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
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
|
package packed
import (
"fmt"
"codeberg.org/lindenii/furgit/internal/intconv"
"codeberg.org/lindenii/furgit/objectid"
"codeberg.org/lindenii/furgit/objecttype"
)
// entryMeta describes one parsed pack entry header.
type entryMeta struct {
// ty is the pack entry type tag.
ty objecttype.Type
// size is the declared resulting content size.
size int64
// dataOffset points to the zlib payload start.
dataOffset int
// baseRefID is set for ref-delta entries.
baseRefID objectid.ObjectID
// baseOfs is set for ofs-delta entries.
baseOfs uint64
}
// parseEntryMeta parses one pack entry header at offset.
func parseEntryMeta(pack *packFile, algo objectid.Algorithm, offset uint64) (entryMeta, error) {
var zero entryMeta
if offset >= uint64(len(pack.data)) {
return zero, fmt.Errorf("objectstore/packed: pack %q offset %d out of bounds", pack.name, offset)
}
pos, err := intconv.Uint64ToInt(offset)
if err != nil {
return zero, fmt.Errorf("objectstore/packed: pack %q offset conversion: %w", pack.name, err)
}
first := pack.data[pos]
pos++
meta := entryMeta{
ty: objecttype.Type((first >> 4) & 0x07),
size: int64(first & 0x0f),
}
shift := uint(4)
b := first
for b&0x80 != 0 {
if pos >= len(pack.data) {
return zero, fmt.Errorf("objectstore/packed: pack %q truncated entry header", pack.name)
}
b = pack.data[pos]
pos++
meta.size |= int64(b&0x7f) << shift
shift += 7
}
if meta.size < 0 {
return zero, fmt.Errorf("objectstore/packed: pack %q entry has negative size", pack.name)
}
switch meta.ty {
case objecttype.TypeCommit, objecttype.TypeTree, objecttype.TypeBlob, objecttype.TypeTag:
// Base object entries have no extra header fields.
case objecttype.TypeRefDelta:
hashSize := algo.Size()
if pos+hashSize > len(pack.data) {
return zero, fmt.Errorf("objectstore/packed: pack %q truncated ref-delta base id", pack.name)
}
baseID, err := objectid.FromBytes(algo, pack.data[pos:pos+hashSize])
if err != nil {
return zero, err
}
meta.baseRefID = baseID
pos += hashSize
case objecttype.TypeOfsDelta:
dist, consumed, err := parseOfsDeltaDistance(pack.data[pos:])
if err != nil {
return zero, err
}
pos += consumed
if offset <= dist {
return zero, fmt.Errorf("objectstore/packed: pack %q has invalid ofs-delta base", pack.name)
}
meta.baseOfs = offset - dist
case objecttype.TypeInvalid, objecttype.TypeFuture:
return zero, fmt.Errorf("objectstore/packed: pack %q has unsupported object type %d", pack.name, meta.ty)
default:
return zero, fmt.Errorf("objectstore/packed: pack %q has unsupported object type %d", pack.name, meta.ty)
}
meta.dataOffset = pos
if meta.dataOffset > len(pack.data) {
return zero, fmt.Errorf("objectstore/packed: pack %q entry data offset out of bounds", pack.name)
}
return meta, nil
}
// parseOfsDeltaDistance parses one ofs-delta backward distance.
func parseOfsDeltaDistance(buf []byte) (uint64, int, error) {
if len(buf) == 0 {
return 0, 0, fmt.Errorf("objectstore/packed: malformed ofs-delta distance")
}
b := buf[0]
dist := uint64(b & 0x7f)
consumed := 1
for b&0x80 != 0 {
if consumed >= len(buf) {
return 0, 0, fmt.Errorf("objectstore/packed: malformed ofs-delta distance")
}
b = buf[consumed]
consumed++
dist = ((dist + 1) << 7) + uint64(b&0x7f)
}
return dist, consumed, nil
}
// isBaseObjectType reports whether ty is one of the four canonical object types.
func isBaseObjectType(ty objecttype.Type) bool {
switch ty {
case objecttype.TypeCommit, objecttype.TypeTree, objecttype.TypeBlob, objecttype.TypeTag:
return true
case objecttype.TypeInvalid, objecttype.TypeFuture, objecttype.TypeOfsDelta, objecttype.TypeRefDelta:
return false
default:
return false
}
}
|
