src/pkg/encoding/git85/git.go - go - Git at Google

 // Copyright 2009 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // Package git85 implements the radix 85 data encoding
 // used in the Git version control system.
 package git85

 import (
 	"bytes"
 	"io"
 	"os"
 	"strconv"
 )

 type CorruptInputError int64

 func (e CorruptInputError) String() string {
 	return "illegal git85 data at input byte " + strconv.Itoa64(int64(e))
 }

 const encode = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~"

 // The decodings are 1+ the actual value, so that the
 // default zero value can be used to mean "not valid".
 var decode = [256]uint8{
 	'0': 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
 	'A': 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
 	24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
 	'a': 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49,
 	50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62,
 	'!': 63,
 	'#': 64, 65, 66, 67,
 	'(': 68, 69, 70, 71,
 	'-': 72,
 	';': 73,
 	'<': 74, 75, 76, 77,
 	'@': 78,
 	'^': 79, 80, 81,
 	'{': 82, 83, 84, 85,
 }

 // Encode encodes src into EncodedLen(len(src))
 // bytes of dst.  As a convenience, it returns the number
 // of bytes written to dst, but this value is always EncodedLen(len(src)).
 // Encode implements the radix 85 encoding used in the
 // Git version control tool.
 //
 // The encoding splits src into chunks of at most 52 bytes
 // and encodes each chunk on its own line.
 func Encode(dst, src []byte) int {
 	ndst := 0
 	for len(src) > 0 {
 		n := len(src)
 		if n > 52 {
 			n = 52
 		}
 		if n <= 27 {
 			dst[ndst] = byte('A' + n - 1)
 		} else {
 			dst[ndst] = byte('a' + n - 26 - 1)
 		}
 		ndst++
 		for i := 0; i < n; i += 4 {
 			var v uint32
 			for j := 0; j < 4 && i+j < n; j++ {
 				v |= uint32(src[i+j]) << uint(24-j*8)
 			}
 			for j := 4; j >= 0; j-- {
 				dst[ndst+j] = encode[v%85]
 				v /= 85
 			}
 			ndst += 5
 		}
 		dst[ndst] = '\n'
 		ndst++
 		src = src[n:]
 	}
 	return ndst
 }

 // EncodedLen returns the length of an encoding of n source bytes.
 func EncodedLen(n int) int {
 	if n == 0 {
 		return 0
 	}
 	// 5 bytes per 4 bytes of input, rounded up.
 	// 2 extra bytes for each line of 52 src bytes, rounded up.
 	return (n+3)/4*5 + (n+51)/52*2
 }

 var newline = []byte{'\n'}

 // Decode decodes src into at most MaxDecodedLen(len(src))
 // bytes, returning the actual number of bytes written to dst.
 //
 // If Decode encounters invalid input, it returns a CorruptInputError.
 //
 func Decode(dst, src []byte) (n int, err os.Error) {
 	ndst := 0
 	nsrc := 0
 	for nsrc < len(src) {
 		var l int
 		switch ch := int(src[nsrc]); {
 		case 'A' <= ch && ch <= 'Z':
 			l = ch - 'A' + 1
 		case 'a' <= ch && ch <= 'z':
 			l = ch - 'a' + 26 + 1
 		default:
 			return ndst, CorruptInputError(nsrc)
 		}
 		if nsrc+1+l > len(src) {
 			return ndst, CorruptInputError(nsrc)
 		}
 		el := (l + 3) / 4 * 5 // encoded len
 		if nsrc+1+el+1 > len(src) || src[nsrc+1+el] != '\n' {
 			return ndst, CorruptInputError(nsrc)
 		}
 		line := src[nsrc+1 : nsrc+1+el]
 		for i := 0; i < el; i += 5 {
 			var v uint32
 			for j := 0; j < 5; j++ {
 				ch := decode[line[i+j]]
 				if ch == 0 {
 					return ndst, CorruptInputError(nsrc + 1 + i + j)
 				}
 				v = v*85 + uint32(ch-1)
 			}
 			for j := 0; j < 4; j++ {
 				dst[ndst] = byte(v >> 24)
 				v <<= 8
 				ndst++
 			}
 		}
 		// Last fragment may have run too far (but there was room in dst).
 		// Back up.
 		if l%4 != 0 {
 			ndst -= 4 - l%4
 		}
 		nsrc += 1 + el + 1
 	}
 	return ndst, nil
 }

 func MaxDecodedLen(n int) int { return n / 5 * 4 }

 // NewEncoder returns a new Git base85 stream encoder.  Data written to
 // the returned writer will be encoded and then written to w.
 // The Git encoding operates on 52-byte blocks; when finished
 // writing, the caller must Close the returned encoder to flush any
 // partially written blocks.
 func NewEncoder(w io.Writer) io.WriteCloser { return &encoder{w: w} }

 type encoder struct {
 	w    io.Writer
 	err  os.Error
 	buf  [52]byte
 	nbuf int
 	out  [1024]byte
 	nout int
 }

 func (e *encoder) Write(p []byte) (n int, err os.Error) {
 	if e.err != nil {
 		return 0, e.err
 	}

 	// Leading fringe.
 	if e.nbuf > 0 {
 		var i int
 		for i = 0; i < len(p) && e.nbuf < 52; i++ {
 			e.buf[e.nbuf] = p[i]
 			e.nbuf++
 		}
 		n += i
 		p = p[i:]
 		if e.nbuf < 52 {
 			return
 		}
 		nout := Encode(e.out[0:], e.buf[0:])
 		if _, e.err = e.w.Write(e.out[0:nout]); e.err != nil {
 			return n, e.err
 		}
 		e.nbuf = 0
 	}

 	// Large interior chunks.
 	for len(p) >= 52 {
 		nn := len(e.out) / (1 + 52/4*5 + 1) * 52
 		if nn > len(p) {
 			nn = len(p) / 52 * 52
 		}
 		if nn > 0 {
 			nout := Encode(e.out[0:], p[0:nn])
 			if _, e.err = e.w.Write(e.out[0:nout]); e.err != nil {
 				return n, e.err
 			}
 		}
 		n += nn
 		p = p[nn:]
 	}

 	// Trailing fringe.
 	for i := 0; i < len(p); i++ {
 		e.buf[i] = p[i]
 	}
 	e.nbuf = len(p)
 	n += len(p)
 	return
 }

 func (e *encoder) Close() os.Error {
 	// If there's anything left in the buffer, flush it out
 	if e.err == nil && e.nbuf > 0 {
 		nout := Encode(e.out[0:], e.buf[0:e.nbuf])
 		e.nbuf = 0
 		_, e.err = e.w.Write(e.out[0:nout])
 	}
 	return e.err
 }

 // NewDecoder returns a new Git base85 stream decoder.
 func NewDecoder(r io.Reader) io.Reader { return &decoder{r: r} }

 type decoder struct {
 	r       io.Reader
 	err     os.Error
 	readErr os.Error
 	buf     [1024]byte
 	nbuf    int
 	out     []byte
 	outbuf  [1024]byte
 	off     int64
 }

 func (d *decoder) Read(p []byte) (n int, err os.Error) {
 	if len(p) == 0 {
 		return 0, nil
 	}

 	for {
 		// Copy leftover output from last decode.
 		if len(d.out) > 0 {
 			n = copy(p, d.out)
 			d.out = d.out[n:]
 			return
 		}

 		// Out of decoded output.  Check errors.
 		if d.err != nil {
 			return 0, d.err
 		}
 		if d.readErr != nil {
 			d.err = d.readErr
 			return 0, d.err
 		}

 		// Read and decode more input.
 		var nn int
 		nn, d.readErr = d.r.Read(d.buf[d.nbuf:])
 		d.nbuf += nn

 		// Send complete lines to Decode.
 		nl := bytes.LastIndex(d.buf[0:d.nbuf], newline)
 		if nl < 0 {
 			continue
 		}
 		nn, d.err = Decode(d.outbuf[0:], d.buf[0:nl+1])
 		if e, ok := d.err.(CorruptInputError); ok {
 			d.err = CorruptInputError(int64(e) + d.off)
 		}
 		d.out = d.outbuf[0:nn]
 		d.nbuf = copy(d.buf[0:], d.buf[nl+1:d.nbuf])
 		d.off += int64(nl + 1)
 	}
 	panic("unreachable")
 }
	// Copyright 2009 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// Package git85 implements the radix 85 data encoding
	// used in the Git version control system.
	package git85

	import (
	"bytes"
	"io"
	"os"
	"strconv"
	)

	type CorruptInputError int64

	func (e CorruptInputError) String() string {
	return "illegal git85 data at input byte " + strconv.Itoa64(int64(e))
	}

	const encode = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{\|}~"

	// The decodings are 1+ the actual value, so that the
	// default zero value can be used to mean "not valid".
	var decode = [256]uint8{
	'0': 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
	'A': 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
	24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
	'a': 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49,
	50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62,
	'!': 63,
	'#': 64, 65, 66, 67,
	'(': 68, 69, 70, 71,
	'-': 72,
	';': 73,
	'<': 74, 75, 76, 77,
	'@': 78,
	'^': 79, 80, 81,
	'{': 82, 83, 84, 85,
	}

	// Encode encodes src into EncodedLen(len(src))
	// bytes of dst. As a convenience, it returns the number
	// of bytes written to dst, but this value is always EncodedLen(len(src)).
	// Encode implements the radix 85 encoding used in the
	// Git version control tool.
	//
	// The encoding splits src into chunks of at most 52 bytes
	// and encodes each chunk on its own line.
	func Encode(dst, src []byte) int {
	ndst := 0
	for len(src) > 0 {
	n := len(src)
	if n > 52 {
	n = 52
	}
	if n <= 27 {
	dst[ndst] = byte('A' + n - 1)
	} else {
	dst[ndst] = byte('a' + n - 26 - 1)
	}
	ndst++
	for i := 0; i < n; i += 4 {
	var v uint32
	for j := 0; j < 4 && i+j < n; j++ {
	v \|= uint32(src[i+j]) << uint(24-j*8)
	}
	for j := 4; j >= 0; j-- {
	dst[ndst+j] = encode[v%85]
	v /= 85
	}
	ndst += 5
	}
	dst[ndst] = '\n'
	ndst++
	src = src[n:]
	}
	return ndst
	}

	// EncodedLen returns the length of an encoding of n source bytes.
	func EncodedLen(n int) int {
	if n == 0 {
	return 0
	}
	// 5 bytes per 4 bytes of input, rounded up.
	// 2 extra bytes for each line of 52 src bytes, rounded up.
	return (n+3)/45 + (n+51)/522
	}

	var newline = []byte{'\n'}

	// Decode decodes src into at most MaxDecodedLen(len(src))
	// bytes, returning the actual number of bytes written to dst.
	//
	// If Decode encounters invalid input, it returns a CorruptInputError.
	//
	func Decode(dst, src []byte) (n int, err os.Error) {
	ndst := 0
	nsrc := 0
	for nsrc < len(src) {
	var l int
	switch ch := int(src[nsrc]); {
	case 'A' <= ch && ch <= 'Z':
	l = ch - 'A' + 1
	case 'a' <= ch && ch <= 'z':
	l = ch - 'a' + 26 + 1
	default:
	return ndst, CorruptInputError(nsrc)
	}
	if nsrc+1+l > len(src) {
	return ndst, CorruptInputError(nsrc)
	}
	el := (l + 3) / 4 * 5 // encoded len
	if nsrc+1+el+1 > len(src) \|\| src[nsrc+1+el] != '\n' {
	return ndst, CorruptInputError(nsrc)
	}
	line := src[nsrc+1 : nsrc+1+el]
	for i := 0; i < el; i += 5 {
	var v uint32
	for j := 0; j < 5; j++ {
	ch := decode[line[i+j]]
	if ch == 0 {
	return ndst, CorruptInputError(nsrc + 1 + i + j)
	}
	v = v*85 + uint32(ch-1)
	}
	for j := 0; j < 4; j++ {
	dst[ndst] = byte(v >> 24)
	v <<= 8
	ndst++
	}
	}
	// Last fragment may have run too far (but there was room in dst).
	// Back up.
	if l%4 != 0 {
	ndst -= 4 - l%4
	}
	nsrc += 1 + el + 1
	}
	return ndst, nil
	}

	func MaxDecodedLen(n int) int { return n / 5 * 4 }

	// NewEncoder returns a new Git base85 stream encoder. Data written to
	// the returned writer will be encoded and then written to w.
	// The Git encoding operates on 52-byte blocks; when finished
	// writing, the caller must Close the returned encoder to flush any
	// partially written blocks.
	func NewEncoder(w io.Writer) io.WriteCloser { return &encoder{w: w} }

	type encoder struct {
	w io.Writer
	err os.Error
	buf [52]byte
	nbuf int
	out [1024]byte
	nout int
	}

	func (e *encoder) Write(p []byte) (n int, err os.Error) {
	if e.err != nil {
	return 0, e.err
	}

	// Leading fringe.
	if e.nbuf > 0 {
	var i int
	for i = 0; i < len(p) && e.nbuf < 52; i++ {
	e.buf[e.nbuf] = p[i]
	e.nbuf++
	}
	n += i
	p = p[i:]
	if e.nbuf < 52 {
	return
	}
	nout := Encode(e.out[0:], e.buf[0:])
	if _, e.err = e.w.Write(e.out[0:nout]); e.err != nil {
	return n, e.err
	}
	e.nbuf = 0
	}

	// Large interior chunks.
	for len(p) >= 52 {
	nn := len(e.out) / (1 + 52/45 + 1) 52
	if nn > len(p) {
	nn = len(p) / 52 * 52
	}
	if nn > 0 {
	nout := Encode(e.out[0:], p[0:nn])
	if _, e.err = e.w.Write(e.out[0:nout]); e.err != nil {
	return n, e.err
	}
	}
	n += nn
	p = p[nn:]
	}

	// Trailing fringe.
	for i := 0; i < len(p); i++ {
	e.buf[i] = p[i]
	}
	e.nbuf = len(p)
	n += len(p)
	return
	}

	func (e *encoder) Close() os.Error {
	// If there's anything left in the buffer, flush it out
	if e.err == nil && e.nbuf > 0 {
	nout := Encode(e.out[0:], e.buf[0:e.nbuf])
	e.nbuf = 0
	_, e.err = e.w.Write(e.out[0:nout])
	}
	return e.err
	}

	// NewDecoder returns a new Git base85 stream decoder.
	func NewDecoder(r io.Reader) io.Reader { return &decoder{r: r} }

	type decoder struct {
	r io.Reader
	err os.Error
	readErr os.Error
	buf [1024]byte
	nbuf int
	out []byte
	outbuf [1024]byte
	off int64
	}

	func (d *decoder) Read(p []byte) (n int, err os.Error) {
	if len(p) == 0 {
	return 0, nil
	}

	for {
	// Copy leftover output from last decode.
	if len(d.out) > 0 {
	n = copy(p, d.out)
	d.out = d.out[n:]
	return
	}

	// Out of decoded output. Check errors.
	if d.err != nil {
	return 0, d.err
	}
	if d.readErr != nil {
	d.err = d.readErr
	return 0, d.err
	}

	// Read and decode more input.
	var nn int
	nn, d.readErr = d.r.Read(d.buf[d.nbuf:])
	d.nbuf += nn

	// Send complete lines to Decode.
	nl := bytes.LastIndex(d.buf[0:d.nbuf], newline)
	if nl < 0 {
	continue
	}
	nn, d.err = Decode(d.outbuf[0:], d.buf[0:nl+1])
	if e, ok := d.err.(CorruptInputError); ok {
	d.err = CorruptInputError(int64(e) + d.off)
	}
	d.out = d.outbuf[0:nn]
	d.nbuf = copy(d.buf[0:], d.buf[nl+1:d.nbuf])
	d.off += int64(nl + 1)
	}
	panic("unreachable")
	}