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package zlibx
import (
"encoding/binary"
"io"
"codeberg.org/lindenii/furgit/internal/adler32"
"codeberg.org/lindenii/furgit/internal/bufpool"
"codeberg.org/lindenii/furgit/internal/flatex"
)
func Decompress(src []byte) (bufpool.Buffer, error) {
out, _, err := DecompressSized(src, 0)
return out, err
}
func DecompressSized(src []byte, sizeHint int) (buf bufpool.Buffer, consumed int, err error) {
if len(src) < 6 {
return bufpool.Buffer{}, 0, io.ErrUnexpectedEOF
}
cmf := src[0]
flg := src[1]
if (cmf&0x0f != zlibDeflate) || (cmf>>4 > zlibMaxWindow) || (binary.BigEndian.Uint16(src[:2])%31 != 0) {
return bufpool.Buffer{}, 0, ErrHeader
}
offset := 2
if flg&0x20 != 0 {
return bufpool.Buffer{}, 0, ErrHeader
}
if len(src[offset:]) < 4 {
return bufpool.Buffer{}, 0, io.ErrUnexpectedEOF
}
deflateData := src[offset:]
out, consumed, err := flatex.DecompressSized(deflateData, sizeHint)
if err != nil {
return bufpool.Buffer{}, 0, err
}
checksumPos := offset + consumed
if checksumPos+4 > len(src) {
out.Release()
return bufpool.Buffer{}, 0, io.ErrUnexpectedEOF
}
expected := binary.BigEndian.Uint32(src[checksumPos : checksumPos+4])
if expected != adler32.Checksum(out.Bytes()) {
out.Release()
return bufpool.Buffer{}, 0, ErrChecksum
}
return out, checksumPos + 4, nil
}
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