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
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
package idxfile
import (
"bufio"
"bytes"
"errors"
"io"
"gopkg.in/src-d/go-git.v4/utils/binary"
)
var (
// ErrUnsupportedVersion is returned by Decode when the idx file version
// is not supported.
ErrUnsupportedVersion = errors.New("Unsupported version")
// ErrMalformedIdxFile is returned by Decode when the idx file is corrupted.
ErrMalformedIdxFile = errors.New("Malformed IDX file")
)
const (
fanout = 256
objectIDLength = 20
)
// Decoder reads and decodes idx files from an input stream.
type Decoder struct {
*bufio.Reader
}
// NewDecoder builds a new idx stream decoder, that reads from r.
func NewDecoder(r io.Reader) *Decoder {
return &Decoder{bufio.NewReader(r)}
}
// Decode reads from the stream and decode the content into the MemoryIndex struct.
func (d *Decoder) Decode(idx *MemoryIndex) error {
if err := validateHeader(d); err != nil {
return err
}
flow := []func(*MemoryIndex, io.Reader) error{
readVersion,
readFanout,
readObjectNames,
readCRC32,
readOffsets,
readChecksums,
}
for _, f := range flow {
if err := f(idx, d); err != nil {
return err
}
}
return nil
}
func validateHeader(r io.Reader) error {
var h = make([]byte, 4)
if _, err := io.ReadFull(r, h); err != nil {
return err
}
if !bytes.Equal(h, idxHeader) {
return ErrMalformedIdxFile
}
return nil
}
func readVersion(idx *MemoryIndex, r io.Reader) error {
v, err := binary.ReadUint32(r)
if err != nil {
return err
}
if v > VersionSupported {
return ErrUnsupportedVersion
}
idx.Version = v
return nil
}
func readFanout(idx *MemoryIndex, r io.Reader) error {
for k := 0; k < fanout; k++ {
n, err := binary.ReadUint32(r)
if err != nil {
return err
}
idx.Fanout[k] = n
idx.FanoutMapping[k] = noMapping
}
return nil
}
func readObjectNames(idx *MemoryIndex, r io.Reader) error {
for k := 0; k < fanout; k++ {
var buckets uint32
if k == 0 {
buckets = idx.Fanout[k]
} else {
buckets = idx.Fanout[k] - idx.Fanout[k-1]
}
if buckets == 0 {
continue
}
idx.FanoutMapping[k] = len(idx.Names)
nameLen := int(buckets * objectIDLength)
bin := make([]byte, nameLen)
if _, err := io.ReadFull(r, bin); err != nil {
return err
}
idx.Names = append(idx.Names, bin)
idx.Offset32 = append(idx.Offset32, make([]byte, buckets*4))
idx.CRC32 = append(idx.CRC32, make([]byte, buckets*4))
}
return nil
}
func readCRC32(idx *MemoryIndex, r io.Reader) error {
for k := 0; k < fanout; k++ {
if pos := idx.FanoutMapping[k]; pos != noMapping {
if _, err := io.ReadFull(r, idx.CRC32[pos]); err != nil {
return err
}
}
}
return nil
}
func readOffsets(idx *MemoryIndex, r io.Reader) error {
var o64cnt int
for k := 0; k < fanout; k++ {
if pos := idx.FanoutMapping[k]; pos != noMapping {
if _, err := io.ReadFull(r, idx.Offset32[pos]); err != nil {
return err
}
for p := 0; p < len(idx.Offset32[pos]); p += 4 {
if idx.Offset32[pos][p]&(byte(1)<<7) > 0 {
o64cnt++
}
}
}
}
if o64cnt > 0 {
idx.Offset64 = make([]byte, o64cnt*8)
if _, err := io.ReadFull(r, idx.Offset64); err != nil {
return err
}
}
return nil
}
func readChecksums(idx *MemoryIndex, r io.Reader) error {
if _, err := io.ReadFull(r, idx.PackfileChecksum[:]); err != nil {
return err
}
if _, err := io.ReadFull(r, idx.IdxChecksum[:]); err != nil {
return err
}
return nil
}
|
