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// 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 patch
import (
"bytes"
"compress/zlib"
"crypto/sha1"
"encoding/git85"
"fmt"
"io"
"os"
)
func gitSHA1(data []byte) []byte {
if len(data) == 0 {
// special case: 0 length is all zeros sum
return make([]byte, 20)
}
h := sha1.New()
fmt.Fprintf(h, "blob %d\x00", len(data))
h.Write(data)
return h.Sum()
}
// BUG(rsc): The Git binary delta format is not implemented, only Git binary literals.
// GitBinaryLiteral represents a Git binary literal diff.
type GitBinaryLiteral struct {
OldSHA1 []byte // if non-empty, the SHA1 hash of the original
New []byte // the new contents
}
// Apply implements the Diff interface's Apply method.
func (d *GitBinaryLiteral) Apply(old []byte) ([]byte, os.Error) {
if sum := gitSHA1(old); !bytes.HasPrefix(sum, d.OldSHA1) {
return nil, ErrPatchFailure
}
return d.New, nil
}
func unhex(c byte) uint8 {
switch {
case '0' <= c && c <= '9':
return c - '0'
case 'a' <= c && c <= 'f':
return c - 'a' + 10
case 'A' <= c && c <= 'F':
return c - 'A' + 10
}
return 255
}
func getHex(s []byte) (data []byte, rest []byte) {
n := 0
for n < len(s) && unhex(s[n]) != 255 {
n++
}
n &^= 1 // Only take an even number of hex digits.
data = make([]byte, n/2)
for i := range data {
data[i] = unhex(s[2*i])<<4 | unhex(s[2*i+1])
}
rest = s[n:]
return
}
// ParseGitBinary parses raw as a Git binary patch.
func ParseGitBinary(raw []byte) (Diff, os.Error) {
var oldSHA1, newSHA1 []byte
var sawBinary bool
for {
var first []byte
first, raw, _ = getLine(raw, 1)
first = bytes.TrimSpace(first)
if s, ok := skip(first, "index "); ok {
oldSHA1, s = getHex(s)
if s, ok = skip(s, ".."); !ok {
continue
}
newSHA1, s = getHex(s)
continue
}
if _, ok := skip(first, "GIT binary patch"); ok {
sawBinary = true
continue
}
if n, _, ok := atoi(first, "literal ", 10); ok && sawBinary {
data := make([]byte, n)
d := git85.NewDecoder(bytes.NewBuffer(raw))
z, err := zlib.NewReader(d)
if err != nil {
return nil, err
}
defer z.Close()
if _, err = io.ReadFull(z, data); err != nil {
if err == os.EOF {
err = io.ErrUnexpectedEOF
}
return nil, err
}
var buf [1]byte
m, err := z.Read(buf[0:])
if m != 0 || err != os.EOF {
return nil, os.NewError("Git binary literal longer than expected")
}
if sum := gitSHA1(data); !bytes.HasPrefix(sum, newSHA1) {
return nil, os.NewError("Git binary literal SHA1 mismatch")
}
return &GitBinaryLiteral{oldSHA1, data}, nil
}
if !sawBinary {
return nil, os.NewError("unexpected Git patch header: " + string(first))
}
}
panic("unreachable")
}
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