v1.14.0

ADDED:
* iox package
* mapsx package
* netx/inetcksum package

go.mod

@@ -1,15 +1,16 @@
 module r00t2.io/goutils
 
-go 1.24.5
+go 1.25
 
 require (
-	github.com/coreos/go-systemd/v22 v22.5.0
+	github.com/coreos/go-systemd/v22 v22.6.0
 	github.com/google/uuid v1.6.0
-	golang.org/x/sys v0.34.0
+	go4.org/netipx v0.0.0-20231129151722-fdeea329fbba
-	r00t2.io/sysutils v1.14.0
+	golang.org/x/sys v0.39.0
+	r00t2.io/sysutils v1.15.1
 )
 
 require (
 	github.com/djherbis/times v1.6.0 // indirect
-	golang.org/x/sync v0.16.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
 )

go.sum

@@ -1,13 +1,15 @@
-github.com/coreos/go-systemd/v22 v22.5.0 h1:RrqgGjYQKalulkV8NGVIfkXQf6YYmOyiJKk8iXXhfZs=
+github.com/coreos/go-systemd/v22 v22.6.0 h1:aGVa/v8B7hpb0TKl0MWoAavPDmHvobFe5R5zn0bCJWo=
-github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
+github.com/coreos/go-systemd/v22 v22.6.0/go.mod h1:iG+pp635Fo7ZmV/j14KUcmEyWF+0X7Lua8rrTWzYgWU=
 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=
+go4.org/netipx v0.0.0-20231129151722-fdeea329fbba h1:0b9z3AuHCjxk0x/opv64kcgZLBseWJUpBw5I82+2U4M=
-golang.org/x/sync v0.16.0/go.mod h1:1dzgHSNfp02xaA81J2MS99Qcpr2w7fw1gpm99rleRqA=
+go4.org/netipx v0.0.0-20231129151722-fdeea329fbba/go.mod h1:PLyyIXexvUFg3Owu6p/WfdlivPbZJsZdgWZlrGope/Y=
+golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=
+golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
 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 v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
-golang.org/x/sys v0.34.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
+golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
-r00t2.io/sysutils v1.14.0/go.mod h1:ZJ7gZxFVQ7QIokQ5fPZr7wl0XO5Iu+LqtE8j3ciRINw=
+r00t2.io/sysutils v1.15.0 h1:FSnREfbXDhBQEO7LMpnRQeKlPshozxk9XHw3YgWRgRg=
+r00t2.io/sysutils v1.15.0/go.mod h1:28qB0074EIRQ8Sy/ybaA5jC3qA32iW2aYLkMCRhyAFM=

iox/docs.go

@@ -1,4 +1,7 @@
 /*
 Package iox includes extensions to the stdlib `io` module.
+
+Not everything in here is considered fully stabilized yet,
+but it should be usable.
 */
 package iox

iox/errs.go

@@ -6,4 +6,12 @@ import (
 
 var (
 	ErrBufTooSmall      error = errors.New("buffer too small; buffer size must be > 0")
+	ErrChunkTooBig      error = errors.New("chunk too big for method")
+	ErrChunkTooSmall    error = errors.New("chunk too small for buffer")
+	ErrInvalidChunkSize error = errors.New("an invalid chunk size was passed")
+	ErrNilCtx           error = errors.New("a nil context was passed")
+	ErrNilReader        error = errors.New("a nil reader was passed")
+	ErrNilWriter        error = errors.New("a nil writer was passed")
+	ErrShortRead        error = errors.New("a read was cut short with no EOF")
+	ErrShortWrite       error = errors.New("a write was cut short with no error")
 )

iox/funcs.go

@@ -1,20 +1,21 @@
 package iox
 
 import (
+	`context`
 	`io`
 )
 
 /*
-CopyBufN is a mix between io.CopyN and io.CopyBuffer.
+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.
+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.
+There are cases where this is dreadfully undesired.
 
-One can, of course, use io.CopyBuffer, but this is a bit annoying since you then have to provide a buffer yourself.
+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.
+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) {
 
@@ -32,10 +33,215 @@ func CopyBufN(dst io.Writer, src io.Reader, n int64) (written int64, err error)
 	return
 }
 
-// CopyBufWith allows for specifying a buffer allocator function, otherwise acts as CopyBufN.
+// CopyCtxBufN copies from `src` to `dst`, `n` bytes at a time, interruptible by `ctx`.
-func CopyBufWith(dst io.Writer, src io.Reader, bufFunc func() (b []byte)) (written int64, err error) {
+func CopyCtxBufN(ctx context.Context, dst io.Writer, src io.Reader, n int64) (written int64, err error) {
 
-	written, err = io.CopyBuffer(dst, src, bufFunc())
+	var nr int
+	var nw int
+	var end bool
+	var buf []byte
+
+	if ctx == nil {
+		err = ErrNilCtx
+		return
+	}
+	if n <= 0 {
+		err = ErrBufTooSmall
+		return
+	}
+
+endCopy:
+	for {
+		select {
+		case <-ctx.Done():
+			err = ctx.Err()
+			return
+		default:
+			buf = make([]byte, n)
+			nr, err = src.Read(buf)
+			if err == io.EOF {
+				err = nil
+				end = true
+			} else if err != nil {
+				return
+			}
+			buf = buf[:nr]
+
+			if nw, err = dst.Write(buf); err != nil {
+				written += int64(nw)
+				return
+			}
+			written += int64(nw)
+			if len(buf) != nw {
+				err = io.ErrShortWrite
+				return
+			}
+			if end {
+				break endCopy
+			}
+		}
+	}
 
 	return
 }
+
+/*
+CopyBufWith allows for specifying a buffer allocator function, otherwise acts as [CopyBufN].
+
+bufFunc *MUST NOT* return a nil or len == 0 buffer. [ErrBufTooSmall] will be returned if it does.
+
+This uses a fixed buffer size from a single call to `bufFunc`.
+If you need something with dynamic buffer sizing according to some state, use [CopyBufWithDynamic] instead.
+(Note that CopyBufWithDynamic is generally a little slower, but it should only be noticeable on very large amounts of data.)
+*/
+func CopyBufWith(dst io.Writer, src io.Reader, bufFunc func() (b []byte)) (written int64, err error) {
+
+	var buf []byte = bufFunc()
+
+	if buf == nil || len(buf) == 0 {
+		err = ErrBufTooSmall
+		return
+	}
+
+	written, err = io.CopyBuffer(dst, src, buf)
+
+	return
+}
+
+/*
+CopyBufWithDynamic is like [CopyBufWith] except it will call bufFunc after each previous buffer is written.
+
+That is to say (using a particularly contrived example):
+
+	import time
+
+	func dynBuf() (b []byte) {
+
+		var t time.Time = time.Now()
+
+		b = make([]byte, t.Seconds())
+
+		return
+	}
+
+Then:
+
+	CopyBufWithDynamic(w, r, dynBuf)
+
+will use a buffer sized to the seconds of the time it reads in/writes out the next buffer, whereas with [CopyBufWith]:
+
+	CopyBufWith(w, r, dynBuf)
+
+would use a *fixed* buffer size of whatever the seconds was equal to at the time of the *first call* to dynBuf.
+
+`src` MUST return an [io.EOF] when its end is reached, but (as per e.g. [io.CopyBuffer]) the io.EOF error will not
+be returned from CopyBufWithDynamic. (Any/all other errors encountered will be returned, however, and copying will
+immediately cease.)
+*/
+func CopyBufWithDynamic(dst io.Writer, src io.Reader, bufFunc func() (b []byte)) (written int64, err error) {
+
+	var nr int
+	var nw int
+	var end bool
+	var buf []byte
+
+	for {
+		buf = bufFunc()
+		if buf == nil || len(buf) == 0 {
+			err = ErrBufTooSmall
+			return
+		}
+		nr, err = src.Read(buf)
+		if err == io.EOF {
+			err = nil
+			end = true
+		} else if err != nil {
+			return
+		}
+		buf = buf[:nr]
+
+		if nw, err = dst.Write(buf); err != nil {
+			written += int64(nw)
+			return
+		}
+		written += int64(nw)
+		if len(buf) != nw {
+			err = ErrShortWrite
+			return
+		}
+		if end {
+			break
+		}
+	}
+
+	return
+}
+
+// NewChunker returns a [ChunkLocker] ready to use.
+func NewChunker(chunkSize uint) (c *ChunkLocker, err error) {
+
+	c = &ChunkLocker{}
+	err = c.SetChunkLen(chunkSize)
+
+	return
+}
+
+// NewCtxIO returns a [CtxIO].
+func NewCtxIO(ctx context.Context, r io.Reader, w io.Writer, chunkSize uint) (c *CtxIO, err error) {
+
+	if r == nil {
+		err = ErrNilReader
+		return
+	}
+	if w == nil {
+		err = ErrNilWriter
+		return
+	}
+
+	if chunkSize == 0 {
+		err = ErrInvalidChunkSize
+		return
+	}
+
+	if ctx == nil {
+		err = ErrNilCtx
+		return
+	}
+
+	c = &CtxIO{
+		r: r,
+		w: w,
+		l: ChunkLocker{
+			chunkLen: chunkSize,
+		},
+		ctx: ctx,
+	}
+
+	return
+}
+
+/*
+	NewXIO returns a nil [XIO].
+
+	A weird "feature" of Golang is that a nil XIO is perfectly fine to use;
+	it's completely stateless and only has pointer receivers that only work with passed in
+	values so `new(XIO)` is completely unnecessary (as is NewXCopier).
+	In other words, this works fine:
+
+		var xc *iox.XIO
+
+		if n, err = xc.Copy(w, r); err != nil {
+			return
+		}
+
+	This function is just to maintain cleaner-looking code if you should so need it,
+	or want an XIO without declaring one:
+
+		if n, err = iox.NewXCopier().Copy(w, r); err != nil {
+			return
+		}
+*/
+func NewXIO() (x *XIO) {
+	// No-op lel
+	return
+}

iox/funcs_chunklocker.go

@@ -0,0 +1,28 @@
+package iox
+
+// GetChunkLen returns the current chunk size/length in bytes.
+func (c *ChunkLocker) GetChunkLen() (size uint) {
+
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+
+	size = c.chunkLen
+
+	return
+}
+
+// SetChunkLen sets the current chunk size/length in bytes.
+func (c *ChunkLocker) SetChunkLen(size uint) (err error) {
+
+	if size == 0 {
+		err = ErrInvalidChunkSize
+		return
+	}
+
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	c.chunkLen = size
+
+	return
+}

iox/funcs_ctxio.go

@@ -0,0 +1,173 @@
+package iox
+
+import (
+	`bytes`
+	`context`
+	`io`
+	`math`
+)
+
+func (c *CtxIO) Copy(dst io.Writer, src io.Reader) (written int64, err error) {
+	if c.l.chunkLen > math.MaxInt64 {
+		err = ErrChunkTooBig
+	}
+	return CopyCtxBufN(c.ctx, dst, src, int64(c.l.chunkLen))
+}
+
+func (c *CtxIO) CopyBufN(dst io.Writer, src io.Reader, n int64) (written int64, err error) {
+	if n <= 0 {
+		err = ErrBufTooSmall
+		return
+	}
+	return CopyCtxBufN(c.ctx, dst, src, n)
+}
+
+func (c *CtxIO) GetChunkLen() (size uint) {
+	return c.l.GetChunkLen()
+}
+
+func (c *CtxIO) Read(p []byte) (n int, err error) {
+
+	var nr int64
+
+	if nr, err = c.ReadWithContext(c.ctx, p); err != nil {
+		if nr > math.MaxInt {
+			n = math.MaxInt
+		} else {
+			n = int(nr)
+		}
+		return
+	}
+
+	if nr > math.MaxInt {
+		n = math.MaxInt
+	} else {
+		n = int(nr)
+	}
+
+	return
+}
+
+func (c *CtxIO) ReadWithContext(ctx context.Context, p []byte) (n int64, err error) {
+
+	var nr int
+	var off int
+	var buf []byte
+
+	if p == nil || len(p) == 0 {
+		return
+	}
+	if c.buf.Len() == 0 {
+		err = io.EOF
+		return
+	}
+
+	if c.l.chunkLen > uint(len(p)) {
+		// Would normally be a single chunk, so one-shot it.
+		nr, err = c.buf.Read(p)
+		n = int64(nr)
+		return
+	}
+
+	// Chunk over it.
+endRead:
+	for {
+		select {
+		case <-ctx.Done():
+			err = ctx.Err()
+			return
+		default:
+			/*
+				off(set) is the index of the *next position* to write to.
+				Therefore the last offset == len(p),
+				therefore:
+
+					* if off == len(p), "done" (return no error, do *not* read from buf)
+					* if off + c.l.chunkLen > len(p), buf should be len(p) - off instead
+			*/
+			if off == len(p) {
+				break endRead
+			}
+			if uint(off)+c.l.chunkLen > uint(len(p)) {
+				buf = make([]byte, len(p)-off)
+			} else {
+				buf = make([]byte, c.l.chunkLen)
+			}
+			nr, err = c.buf.Read(buf)
+			n += int64(nr)
+			if nr > 0 {
+				off += nr
+				copy(p[off:], buf[:nr])
+			}
+			if err == io.EOF {
+				break endRead
+			} else if err != nil {
+				return
+			}
+		}
+	}
+
+	return
+}
+
+func (c *CtxIO) SetChunkLen(size uint) (err error) {
+	return c.l.SetChunkLen(size)
+}
+
+func (c *CtxIO) SetContext(ctx context.Context) (err error) {
+
+	if ctx == nil {
+		err = ErrNilCtx
+		return
+	}
+
+	c.ctx = ctx
+
+	return
+}
+
+func (c *CtxIO) Write(p []byte) (n int, err error) {
+
+	var nw int64
+
+	if c.l.chunkLen > math.MaxInt64 {
+		err = ErrChunkTooBig
+		return
+	}
+	if nw, err = c.WriteNWithContext(c.ctx, p, int64(c.l.chunkLen)); err != nil {
+		if nw > math.MaxInt {
+			n = math.MaxInt
+		} else {
+			n = int(nw)
+		}
+		return
+	}
+
+	if nw > math.MaxInt {
+		n = math.MaxInt
+	} else {
+		n = int(nw)
+	}
+
+	return
+}
+
+func (c *CtxIO) WriteNWithContext(ctx context.Context, p []byte, n int64) (written int64, err error) {
+	return CopyCtxBufN(ctx, &c.buf, bytes.NewReader(p), n)
+}
+
+func (c *CtxIO) WriteRune(r rune) (n int, err error) {
+
+	// We don't even bother listening for the ctx.Done because it's a single rune.
+	n, err = c.buf.WriteRune(r)
+
+	return
+}
+
+func (c *CtxIO) WriteWithContext(ctx context.Context, p []byte) (n int64, err error) {
+	if c.l.chunkLen > math.MaxInt64 {
+		err = ErrChunkTooBig
+		return
+	}
+	return CopyCtxBufN(ctx, &c.buf, bytes.NewReader(p), int64(c.l.chunkLen))
+}

iox/funcs_xio.go

@@ -0,0 +1,40 @@
+package iox
+
+import (
+	`io`
+)
+
+// Copy copies [io.Reader] `src` to [io.Writer] `dst`. It implements [Copier].
+func (x *XIO) Copy(dst io.Writer, src io.Reader) (written int64, err error) {
+	return io.Copy(dst, src)
+}
+
+// CopyBuffer copies [io.Reader] `src` to [io.Writer] `dst` using buffer `buf`. It implements [CopyBufferer].
+func (x *XIO) CopyBuffer(dst io.Writer, src io.Reader, buf []byte) (written int64, err error) {
+	return io.CopyBuffer(dst, src, buf)
+}
+
+// CopyBufWith copies [io.Reader] `src` to [io.Writer] `dst` using buffer returner `bufFunc`. It implements [SizedCopyBufferInvoker].
+func (x *XIO) CopyBufWith(dst io.Writer, src io.Reader, bufFunc func() (b []byte)) (written int64, err error) {
+	return CopyBufWith(dst, src, bufFunc)
+}
+
+// CopyBufWithDynamic copies [io.Reader] `src` to [io.Writer] `dst` using buffer returner `bufFunc` for each chunk. It implements [DynamicSizedCopyBufferInvoker].
+func (x *XIO) CopyBufWithDynamic(dst io.Writer, src io.Reader, bufFunc func() (b []byte)) (written int64, err error) {
+	return CopyBufWithDynamic(dst, src, bufFunc)
+}
+
+/*
+CopyBufN reads buffered bytes from [io.Reader] `src` and copies to [io.Writer] `dst`
+using the synchronous buffer size `n`.
+
+It implements [SizedCopyBufferer].
+*/
+func (x *XIO) CopyBufN(dst io.Writer, src io.Reader, n int64) (written int64, err error) {
+	return CopyBufN(dst, src, n)
+}
+
+// CopyN copies from [io.Reader] `src` to [io.Writer] `w`, `n` bytes at a time. It implements [SizedCopier].
+func (x *XIO) CopyN(dst io.Writer, src io.Reader, n int64) (written int64, err error) {
+	return io.CopyN(dst, src, n)
+}

iox/types.go

@@ -1,8 +1,209 @@
 package iox
 
+import (
+	`bytes`
+	`context`
+	`io`
+	`sync`
+)
+
 type (
-	// RuneWriter matches the behavior of *(bytes.Buffer).WriteRune and *(bufio.Writer).WriteRune
+	/*
+		RuneWriter matches the behavior of [bytes.Buffer.WriteRune] and [bufio.Writer.WriteRune].
+
+		(Note that this package does not have a "RuneReader"; see [io.RuneReader] instead.)
+	*/
 	RuneWriter interface {
 		WriteRune(r rune) (n int, err error)
 	}
+
+	// Copier matches the signature/behavior of [io.Copy]. Implemented by [XIO].
+	Copier interface {
+		Copy(dst io.Writer, src io.Reader) (written int64, err error)
+	}
+
+	// CopyBufferer matches the signature/behavior of [io.CopyBuffer]. Implemented by [XIO].
+	CopyBufferer interface {
+		CopyBuffer(dst io.Writer, src io.Reader, buf []byte) (written int64, err error)
+	}
+
+	// SizedCopier matches the signature/behavior of [io.CopyN]. Implemented by [XIO].
+	SizedCopier interface {
+		CopyN(dst io.Writer, src io.Reader, n int64) (written int64, err error)
+	}
+
+	// SizedCopyBufferer matches the signature/behavior of [CopyBufN]. Implemented by [XIO].
+	SizedCopyBufferer interface {
+		CopyBufN(dst io.Writer, src io.Reader, n int64) (written int64, err error)
+	}
+
+	// SizedCopyBufferInvoker matches the signature/behavior of [CopyBufWith]. Implemented by [XIO].
+	SizedCopyBufferInvoker interface {
+		CopyBufWith(dst io.Writer, src io.Reader, bufFunc func() (b []byte)) (written int64, err error)
+	}
+
+	// DynamicSizedCopyBufferInvoker matches the signature/behavior of [CopyBufWithDynamic]. Implemented by [XIO].
+	DynamicSizedCopyBufferInvoker interface {
+		CopyBufWithDynamic(dst io.Writer, src io.Reader, bufFunc func() (b []byte)) (written int64, err error)
+	}
+
+	/*
+		Chunker is used by both [ContextReader] and [ContextWriter] to set/get the current chunk size.
+		Chunking is inherently required to be specified in order to interrupt reads/writes/copies with a [context.Context].
+
+		Implementations *must* use a [sync.RWMutex] to get (RLock) and set (Lock) the chunk size.
+		The chunk size *must not* be directly accessible to maintain concurrency safety assumptions.
+	*/
+	Chunker interface {
+		// GetChunkLen returns the current chunk size/length in bytes.
+		GetChunkLen() (size uint)
+		// SetChunkLen sets the current chunk size/length in bytes.
+		SetChunkLen(size uint) (err error)
+	}
+
+	/*
+		ChunkReader implements a chunking reader.
+		Third-party implementations *must* respect the chunk size locking (see [Chunker]).
+
+		The Read method should read in chunks of the internal chunk size.
+	*/
+	ChunkReader interface {
+		io.Reader
+		Chunker
+	}
+
+	/*
+		ChunkWriter implements a chunking writer.
+		Third-party implementations *must* respect the chunk size locking (see [Chunker]).
+
+		The Write method should write out in chunks of the internal chunk size.
+	*/
+	ChunkWriter interface {
+		io.Writer
+		Chunker
+	}
+
+	// ChunkReadWriter implements a chunking reader/writer.
+	ChunkReadWriter interface {
+		ChunkReader
+		ChunkWriter
+	}
+
+	/*
+		ContextSetter allows one to set an internal context.
+
+		A nil context should return an error.
+	*/
+	ContextSetter interface {
+		SetContext(context context.Context) (err error)
+	}
+
+	/*
+		ContextCopier is defined to allow for consumer-provided types. See [CtxIO] for a package-provided type.
+
+		The Copy method should use an internal context and chunk size
+		(and thus wrap [CopyCtxBufN] internally on an external call to Copy, etc.).
+	*/
+	ContextCopier interface {
+		Copier
+		Chunker
+		ContextSetter
+		SizedCopyBufferer
+	}
+
+	/*
+		ContextReader is primarily here to allow for consumer-provided types. See [CtxIO] for a package-provided type.
+
+		The Read method should use an internal context and chunk size.
+
+		The ReadWithContext method should use an internal chunk size.
+	*/
+	ContextReader interface {
+		ChunkReader
+		ContextSetter
+		ReadWithContext(ctx context.Context, p []byte) (n int64, err error)
+	}
+
+	/*
+		ContextWriter is primarily here to allow for consumer-provided types. See [CtxIO] for a package-provided type.
+
+		The Write method should use an internal context.
+
+		The WriteWithContext should use an internal chunk size.
+	*/
+	ContextWriter interface {
+		ChunkWriter
+		ContextSetter
+		WriteWithContext(ctx context.Context, p []byte) (n int64, err error)
+		WriteNWithContext(ctx context.Context, p []byte, n int64) (written int64, err error)
+	}
+
+	/*
+		ContextReadWriter is primarily here to allow for consumer-provided types.
+
+		See [CtxIO] for a package-provided type.
+	*/
+	ContextReadWriter interface {
+		ContextReader
+		ContextWriter
+	}
+)
+
+type (
+	// ChunkLocker implements [Chunker].
+	ChunkLocker struct {
+		lock     sync.RWMutex
+		chunkLen uint
+	}
+
+	/*
+		CtxIO is a type used to demonstrate "stateful" I/O introduced by this package.
+		It implements:
+
+			* [Copier]
+			* [Chunker]
+			* [RuneWriter]
+			* [ChunkReader]
+			* [ChunkWriter]
+			* [ContextCopier]
+			* [ContextSetter]
+			* [ContextReader]
+			* [ContextWriter]
+			* [ChunkReadWriter]
+			* [ContextReadWriter]
+			* [SizedCopyBufferer]
+
+		Unlike [XIO], it must be non-nil (see [NewCtxIO]) since it maintains state
+		(though technically, one does not need to call [NewCtxIO] if they call
+		[CtxIO.SetChunkLen] and [CtxIO.SetContext] before any other methods).
+
+		[CtxIO.Read] and other Read methods writes to an internal buffer,
+		and [CtxIO.Write] and other Write methods writes out from it.
+	*/
+	CtxIO struct {
+		r   io.Reader
+		w   io.Writer
+		l   ChunkLocker
+		buf bytes.Buffer
+		ctx context.Context
+	}
+
+	/*
+		XIO is a type used to demonstrate "stateless" I/O introduced by this package.
+		It implements:
+
+			* [Copier]
+			* [CopyBufferer]
+			* [SizedCopier]
+			* [SizedCopyBufferer]
+			* [SizedCopyBufferInvoker]
+			* [DynamicSizedCopyBufferInvoker]
+
+		Unlike [CtxIO], the zero-value is ready to use since it holds no state
+		or configuration whatsoever.
+
+		A nil XIO is perfectly usable but if you want something more idiomatic,
+		see [NewXIO].
+	*/
+	XIO struct{}
 )

logging/TODO

@@ -1,3 +1,5 @@
+- logging probably needs mutexes
+
 - 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

logging/funcs_multilogger_mgr_windows.go

@@ -21,7 +21,7 @@ import (
 	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) {
+func (m *MultiLogger) AddDefaultLogger(identifier string, logFlags int, logPaths ...string) (err error) {
 
 	var l Logger
 	var exists bool
@@ -36,9 +36,9 @@ func (m *MultiLogger) AddDefaultLogger(identifier string, eventIDs *WinEventID,
 	}
 
 	if logPaths != nil {
-		l, err = GetLogger(m.EnableDebug, m.Prefix, eventIDs, logFlags, logPaths...)
+		l, err = GetLogger(m.EnableDebug, m.Prefix, logFlags, logPaths...)
 	} else {
-		l, err = GetLogger(m.EnableDebug, m.Prefix, eventIDs, logFlags)
+		l, err = GetLogger(m.EnableDebug, m.Prefix, logFlags)
 	}
 	if err != nil {
 		return

logging/funcs_windows.go

@@ -10,32 +10,63 @@ import (
 )
 
 /*
-	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.
+	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 to conform with multiplatform compat.
+	You'd have a little more flexibility with [GetLoggerWindows] (this function wraps that one).
+	If you need more custom behavior than that, I recommend using [golang.org/x/sys/windows/svc/eventlog] directly
+	(or using another logging module).
+
+	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).
+
+	The `prefix` correlates to the `source` parameter in [GetLoggerWindows], and this function inherently uses [DefaultEventID],
+	but otherwise it remains the same as [GetLoggerWindows] - refer to it for documentation on the other parameters.
+
+	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) {
+
+	if logger, err = GetLoggerWindows(enableDebug, prefix, DefaultEventID, logConfigFlags, logPaths...); err != nil {
+		return
+	}
+
+	return
+}
+
+/*
+	GetLoggerWindows returns an instance of Logger that best suits your system's capabilities.
+	This is a slightly less (but still quite) generalized interface to the Windows Event Log than [GetLogger].
 
 	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).
+	you will want to set up your own logger via [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).
+	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 blank `source` will return an error as it's used as the source name.
+	Throughout the rest of this documentation you will see this referred to as the `prefix` to remain platform-agnostic.
 
-	A pointer to a WinEventID struct may be specified for eventIDs to map extended logging levels (as Windows only supports three levels natively).
+	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
+	`logConfigFlags` is the corresponding flag(s) OR'd for [StdLogger.LogFlags] (and/or the [StdLogger.LogFlags] for [FileLogger])
-	https://pkg.go.dev/log#pkg-constants for details.
+	if either is selected. See [StdLogger.LogFlags] and [stdlib log's 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,
+	`logPaths` is an (optional) list of strings to use as paths to test for writing.
-	it will be used (assuming you have no higher-level loggers available).
+	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.
+	Only the first `logPaths` entry that "works" will be used, later entries will be ignored.
-	Currently this will almost always return a WinLogger.
+	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 call [GetLoggerWindows], 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),
+	If you want to log to multiple [Logger] destinations at once (or want to log to an explicit [Logger] type),
-	use GetMultiLogger.
+	use [GetMultiLogger].
+
+	[stdlib log's constants]: https://pkg.go.dev/log#pkg-constants
 */
-func GetLogger(enableDebug bool, source string, eventIDs *WinEventID, logConfigFlags int, logPaths ...string) (logger Logger, err error) {
+func GetLoggerWindows(enableDebug bool, source string, eventIDs *WinEventID, logConfigFlags int, logPaths ...string) (logger Logger, err error) {
 
 	var logPath string
 	var logFlags bitmask.MaskBit

logging/funcs_windows_test.go

@@ -124,7 +124,7 @@ func TestDefaultLogger(t *testing.T) {
 		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 {
+	if l, err = GetLoggerWindows(true, TestLogPrefix, DefaultEventID, logFlags, tempfilePath); err != nil {
 		t.Fatalf("error when spawning default Windows logger via GetLogger: %v", err.Error())
 	}
 

logging/multilogger_windows_test.go

@@ -35,7 +35,7 @@ func TestMultiLogger(t *testing.T) {
 		t.Fatalf("error when adding FileLogger to MultiLogger: %v", err.Error())
 	}
 
-	if err = l.AddDefaultLogger("DefaultLogger", DefaultEventID, logFlags, tempfilePath); err != nil {
+	if err = l.AddDefaultLogger("DefaultLogger", logFlags, tempfilePath); err != nil {
 		t.Fatalf("error when adding default logger to MultiLogger: %v", err.Error())
 	}
 

mapsx/doc.go

@@ -0,0 +1,4 @@
+/*
+Package mapsx includes functions that probably should have been in [maps] but aren't.
+*/
+package mapsx

mapsx/errs.go

@@ -0,0 +1,9 @@
+package mapsx
+
+import (
+	`errors`
+)
+
+var (
+	ErrNotFound = errors.New("key not found")
+)

mapsx/funcs.go

@@ -0,0 +1,43 @@
+package mapsx
+
+/*
+Get mimics Python's [dict.get()] behavior, returning value `v` if key `k`
+is not found in map `m`.
+
+See also [GetOk], [Must].
+
+[dict.get()]: https://docs.python.org/3/library/stdtypes.html#dict.get
+*/
+func Get[Map ~map[K]V, K comparable, V any](m Map, k K, v V) (val V) {
+
+	val, _ = GetOk(m, k, v)
+
+	return
+}
+
+// GetOk is like [Get] but also explicitly indicates whether `k` was found or not. See also [Must].
+func GetOk[Map ~map[K]V, K comparable, V any](m Map, k K, v V) (val V, found bool) {
+
+	if val, found = m[k]; !found {
+		val = v
+	}
+
+	return
+}
+
+/*
+	Must, unlike [Get] or [GetOk], requires that `k` be in map `m`.
+
+	A panic with error [ErrNotFound] will be raised if `k` is not present.
+	Otherwise the found value will be returned.
+*/
+func Must[Map ~map[K]V, K comparable, V any](m Map, k K) (val V) {
+
+	var ok bool
+
+	if val, ok = m[k]; !ok {
+		panic(ErrNotFound)
+	}
+
+	return
+}

netx/inetcksum/consts.go

@@ -10,11 +10,20 @@ const (
 )
 
 const (
-	// cksumMask is AND'd with a checksum to get the "carried ones".
+	/*
+		cksumMask is AND'd with a checksum to get the "carried ones"
+		(the lower 16 bits before folding carries).
+	*/
 	cksumMask uint32 = 0x0000ffff
-	// cksumShift is used in the "carried-ones folding".
+	/*
+		cksumShift is used in the "carried-ones folding";
+		it's the number of bits to right-shift the carry-over.
+	*/
 	cksumShift uint32 = 0x00000010
-	// padShift is used to "pad out" a checksum for odd-length buffers by left-shifting.
+	/*
+		padShift is used to "pad out" a checksum for odd-length buffers by left-shifting.
+		It positions the high-byte of a 16-byte "word" (big-endian, as per ord below).
+	*/
 	padShift uint32 = 0x00000008
 )
 

netx/inetcksum/docs.go

@@ -25,6 +25,9 @@ safety and no data retention, which can be used as a:
 	* [io.StringWriter]
 	* [io.Writer]
 
+If you don't need all these interfaces, a reasonable alternative may be
+to use gVisor's [gvisor.dev/gvisor/pkg/tcpip/checksum] instead.
+
 [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

netx/inetcksum/funcs.go

@@ -7,8 +7,9 @@ import (
 // New returns a new initialized [InetChecksum]. It will never panic.
 func New() (i *InetChecksum) {
 
-	i = &InetChecksum{}
+	i = &InetChecksum{
-	_ = i.Aligned()
+		aligned: true,
+	}
 
 	return
 }
@@ -21,15 +22,14 @@ 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
+	var cptr *InetChecksum = &cksum
+
+	cksum.aligned = true
 
 	if b != nil && len(b) > 0 {
-		if copied, err = cksum.Write(b); err != nil {
+		if copied, err = cptr.Write(b); err != nil {
 			return
 		}
-		_ = i.Aligned()
-	} else {
-		i = New()
-		return
 	}
 
 	i = &cksum
@@ -48,7 +48,64 @@ func NewFromBuf(buf io.Reader) (i *InetChecksum, copied int64, err error) {
 
 	var cksum InetChecksum
 
-	_ = i.Aligned()
+	cksum.aligned = true
+
+	if buf != nil {
+		if copied, err = io.Copy(&cksum, buf); err != nil {
+			return
+		}
+	}
+
+	i = &cksum
+
+	return
+}
+
+// NewSimple returns a new initialized [InetChecksumSimple]. It will never panic.
+func NewSimple() (i *InetChecksumSimple) {
+
+	i = &InetChecksumSimple{
+		aligned: true,
+	}
+
+	return
+}
+
+/*
+	NewSimpleFromBytes returns a new [InetChecksumSimple] initialized with explicit bytes.
+
+	b may be nil or 0-length; this will not cause an error.
+*/
+func NewSimpleFromBytes(b []byte) (i *InetChecksumSimple, copied int, err error) {
+
+	var cksum InetChecksumSimple
+	var cptr *InetChecksumSimple = &cksum
+
+	cksum.aligned = true
+
+	if b != nil && len(b) > 0 {
+		if copied, err = cptr.Write(b); err != nil {
+			return
+		}
+	}
+
+	i = &cksum
+
+	return
+}
+
+/*
+	NewSimpleFromBuf returns an [InetChecksumSimple] from a specified [io.Reader].
+
+	buf may be nil. If it isn't, NewSimpleFromBuf 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 NewSimpleFromBuf(buf io.Reader) (i *InetChecksumSimple, copied int64, err error) {
+
+	var cksum InetChecksumSimple
+
+	cksum.aligned = true
 
 	if buf != nil {
 		if copied, err = io.Copy(&cksum, buf); err != nil {

netx/inetcksum/funcs_inetchecksum.go

@@ -22,7 +22,7 @@ func (i *InetChecksum) Aligned() (aligned bool) {
 	defer i.alignLock.Unlock()
 
 	i.bufLock.RLock()
-	aligned = i.buf.Len()&2 == 0
+	aligned = i.buf.Len()%2 == 0
 	i.bufLock.RUnlock()
 
 	i.aligned = aligned
@@ -113,7 +113,7 @@ func (i *InetChecksum) Reset() {
 	i.sumLock.Lock()
 	i.lastLock.Lock()
 
-	i.aligned = false
+	i.aligned = true
 	i.alignLock.Unlock()
 
 	i.buf.Reset()
@@ -308,7 +308,7 @@ func (i *InetChecksum) WriteByte(c byte) (err error) {
 	}
 
 	if !i.disabledBuf {
-		if err = i.WriteByte(c); err != nil {
+		if err = i.buf.WriteByte(c); err != nil {
 			i.sum = origSum
 			i.aligned = origAligned
 			i.last = origLast

netx/inetcksum/funcs_inetchecksumsimple.go

@@ -27,7 +27,7 @@ func (i *InetChecksumSimple) Reset() {
 
 	i.last = 0x00
 	i.sum = 0
-	i.last = 0x00
+	i.aligned = true
 
 }
 

netx/inetcksum/types.go

@@ -17,8 +17,8 @@ type (
 		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
+		applied *at the time of the Sum/Sum32 call* and is NOT applied to
-		the persistent underlying storage.
+		the persistent underlying storage).
 
 		InetChecksum differs from [InetChecksumSimple] in that it:
 

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 +1,6 @@
+package stringsx
+
+const (
+	// DefMaskStr is the string used as the default maskStr if left empty in [Redact].
+	DefMaskStr string = "***"
+)

stringsx/doc.go

@@ -0,0 +1,17 @@
+/*
+Package stringsx aims to extend functionality of the stdlib [strings] module.
+
+Note that if you need a way of mimicking Bash's shell quoting rules, [desertbit/shlex] or [buildkite/shellwords]
+would be better options than [google/shlex] but this package does not attempt to reproduce
+any of that functionality.
+
+For line splitting, one should use [muesli/reflow/wordwrap].
+Likewise for indentation, one should use [muesli/reflow/indent].
+
+[desertbit/shlex]: https://pkg.go.dev/github.com/desertbit/go-shlex
+[buildkite/shellwords]: https://pkg.go.dev/github.com/buildkite/shellwords
+[google/shlex]: https://pkg.go.dev/github.com/google/shlex
+[muesli/reflow/wordwrap]: https://pkg.go.dev/github.com/muesli/reflow/wordwrap
+[muesli/reflow/indent]: https://pkg.go.dev/github.com/muesli/reflow/indent
+*/
+package stringsx

stringsx/funcs.go

@@ -0,0 +1,326 @@
+package stringsx
+
+import (
+	`fmt`
+	`strings`
+	`unicode`
+)
+
+/*
+LenSplit formats string `s` to break at, at most, every `width` characters.
+
+Any existing newlines (e.g. \r\n) will be removed during a string/
+substring/line's length calculation. (e.g. `foobarbaz\n` and `foobarbaz\r\n` are
+both considered to be lines of length 9, not 10 and 11 respectively).
+
+This also means that any newlines (\n or \r\n) are inherently removed from
+`out` (even if included in `wordWrap`; see below).
+
+Note that if `s` is multiline (already contains newlines), they will be respected
+as-is - that is, if a line ends with less than `width` chars and then has a newline,
+it will be preserved as an empty element. That is to say:
+
+	"foo\nbar\n\n" → []string{"foo", "bar", ""}
+	"foo\n\nbar\n" → []string{"foo", "", "bar"}
+
+This splitter is particularly simple. If you need wordwrapping, it should be done
+with e.g. [github.com/muesli/reflow/wordwrap].
+*/
+func LenSplit(s string, width uint) (out []string) {
+
+	var end int
+	var line string
+	var lineRunes []rune
+
+	if width == 0 {
+		out = []string{s}
+		return
+	}
+
+	for line = range strings.Lines(s) {
+		line = strings.TrimRight(line, "\n")
+		line = strings.TrimRight(line, "\r")
+
+		lineRunes = []rune(line)
+
+		if uint(len(lineRunes)) <= width {
+			out = append(out, line)
+			continue
+		}
+
+		for i := 0; i < len(lineRunes); i += int(width) {
+			end = i + int(width)
+			if end > len(lineRunes) {
+				end = len(lineRunes)
+			}
+			out = append(out, string(lineRunes[i:end]))
+		}
+	}
+
+	return
+}
+
+/*
+LenSplitStr wraps [LenSplit] but recombines into a new string with newlines.
+
+It's mostly just a convenience wrapper.
+
+All arguments remain the same as in [LenSplit] with an additional one,
+`winNewLine`, which if true will use \r\n as the newline instead of \n.
+*/
+func LenSplitStr(s string, width uint, winNewline bool) (out string) {
+
+	var outSl []string = LenSplit(s, width)
+
+	if winNewline {
+		out = strings.Join(outSl, "\r\n")
+	} else {
+		out = strings.Join(outSl, "\n")
+	}
+
+	return
+}
+
+/*
+Pad pads each element in `s` to length `width` using `pad`.
+If `pad` is empty, a single space (0x20) will be assumed.
+Note that `width` operates on rune size, not byte size.
+(In ASCII, they will be the same size.)
+
+If a line in `s` is greater than or equal to `width`,
+no padding will be performed.
+
+If `leftPad` is true, padding will be applied to the "left" (beginning")
+of each element instead of the "right" ("end").
+*/
+func Pad(s []string, width uint, pad string, leftPad bool) (out []string) {
+
+	var idx int
+	var padIdx int
+	var runeIdx int
+	var padLen uint
+	var elem string
+	var unpadLen uint
+	var tmpPadLen int
+	var padRunes []rune
+	var tmpPad []rune
+
+	if width == 0 {
+		out = s
+		return
+	}
+
+	out = make([]string, len(s))
+
+	// Easy; supported directly in fmt.
+	if pad == "" {
+		for idx, elem = range s {
+			if leftPad {
+				out[idx] = fmt.Sprintf("%*s", width, elem)
+			} else {
+				out[idx] = fmt.Sprintf("%-*s", width, elem)
+			}
+		}
+		return
+	}
+
+	// This gets a little more tricky.
+	padRunes = []rune(pad)
+	padLen = uint(len(padRunes))
+	for idx, elem = range s {
+		// First we need to know the number of runes in elem.
+		unpadLen = uint(len([]rune(elem)))
+		// If it's more than/equal to width, as-is.
+		if unpadLen >= width {
+			out[idx] = elem
+		} else {
+			// Otherwise, we need to construct/calculate a pad.
+			if (width-unpadLen)%padLen == 0 {
+				// Also easy enough.
+				if leftPad {
+					out[idx] = fmt.Sprintf("%s%s", strings.Repeat(pad, int((width-unpadLen)/padLen)), elem)
+				} else {
+					out[idx] = fmt.Sprintf("%s%s", elem, strings.Repeat(pad, int((width-unpadLen)/padLen)))
+				}
+			} else {
+				// This is where it gets a little hairy.
+				tmpPad = []rune{}
+				tmpPadLen = int(width - unpadLen)
+				idx = 0
+				padIdx = 0
+				for runeIdx = range tmpPadLen {
+					tmpPad[runeIdx] = padRunes[padIdx]
+					if uint(padIdx) >= padLen {
+						padIdx = 0
+					} else {
+						padIdx++
+					}
+					runeIdx++
+				}
+				if leftPad {
+					out[idx] = fmt.Sprintf("%s%s", string(tmpPad), elem)
+				} else {
+					out[idx] = fmt.Sprintf("%s%s", elem, string(tmpPad))
+				}
+			}
+		}
+	}
+
+	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.
+
+Note that this DOES NOT do a string *replace*, it provides a masked version of `s` itself.
+Wrap Redact with [strings.ReplaceAll] if you want to replace a certain value with a masked one.
+*/
+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/nuanced to be used as part of a public API promise 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 +1,344 @@
+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 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,
+			)
+		}
+	}
+
+}