1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
|
package zlibx
import (
"encoding/binary"
"io"
"git.sr.ht/~runxiyu/furgit/internal/adler32"
"git.sr.ht/~runxiyu/furgit/internal/bufpool"
"git.sr.ht/~runxiyu/furgit/internal/flatex"
)
// Decompress inflates the provided zlib wrapped stream and returns the
// uncompressed data inside a pooled bufpool.Buffer.
func Decompress(src []byte) (bufpool.Buffer, error) {
return DecompressDict(src, nil)
}
// DecompressDict is like Decompress but accepts a preset dictionary. The
// dictionary must match the checksum embedded in the stream if the dictionary
// flag is present.
func DecompressDict(src []byte, dict []byte) (bufpool.Buffer, error) {
if len(src) < 6 {
return bufpool.Buffer{}, 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{}, ErrHeader
}
offset := 2
haveDict := flg&0x20 != 0
if haveDict {
if len(src) < offset+4 {
return bufpool.Buffer{}, io.ErrUnexpectedEOF
}
if dict == nil {
return bufpool.Buffer{}, ErrDictionary
}
checksum := binary.BigEndian.Uint32(src[offset : offset+4])
if checksum != adler32.Checksum(dict) {
return bufpool.Buffer{}, ErrDictionary
}
offset += 4
}
if len(src[offset:]) < 4 {
return bufpool.Buffer{}, io.ErrUnexpectedEOF
}
deflateData := src[offset:]
out, consumed, err := flatex.DecompressDict(deflateData, dict)
if err != nil {
return bufpool.Buffer{}, err
}
checksumPos := offset + consumed
if checksumPos+4 > len(src) {
out.Release()
return bufpool.Buffer{}, io.ErrUnexpectedEOF
}
expected := binary.BigEndian.Uint32(src[checksumPos : checksumPos+4])
if expected != adler32.Checksum(out.Bytes()) {
out.Release()
return bufpool.Buffer{}, ErrChecksum
}
return out, nil
}
|
