NOT be cleared out if DisablePersist is called.
+You must call [InetChecksum.Clear] to do that.
+
+Persistence CANNOT be reenabled once disabled. [InetChecksum.Reset]
+must be called to re-enable persistence.
+*/
+func (i *InetChecksum) DisablePersist() {
+
+	i.bufLock.Lock()
+	defer i.bufLock.Unlock()
+
+	i.disabledBuf = true
+}
+
+// Len returns the current amount of bytes stored in this InetChecksum's internal buffer.
+func (i *InetChecksum) Len() (l int) {
+
+	i.bufLock.RLock()
+	defer i.bufLock.RUnlock()
+	l = i.buf.Len()
+
+	return
+}
+
+/*
+Reset resets the internal buffer/storage to an empty state.
+
+If persistence was disabled ([InetChecksum.DisablePersist]),
+this method will re-enable it with an empty buffer.
+If you wish the buffer to be disabled, you must invoke [InetChecksum.DisablePersist]
+again.
+
+If you only wish to clear the buffer without losing the checksum state,
+use [InetChecksum.Clear].
+*/
+func (i *InetChecksum) Reset() {
+
+	i.alignLock.Lock()
+	i.bufLock.Lock()
+	i.sumLock.Lock()
+	i.lastLock.Lock()
+
+	i.aligned = false
+	i.alignLock.Unlock()
+
+	i.buf.Reset()
+	i.disabledBuf = false
+	i.bufLock.Unlock()
+
+	i.last = 0x00
+	i.lastLock.Unlock()
+
+	i.sum = 0
+	i.sumLock.Unlock()
+}
+
+// Size returns how many bytes a checksum is. (It will always return 2.)
+func (i *InetChecksum) Size() (bufSize int) {
+
+	bufSize = 2
+
+	return
+}
+
+// Sum computes the checksum cksum of the current buffer and appends it as big-endian bytes to b.
+func (i *InetChecksum) Sum(b []byte) (cksumAppended []byte) {
+
+	var sum16 []byte = i.Sum16Bytes()
+
+	cksumAppended = append(b, sum16...)
+
+	return
+}
+
+/*
+Sum16 computes the checksum of the current buffer and returns it as a uint16.
+
+This is the native number used in the IPv4 header.
+All other Sum* methods wrap this method.
+
+If the underlying buffer is empty or nil, cksum will be 0xffff (65535)
+in line with common implementations.
+*/
+func (i *InetChecksum) Sum16() (cksum uint16) {
+
+	var thisSum uint32
+
+	i.alignLock.RLock()
+	i.lastLock.RLock()
+	i.sumLock.RLock()
+
+	thisSum = i.sum
+	i.sumLock.RUnlock()
+
+	if !i.aligned {
+		/*
+			"Pad" at the end of the additive ops - a bitshift is used on the sum integer itself
+			instead of a binary.Append() or append() or such to avoid additional memory allocation.
+		*/
+		thisSum += uint32(i.last) << padShift
+	}
+	i.lastLock.RUnlock()
+	i.alignLock.RUnlock()
+
+	// Fold the "carried ones".
+	for thisSum > cksumMask {
+		thisSum = (thisSum & cksumMask) + (thisSum >> cksumShift)
+	}
+	cksum = ^uint16(thisSum)
+
+	return
+}
+
+/*
+Sum16Bytes is a convenience wrapper around [InetChecksum.Sum16]
+which returns a slice of the uint16 as a 2-byte-long slice instead.
+*/
+func (i *InetChecksum) Sum16Bytes() (cksum []byte) {
+
+	var sum16 uint16 = i.Sum16()
+
+	cksum = make([]byte, 2)
+
+	ord.PutUint16(cksum, sum16)
+
+	return
+}
+
+/*
+Write writes data to the underlying InetChecksum buffer. It conforms to [io.Writer].
+
+If this operation returns an error, you MUST call [InetChecksum.Reset] as the instance
+being used can no longer be considered to be in a consistent state.
+
+p may be nil or empty; no error will be returned and n will be 0 if so.
+
+Write is concurrency safe; a copy of p is made first and all hashing/internal
+storage writing is performed on/which that copy.
+*/
+func (i *InetChecksum) Write(p []byte) (n int, err error) {
+
+	var idx int
+	var bufLen int
+	var buf []byte
+	var iter int
+	var origLast byte
+	var origAligned bool
+	var origSum uint32
+
+	if p == nil || len(p) == 0 {
+		return
+	}
+
+	// The TL;DR here is the checksum boils down to:
+	// cksum = cksum + ((high << 8) | low)
+
+	bufLen = len(p)
+	buf = make([]byte, bufLen)
+	copy(buf, p)
+
+	i.alignLock.Lock()
+	defer i.alignLock.Unlock()
+	i.bufLock.Lock()
+	defer i.bufLock.Unlock()
+	i.sumLock.Lock()
+	defer i.sumLock.Unlock()
+	i.lastLock.Lock()
+	defer i.lastLock.Unlock()
+
+	origLast = i.last
+	origAligned = i.aligned
+	origSum = i.sum
+
+	if !i.aligned {
+		// Last write was unaligned, so pair i.last in.
+		i.sum += (uint32(i.last) << padShift) | uint32(buf[0])
+		i.aligned = true
+		idx = 1
+	}
+
+	// Operate on bytepairs.
+	// Note that idx is set to either 0 or 1 depending on if
+	// buf[0] has already been summed in.
+	for iter = idx; iter < bufLen; iter += 2 {
+		if iter+1 < bufLen {
+			// Technically could use "i.sum += uint32(ord.Uint16(buf[iter:iter+2))" here instead.
+			i.sum += (uint32(buf[iter]) << padShift) | uint32(buf[iter+1])
+		} else {
+			i.last = buf[iter]
+			i.aligned = false
+			break
+		}
+	}
+
+	if !i.disabledBuf {
+		if n, err = i.buf.Write(buf); err != nil {
+			i.sum = origSum
+			i.aligned = origAligned
+			i.last = origLast
+			return
+		}
+	}
+
+	return
+}
+
+// WriteByte writes a single byte to the underlying storage. It conforms to [io.ByteWriter].
+func (i *InetChecksum) WriteByte(c byte) (err error) {
+
+	var origLast byte
+	var origAligned bool
+	var origSum uint32
+
+	i.alignLock.Lock()
+	defer i.alignLock.Unlock()
+	i.bufLock.Lock()
+	defer i.bufLock.Unlock()
+	i.sumLock.Lock()
+	defer i.sumLock.Unlock()
+	i.lastLock.Lock()
+	defer i.lastLock.Unlock()
+
+	origLast = i.last
+	origAligned = i.aligned
+	origSum = i.sum
+
+	if i.aligned {
+		// Since it's a single byte, we just set i.last and unalign.
+		i.last = c
+		i.aligned = false
+	} else {
+		// It's unaligned, so join with i.last and align.
+		i.sum += (uint32(i.last) << padShift) | uint32(c)
+		i.aligned = true
+	}
+
+	if !i.disabledBuf {
+		if err = i.WriteByte(c); err != nil {
+			i.sum = origSum
+			i.aligned = origAligned
+			i.last = origLast
+			return
+		}
+	}
+
+	return
+}
+
+// WriteString writes a string to the underlying storage. It conforms to [io.StringWriter].
+func (i *InetChecksum) WriteString(s string) (n int, err error) {
+
+	if n, err = i.Write([]byte(s)); err != nil {
+		return
+	}
+
+	return
+}
+
+// WriteTo writes the current contents of the underlying buffer to w. The contents are not drained. Noop if persistence is disabled.
+func (i *InetChecksum) WriteTo(w io.Writer) (n int64, err error) {
+
+	var wrtn int
+
+	if i.disabledBuf {
+		return
+	}
+
+	i.bufLock.RLock()
+	defer i.bufLock.RUnlock()
+
+	if wrtn, err = w.Write(i.buf.Bytes()); err != nil {
+		n = int64(wrtn)
+		return
+	}
+	n = int64(wrtn)
+
+	return
+}

netx/inetcksum/funcs_inetchecksumsimple.go

@@ -0,0 +1,153 @@
+package inetcksum
+
+/*
+Aligned returns true if the current checksum for an InetChecksumSimple is
+aligned to the algorithm's requirement for an even number of bytes.
+
+Note that if Aligned returns false, a single null pad byte will be applied
+to the underlying data buffer at time of a Sum* call.
+*/
+func (i *InetChecksumSimple) Aligned() (aligned bool) {
+
+	aligned = i.aligned
+
+	return
+}
+
+// BlockSize returns the number of bytes at a time that InetChecksumSimple operates on. (It will always return 1.)
+func (i *InetChecksumSimple) BlockSize() (blockSize int) {
+
+	blockSize = 1
+
+	return
+}
+
+// Size returns how many bytes a checksum is. (It will always return 2.)
+func (i *InetChecksumSimple) Size() (bufSize int) {
+
+	bufSize = 2
+
+	return
+}
+
+// Sum computes the checksum cksum of the current buffer and appends it as big-endian bytes to b.
+func (i *InetChecksumSimple) Sum(b []byte) (cksumAppended []byte) {
+
+	var sum16 []byte = i.Sum16Bytes()
+
+	cksumAppended = append(b, sum16...)
+
+	return
+}
+
+/*
+Sum16 computes the checksum of the current buffer and returns it as a uint16.
+
+This is the native number used in the IPv4 header.
+All other Sum* methods wrap this method.
+
+If the underlying buffer is empty or nil, cksum will be 0xffff (65535)
+in line with common implementations.
+*/
+func (i *InetChecksumSimple) Sum16() (cksum uint16) {
+
+	var thisSum uint32
+
+	thisSum = i.sum
+
+	if !i.aligned {
+		/*
+			"Pad" at the end of the additive ops - a bitshift is used on the sum integer itself
+			instead of a binary.Append() or append() or such to avoid additional memory allocation.
+		*/
+		thisSum += uint32(i.last) << padShift
+	}
+
+	// Fold the "carried ones".
+	for thisSum > cksumMask {
+		thisSum = (thisSum & cksumMask) + (thisSum >> cksumShift)
+	}
+	cksum = ^uint16(thisSum)
+
+	return
+}
+
+/*
+Sum16Bytes is a convenience wrapper around [InetChecksumSimple.Sum16]
+which returns a slice of the uint16 as a 2-byte-long slice instead.
+*/
+func (i *InetChecksumSimple) Sum16Bytes() (cksum []byte) {
+
+	var sum16 uint16 = i.Sum16()
+
+	cksum = make([]byte, 2)
+
+	ord.PutUint16(cksum, sum16)
+
+	return
+}
+
+/*
+Write writes data to the underlying InetChecksumSimple buffer. It conforms to [io.Writer].
+
+p may be nil or empty; no error will be returned and n will be 0 if so.
+
+A copy of p is made first and all hashing operations are performed on that copy.
+*/
+func (i *InetChecksumSimple) Write(p []byte) (n int, err error) {
+
+	var idx int
+	var bufLen int
+	var buf []byte
+	var iter int
+
+	if p == nil || len(p) == 0 {
+		return
+	}
+
+	// The TL;DR here is the checksum boils down to:
+	// cksum = cksum + ((high << 8) | low)
+
+	bufLen = len(p)
+	buf = make([]byte, bufLen)
+	copy(buf, p)
+
+	if !i.aligned {
+		// Last write was unaligned, so pair i.last in.
+		i.sum += (uint32(i.last) << padShift) | uint32(buf[0])
+		i.aligned = true
+		idx = 1
+	}
+
+	// Operate on bytepairs.
+	// Note that idx is set to either 0 or 1 depending on if
+	// buf[0] has already been summed in.
+	for iter = idx; iter < bufLen; iter += 2 {
+		if iter+1 < bufLen {
+			// Technically could use "i.sum += uint32(ord.Uint16(buf[iter:iter+2))" here instead.
+			i.sum += (uint32(buf[iter]) << padShift) | uint32(buf[iter+1])
+		} else {
+			i.last = buf[iter]
+			i.aligned = false
+			break
+		}
+	}
+
+	return
+}
+
+// WriteByte checksums a single byte. It conforms to [io.ByteWriter].
+func (i *InetChecksumSimple) WriteByte(c byte) (err error) {
+
+	if i.aligned {
+		// Since it's a single byte, we just set i.last and unalign.
+		i.last = c
+		i.aligned = false
+	} else {
+		// It's unaligned, so join with i.last and align.
+		i.sum += (uint32(i.last) << padShift) | uint32(c)
+		i.aligned = true
+	}
+
+	return
+}

netx/inetcksum/types.go

@@ -0,0 +1,68 @@
+package inetcksum
+
+import (
+	`bytes`
+	`sync`
+)
+
+type (
+	/*
+		InetChecksum implements [hash.Hash] and various other stdlib interfaces.
+
+		If the current data in an InetChecksum's buffer is not aligned
+		to an even number of bytes -- e.g. InetChecksum.buf.Len() % 2 != 0,
+		[InetChecksum.Aligned] will return false (otherwise it will return
+		true).
+
+		If [InetChecksum.Aligned] returns false, the checksum result of an
+		[InetChecksum.Sum] or [InetChecksum.Sum16] (or any other operation
+		returning a sum) will INCLUDE THE PAD NULL BYTE (which is only
+		applied *at the time of the Sum/Sum32 call) and is NOT applied to
+		the persistent underlying storage.
+
+		InetChecksum differs from [InetChecksumSimple] in that it:
+
+			* Is MUCH better-suited/safer for concurrent operations - ALL
+				methods are concurrency-safe.
+			* Allows the data that is hashed to be recovered from a
+				sequential internal buffer. (See [InetChecksum.DisablePersist]
+				to disable the persistent internal buffer.)
+
+		At the cost of increased memory usage and additional cycles for mutexing.
+
+		Note that once persistence is disabled for an InetChecksum, it cannot be
+		re-enabled until/unless [InetChecksum.Reset] is called (which will reset
+		the persistence to enabled with a fresh buffer). Any data within the
+		persistent buffer will be removed if [InetChecksum.DisablePersist] is called.
+	*/
+	InetChecksum struct {
+		buf         bytes.Buffer
+		disabledBuf bool
+		aligned     bool
+		last        byte
+		sum         uint32
+		bufLock     sync.RWMutex
+		alignLock   sync.RWMutex
+		lastLock    sync.RWMutex
+		sumLock     sync.RWMutex
+	}
+
+	/*
+		InetChecksumSimple is like [InetChecksum], but with a few key differences.
+
+		It is MUCH much more performant/optimized for *single throughput* operations.
+		Because it also does not retain a buffer of what was hashed, it uses *far* less
+		memory over time.
+
+		However, the downside is it is NOT concurrency safe. There are no promises made
+		about safety or proper checksum ordering with concurrency for this type, but it
+		should have much better performance for non-concurrent use.
+
+		It behaves much more like a traditional [hash.Hash].
+	*/
+	InetChecksumSimple struct {
+		aligned bool
+		last    byte
+		sum     uint32
+	}
+)

remap/doc.go

@@ -0,0 +1,4 @@
+/*
+Package remap provides convenience functions around regular expressions, primarily offering maps for named capture groups.
+*/
+package remap

remap/funcs_remap.go

@@ -0,0 +1,488 @@
+package remap
+
+/*
+Map returns a map[string][]<match bytes> for regexes with named capture groups matched in bytes b.
+Note that this supports non-unique group names; [regexp.Regexp] allows for patterns with multiple groups
+using the same group name (though your IDE might complain; I know GoLand does).
+
+Each match for each group is in a slice keyed under that group name, with that slice
+ordered by the indexing done by the regex match itself.
+
+In summary, the parameters are as follows:
+
+# inclNoMatch
+
+If true, then attempt to return a non-nil matches (as long as b isn't nil).
+Group keys will be populated and explicitly defined as nil.
+
+For example, if a pattern
+
+	^(?P<g1>foo)(?P<g1>bar)(?P<g2>baz)$
+
+is provided but b does not match then matches will be:
+
+	map[string][][]byte{
+		"g1": nil,
+		"g2": nil,
+	}
+
+# inclNoMatchStrict
+
+If true (and inclNoMatch is true), instead of a single nil the group's values will be
+a slice of nil values explicitly matching the number of times the group name is specified
+in the pattern.
+
+For example, if a pattern:
+
+	^(?P<g1>foo)(?P<g1>bar)(?P<g2>baz)$
+
+is provided but b does not match then matches will be:
+
+	map[string][][]byte{
+		"g1": [][]byte{
+			nil,
+			nil,
+		},
+		"g2": [][]byte{
+			nil,
+		},
+	}
+
+# mustMatch
+
+If true, matches will be nil if the entirety of b does not match the pattern (and thus
+no capture groups matched) (overrides inclNoMatch) -- explicitly:
+
+	matches == nil
+
+Otherwise if false (and assuming inclNoMatch is false), matches will be:
+
+	map[string][][]byte{}{}
+
+# Condition Tree
+
+In detail, matches and/or its values may be nil or empty under the following condition tree:
+
+	IF b is nil:
+		THEN matches will always be nil
+	ELSE:
+		IF all of b does not match pattern
+			IF mustMuch is true
+				THEN matches == nil
+			ELSE
+				THEN matches == map[string][][]byte{} (non-nil but empty)
+		ELSE IF pattern has no named capture groups
+			IF inclNoMatch is true
+				THEN matches == map[string][][]byte{} (non-nil but empty)
+			ELSE
+				THEN matches == nil
+		ELSE
+			IF there are no named group matches
+				IF inclNoMatch is true
+					THEN matches is non-nil; matches[<group name>, ...] is/are defined but nil (_, ok = matches[<group name>]; ok == true)
+				ELSE
+					THEN matches == nil
+			ELSE
+				IF <group name> does not have a match
+					IF inclNoMatch is true
+						IF inclNoMatchStrict is true
+							THEN matches[<group name>] is defined and non-nil, but populated with placeholder nils
+								(matches[<group name>] == [][]byte{nil[, nil...]})
+						ELSE
+							THEN matches[<group name>] is guaranteed defined but may be nil (_, ok = matches[<group name>]; ok == true)
+					ELSE
+						THEN matches[<group name>] is not defined (_, ok = matches[<group name>]; ok == false)
+				ELSE
+					matches[<group name>] == []{<match>[, <match>...]}
+*/
+func (r *ReMap) Map(b []byte, inclNoMatch, inclNoMatchStrict, mustMatch bool) (matches map[string][][]byte) {
+
+	var ok bool
+	var mIdx int
+	var match []byte
+	var grpNm string
+	var names []string
+	var matchBytes [][]byte
+	var tmpMap map[string][][]byte = make(map[string][][]byte)
+
+	if b == nil {
+		return
+	}
+
+	names = r.Regexp.SubexpNames()
+	matchBytes = r.Regexp.FindSubmatch(b)
+
+	if matchBytes == nil {
+		// b does not match pattern
+		if !mustMatch {
+			matches = make(map[string][][]byte)
+		}
+		return
+	}
+
+	if names == nil || len(names) == 0 || len(names) == 1 {
+		/*
+			no named capture groups;
+			technically only the last condition would be the case.
+		*/
+		if inclNoMatch {
+			matches = make(map[string][][]byte)
+		}
+		return
+	}
+	names = names[1:]
+
+	if len(matchBytes) == 0 || len(matchBytes) == 1 {
+		/*
+			no submatches whatsoever.
+			*Technically* I don't think this condition can actually be reached.
+			This is more of a safe-return before we re-slice.
+		*/
+		matches = make(map[string][][]byte)
+		if inclNoMatch {
+			if len(names) >= 1 {
+				for _, grpNm = range names {
+					matches[grpNm] = nil
+				}
+			}
+		}
+		return
+	}
+	matchBytes = matchBytes[1:]
+
+	for mIdx, match = range matchBytes {
+		grpNm = names[mIdx]
+		/*
+			Thankfully, it's actually a build error if a pattern specifies a named
+			capture group with an empty name.
+			So we don't need to worry about accounting for that,
+			and can just skip over grpNm == "" (which is an *unnamed* capture group).
+		*/
+		if grpNm == "" {
+			continue
+		}
+
+		if match == nil {
+			// group did not match
+			if !inclNoMatch {
+				continue
+			}
+			if _, ok = tmpMap[grpNm]; !ok {
+				if !inclNoMatchStrict {
+					tmpMap[grpNm] = nil
+				} else {
+					tmpMap[grpNm] = [][]byte{nil}
+				}
+			} else {
+				if inclNoMatchStrict {
+					tmpMap[grpNm] = append(tmpMap[grpNm], nil)
+				}
+			}
+			continue
+		}
+
+		if _, ok = tmpMap[grpNm]; !ok {
+			tmpMap[grpNm] = make([][]byte, 0)
+		}
+		tmpMap[grpNm] = append(tmpMap[grpNm], match)
+	}
+
+	// This *technically* should be completely handled above.
+	if inclNoMatch {
+		for _, grpNm = range names {
+			if _, ok = tmpMap[grpNm]; !ok {
+				tmpMap[grpNm] = nil
+			}
+		}
+	}
+
+	if len(tmpMap) > 0 {
+		matches = tmpMap
+	}
+
+	return
+}
+
+/*
+MapString is exactly like ReMap.Map(), but operates on (and returns) strings instead.
+(matches will always be nil if s == “.)
+
+A small deviation, though; empty strings instead of nils (because duh) will occupy slice placeholders (if `inclNoMatchStrict` is specified).
+This unfortunately *does not provide any indication* if an empty string positively matched the pattern (a "hit") or if it was simply
+not matched at all (a "miss"). If you need definitive determination between the two conditions, it is instead recommended to either
+*not* use inclNoMatchStrict or to use ReMap.Map() instead and convert any non-nil values to strings after.
+
+Particularly:
+
+# inclNoMatch
+
+If true, then attempt to return a non-nil matches (as long as s isn't empty).
+Group keys will be populated and explicitly defined as nil.
+
+For example, if a pattern
+
+	^(?P<g1>foo)(?P<g1>bar)(?P<g2>baz)$
+
+is provided but s does not match then matches will be:
+
+	map[string][]string{
+		"g1": nil,
+		"g2": nil,
+	}
+
+# inclNoMatchStrict
+
+If true (and inclNoMatch is true), instead of a single nil the group's values will be
+a slice of eempty string values explicitly matching the number of times the group name is specified
+in the pattern.
+
+For example, if a pattern:
+
+	^(?P<g1>foo)(?P<g1>bar)(?P<g2>baz)$
+
+is provided but s does not match then matches will be:
+
+	map[string][]string{
+		"g1": []string{
+			"",
+			"",
+		},
+		"g2": []string{
+			"",
+		},
+	}
+
+# mustMatch
+
+If true, matches will be nil if the entirety of s does not match the pattern (and thus
+no capture groups matched) (overrides inclNoMatch) -- explicitly:
+
+	matches == nil
+
+Otherwise if false (and assuming inclNoMatch is false), matches will be:
+
+	map[string][]string{}{}
+
+# Condition Tree
+
+In detail, matches and/or its values may be nil or empty under the following condition tree:
+
+	IF s is empty:
+		THEN matches will always be nil
+	ELSE:
+		IF all of s does not match pattern
+			IF mustMuch is true
+				THEN matches == nil
+			ELSE
+				THEN matches == map[string][]string{} (non-nil but empty)
+		ELSE IF pattern has no named capture groups
+			IF inclNoMatch is true
+				THEN matches == map[string][]string{} (non-nil but empty)
+			ELSE
+				THEN matches == nil
+		ELSE
+			IF there are no named group matches
+				IF inclNoMatch is true
+					THEN matches is non-nil; matches[<group name>, ...] is/are defined but nil (_, ok = matches[<group name>]; ok == true)
+				ELSE
+					THEN matches == nil
+			ELSE
+				IF <group name> does not have a match
+					IF inclNoMatch is true
+						IF inclNoMatchStrict is true
+							THEN matches[<group name>] is defined and non-nil, but populated with placeholder nils
+								(matches[<group name>] == []string{""[, ""...]})
+						ELSE
+							THEN matches[<group name>] is guaranteed defined but may be nil (_, ok = matches[<group name>]; ok == true)
+					ELSE
+						THEN matches[<group name>] is not defined (_, ok = matches[<group name>]; ok == false)
+				ELSE
+					matches[<group name>] == []{<match>[, <match>...]}
+*/
+func (r *ReMap) MapString(s string, inclNoMatch, inclNoMatchStrict, mustMatch bool) (matches map[string][]string) {
+
+	var ok bool
+	var endIdx int
+	var startIdx int
+	var chunkIdx int
+	var grpNm string
+	var names []string
+	var matchStr string
+	/*
+		A slice of indices or index pairs.
+		For each element `e` in idxChunks,
+		* if `e` is nil, no group match.
+		* if len(e) == 1, only a single character was matched.
+		* otherwise len(e) == 2, the start and end of the match.
+	*/
+	var idxChunks [][]int
+	var matchIndices []int
+	var chunkIndices []int // always 2 elements; start pos and end pos
+	var tmpMap map[string][]string = make(map[string][]string)
+
+	/*
+		OK so this is a bit of a deviation.
+
+		It's not as straightforward as above, because there isn't an explicit way
+		like above to determine if a pattern was *matched as an empty string* vs.
+		*not matched*.
+
+		So instead do roundabout index-y things.
+	*/
+
+	if s == "" {
+		return
+	}
+	/*
+		I'm not entirely sure how serious they are about "the slice should not be modified"...
+
+		DO NOT sort or dedupe `names`! If the same name for groups is duplicated,
+		it will be duplicated here in proper order and the ordering is tied to
+		the ordering of matchIndices.
+	*/
+	names = r.Regexp.SubexpNames()[:]
+	matchIndices = r.Regexp.FindStringSubmatchIndex(s)
+
+	if matchIndices == nil {
+		// s does not match pattern at all.
+		if !mustMatch {
+			matches = make(map[string][]string)
+		}
+		return
+	}
+
+	if names == nil || len(names) <= 1 {
+		/*
+			No named capture groups;
+			technically only the last condition would be the case,
+			as (regexp.Regexp).SubexpNames() will ALWAYS at the LEAST
+			return a `[]string{""}`.
+		*/
+		if inclNoMatch {
+			matches = make(map[string][]string)
+		}
+		return
+	}
+
+	if len(matchIndices) == 0 || len(matchIndices) == 1 {
+		/*
+			No (sub)matches whatsoever.
+			*technically* I don't think this condition can actually be reached;
+			matchIndices should ALWAYS either be `nil` or len will be at LEAST 2,
+			and modulo 2 thereafter since they're PAIRS of indices...
+			Why they didn't just return a [][]int or [][2]int or something
+			instead of an []int, who knows.
+			But we're correcting that poor design.
+			This is more of a safe-return before we chunk the indices.
+		*/
+		matches = make(map[string][]string)
+		if inclNoMatch {
+			for _, grpNm = range names {
+				if grpNm != "" {
+					matches[grpNm] = nil
+				}
+			}
+		}
+		return
+	}
+
+	/*
+		A reslice of `matchIndices` could technically start at 2 (as long as `names` is sliced [1:])
+		because they're in pairs: []int{<start>, <end>, <start>, <end>, ...}
+		and the first pair is the entire pattern match (un-resliced names[0]).
+		Thus the len(matchIndices) == 2*len(names), *even* if you
+		Keep in mind that since the first element of names is removed,
+		the first pair here is skipped.
+		This provides a bit more consistent readability, though.
+	*/
+	idxChunks = make([][]int, len(names))
+	chunkIdx = 0
+	endIdx = 0
+	for startIdx = 0; endIdx < len(matchIndices); startIdx += 2 {
+		endIdx = startIdx + 2
+		// This technically should never happen.
+		if endIdx > len(matchIndices) {
+			endIdx = len(matchIndices)
+		}
+
+		chunkIndices = matchIndices[startIdx:endIdx]
+
+		if chunkIndices[0] == -1 || chunkIndices[1] == -1 {
+			// group did not match
+			chunkIndices = nil
+		} else {
+			if chunkIndices[0] == chunkIndices[1] {
+				chunkIndices = []int{chunkIndices[0]}
+			} else {
+				chunkIndices = matchIndices[startIdx:endIdx]
+			}
+		}
+		idxChunks[chunkIdx] = chunkIndices
+		chunkIdx++
+	}
+
+	// Now associate with names and pull the string sequence.
+	for chunkIdx, chunkIndices = range idxChunks {
+		grpNm = names[chunkIdx]
+		/*
+			Thankfully, it's actually a build error if a pattern specifies a named
+			capture group with an empty name.
+			So we don't need to worry about accounting for that,
+			and can just skip over grpNm == ""
+			(which is either an *unnamed* capture group
+			OR the first element in `names`, which is always
+			the entire match).
+		*/
+		if grpNm == "" {
+			continue
+		}
+
+		if chunkIndices == nil || len(chunkIndices) == 0 {
+			// group did not match
+			if !inclNoMatch {
+				continue
+			}
+			if _, ok = tmpMap[grpNm]; !ok {
+				if !inclNoMatchStrict {
+					tmpMap[grpNm] = nil
+				} else {
+					tmpMap[grpNm] = []string{""}
+				}
+			} else {
+				if inclNoMatchStrict {
+					tmpMap[grpNm] = append(tmpMap[grpNm], "")
+				}
+			}
+			continue
+		}
+
+		switch len(chunkIndices) {
+		case 1:
+			// Single character
+			matchStr = string(s[chunkIndices[0]])
+		case 2:
+			// Multiple characters
+			matchStr = s[chunkIndices[0]:chunkIndices[1]]
+		}
+
+		if _, ok = tmpMap[grpNm]; !ok {
+			tmpMap[grpNm] = make([]string, 0)
+		}
+		tmpMap[grpNm] = append(tmpMap[grpNm], matchStr)
+	}
+
+	// This *technically* should be completely handled above.
+	if inclNoMatch {
+		for _, grpNm = range names {
+			if _, ok = tmpMap[grpNm]; !ok {
+				tmpMap[grpNm] = nil
+			}
+		}
+	}
+
+	if len(tmpMap) > 0 {
+		matches = tmpMap
+	}
+
+	return
+}

remap/types.go

@@ -0,0 +1,27 @@
+package remap
+
+import (
+	"regexp"
+)
+
+type (
+	// ReMap provides some map-related functions around a regexp.Regexp.
+	ReMap struct {
+		*regexp.Regexp
+	}
+
+	// TODO?
+	/*
+		ExplicitStringMatch is used with ReMap.MapStringExplicit to indicate if a
+		capture group result is a hit (a group matched, but e.g. the match value is empty string)
+		or not (a group did not match).
+	*/
+	/*
+		ExplicitStringMatch struct {
+			Group   string
+			IsMatch bool
+			Value   string
+		}
+
+	*/
+)

structutils/consts.go

@@ -0,0 +1,5 @@
+package structutils
+
+const (
+	TagMapTrim tagMapOpt = iota
+)

structutils/funcs.go

@@ -0,0 +1,362 @@
+/*
+   GoUtils - a library to assist with various Golang-related functions
+   Copyright (C) 2020  Brent Saner
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package structutils
+
+import (
+	`reflect`
+	`strings`
+)
+
+/*
+	TagToBoolMap takes struct field `field` and tag name `tagName`,
+	 optionally with options `opts`, and returns a map of the tag values.
+	The tag value string is assumed to be in the form of:
+		option[,option,option...]
+	and returns a map[string]bool (map[option]true).
+
+	If field does not have tag tagName, m will be nil.
+
+	See the TagMap* constants for opts.
+*/
+func TagToBoolMap(field reflect.StructField, tagName string, opts ...tagMapOpt) (m map[string]bool) {
+
+	var s string
+	var optSplit []string
+	var tagOpts map[tagMapOpt]bool = getTagMapOpts(opts)
+
+	s = field.Tag.Get(tagName)
+
+	if strings.TrimSpace(s) == "" {
+		return
+	}
+
+	optSplit = strings.Split(s, ",")
+	if optSplit == nil || len(optSplit) == 0 {
+		return
+	}
+	m = make(map[string]bool)
+	for _, o := range optSplit {
+		if tagOpts[TagMapTrim] {
+			o = strings.TrimSpace(o)
+		}
+		m[o] = true
+	}
+
+	return
+}
+
+/*
+	TagToBoolMapWithValue is like TagToBoolMap but additionally assumes the first value is an "identifier".
+	The tag value string is assumed to be in the form of:
+		value,option[,option,option...]
+	and returns a map[string]bool (map[option]true) with the value.
+*/
+func TagToBoolMapWithValue(field reflect.StructField, tagName string, opts ...tagMapOpt) (value string, m map[string]bool) {
+
+	var s string
+	var optSplit []string
+	var tagOpts map[tagMapOpt]bool = getTagMapOpts(opts)
+
+	s = field.Tag.Get(tagName)
+
+	if strings.TrimSpace(s) == "" {
+		return
+	}
+
+	optSplit = strings.Split(s, ",")
+	if optSplit == nil || len(optSplit) == 0 {
+		return
+	}
+	m = make(map[string]bool)
+	for idx, o := range optSplit {
+		if idx == 0 {
+			if tagOpts[TagMapTrim] {
+				o = strings.TrimSpace(o)
+			}
+			value = o
+			continue
+		}
+		if tagOpts[TagMapTrim] {
+			o = strings.TrimSpace(o)
+		}
+		m[o] = true
+	}
+
+	return
+}
+
+/*
+	TagToMixedMap combines TagToBoolMap and TagToStringMap.
+	It takes struct field `field` and tag name `tagName`,
+	and returns all single-value options in mapBool, and all key/value options in mapString.
+
+	If field does not have tag tagName, m will be nil.
+
+	See the TagMap* constants for opts.
+*/
+func TagToMixedMap(field reflect.StructField, tagName string, opts ...tagMapOpt) (mapBool map[string]bool, mapString map[string]string) {
+
+	var s string
+	var valStr string
+	var split []string
+	var kvSplit []string
+	var valSplit []string
+	var k string
+	var v string
+	var tagOpts map[tagMapOpt]bool = getTagMapOpts(opts)
+
+	s = field.Tag.Get(tagName)
+
+	if strings.TrimSpace(s) == "" {
+		return
+	}
+
+	split = strings.Split(s, ",")
+	if split == nil || len(split) == 0 {
+		return
+	}
+	mapBool = make(map[string]bool)
+	mapString = make(map[string]string)
+	for _, valStr = range split {
+		if strings.Contains(valStr, "=") {
+			kvSplit = strings.SplitN(valStr, "=", 2)
+			if kvSplit == nil || len(kvSplit) == 0 {
+				continue
+			}
+			k = valSplit[0]
+			switch len(valSplit) {
+			case 1:
+				v = ""
+			case 2:
+				v = kvSplit[1]
+			}
+			if tagOpts[TagMapTrim] {
+				k = strings.TrimSpace(k)
+				v = strings.TrimSpace(v)
+			}
+			mapString[k] = v
+		} else {
+			if tagOpts[TagMapTrim] {
+				valStr = strings.TrimSpace(valStr)
+			}
+			mapBool[valStr] = true
+		}
+	}
+
+	return
+}
+
+/*
+	TagToMixedMapWithValue combines TagToBoolMapWithValue and TagToStringMapWithValue.
+	It takes struct field `field` and tag name `tagName`,
+	and returns all single-value options in mapBool, and all key/value options in mapString
+	along with the first single-value option as value..
+
+	If field does not have tag tagName, m will be nil.
+
+	See the TagMap* constants for opts.
+*/
+func TagToMixedMapWithValue(field reflect.StructField, tagName string, opts ...tagMapOpt) (value string, mapBool map[string]bool, mapString map[string]string) {
+
+	var s string
+	var idx int
+	var valStr string
+	var split []string
+	var kvSplit []string
+	var valSplit []string
+	var k string
+	var v string
+	var tagOpts map[tagMapOpt]bool = getTagMapOpts(opts)
+
+	s = field.Tag.Get(tagName)
+
+	if strings.TrimSpace(s) == "" {
+		return
+	}
+
+	split = strings.Split(s, ",")
+	if split == nil || len(split) == 0 {
+		return
+	}
+	mapBool = make(map[string]bool)
+	mapString = make(map[string]string)
+	for idx, valStr = range split {
+		if idx == 0 {
+			if tagOpts[TagMapTrim] {
+				valStr = strings.TrimSpace(valStr)
+			}
+			value = valStr
+			continue
+		}
+		if strings.Contains(valStr, "=") {
+			kvSplit = strings.SplitN(valStr, "=", 2)
+			if kvSplit == nil || len(kvSplit) == 0 {
+				continue
+			}
+			k = valSplit[0]
+			switch len(valSplit) {
+			case 1:
+				v = ""
+			case 2:
+				v = kvSplit[1]
+			}
+			if tagOpts[TagMapTrim] {
+				k = strings.TrimSpace(k)
+				v = strings.TrimSpace(v)
+			}
+			mapString[k] = v
+		} else {
+			if tagOpts[TagMapTrim] {
+				valStr = strings.TrimSpace(valStr)
+			}
+			mapBool[valStr] = true
+		}
+	}
+
+	return
+}
+
+/*
+	TagToStringMap takes struct field `field` and tag name `tagName`,
+	 optionally with options `opts`, and returns a map of the tag values.
+	The tag value string is assumed to be in the form of:
+		key=value[,key=value,key=value...]
+	and returns a map[string]string (map[key]value).
+	It is proccessed in order; later duplicate keys overwrite previous ones.
+
+	If field does not have tag tagName, m will be nil.
+
+	If only a key is provided with no value, the value in the map will be an empty string.
+	(e.g. "foo,bar=baz" => map[string]string{"foo": "", "bar: "baz"}
+
+	See the TagMap* constants for opts.
+*/
+func TagToStringMap(field reflect.StructField, tagName string, opts ...tagMapOpt) (m map[string]string) {
+
+	var s string
+	var kvSplit []string
+	var valSplit []string
+	var k string
+	var v string
+	var tagOpts map[tagMapOpt]bool = getTagMapOpts(opts)
+
+	s = field.Tag.Get(tagName)
+
+	if strings.TrimSpace(s) == "" {
+		return
+	}
+
+	kvSplit = strings.Split(s, ",")
+	if kvSplit == nil || len(kvSplit) == 0 {
+		return
+	}
+	for _, kv := range kvSplit {
+		valSplit = strings.SplitN(kv, "=", 2)
+		if valSplit == nil || len(valSplit) == 0 {
+			continue
+		}
+		k = valSplit[0]
+		switch len(valSplit) {
+		case 1:
+			v = ""
+		case 2:
+			v = valSplit[1]
+			// It's not possible to have more than 2.
+		}
+		if m == nil {
+			m = make(map[string]string)
+		}
+		if tagOpts[TagMapTrim] {
+			k = strings.TrimSpace(k)
+			v = strings.TrimSpace(v)
+		}
+		m[k] = v
+	}
+
+	return
+}
+
+/*
+	TagToStringMapWithValue is like TagToStringMap but additionally assumes the first value is an "identifier".
+	The tag value string is assumed to be in the form of:
+		value,key=value[,key=value,key=value...]
+	and returns a map[string]string (map[key]value) with the value.
+*/
+func TagToStringMapWithValue(field reflect.StructField, tagName string, opts ...tagMapOpt) (value string, m map[string]string) {
+
+	var s string
+	var kvSplit []string
+	var valSplit []string
+	var k string
+	var v string
+	var tagOpts map[tagMapOpt]bool = getTagMapOpts(opts)
+
+	s = field.Tag.Get(tagName)
+
+	if strings.TrimSpace(s) == "" {
+		return
+	}
+
+	kvSplit = strings.Split(s, ",")
+	if kvSplit == nil || len(kvSplit) == 0 {
+		return
+	}
+	for idx, kv := range kvSplit {
+		if idx == 0 {
+			if tagOpts[TagMapTrim] {
+				kv = strings.TrimSpace(kv)
+			}
+			value = kv
+			continue
+		}
+		valSplit = strings.SplitN(kv, "=", 2)
+		if valSplit == nil || len(valSplit) == 0 {
+			continue
+		}
+		k = valSplit[0]
+		switch len(valSplit) {
+		case 1:
+			v = ""
+		case 2:
+			v = valSplit[1]
+			// It's not possible to have more than 2.
+		}
+		if m == nil {
+			m = make(map[string]string)
+		}
+		if tagOpts[TagMapTrim] {
+			k = strings.TrimSpace(k)
+			v = strings.TrimSpace(v)
+		}
+		m[k] = v
+	}
+
+	return
+}
+
+func getTagMapOpts(opts []tagMapOpt) (optMap map[tagMapOpt]bool) {
+
+	optMap = make(map[tagMapOpt]bool)
+
+	if opts == nil {
+		return
+	}
+
+	return
+}

structutils/types.go

@@ -0,0 +1,5 @@
+package structutils
+
+type (
+	tagMapOpt uint8
+)