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repo_utils_reader.go
244 lines (209 loc) · 4.23 KB
/
repo_utils_reader.go
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package git
import (
"bytes"
"compress/zlib"
"errors"
"io"
"os"
)
var (
// ObjectReader implemented ReadCloser
_ io.ReadCloser = new(readCloser)
_ io.ReaderAt = new(readAter)
tmpBufLen = int64(1024)
tmpBuf = make([]byte, tmpBufLen)
)
type readCloser struct {
r io.Reader
c io.Closer
}
func (o *readCloser) Read(p []byte) (n int, err error) {
return o.r.Read(p)
}
func (o *readCloser) Close() error {
return o.c.Close()
}
func newReadCloser(r io.Reader, c io.Closer) io.ReadCloser {
return &readCloser{r, c}
}
type bufReadCloser struct {
r *bytes.Buffer
}
func (o *bufReadCloser) Read(p []byte) (n int, err error) {
return o.r.Read(p)
}
func (o *bufReadCloser) Close() error {
return nil
}
func newBufReadCloser(buf []byte) io.ReadCloser {
o := new(bufReadCloser)
o.r = bytes.NewBuffer(buf)
return o
}
type readAter struct {
buf []byte
}
func (o *readAter) ReadAt(p []byte, off int64) (n int, err error) {
if int(off) >= len(o.buf) {
err = io.EOF
return
}
length := len(p)
if length == 0 {
return
}
if length > len(o.buf[off:]) {
length = len(o.buf[off:])
}
copy(p, o.buf[off:])
n = length
return
}
// Read deflated object from the file.
func readerDecompressed(r io.Reader, inflatedSize int64) (io.ReadCloser, error) {
zr, err := zlib.NewReader(r)
if err != nil {
return nil, err
}
return newReadCloser(readerLimit(zr, inflatedSize), zr), nil
}
func readerLimit(r io.Reader, limit int64) io.Reader {
return io.LimitReader(r, limit)
}
func readerSeek(r io.ReadSeeker, offset int64) int64 {
cur, _ := r.Seek(offset, os.SEEK_SET)
return cur
}
func readerSkip(r io.Reader, offset int64) (cnt int64) {
if offset > 0 {
for cnt < offset {
remain := offset - cnt
if remain > tmpBufLen {
remain = tmpBufLen
}
n, err := r.Read(tmpBuf[:remain])
if n == 0 || err != nil {
return
}
cnt += int64(n)
}
}
return cnt
}
// buf must be large enough to read the number.
func readerLittleEndianBase128Number(r io.Reader) (int64, int) {
zpos := 0
buf := []byte{0}
n, err := r.Read(buf)
if err != nil {
return 0, n
}
length := int64(buf[0] & 0x7f)
shift := uint64(0)
for buf[0]&0x80 > 0 {
shift += 7
n, err := r.Read(buf)
if err != nil {
return 0, zpos + n
}
zpos += n
length |= int64(buf[0]&0x7f) << shift
}
zpos += 1
return length, zpos
}
func readerApplyDelta(br io.ReaderAt, dr io.Reader, resultLen int64) (res []byte, err error) {
var (
resultpos uint64
)
buf := []byte{0}
res = make([]byte, resultLen)
read := func(r io.Reader) (ret bool) {
var n int
n, err = r.Read(buf)
if err == io.EOF {
err = nil
return
}
if n == 0 || err != nil {
return
}
ret = true
return
}
readAt := func(r io.ReaderAt, off int64) (ret bool) {
var n int
n, err = r.ReadAt(buf, off)
if err == io.EOF {
err = nil
return
}
if n == 0 || err != nil {
return
}
ret = true
return
}
for {
// two modes: copy and insert. copy reads offset and len from the delta
// instructions and copy len bytes from offset into the resulting object
// insert takes up to 127 bytes and insert them into the
// resulting object
if !read(dr) {
return
}
opcode := buf[0]
if opcode&0x80 > 0 {
// Copy from base to dest
copy_offset := uint64(0)
copy_length := uint64(0)
shift := uint(0)
for i := 0; i < 4; i++ {
if opcode&0x01 > 0 {
if !read(dr) {
return
}
copy_offset |= uint64(buf[0]) << shift
}
opcode >>= 1
shift += 8
}
shift = 0
for i := 0; i < 3; i++ {
if opcode&0x01 > 0 {
if !read(dr) {
return
}
copy_length |= uint64(buf[0]) << shift
}
opcode >>= 1
shift += 8
}
if copy_length == 0 {
copy_length = 1 << 16
}
brOffset := int64(copy_offset)
for i := uint64(0); i < copy_length; i++ {
if !readAt(br, brOffset) {
return
}
res[resultpos] = buf[0]
resultpos++
brOffset++
}
} else if opcode > 0 {
// insert n bytes at the end of the resulting object. n==opcode
for i := 0; i < int(opcode); i++ {
if !read(dr) {
return
}
res[resultpos] = buf[0]
resultpos++
}
} else {
return nil, errors.New("[readerApplyDelta] opcode == 0")
}
}
// TODO: check if resultlen == resultpos
return
}