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binary.go
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binary.go
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package gitdiff
import (
"bytes"
"compress/zlib"
"fmt"
"io"
"io/ioutil"
"strconv"
"strings"
)
func (p *parser) ParseBinaryFragments(f *File) (n int, err error) {
isBinary, hasData, err := p.ParseBinaryMarker()
if err != nil || !isBinary {
return 0, err
}
f.IsBinary = true
if !hasData {
return 0, nil
}
forward, err := p.ParseBinaryFragmentHeader()
if err != nil {
return 0, err
}
if forward == nil {
return 0, p.Errorf(0, "missing data for binary patch")
}
if err := p.ParseBinaryChunk(forward); err != nil {
return 0, err
}
f.BinaryFragment = forward
// valid for reverse to not exist, but it must be valid if present
reverse, err := p.ParseBinaryFragmentHeader()
if err != nil {
return 1, err
}
if reverse == nil {
return 1, nil
}
if err := p.ParseBinaryChunk(reverse); err != nil {
return 1, err
}
f.ReverseBinaryFragment = reverse
return 1, nil
}
func (p *parser) ParseBinaryMarker() (isBinary bool, hasData bool, err error) {
switch p.Line(0) {
case "GIT binary patch\n":
hasData = true
case "Binary files differ\n":
case "Files differ\n":
default:
return false, false, nil
}
if err = p.Next(); err != nil && err != io.EOF {
return false, false, err
}
return true, hasData, nil
}
func (p *parser) ParseBinaryFragmentHeader() (*BinaryFragment, error) {
parts := strings.SplitN(strings.TrimSuffix(p.Line(0), "\n"), " ", 2)
if len(parts) < 2 {
return nil, nil
}
frag := &BinaryFragment{}
switch parts[0] {
case "delta":
frag.Method = BinaryPatchDelta
case "literal":
frag.Method = BinaryPatchLiteral
default:
return nil, nil
}
var err error
if frag.Size, err = strconv.ParseInt(parts[1], 10, 64); err != nil {
nerr := err.(*strconv.NumError)
return nil, p.Errorf(0, "binary patch: invalid size: %v", nerr.Err)
}
if err := p.Next(); err != nil && err != io.EOF {
return nil, err
}
return frag, nil
}
func (p *parser) ParseBinaryChunk(frag *BinaryFragment) error {
// Binary fragments are encoded as a series of base85 encoded lines. Each
// line starts with a character in [A-Za-z] giving the number of bytes on
// the line, where A = 1 and z = 52, and ends with a newline character.
//
// The base85 encoding means each line is a multiple of 5 characters + 2
// additional characters for the length byte and the newline. The fragment
// ends with a blank line.
const (
shortestValidLine = "A00000\n"
maxBytesPerLine = 52
)
var data bytes.Buffer
buf := make([]byte, maxBytesPerLine)
for {
line := p.Line(0)
if line == "\n" {
break
}
if len(line) < len(shortestValidLine) || (len(line)-2)%5 != 0 {
return p.Errorf(0, "binary patch: corrupt data line")
}
byteCount, seq := int(line[0]), line[1:len(line)-1]
switch {
case 'A' <= byteCount && byteCount <= 'Z':
byteCount = byteCount - 'A' + 1
case 'a' <= byteCount && byteCount <= 'z':
byteCount = byteCount - 'a' + 27
default:
return p.Errorf(0, "binary patch: invalid length byte")
}
// base85 encodes every 4 bytes into 5 characters, with up to 3 bytes of end padding
maxByteCount := len(seq) / 5 * 4
if byteCount > maxByteCount || byteCount < maxByteCount-3 {
return p.Errorf(0, "binary patch: incorrect byte count")
}
if err := base85Decode(buf[:byteCount], []byte(seq)); err != nil {
return p.Errorf(0, "binary patch: %v", err)
}
data.Write(buf[:byteCount])
if err := p.Next(); err != nil {
if err == io.EOF {
return p.Errorf(0, "binary patch: unexpected EOF")
}
return err
}
}
if err := inflateBinaryChunk(frag, &data); err != nil {
return p.Errorf(0, "binary patch: %v", err)
}
// consume the empty line that ended the fragment
if err := p.Next(); err != nil && err != io.EOF {
return err
}
return nil
}
func inflateBinaryChunk(frag *BinaryFragment, r io.Reader) error {
zr, err := zlib.NewReader(r)
if err != nil {
return err
}
data, err := ioutil.ReadAll(zr)
if err != nil {
return err
}
if err := zr.Close(); err != nil {
return err
}
if int64(len(data)) != frag.Size {
return fmt.Errorf("%d byte fragment inflated to %d", frag.Size, len(data))
}
frag.Data = data
return nil
}