1 files changed, 445 insertions, 0 deletions
diff --git a/vendor/github.com/philhofer/fwd/reader.go b/vendor/github.com/philhofer/fwd/reader.go
new file mode 100644
index 000000000..a24a896e2
--- /dev/null
+++ b/vendor/github.com/philhofer/fwd/reader.go
@@ -0,0 +1,445 @@
+// Package fwd provides a buffered reader
+// and writer. Each has methods that help improve
+// the encoding/decoding performance of some binary
+// protocols.
+//
+// The [Writer] and [Reader] type provide similar
+// functionality to their counterparts in [bufio], plus
+// a few extra utility methods that simplify read-ahead
+// and write-ahead. I wrote this package to improve serialization
+// performance for http://github.com/tinylib/msgp,
+// where it provided about a 2x speedup over `bufio` for certain
+// workloads. However, care must be taken to understand the semantics of the
+// extra methods provided by this package, as they allow
+// the user to access and manipulate the buffer memory
+// directly.
+//
+// The extra methods for [Reader] are [Reader.Peek], [Reader.Skip]
+// and [Reader.Next]. (*fwd.Reader).Peek, unlike (*bufio.Reader).Peek,
+// will re-allocate the read buffer in order to accommodate arbitrarily
+// large read-ahead. (*fwd.Reader).Skip skips the next 'n' bytes
+// in the stream, and uses the [io.Seeker] interface if the underlying
+// stream implements it. (*fwd.Reader).Next returns a slice pointing
+// to the next 'n' bytes in the read buffer (like Reader.Peek), but also
+// increments the read position. This allows users to process streams
+// in arbitrary block sizes without having to manage appropriately-sized
+// slices. Additionally, obviating the need to copy the data from the
+// buffer to another location in memory can improve performance dramatically
+// in CPU-bound applications.
+//
+// [Writer] only has one extra method, which is (*fwd.Writer).Next, which
+// returns a slice pointing to the next 'n' bytes of the writer, and increments
+// the write position by the length of the returned slice. This allows users
+// to write directly to the end of the buffer.
+package fwd
+
+import (
+	"io"
+	"os"
+)
+
+const (
+	// DefaultReaderSize is the default size of the read buffer
+	DefaultReaderSize = 2048
+
+	// minimum read buffer; straight from bufio
+	minReaderSize = 16
+)
+
+// NewReader returns a new *Reader that reads from 'r'
+func NewReader(r io.Reader) *Reader {
+	return NewReaderSize(r, DefaultReaderSize)
+}
+
+// NewReaderSize returns a new *Reader that
+// reads from 'r' and has a buffer size 'n'.
+func NewReaderSize(r io.Reader, n int) *Reader {
+	buf := make([]byte, 0, max(n, minReaderSize))
+	return NewReaderBuf(r, buf)
+}
+
+// NewReaderBuf returns a new *Reader that
+// reads from 'r' and uses 'buf' as a buffer.
+// 'buf' is not used when has smaller capacity than 16,
+// custom buffer is allocated instead.
+func NewReaderBuf(r io.Reader, buf []byte) *Reader {
+	if cap(buf) < minReaderSize {
+		buf = make([]byte, 0, minReaderSize)
+	}
+	buf = buf[:0]
+	rd := &Reader{
+		r:    r,
+		data: buf,
+	}
+	if s, ok := r.(io.Seeker); ok {
+		rd.rs = s
+	}
+	return rd
+}
+
+// Reader is a buffered look-ahead reader
+type Reader struct {
+	r io.Reader // underlying reader
+
+	// data[n:len(data)] is buffered data; data[len(data):cap(data)] is free buffer space
+	data        []byte // data
+	n           int    // read offset
+	inputOffset int64  // offset in the input stream
+	state       error  // last read error
+
+	// if the reader past to NewReader was
+	// also an io.Seeker, this is non-nil
+	rs io.Seeker
+}
+
+// Reset resets the underlying reader
+// and the read buffer.
+func (r *Reader) Reset(rd io.Reader) {
+	r.r = rd
+	r.data = r.data[0:0]
+	r.n = 0
+	r.inputOffset = 0
+	r.state = nil
+	if s, ok := rd.(io.Seeker); ok {
+		r.rs = s
+	} else {
+		r.rs = nil
+	}
+}
+
+// more() does one read on the underlying reader
+func (r *Reader) more() {
+	// move data backwards so that
+	// the read offset is 0; this way
+	// we can supply the maximum number of
+	// bytes to the reader
+	if r.n != 0 {
+		if r.n < len(r.data) {
+			r.data = r.data[:copy(r.data[0:], r.data[r.n:])]
+		} else {
+			r.data = r.data[:0]
+		}
+		r.n = 0
+	}
+	var a int
+	a, r.state = r.r.Read(r.data[len(r.data):cap(r.data)])
+	if a == 0 && r.state == nil {
+		r.state = io.ErrNoProgress
+		return
+	} else if a > 0 && r.state == io.EOF {
+		// discard the io.EOF if we read more than 0 bytes.
+		// the next call to Read should return io.EOF again.
+		r.state = nil
+	} else if r.state != nil {
+		return
+	}
+	r.data = r.data[:len(r.data)+a]
+}
+
+// pop error
+func (r *Reader) err() (e error) {
+	e, r.state = r.state, nil
+	return
+}
+
+// pop error; EOF -> io.ErrUnexpectedEOF
+func (r *Reader) noEOF() (e error) {
+	e, r.state = r.state, nil
+	if e == io.EOF {
+		e = io.ErrUnexpectedEOF
+	}
+	return
+}
+
+// buffered bytes
+func (r *Reader) buffered() int { return len(r.data) - r.n }
+
+// Buffered returns the number of bytes currently in the buffer
+func (r *Reader) Buffered() int { return len(r.data) - r.n }
+
+// BufferSize returns the total size of the buffer
+func (r *Reader) BufferSize() int { return cap(r.data) }
+
+// InputOffset returns the input stream byte offset of the current reader position
+func (r *Reader) InputOffset() int64 { return r.inputOffset }
+
+// Peek returns the next 'n' buffered bytes,
+// reading from the underlying reader if necessary.
+// It will only return a slice shorter than 'n' bytes
+// if it also returns an error. Peek does not advance
+// the reader. EOF errors are *not* returned as
+// io.ErrUnexpectedEOF.
+func (r *Reader) Peek(n int) ([]byte, error) {
+	// in the degenerate case,
+	// we may need to realloc
+	// (the caller asked for more
+	// bytes than the size of the buffer)
+	if cap(r.data) < n {
+		old := r.data[r.n:]
+		r.data = make([]byte, n+r.buffered())
+		r.data = r.data[:copy(r.data, old)]
+		r.n = 0
+	}
+
+	// keep filling until
+	// we hit an error or
+	// read enough bytes
+	for r.buffered() < n && r.state == nil {
+		r.more()
+	}
+
+	// we must have hit an error
+	if r.buffered() < n {
+		return r.data[r.n:], r.err()
+	}
+
+	return r.data[r.n : r.n+n], nil
+}
+
+func (r *Reader) PeekByte() (b byte, err error) {
+	if len(r.data)-r.n >= 1 {
+		b = r.data[r.n]
+	} else {
+		b, err = r.peekByte()
+	}
+	return
+}
+
+func (r *Reader) peekByte() (byte, error) {
+	const n = 1
+	if cap(r.data) < n {
+		old := r.data[r.n:]
+		r.data = make([]byte, n+r.buffered())
+		r.data = r.data[:copy(r.data, old)]
+		r.n = 0
+	}
+
+	// keep filling until
+	// we hit an error or
+	// read enough bytes
+	for r.buffered() < n && r.state == nil {
+		r.more()
+	}
+
+	// we must have hit an error
+	if r.buffered() < n {
+		return 0, r.err()
+	}
+	return r.data[r.n], nil
+}
+
+// discard(n) discards up to 'n' buffered bytes, and
+// and returns the number of bytes discarded
+func (r *Reader) discard(n int) int {
+	inbuf := r.buffered()
+	if inbuf <= n {
+		r.n = 0
+		r.inputOffset += int64(inbuf)
+		r.data = r.data[:0]
+		return inbuf
+	}
+	r.n += n
+	r.inputOffset += int64(n)
+	return n
+}
+
+// Skip moves the reader forward 'n' bytes.
+// Returns the number of bytes skipped and any
+// errors encountered. It is analogous to Seek(n, 1).
+// If the underlying reader implements io.Seeker, then
+// that method will be used to skip forward.
+//
+// If the reader encounters
+// an EOF before skipping 'n' bytes, it
+// returns [io.ErrUnexpectedEOF]. If the
+// underlying reader implements [io.Seeker], then
+// those rules apply instead. (Many implementations
+// will not return [io.EOF] until the next call
+// to Read).
+func (r *Reader) Skip(n int) (int, error) {
+	if n < 0 {
+		return 0, os.ErrInvalid
+	}
+
+	// discard some or all of the current buffer
+	skipped := r.discard(n)
+
+	// if we can Seek() through the remaining bytes, do that
+	if n > skipped && r.rs != nil {
+		nn, err := r.rs.Seek(int64(n-skipped), 1)
+		r.inputOffset += nn
+		return int(nn) + skipped, err
+	}
+	// otherwise, keep filling the buffer
+	// and discarding it up to 'n'
+	for skipped < n && r.state == nil {
+		r.more()
+		skipped += r.discard(n - skipped)
+	}
+	return skipped, r.noEOF()
+}
+
+// Next returns the next 'n' bytes in the stream.
+// Unlike Peek, Next advances the reader position.
+// The returned bytes point to the same
+// data as the buffer, so the slice is
+// only valid until the next reader method call.
+// An EOF is considered an unexpected error.
+// If an the returned slice is less than the
+// length asked for, an error will be returned,
+// and the reader position will not be incremented.
+func (r *Reader) Next(n int) (b []byte, err error) {
+	if r.state == nil && len(r.data)-r.n >= n {
+		b = r.data[r.n : r.n+n]
+		r.n += n
+		r.inputOffset += int64(n)
+	} else {
+		b, err = r.next(n)
+	}
+	return
+}
+
+func (r *Reader) next(n int) ([]byte, error) {
+	// in case the buffer is too small
+	if cap(r.data) < n {
+		old := r.data[r.n:]
+		r.data = make([]byte, n+r.buffered())
+		r.data = r.data[:copy(r.data, old)]
+		r.n = 0
+	}
+
+	// fill at least 'n' bytes
+	for r.buffered() < n && r.state == nil {
+		r.more()
+	}
+
+	if r.buffered() < n {
+		return r.data[r.n:], r.noEOF()
+	}
+	out := r.data[r.n : r.n+n]
+	r.n += n
+	r.inputOffset += int64(n)
+	return out, nil
+}
+
+// Read implements [io.Reader].
+func (r *Reader) Read(b []byte) (int, error) {
+	// if we have data in the buffer, just
+	// return that.
+	if r.buffered() != 0 {
+		x := copy(b, r.data[r.n:])
+		r.n += x
+		r.inputOffset += int64(x)
+		return x, nil
+	}
+	var n int
+	// we have no buffered data; determine
+	// whether or not to buffer or call
+	// the underlying reader directly
+	if len(b) >= cap(r.data) {
+		n, r.state = r.r.Read(b)
+	} else {
+		r.more()
+		n = copy(b, r.data)
+		r.n = n
+	}
+	if n == 0 {
+		return 0, r.err()
+	}
+
+	r.inputOffset += int64(n)
+
+	return n, nil
+}
+
+// ReadFull attempts to read len(b) bytes into
+// 'b'. It returns the number of bytes read into
+// 'b', and an error if it does not return len(b).
+// EOF is considered an unexpected error.
+func (r *Reader) ReadFull(b []byte) (int, error) {
+	var n int  // read into b
+	var nn int // scratch
+	l := len(b)
+	// either read buffered data,
+	// or read directly for the underlying
+	// buffer, or fetch more buffered data.
+	for n < l && r.state == nil {
+		if r.buffered() != 0 {
+			nn = copy(b[n:], r.data[r.n:])
+			n += nn
+			r.n += nn
+			r.inputOffset += int64(nn)
+		} else if l-n > cap(r.data) {
+			nn, r.state = r.r.Read(b[n:])
+			n += nn
+			r.inputOffset += int64(nn)
+		} else {
+			r.more()
+		}
+	}
+	if n < l {
+		return n, r.noEOF()
+	}
+	return n, nil
+}
+
+// ReadByte implements [io.ByteReader].
+func (r *Reader) ReadByte() (byte, error) {
+	for r.buffered() < 1 && r.state == nil {
+		r.more()
+	}
+	if r.buffered() < 1 {
+		return 0, r.err()
+	}
+	b := r.data[r.n]
+	r.n++
+	r.inputOffset++
+
+	return b, nil
+}
+
+// WriteTo implements [io.WriterTo].
+func (r *Reader) WriteTo(w io.Writer) (int64, error) {
+	var (
+		i   int64
+		ii  int
+		err error
+	)
+	// first, clear buffer
+	if r.buffered() > 0 {
+		ii, err = w.Write(r.data[r.n:])
+		i += int64(ii)
+		if err != nil {
+			return i, err
+		}
+		r.data = r.data[0:0]
+		r.n = 0
+		r.inputOffset += int64(ii)
+	}
+	for r.state == nil {
+		// here we just do
+		// 1:1 reads and writes
+		r.more()
+		if r.buffered() > 0 {
+			ii, err = w.Write(r.data)
+			i += int64(ii)
+			if err != nil {
+				return i, err
+			}
+			r.data = r.data[0:0]
+			r.n = 0
+			r.inputOffset += int64(ii)
+		}
+	}
+	if r.state != io.EOF {
+		return i, r.err()
+	}
+	return i, nil
+}
+
+func max(a int, b int) int {
+	if a < b {
+		return b
+	}
+	return a
+}