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
|
package packfile
import (
"compress/zlib"
"crypto/sha1"
"fmt"
"io"
"gopkg.in/src-d/go-git.v4/plumbing"
"gopkg.in/src-d/go-git.v4/plumbing/storer"
"gopkg.in/src-d/go-git.v4/utils/binary"
)
// Encoder gets the data from the storage and write it into the writer in PACK
// format
type Encoder struct {
storage storer.EncodedObjectStorer
w *offsetWriter
zw *zlib.Writer
hasher plumbing.Hasher
offsets map[plumbing.Hash]int64
}
// NewEncoder creates a new packfile encoder using a specific Writer and
// ObjectStorer
func NewEncoder(w io.Writer, s storer.EncodedObjectStorer) *Encoder {
h := plumbing.Hasher{
Hash: sha1.New(),
}
mw := io.MultiWriter(w, h)
ow := newOffsetWriter(mw)
zw := zlib.NewWriter(mw)
return &Encoder{
storage: s,
w: ow,
zw: zw,
hasher: h,
offsets: make(map[plumbing.Hash]int64),
}
}
// Encode creates a packfile containing all the objects referenced in hashes
// and writes it to the writer in the Encoder.
func (e *Encoder) Encode(hashes []plumbing.Hash) (plumbing.Hash, error) {
var objects []*ObjectToPack
for _, h := range hashes {
o, err := e.storage.EncodedObject(plumbing.AnyObject, h)
if err != nil {
return plumbing.ZeroHash, err
}
// TODO delta selection logic
objects = append(objects, newObjectToPack(o))
}
return e.encode(objects)
}
func (e *Encoder) encode(objects []*ObjectToPack) (plumbing.Hash, error) {
if err := e.head(len(objects)); err != nil {
return plumbing.ZeroHash, err
}
for _, o := range objects {
if err := e.entry(o); err != nil {
return plumbing.ZeroHash, err
}
}
return e.footer()
}
func (e *Encoder) head(numEntries int) error {
return binary.Write(
e.w,
signature,
int32(VersionSupported),
int32(numEntries),
)
}
func (e *Encoder) entry(o *ObjectToPack) error {
offset := e.w.Offset()
if err := e.entryHead(o.Object.Type(), o.Object.Size()); err != nil {
return err
}
// Save the position using the original hash, maybe a delta will need it
e.offsets[o.Original.Hash()] = offset
if err := e.writeDeltaHeaderIfAny(o, offset); err != nil {
return err
}
e.zw.Reset(e.w)
or, err := o.Object.Reader()
if err != nil {
return err
}
_, err = io.Copy(e.zw, or)
if err != nil {
return err
}
return e.zw.Close()
}
func (e *Encoder) writeDeltaHeaderIfAny(o *ObjectToPack, offset int64) error {
if o.IsDelta() {
switch o.Object.Type() {
case plumbing.OFSDeltaObject:
if err := e.writeOfsDeltaHeader(offset, o.Base.Original.Hash()); err != nil {
return err
}
case plumbing.REFDeltaObject:
if err := e.writeRefDeltaHeader(o.Base.Original.Hash()); err != nil {
return err
}
}
}
return nil
}
func (e *Encoder) writeRefDeltaHeader(source plumbing.Hash) error {
return binary.Write(e.w, source)
}
func (e *Encoder) writeOfsDeltaHeader(deltaOffset int64, source plumbing.Hash) error {
// because it is an offset delta, we need the source
// object position
offset, ok := e.offsets[source]
if !ok {
return fmt.Errorf("delta source not found. Hash: %v", source)
}
return binary.WriteVariableWidthInt(e.w, deltaOffset-offset)
}
func (e *Encoder) entryHead(typeNum plumbing.ObjectType, size int64) error {
t := int64(typeNum)
header := []byte{}
c := (t << firstLengthBits) | (size & maskFirstLength)
size >>= firstLengthBits
for {
if size == 0 {
break
}
header = append(header, byte(c|maskContinue))
c = size & int64(maskLength)
size >>= lengthBits
}
header = append(header, byte(c))
_, err := e.w.Write(header)
return err
}
func (e *Encoder) footer() (plumbing.Hash, error) {
h := e.hasher.Sum()
return h, binary.Write(e.w, h)
}
type offsetWriter struct {
w io.Writer
offset int64
}
func newOffsetWriter(w io.Writer) *offsetWriter {
return &offsetWriter{w: w}
}
func (ow *offsetWriter) Write(p []byte) (n int, err error) {
n, err = ow.w.Write(p)
ow.offset += int64(n)
return n, err
}
func (ow *offsetWriter) Offset() int64 {
return ow.offset
}
|
