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|
package furgit
import (
"io"
"codeberg.org/lindenii/furgit/internal/bufpool"
)
func packDeltaReadOfsDistance(data []byte) (uint64, int, error) {
if len(data) == 0 {
return 0, 0, io.ErrUnexpectedEOF
}
b := data[0]
dist := uint64(b & 0x7f)
consumed := 1
for (b & 0x80) != 0 {
if consumed >= len(data) {
return 0, 0, io.ErrUnexpectedEOF
}
b = data[consumed]
consumed++
dist += 1
dist <<= 7
dist |= uint64(b & 0x7f)
}
return dist, consumed, nil
}
func packDeltaApply(base, delta bufpool.Buffer) (bufpool.Buffer, error) {
pos := 0
baseBytes := base.Bytes()
deltaBytes := delta.Bytes()
srcSize, err := packVarintRead(deltaBytes, &pos)
if err != nil {
return bufpool.Buffer{}, err
}
dstSize, err := packVarintRead(deltaBytes, &pos)
if err != nil {
return bufpool.Buffer{}, err
}
if srcSize != len(baseBytes) {
return bufpool.Buffer{}, ErrInvalidObject
}
out := bufpool.Borrow(dstSize)
out.Resize(dstSize)
outBytes := out.Bytes()
outPos := 0
for pos < len(deltaBytes) {
op := deltaBytes[pos]
pos++
switch {
case op&0x80 != 0:
off := 0
n := 0
if op&0x01 != 0 {
if pos >= len(deltaBytes) {
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
off |= int(deltaBytes[pos])
pos++
}
if op&0x02 != 0 {
if pos >= len(deltaBytes) {
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
off |= int(deltaBytes[pos]) << 8
pos++
}
if op&0x04 != 0 {
if pos >= len(deltaBytes) {
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
off |= int(deltaBytes[pos]) << 16
pos++
}
if op&0x08 != 0 {
if pos >= len(deltaBytes) {
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
off |= int(deltaBytes[pos]) << 24
pos++
}
if op&0x10 != 0 {
if pos >= len(deltaBytes) {
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
n |= int(deltaBytes[pos])
pos++
}
if op&0x20 != 0 {
if pos >= len(deltaBytes) {
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
n |= int(deltaBytes[pos]) << 8
pos++
}
if op&0x40 != 0 {
if pos >= len(deltaBytes) {
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
n |= int(deltaBytes[pos]) << 16
pos++
}
if n == 0 {
n = 0x10000
}
if off+n > len(baseBytes) || outPos+n > len(outBytes) {
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
copy(outBytes[outPos:], baseBytes[off:off+n])
outPos += n
case op != 0:
n := int(op)
if pos+n > len(deltaBytes) || outPos+n > len(outBytes) {
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
copy(outBytes[outPos:], deltaBytes[pos:pos+n])
pos += n
outPos += n
default:
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
}
if outPos != len(outBytes) {
out.Release()
return bufpool.Buffer{}, ErrInvalidObject
}
return out, nil
}
func packVarintRead(buf []byte, pos *int) (int, error) {
res := 0
shift := 0
for {
if *pos >= len(buf) {
return 0, ErrInvalidObject
}
b := buf[*pos]
*pos++
res |= int(b&0x7f) << shift
if (b & 0x80) == 0 {
break
}
shift += 7
}
return res, nil
}
|
