v1.11.0

ADDED:
* `stringsx` package
** `stringsx.Indent()`, to indent/prefix multiline strings
** `stringsx.Redact()`, to mask strings
** `stringsx.TrimLines()`, like strings.TrimSpace() but multiline
** `stringsx.TrimSpaceLeft()`, like strings.TrimSpace() but only to the
    left of a string.
** `stringsx.TrimSpaceRight()`, like strings.TrimSpace() but only to the
    right of a string.

go.mod

@@ -5,6 +5,7 @@ go 1.24.5
 require (
 	github.com/coreos/go-systemd/v22 v22.5.0
 	github.com/google/uuid v1.6.0
+	go4.org/netipx v0.0.0-20231129151722-fdeea329fbba
 	golang.org/x/sys v0.34.0
 	r00t2.io/sysutils v1.14.0
 )

go.sum

@@ -5,9 +5,12 @@ github.com/djherbis/times v1.6.0/go.mod h1:gOHeRAz2h+VJNZ5Gmc/o7iD9k4wW7NMVqieYC
 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=
+go4.org/netipx v0.0.0-20231129151722-fdeea329fbba h1:0b9z3AuHCjxk0x/opv64kcgZLBseWJUpBw5I82+2U4M=
+go4.org/netipx v0.0.0-20231129151722-fdeea329fbba/go.mod h1:PLyyIXexvUFg3Owu6p/WfdlivPbZJsZdgWZlrGope/Y=
 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 h1:Lrio3uPi9CuUdg+sg3WkVV1CK/qcOpV9GdFCGFG1KJs=
 r00t2.io/sysutils v1.14.0/go.mod h1:ZJ7gZxFVQ7QIokQ5fPZr7wl0XO5Iu+LqtE8j3ciRINw=

netx/consts_nix.go

@@ -0,0 +1,13 @@
+//go:build !windows
+
+package netx
+
+import (
+	`golang.org/x/sys/unix`
+)
+
+const (
+	AFUnspec uint16 = unix.AF_UNSPEC
+	AFInet   uint16 = unix.AF_INET
+	AFInet6  uint16 = unix.AF_INET6
+)

netx/consts_windows.go

@@ -0,0 +1,13 @@
+//go:build windows
+
+package netx
+
+import (
+	`golang.org/x/sys/windows`
+)
+
+const (
+	AFUnspec uint16 = windows.AF_UNSPEC
+	AFInet   uint16 = windows.AF_INET
+	AFInet6  uint16 = windows.AF_INET6
+)

netx/errors.go

@@ -0,0 +1,10 @@
+package netx
+
+import (
+	`errors`
+)
+
+var (
+	ErrBadMask4Str error = errors.New("netx: unknown/bad IPv4 netmask dotted quad")
+	ErrBadNetFam   error = errors.New("netx: unknown/bad IP network family")
+)

netx/funcs.go

@@ -0,0 +1,410 @@
+package netx
+
+import (
+	`math/bits`
+	`net`
+	`net/netip`
+	`strconv`
+	`strings`
+
+	`go4.org/netipx`
+)
+
+/*
+AddrRfc returns an RFC-friendly string from an IP address ([net/netip.Addr]).
+
+If addr is an IPv4 address, it will simmply be the string representation (e.g. "203.0.113.1").
+
+If addr is an IPv6 address, it will be enclosed in brackets (e.g. "[2001:db8::1]").
+
+If the version can't be determined, rfcStr will be an empty string.
+*/
+func AddrRfc(addr netip.Addr) (rfcStr string) {
+
+	if addr.Is4() {
+		rfcStr = addr.String()
+	} else if addr.Is6() {
+		rfcStr = "[" + addr.String() + "]"
+	}
+
+	return
+}
+
+/*
+Cidr4ToIPMask takes an IPv4 CIDR/bit size/prefix length and returns the [net.IPMask].
+It's (essentially) the inverse of [net.IPMask.Size].
+
+See also:
+
+ * [Cidr4ToMask]
+ * [Cidr4ToStr]
+
+Inverse of [IPMask4ToCidr].
+*/
+func Cidr4ToIPMask(cidr uint8) (ipMask net.IPMask, err error) {
+
+	if cidr > 32 {
+		err = ErrBadNetFam
+		return
+	}
+
+	ipMask = net.CIDRMask(int(cidr), 32)
+
+	return
+}
+
+/*
+Cidr4ToMask takes an IPv4 CIDR/bit size/prefix length and returns the netmask *in bitmask form*.
+
+See also:
+
+ * [Cidr4ToIPMask]
+ * [Cidr4ToStr]
+
+Inverse of [Mask4ToCidr].
+*/
+func Cidr4ToMask(cidr uint8) (mask uint32, err error) {
+
+	if cidr > 32 {
+		err = ErrBadNetFam
+		return
+	}
+
+	// COULD do (1 << 32) - (1 << (32 - ip.Bits())) instead but in EXTREME edge cases that could cause an overflow.
+	// We're basically converting the CIDR size ("number of bits"/"number of ones") to an integer mask ("number AS bits")
+	mask = uint32(0xffffffff) << uint32(32-cidr)
+
+	return
+}
+
+/*
+Cidr4ToStr is a convenience wrapper around [IPMask4ToStr]([Cidr4ToMask](cidr)).
+
+See also:
+
+ * [Cidr4ToIPMask]
+ * [Cidr4ToMask]
+
+Inverse of [Mask4StrToCidr].
+*/
+func Cidr4ToStr(cidr uint8) (maskStr string, err error) {
+
+	var ipMask net.IPMask
+
+	if ipMask, err = Cidr4ToIPMask(cidr); err != nil {
+		return
+	}
+
+	if maskStr, err = IPMask4ToStr(ipMask); err != nil {
+		return
+	}
+
+	return
+}
+
+/*
+GetAddrFamily returns the network family of a [net/netip.Addr].
+
+See also [GetIpFamily].
+
+If addr is not a "valid" IP address or the version can't be determined, family will be AFUnspec (usually 0x00/0).
+*/
+func GetAddrFamily(addr netip.Addr) (family uint16) {
+
+	family = AFUnspec
+
+	if !addr.IsValid() {
+		return
+	}
+
+	if addr.Is4() {
+		family = AFInet
+	} else if addr.Is6() {
+		family = AFInet6
+	} else {
+		return
+	}
+
+	return
+}
+
+/*
+GetIpFamily returns the network family of a [net.IP].
+
+See also [GetAddrFamily].
+
+If ip is not a "valid" IP address or the version can't be determined,
+family will be [golang.org/x/sys/unix.AF_UNSPEC] or [golang.org/x/sys/windows.AF_UNSPEC] depending on platform (usually 0x00/0).
+*/
+func GetIpFamily(ip net.IP) (family uint16) {
+
+	var ok bool
+	var addr netip.Addr
+
+	if addr, ok = netipx.FromStdIP(ip); !ok {
+		return
+	}
+
+	family = GetAddrFamily(addr)
+
+	return
+}
+
+/*
+IpRfc returns an RFC-friendly string from an IP address ([net.IP]).
+
+If ip is an IPv4 address, it will simmply be the string representation (e.g. "203.0.113.1").
+
+If ip is an IPv6 address, it will be enclosed in brackets (e.g. "[2001:db8::1]").
+
+If the version can't be determined, rfcStr will be an empty string.
+*/
+func IpRfc(ip net.IP) (rfcStr string) {
+
+	if ip.To4() != nil {
+		rfcStr = ip.To4().String()
+	} else if ip.To16() != nil {
+		rfcStr = "[" + ip.To16().String() + "]"
+	}
+
+	return
+}
+
+/*
+IPMask4ToCidr returns a CIDR prefix size/bit size/bit length from a [net.IPMask].
+
+See also:
+
+ * [IPMask4ToMask]
+ * [IPMask4ToStr]
+
+Inverse of [Cidr4ToIPMask].
+*/
+func IPMask4ToCidr(ipMask net.IPMask) (cidr uint8, err error) {
+
+	var ones int
+	var total int
+
+	ones, total = ipMask.Size()
+
+	if total != 32 {
+		err = ErrBadNetFam
+		return
+	}
+	if ones > 32 {
+		err = ErrBadNetFam
+		return
+	}
+
+	cidr = uint8(ones)
+
+	return
+}
+
+/*
+IPMask4ToMask returns the mask *in bitmask form* from a [net.IPMask].
+
+See also:
+
+ * [IPMask4ToCidr]
+ * [IPMask4ToStr]
+
+Inverse of [Mask4ToIPMask].
+*/
+func IPMask4ToMask(ipMask net.IPMask) (mask uint32, err error) {
+
+	var cidr uint8
+
+	if cidr, err = IPMask4ToCidr(ipMask); err != nil {
+		return
+	}
+
+	if mask, err = Cidr4ToMask(cidr); err != nil {
+		return
+	}
+
+	return
+}
+
+/*
+IPMask4ToStr returns a string representation of an IPv4 netmask (e.g. "255.255.255.0" for a /24) from a [net.IPMask].
+
+See also:
+
+ * [IPMask4ToCidr]
+ * [IPMask4ToMask]
+
+Inverse of [Mask4StrToIPMask].
+*/
+func IPMask4ToStr(ipMask net.IPMask) (maskStr string, err error) {
+
+	var idx int
+	var b []byte
+	var quads []string = make([]string, 4)
+
+	b = []byte(ipMask)
+	if len(b) != 4 {
+		err = ErrBadNetFam
+		return
+	}
+
+	for idx = 0; idx < len(b); idx++ {
+		quads[idx] = strconv.Itoa(int(b[idx]))
+	}
+
+	maskStr = strings.Join(quads, ".")
+
+	return
+}
+
+/*
+Mask4ToCidr converts an IPv4 netmask *in bitmask form* to a CIDR prefix size/bit size/bit length.
+
+See also:
+
+ * [Mask4ToIPMask]
+ * [Mask4ToStr]
+
+Inverse of [Cidr4ToMask].
+*/
+func Mask4ToCidr(mask uint32) (cidr uint8, err error) {
+
+	cidr = 32 - uint8(bits.LeadingZeros32(mask))
+
+	return
+}
+
+/*
+Mask4ToIPMask returns mask *in bitmask form* as a [net.IPMask].
+
+See also:
+
+ * [Mask4ToCidr]
+ * [Mask4ToStr]
+
+Inverse of [IPMask4ToMask].
+*/
+func Mask4ToIPMask(mask uint32) (ipMask net.IPMask, err error) {
+
+	var cidr uint8
+
+	if cidr, err = Mask4ToCidr(mask); err != nil {
+		return
+	}
+
+	ipMask = net.CIDRMask(int(cidr), 32)
+
+	return
+}
+
+/*
+Mask4ToStr returns a string representation of an IPv4 netmask (e.g. "255.255.255.0" for a /24) from a netmask *in bitmask form*.
+
+See also:
+
+ * [Mask4ToCidr]
+ * [Mask4ToIPMask]
+
+Inverse of [Mask4StrToMask].
+*/
+func Mask4ToStr(mask uint32) (maskStr string, err error) {
+
+	var ipMask net.IPMask
+
+	if ipMask, err = Mask4ToIPMask(mask); err != nil {
+		return
+	}
+
+	if maskStr, err = IPMask4ToStr(ipMask); err != nil {
+		return
+	}
+
+	return
+}
+
+/*
+Mask4StrToCidr parses a "dotted-quad" IPv4 netmask (e.g. "255.255.255.0" for a /24) and returns am IPv4 CIDR/bit size/prefix length.
+
+See also:
+
+ * [Mask4StrToIPMask]
+ * [Mask4StrToMask]
+
+Inverse of [Cidr4ToMaskStr].
+*/
+func Mask4StrToCidr(maskStr string) (cidr uint8, err error) {
+
+	var ipMask net.IPMask
+
+	if ipMask, err = Mask4StrToIPMask(maskStr); err != nil {
+		return
+	}
+
+	if cidr, err = IPMask4ToCidr(ipMask); err != nil {
+		return
+	}
+
+	return
+}
+
+/*
+Mask4StrToIPMask parses a "dotted-quad" IPv4 netmask (e.g. "255.255.255.0" for a /24) and returns a [net.IPMask].
+
+See also:
+
+ * [Mask4StrToCidr]
+ * [Mask4StrToMask]
+
+Inverse of [IPMask4ToStr].
+*/
+func Mask4StrToIPMask(maskStr string) (mask net.IPMask, err error) {
+
+	var idx int
+	var s string
+	var u64 uint64
+	var b []byte = make([]byte, 4)
+	var sl []string = strings.Split(maskStr, ".")
+
+	if len(sl) != 4 {
+		err = ErrBadMask4Str
+		return
+	}
+
+	// A net.IPMask is just a []byte.
+	for idx = 0; idx < len(sl); idx++ {
+		s = sl[idx]
+		if u64, err = strconv.ParseUint(s, 10, 8); err != nil {
+			return
+		}
+		b[idx] = byte(u64)
+	}
+
+	mask = net.IPMask(b)
+
+	return
+}
+
+/*
+Mask4StrToMask parses a "dotted-quad" IPv4 netmask (e.g. "255.255.255.0" for a /24) and returns a netmask *in bitmask form*.
+
+See also:
+
+ * [Mask4StrToCidr]
+ * [Mask4StrToIPMask]
+
+Inverse of [Mask4ToStr].
+*/
+func Mask4StrToMask(maskStr string) (mask uint32, err error) {
+
+	var ipMask net.IPMask
+
+	if ipMask, err = Mask4StrToIPMask(maskStr); err != nil {
+		return
+	}
+
+	if mask, err = IPMask4ToMask(ipMask); err != nil {
+		return
+	}
+
+	return
+}

netx/funcs_test.go

@@ -0,0 +1,134 @@
+package netx
+
+import (
+	`math`
+	`net`
+	`net/netip`
+	"testing"
+)
+
+func TestFuncsIP(t *testing.T) {
+
+	var err error
+	var ip net.IP
+	var addr netip.Addr
+	var ipFamily uint16
+	var tgtFamily uint16
+	var addrFamily uint16
+
+	// IPv4 on even indexes, IPv6 on odd.
+	for idx, s := range []string{
+		"203.0.113.10",
+		"2001:db8::203:0:113:10",
+	} {
+		if ip = net.ParseIP(s); ip == nil {
+			t.Fatalf("ip %s not valid", s)
+		}
+		if addr, err = netip.ParseAddr(s); err != nil {
+			t.Fatalf("addr %s not valid", s)
+		}
+		ipFamily = GetIpFamily(ip)
+		addrFamily = GetAddrFamily(addr)
+		if ipFamily == AFUnspec {
+			t.Fatalf("GetIpFamily: Failed on IP %s (unspecified family)", s)
+		}
+		if addrFamily == AFUnspec {
+			t.Fatalf("GetAddrFamily: Failed on IP %s (unspecified family)", s)
+		}
+		switch idx%2 == 0 {
+		case true:
+			tgtFamily = AFInet
+		case false:
+			tgtFamily = AFInet6
+		}
+		if ipFamily != tgtFamily {
+			t.Fatalf("GetIpFamily: Failed on IP %s (expected %d, got %d)", s, AFInet, tgtFamily)
+		}
+		if addrFamily != tgtFamily {
+			t.Fatalf("GetAddrFamily: Failed on IP %s (expected %d, got %d)", s, AFInet, tgtFamily)
+		}
+	}
+}
+
+func TestFuncsMask(t *testing.T) {
+
+	var err error
+
+	var cidr uint8
+	var mask uint32
+	var maskStr string
+	var ipMask net.IPMask
+
+	var cidrTgt uint8 = 32
+	var maskTgt uint32 = math.MaxUint32
+	var maskStrTgt string = "255.255.255.255"
+	var ipMaskTgt net.IPMask = net.IPMask{255, 255, 255, 255}
+
+	// To CIDR
+	if cidr, err = Mask4ToCidr(maskTgt); err != nil {
+		t.Fatal(err)
+	} else if cidr != cidrTgt {
+		t.Fatalf("Mask4ToCidr: cidr %d != cidrTgt %d", cidr, cidrTgt)
+	}
+	if cidr, err = IPMask4ToCidr(ipMaskTgt); err != nil {
+		t.Fatal(err)
+	} else if cidr != cidrTgt {
+		t.Fatalf("IPMask4ToCidr: cidr %d != cidrTgt %d", cidr, cidrTgt)
+	}
+	if cidr, err = Mask4StrToCidr(maskStrTgt); err != nil {
+		t.Fatal(err)
+	} else if cidr != cidrTgt {
+		t.Fatalf("Mask4StrToCidr cidr %d != cidrTgt %d", cidr, cidrTgt)
+	}
+
+	// To net.IPMask
+	if ipMask, err = Cidr4ToIPMask(cidrTgt); err != nil {
+		t.Fatal(err)
+	} else if ipMaskTgt.String() != ipMask.String() {
+		t.Fatalf("Cidr4ToIPMask ipMask %s != ipMaskTgt %s", ipMask.String(), ipMaskTgt.String())
+	}
+	if ipMask, err = Mask4ToIPMask(maskTgt); err != nil {
+		t.Fatal(err)
+	} else if ipMaskTgt.String() != ipMask.String() {
+		t.Fatalf("Mask4ToIPMask ipMask %s != ipMaskTgt %s", ipMask.String(), ipMaskTgt.String())
+	}
+	if ipMask, err = Mask4StrToIPMask(maskStrTgt); err != nil {
+		t.Fatal(err)
+	} else if ipMaskTgt.String() != ipMask.String() {
+		t.Fatalf("Mask4StrToIPMask ipMask %s != ipMaskTgt %s", ipMask.String(), ipMaskTgt.String())
+	}
+
+	// To bitmask
+	if mask, err = Cidr4ToMask(cidrTgt); err != nil {
+		t.Fatal(err)
+	} else if mask != maskTgt {
+		t.Fatalf("Cidr4ToMask mask %d != maskTgt %d", mask, maskTgt)
+	}
+	if mask, err = IPMask4ToMask(ipMaskTgt); err != nil {
+		t.Fatal(err)
+	} else if mask != maskTgt {
+		t.Fatalf("IPMask4ToMask mask %d != maskTgt %d", mask, maskTgt)
+	}
+	if mask, err = Mask4StrToMask(maskStrTgt); err != nil {
+		t.Fatal(err)
+	} else if mask != maskTgt {
+		t.Fatalf("Mask4StrToMask mask %d != maskTgt %d", mask, maskTgt)
+	}
+
+	// To string
+	if maskStr, err = Cidr4ToStr(cidrTgt); err != nil {
+		t.Fatal(err)
+	} else if maskStr != maskStrTgt {
+		t.Fatalf("Cidr4ToStr maskStr %s != maskStrTgt %s", maskStr, maskStrTgt)
+	}
+	if maskStr, err = IPMask4ToStr(ipMaskTgt); err != nil {
+		t.Fatal(err)
+	} else if maskStr != maskStrTgt {
+		t.Fatalf("IPMask4ToStr maskStr %s != maskStrTgt %s", maskStr, maskStrTgt)
+	}
+	if maskStr, err = Mask4ToStr(maskTgt); err != nil {
+		t.Fatal(err)
+	} else if maskStr != maskStrTgt {
+		t.Fatalf("Mask4ToStr maskStr %s != maskStrTgt %s", maskStr, maskStrTgt)
+	}
+}

stringsx/TODO

@@ -0,0 +1,5 @@
+- Banner struct, with .Format(s string) method
+-- draw border around multiline s
+-- i have a version in python somewhere that does this, should dig that up
+
+- create bytesx package that duplicates the functions here?

stringsx/consts.go

@@ -0,0 +1,11 @@
+package stringsx
+
+const (
+	// DefMaskStr is the string used as the default maskStr if left empty in [Redact].
+	DefMaskStr string = "***"
+)
+
+const (
+	// DefIndentStr is the string used as the default indent if left empty in [Indent].
+	DefIndentStr string = "\t"
+)

stringsx/doc.go

@@ -0,0 +1,4 @@
+/*
+Package stringsx aims to extend functionality of the stdlib [strings] module.
+*/
+package stringsx

stringsx/funcs.go

@@ -0,0 +1,249 @@
+package stringsx
+
+import (
+	`strings`
+	`unicode`
+)
+
+/*
+Indent takes string s and indents it with string `indent` `level` times.
+
+If indent is an empty string, [DefIndentStr] will be used.
+
+If ws is true, lines consisting of only whitespace will be indented as well.
+(To then trim any extraneous trailing space, you may want to use [TrimSpaceRight]
+or [TrimLines].)
+
+If empty is true, lines with no content will be replaced with lines that purely
+consist of (indent * level) (otherwise they will be left as empty lines).
+
+This function can also be used to prefix lines with arbitrary strings as well.
+e.g:
+
+	Indent("foo\nbar\nbaz\n", "# ", 1, false, false)
+
+would yield:
+
+	# foo
+	# bar
+	# baz
+	<empty line>
+
+thus allowing you to "comment out" multiple lines at once.
+*/
+func Indent(s, indent string, level uint, ws, empty bool) (indented string) {
+
+	var i string
+	var nl string
+	var endsNewline bool
+	var sb strings.Builder
+	var lineStripped string
+
+	if indent == "" {
+		indent = DefIndentStr
+	}
+
+	// This condition functionally won't do anything, so just return the input as-is.
+	if level == 0 {
+		indented = s
+		return
+	}
+
+	i = strings.Repeat(indent, int(level))
+
+	// This condition functionally won't do anything, so just return the input as-is.
+	if s == "" {
+		if empty {
+			indented = i
+		}
+		return
+	}
+
+	for line := range strings.Lines(s) {
+		lineStripped = strings.TrimSpace(line)
+		nl = getNewLine(line)
+		endsNewline = nl != ""
+		// fmt.Printf("%#v => %#v\n", line, lineStripped)
+		if lineStripped == "" {
+			// fmt.Printf("WS/EMPTY LINE (%#v) (ws %v, empty %v): \n", s, ws, empty)
+			if line != (lineStripped + nl) {
+				// whitespace-only line
+				if ws {
+					sb.WriteString(i)
+				}
+			} else {
+				// empty line
+				if empty {
+					sb.WriteString(i)
+				}
+			}
+			sb.WriteString(line)
+			continue
+		}
+		// non-empty/non-whitespace-only line.
+		sb.WriteString(i + line)
+	}
+
+	// If it ends with a trailing newline and nothing after, strings.Lines() will skip the last (empty) line.
+	if endsNewline && empty {
+		nl = getNewLine(s)
+		sb.WriteString(i)
+	}
+
+	indented = sb.String()
+
+	return
+}
+
+/*
+Redact provides a "masked" version of string s (e.g. `my_terrible_password` -> `my****************rd`).
+
+maskStr is the character or sequence of characters
+to repeat for every masked character of s.
+If an empty string, the default [DefMaskStr] will be used.
+(maskStr does not need to be a single character.
+It is recommended to use a multi-char mask to help obfuscate a string's length.)
+
+leading specifies the number of leading characters of s to leave *unmasked*.
+If 0, no leading characters will be unmasked.
+
+trailing specifies the number of trailing characters of s to leave *unmasked*.
+if 0, no trailing characters will be unmasked.
+
+newlines, if true, will preserve newline characters - otherwise
+they will be treated as regular characters.
+
+As a safety precaution, if:
+
+	len(s) <= (leading + trailing)
+
+then the entire string will be *masked* and no unmasking will be performed.
+*/
+func Redact(s, maskStr string, leading, trailing uint, newlines bool) (redacted string) {
+
+	var nl string
+	var numMasked int
+	var sb strings.Builder
+	var endIdx int = int(leading)
+
+	// This condition functionally won't do anything, so just return the input as-is.
+	if s == "" {
+		return
+	}
+
+	if maskStr == "" {
+		maskStr = DefMaskStr
+	}
+
+	if newlines {
+		for line := range strings.Lines(s) {
+			nl = getNewLine(line)
+			sb.WriteString(
+				Redact(
+					strings.TrimSuffix(line, nl), maskStr, leading, trailing, false,
+				),
+			)
+			sb.WriteString(nl)
+		}
+	} else {
+		if len(s) <= int(leading+trailing) {
+			redacted = strings.Repeat(maskStr, len(s))
+			return
+		}
+
+		if leading == 0 && trailing == 0 {
+			redacted = strings.Repeat(maskStr, len(s))
+			return
+		}
+
+		numMasked = len(s) - int(leading+trailing)
+		endIdx = endIdx + numMasked
+
+		if leading > 0 {
+			sb.WriteString(s[:int(leading)])
+		}
+
+		sb.WriteString(strings.Repeat(maskStr, numMasked))
+
+		if trailing > 0 {
+			sb.WriteString(s[endIdx:])
+		}
+	}
+
+	redacted = sb.String()
+
+	return
+}
+
+/*
+TrimLines is like [strings.TrimSpace] but operates on *each line* of s.
+It is *NIX-newline (`\n`) vs. Windows-newline (`\r\n`) agnostic.
+The first encountered linebreak (`\n` vs. `\r\n`) are assumed to be
+the canonical linebreak for the rest of s.
+
+left, if true, performs a [TrimSpaceLeft] on each line (retaining the newline).
+
+right, if true, performs a [TrimSpaceRight] on each line (retaining the newline).
+*/
+func TrimLines(s string, left, right bool) (trimmed string) {
+
+	var sl string
+	var nl string
+	var sb strings.Builder
+
+	// These conditions functionally won't do anything, so just return the input as-is.
+	if s == "" {
+		return
+	}
+	if !left && !right {
+		trimmed = s
+		return
+	}
+
+	for line := range strings.Lines(s) {
+		nl = getNewLine(line)
+		sl = strings.TrimSuffix(line, nl)
+		if left && right {
+			sl = strings.TrimSpace(sl)
+		} else if left {
+			sl = TrimSpaceLeft(sl)
+		} else if right {
+			sl = TrimSpaceRight(sl)
+		}
+		sb.WriteString(sl + nl)
+	}
+
+	trimmed = sb.String()
+
+	return
+}
+
+// TrimSpaceLeft is like [strings.TrimSpace] but only removes leading whitespace from string s.
+func TrimSpaceLeft(s string) (trimmed string) {
+
+	trimmed = strings.TrimLeftFunc(s, unicode.IsSpace)
+
+	return
+}
+
+/*
+TrimSpaceRight is like [strings.TrimSpace] but only removes trailing whitespace from string s.
+*/
+func TrimSpaceRight(s string) (trimmed string) {
+
+	trimmed = strings.TrimRightFunc(s, unicode.IsSpace)
+
+	return
+}
+
+// getNewLine is too unpredictable to be used outside of this package so it isn't exported.
+func getNewLine(s string) (nl string) {
+
+	if strings.HasSuffix(s, "\r\n") {
+		nl = "\r\n"
+	} else if strings.HasSuffix(s, "\n") {
+		nl = "\n"
+	}
+
+	return
+}

stringsx/funcs_test.go

@@ -0,0 +1,451 @@
+package stringsx
+
+import (
+	"testing"
+)
+
+type (
+	testIndentSet struct {
+		name   string
+		orig   string
+		indent string
+		lvl    uint
+		ws     bool
+		empty  bool
+		tgt    string
+	}
+	testRedactSet struct {
+		name     string
+		orig     string
+		leading  uint
+		trailing uint
+		tgt      string
+		newline  bool
+		mask     string // defaults to DefMaskStr.
+	}
+	testTrimLinesSet struct {
+		name  string
+		orig  string
+		left  bool
+		right bool
+		tgt   string
+	}
+	testTrimSet struct {
+		name string
+		orig string
+		tgt  string
+	}
+)
+
+func TestIndent(t *testing.T) {
+
+	var out string
+	var tests []testIndentSet = []testIndentSet{
+		testIndentSet{
+			name:   "standard, no trailing newline",
+			orig:   "foo\nbar\nbaz",
+			indent: "",
+			lvl:    1,
+			ws:     false,
+			empty:  false,
+			tgt:    "\tfoo\n\tbar\n\tbaz",
+		},
+		testIndentSet{
+			name:   "standard, trailing newline",
+			orig:   "foo\nbar\nbaz\n",
+			indent: "",
+			lvl:    1,
+			ws:     false,
+			empty:  false,
+			tgt:    "\tfoo\n\tbar\n\tbaz\n",
+		},
+		testIndentSet{
+			name:   "standard, trailing newline with empty",
+			orig:   "foo\nbar\nbaz\n",
+			indent: "",
+			lvl:    1,
+			ws:     false,
+			empty:  true,
+			tgt:    "\tfoo\n\tbar\n\tbaz\n\t",
+		},
+		testIndentSet{
+			name:   "standard, trailing newline with ws",
+			orig:   "foo\nbar\nbaz\n",
+			indent: "",
+			lvl:    1,
+			ws:     true,
+			empty:  false,
+			tgt:    "\tfoo\n\tbar\n\tbaz\n",
+		},
+		testIndentSet{
+			name:   "standard, trailing newline with ws and empty",
+			orig:   "foo\nbar\nbaz\n",
+			indent: "",
+			lvl:    1,
+			ws:     true,
+			empty:  true,
+			tgt:    "\tfoo\n\tbar\n\tbaz\n\t",
+		},
+		testIndentSet{
+			name:   "standard, trailing ws newline with empty",
+			orig:   "foo\nbar\nbaz\n   ",
+			indent: "",
+			lvl:    1,
+			ws:     false,
+			empty:  true,
+			tgt:    "\tfoo\n\tbar\n\tbaz\n   ",
+		},
+		testIndentSet{
+			name:   "standard, trailing ws newline with ws",
+			orig:   "foo\nbar\nbaz\n   ",
+			indent: "",
+			lvl:    1,
+			ws:     true,
+			empty:  false,
+			tgt:    "\tfoo\n\tbar\n\tbaz\n\t   ",
+		},
+		testIndentSet{
+			name:   "standard, trailing ws newline with ws and empty",
+			orig:   "foo\nbar\nbaz\n   \n",
+			indent: "",
+			lvl:    1,
+			ws:     true,
+			empty:  true,
+			tgt:    "\tfoo\n\tbar\n\tbaz\n\t   \n\t",
+		},
+		testIndentSet{
+			name:   "comment",
+			orig:   "foo\nbar\nbaz",
+			indent: "# ",
+			lvl:    1,
+			ws:     false,
+			empty:  false,
+			tgt:    "# foo\n# bar\n# baz",
+		},
+	}
+
+	for idx, ts := range tests {
+		out = Indent(ts.orig, ts.indent, ts.lvl, ts.ws, ts.empty)
+		if out == ts.tgt {
+			t.Logf("[%d] OK (%s): %#v: got %#v", idx, ts.name, ts.orig, out)
+		} else {
+			t.Errorf(
+				"[%d] FAIL (%s): %#v (len %d):\n"+
+					"\t\t\texpected (len %d): %#v\n"+
+					"\t\t\tgot      (len %d): %#v\n"+
+					"\t\t%#v",
+				idx, ts.name, ts.orig, len(ts.orig),
+				len(ts.tgt), ts.tgt,
+				len(out), out,
+				ts,
+			)
+		}
+	}
+
+}
+
+func TestRedact(t *testing.T) {
+
+	var out string
+	var tests []testRedactSet = []testRedactSet{
+		testRedactSet{
+			name:     "empty in, empty out",
+			orig:     "",
+			leading:  0,
+			trailing: 0,
+			tgt:      "",
+		},
+		testRedactSet{
+			name:     "standard",
+			orig:     "password",
+			leading:  0,
+			trailing: 0,
+			tgt:      "************************",
+		},
+		testRedactSet{
+			name:     "standard with newline",
+			orig:     "pass\nword",
+			leading:  0,
+			trailing: 0,
+			tgt:      "************\n************",
+			newline:  true,
+		},
+		testRedactSet{
+			name:     "standard with Windows newline",
+			orig:     "pass\r\nword",
+			leading:  0,
+			trailing: 0,
+			tgt:      "************\r\n************",
+			newline:  true,
+		},
+		testRedactSet{
+			name:     "standard with newline without newlines",
+			orig:     "pass\nword",
+			leading:  0,
+			trailing: 0,
+			tgt:      "***************************",
+		},
+		testRedactSet{
+			name:     "single leading",
+			orig:     "password",
+			leading:  1,
+			trailing: 0,
+			tgt:      "p*********************",
+		},
+		testRedactSet{
+			name:     "single trailing",
+			orig:     "password",
+			leading:  0,
+			trailing: 1,
+			tgt:      "*********************d",
+		},
+		testRedactSet{
+			name:     "three leading",
+			orig:     "password",
+			leading:  3,
+			trailing: 0,
+			tgt:      "pas***************",
+		},
+		testRedactSet{
+			name:     "three trailing",
+			orig:     "password",
+			leading:  0,
+			trailing: 3,
+			tgt:      "***************ord",
+		},
+		testRedactSet{
+			name:     "three leading and trailing",
+			orig:     "password",
+			leading:  3,
+			trailing: 3,
+			tgt:      "pas******ord",
+		},
+		testRedactSet{
+			name:     "unmask overflow leading",
+			orig:     "password",
+			leading:  5,
+			trailing: 4,
+			tgt:      "************************",
+		},
+		testRedactSet{
+			name:     "unmask overflow trailing",
+			orig:     "password",
+			leading:  4,
+			trailing: 5,
+			tgt:      "************************",
+		},
+		testRedactSet{
+			name:     "single mask",
+			orig:     "password",
+			leading:  0,
+			trailing: 0,
+			tgt:      "********",
+			mask:     "*",
+		},
+		testRedactSet{
+			name:     "standard trailing newline with newlines",
+			orig:     "password\n",
+			leading:  0,
+			trailing: 0,
+			tgt:      "************************\n",
+			newline:  true,
+		},
+		testRedactSet{
+			name:     "standard trailing newline without newlines",
+			orig:     "password\n",
+			leading:  0,
+			trailing: 0,
+			tgt:      "***************************",
+		},
+	}
+
+	for idx, ts := range tests {
+		out = Redact(ts.orig, ts.mask, ts.leading, ts.trailing, ts.newline)
+		if out == ts.tgt {
+			t.Logf("[%d] OK (%s): %#v: got %#v", idx, ts.name, ts.orig, out)
+		} else {
+			t.Errorf(
+				"[%d] FAIL (%s): %#v (len %d):\n"+
+					"\t\t\texpected (len %d): %#v\n"+
+					"\t\t\tgot      (len %d): %#v\n"+
+					"\t\t%#v",
+				idx, ts.name, ts.orig, len(ts.orig),
+				len(ts.tgt), ts.tgt,
+				len(out), out,
+				ts,
+			)
+		}
+	}
+}
+
+func TestTrimLines(t *testing.T) {
+
+	var out string
+	var tests []testTrimLinesSet = []testTrimLinesSet{
+		testTrimLinesSet{
+			name:  "none",
+			orig:  "   foo   \n   bar   \n   baz   ",
+			left:  false,
+			right: false,
+			tgt:   "   foo   \n   bar   \n   baz   ",
+		},
+		testTrimLinesSet{
+			name:  "standard",
+			orig:  "   foo   \n   bar   \n   baz   ",
+			left:  true,
+			right: true,
+			tgt:   "foo\nbar\nbaz",
+		},
+		testTrimLinesSet{
+			name:  "left only",
+			orig:  "   foo   \n   bar   \n   baz   ",
+			left:  true,
+			right: false,
+			tgt:   "foo   \nbar   \nbaz   ",
+		},
+		testTrimLinesSet{
+			name:  "right only",
+			orig:  "   foo   \n   bar   \n   baz   ",
+			left:  false,
+			right: true,
+			tgt:   "   foo\n   bar\n   baz",
+		},
+		testTrimLinesSet{
+			name:  "standard, trailing newline",
+			orig:  "   foo   \n   bar   \n   baz   \n",
+			left:  true,
+			right: true,
+			tgt:   "foo\nbar\nbaz\n",
+		},
+		testTrimLinesSet{
+			name:  "left only, trailing newline",
+			orig:  "   foo   \n   bar   \n   baz   \n",
+			left:  true,
+			right: false,
+			tgt:   "foo   \nbar   \nbaz   \n",
+		},
+		testTrimLinesSet{
+			name:  "right only, trailing newline",
+			orig:  "   foo   \n   bar   \n   baz   \n",
+			left:  false,
+			right: true,
+			tgt:   "   foo\n   bar\n   baz\n",
+		},
+		// Since there's no "non-space" boundary, both of these condition tests do the same thing.
+		testTrimLinesSet{
+			name:  "left only, trailing newline and ws",
+			orig:  "   foo   \n   bar   \n   baz   \n   ",
+			left:  true,
+			right: false,
+			tgt:   "foo   \nbar   \nbaz   \n",
+		},
+		testTrimLinesSet{
+			name:  "right only, trailing newline and ws",
+			orig:  "   foo   \n   bar   \n   baz   \n   ",
+			left:  false,
+			right: true,
+			tgt:   "   foo\n   bar\n   baz\n",
+		},
+	}
+
+	for idx, ts := range tests {
+		out = TrimLines(ts.orig, ts.left, ts.right)
+		if out == ts.tgt {
+			t.Logf("[%d] OK (%s): %#v: got %#v", idx, ts.name, ts.orig, out)
+		} else {
+			t.Errorf(
+				"[%d] FAIL (%s): %#v (len %d):\n"+
+					"\t\t\texpected (len %d): %#v\n"+
+					"\t\t\tgot      (len %d): %#v\n"+
+					"\t\t%#v",
+				idx, ts.name, ts.orig, len(ts.orig),
+				len(ts.tgt), ts.tgt,
+				len(out), out,
+				ts,
+			)
+		}
+	}
+
+}
+
+func TestTrimSpaceLeft(t *testing.T) {
+
+	var out string
+	var tests []testTrimSet = []testTrimSet{
+		testTrimSet{
+			name: "standard",
+			orig: "   foo   ",
+			tgt:  "foo   ",
+		},
+		testTrimSet{
+			name: "tabs",
+			orig: "\t\tfoo\t\t",
+			tgt:  "foo\t\t",
+		},
+		testTrimSet{
+			name: "newlines",
+			orig: "\n\nfoo\n\n",
+			tgt:  "foo\n\n",
+		},
+	}
+
+	for idx, ts := range tests {
+		out = TrimSpaceLeft(ts.orig)
+		if out == ts.tgt {
+			t.Logf("[%d] OK (%s): %#v: got %#v", idx, ts.name, ts.orig, out)
+		} else {
+			t.Errorf(
+				"[%d] FAIL (%s): %#v (len %d):\n"+
+					"\t\t\texpected (len %d): %#v\n"+
+					"\t\t\tgot      (len %d): %#v\n"+
+					"\t\t%#v",
+				idx, ts.name, ts.orig, len(ts.orig),
+				len(ts.tgt), ts.tgt,
+				len(out), out,
+				ts,
+			)
+		}
+	}
+
+}
+
+func TestTrimSpaceRight(t *testing.T) {
+
+	var out string
+	var tests []testTrimSet = []testTrimSet{
+		testTrimSet{
+			name: "standard",
+			orig: "   foo   ",
+			tgt:  "   foo",
+		},
+		testTrimSet{
+			name: "tabs",
+			orig: "\t\tfoo\t\t",
+			tgt:  "\t\tfoo",
+		},
+		testTrimSet{
+			name: "newlines",
+			orig: "\n\nfoo\n\n",
+			tgt:  "\n\nfoo",
+		},
+	}
+
+	for idx, ts := range tests {
+		out = TrimSpaceRight(ts.orig)
+		if out == ts.tgt {
+			t.Logf("[%d] OK (%s): %#v: got %#v", idx, ts.name, ts.orig, out)
+		} else {
+			t.Errorf(
+				"[%d] FAIL (%s): %#v (len %d):\n"+
+					"\t\t\texpected (len %d): %#v\n"+
+					"\t\t\tgot      (len %d): %#v\n"+
+					"\t\t%#v",
+				idx, ts.name, ts.orig, len(ts.orig),
+				len(ts.tgt), ts.tgt,
+				len(out), out,
+				ts,
+			)
+		}
+	}
+
+}