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
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
|
package commitgraph
import (
"crypto"
"io"
"github.com/go-git/go-git/v5/plumbing"
"github.com/go-git/go-git/v5/plumbing/hash"
"github.com/go-git/go-git/v5/utils/binary"
)
// Encoder writes MemoryIndex structs to an output stream.
type Encoder struct {
io.Writer
hash hash.Hash
}
// NewEncoder returns a new stream encoder that writes to w.
func NewEncoder(w io.Writer) *Encoder {
h := hash.New(hash.CryptoType)
mw := io.MultiWriter(w, h)
return &Encoder{mw, h}
}
// Encode writes an index into the commit-graph file
func (e *Encoder) Encode(idx Index) error {
// Get all the hashes in the input index
hashes := idx.Hashes()
// Sort the inout and prepare helper structures we'll need for encoding
hashToIndex, fanout, extraEdgesCount := e.prepare(idx, hashes)
chunkSignatures := [][]byte{oidFanoutSignature, oidLookupSignature, commitDataSignature}
chunkSizes := []uint64{4 * 256, uint64(len(hashes)) * hash.Size, uint64(len(hashes)) * (hash.Size + commitDataSize)}
if extraEdgesCount > 0 {
chunkSignatures = append(chunkSignatures, extraEdgeListSignature)
chunkSizes = append(chunkSizes, uint64(extraEdgesCount)*4)
}
if err := e.encodeFileHeader(len(chunkSignatures)); err != nil {
return err
}
if err := e.encodeChunkHeaders(chunkSignatures, chunkSizes); err != nil {
return err
}
if err := e.encodeFanout(fanout); err != nil {
return err
}
if err := e.encodeOidLookup(hashes); err != nil {
return err
}
if extraEdges, err := e.encodeCommitData(hashes, hashToIndex, idx); err == nil {
if err = e.encodeExtraEdges(extraEdges); err != nil {
return err
}
} else {
return err
}
return e.encodeChecksum()
}
func (e *Encoder) prepare(idx Index, hashes []plumbing.Hash) (hashToIndex map[plumbing.Hash]uint32, fanout []uint32, extraEdgesCount uint32) {
// Sort the hashes and build our index
plumbing.HashesSort(hashes)
hashToIndex = make(map[plumbing.Hash]uint32)
fanout = make([]uint32, 256)
for i, hash := range hashes {
hashToIndex[hash] = uint32(i)
fanout[hash[0]]++
}
// Convert the fanout to cumulative values
for i := 1; i <= 0xff; i++ {
fanout[i] += fanout[i-1]
}
// Find out if we will need extra edge table
for i := 0; i < len(hashes); i++ {
v, _ := idx.GetCommitDataByIndex(i)
if len(v.ParentHashes) > 2 {
extraEdgesCount += uint32(len(v.ParentHashes) - 1)
break
}
}
return
}
func (e *Encoder) encodeFileHeader(chunkCount int) (err error) {
if _, err = e.Write(commitFileSignature); err == nil {
version := byte(1)
if hash.CryptoType == crypto.SHA256 {
version = byte(2)
}
_, err = e.Write([]byte{1, version, byte(chunkCount), 0})
}
return
}
func (e *Encoder) encodeChunkHeaders(chunkSignatures [][]byte, chunkSizes []uint64) (err error) {
// 8 bytes of file header, 12 bytes for each chunk header and 12 byte for terminator
offset := uint64(8 + len(chunkSignatures)*12 + 12)
for i, signature := range chunkSignatures {
if _, err = e.Write(signature); err == nil {
err = binary.WriteUint64(e, offset)
}
if err != nil {
return
}
offset += chunkSizes[i]
}
if _, err = e.Write(lastSignature); err == nil {
err = binary.WriteUint64(e, offset)
}
return
}
func (e *Encoder) encodeFanout(fanout []uint32) (err error) {
for i := 0; i <= 0xff; i++ {
if err = binary.WriteUint32(e, fanout[i]); err != nil {
return
}
}
return
}
func (e *Encoder) encodeOidLookup(hashes []plumbing.Hash) (err error) {
for _, hash := range hashes {
if _, err = e.Write(hash[:]); err != nil {
return err
}
}
return
}
func (e *Encoder) encodeCommitData(hashes []plumbing.Hash, hashToIndex map[plumbing.Hash]uint32, idx Index) (extraEdges []uint32, err error) {
for _, hash := range hashes {
origIndex, _ := idx.GetIndexByHash(hash)
commitData, _ := idx.GetCommitDataByIndex(origIndex)
if _, err = e.Write(commitData.TreeHash[:]); err != nil {
return
}
var parent1, parent2 uint32
if len(commitData.ParentHashes) == 0 {
parent1 = parentNone
parent2 = parentNone
} else if len(commitData.ParentHashes) == 1 {
parent1 = hashToIndex[commitData.ParentHashes[0]]
parent2 = parentNone
} else if len(commitData.ParentHashes) == 2 {
parent1 = hashToIndex[commitData.ParentHashes[0]]
parent2 = hashToIndex[commitData.ParentHashes[1]]
} else if len(commitData.ParentHashes) > 2 {
parent1 = hashToIndex[commitData.ParentHashes[0]]
parent2 = uint32(len(extraEdges)) | parentOctopusUsed
for _, parentHash := range commitData.ParentHashes[1:] {
extraEdges = append(extraEdges, hashToIndex[parentHash])
}
extraEdges[len(extraEdges)-1] |= parentLast
}
if err = binary.WriteUint32(e, parent1); err == nil {
err = binary.WriteUint32(e, parent2)
}
if err != nil {
return
}
unixTime := uint64(commitData.When.Unix())
unixTime |= uint64(commitData.Generation) << 34
if err = binary.WriteUint64(e, unixTime); err != nil {
return
}
}
return
}
func (e *Encoder) encodeExtraEdges(extraEdges []uint32) (err error) {
for _, parent := range extraEdges {
if err = binary.WriteUint32(e, parent); err != nil {
return
}
}
return
}
func (e *Encoder) encodeChecksum() error {
_, err := e.Write(e.hash.Sum(nil)[:hash.Size])
return err
}
|
