v1.14.0

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

go.mod

@@ -1,16 +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
 	go4.org/netipx v0.0.0-20231129151722-fdeea329fbba
-	golang.org/x/sys v0.34.0
-	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

@@ -1,16 +1,15 @@
-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/coreos/go-systemd/v22 v22.6.0 h1:aGVa/v8B7hpb0TKl0MWoAavPDmHvobFe5R5zn0bCJWo=
+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=
 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/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 v0.34.0/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=
+golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
+golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+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.
-func CopyBufWith(dst io.Writer, src io.Reader, bufFunc func() (b []byte)) (written int64, err error) {
+// CopyCtxBufN copies from `src` to `dst`, `n` bytes at a time, interruptible by `ctx`.
+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{}
 )

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.Aligned()
+	i = &InetChecksum{
+		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
-		the persistent underlying storage.
+		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:
 

stringsx/funcs_test.go

@@ -37,113 +37,6 @@ type (
 	}
 )
 
-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