forked from zrepl/zrepl
-
Notifications
You must be signed in to change notification settings - Fork 0
/
chunking.go
204 lines (162 loc) · 4.14 KB
/
chunking.go
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
193
194
195
196
197
198
199
200
201
202
203
204
package chunking
import (
"bytes"
"encoding/binary"
"io"
)
var ChunkBufSize uint32 = 32 * 1024
var ChunkHeaderByteOrder = binary.LittleEndian
type Unchunker struct {
ChunkCount int
in io.Reader
remainingChunkBytes uint32
finishErr error
}
func NewUnchunker(conn io.Reader) *Unchunker {
return &Unchunker{
in: conn,
remainingChunkBytes: 0,
}
}
func (c *Unchunker) Read(b []byte) (n int, err error) {
if c.finishErr != nil {
return 0, c.finishErr
}
if c.remainingChunkBytes == 0 {
var nextChunkLen uint32
err = binary.Read(c.in, ChunkHeaderByteOrder, &nextChunkLen)
if err != nil {
c.finishErr = err // can't handle this
return
}
// A chunk of len 0 indicates end of stream
if nextChunkLen == 0 {
c.finishErr = io.EOF
return 0, c.finishErr
}
c.remainingChunkBytes = nextChunkLen
c.ChunkCount++
}
if c.remainingChunkBytes == 0 {
panic("internal inconsistency: c.remainingChunkBytes must be > 0")
}
if len(b) <= 0 {
panic("cannot read into buffer of length 0")
}
maxRead := min(int(c.remainingChunkBytes), len(b))
n, err = c.in.Read(b[0:maxRead])
if err != nil {
return
}
c.remainingChunkBytes -= uint32(n)
return
}
func (c *Unchunker) Close() (err error) {
buf := make([]byte, 4096)
for err == nil {
_, err = c.Read(buf)
if err == io.EOF {
err = nil
break
}
}
return
}
func min(a, b int) int {
if a < b {
return a
} else {
return b
}
}
type Chunker struct {
ChunkCount int
in io.Reader
inEOF bool
remainingChunkBytes int
payloadBufLen int
payloadBuf []byte
headerBuf *bytes.Buffer
finalHeaderBuffered bool
}
func NewChunker(conn io.Reader) Chunker {
return NewChunkerSized(conn, ChunkBufSize)
}
func NewChunkerSized(conn io.Reader, chunkSize uint32) Chunker {
buf := make([]byte, int(chunkSize)-binary.Size(chunkSize))
return Chunker{
in: conn,
remainingChunkBytes: 0,
payloadBufLen: 0,
payloadBuf: buf,
headerBuf: &bytes.Buffer{},
}
}
func (c *Chunker) Read(b []byte) (n int, err error) {
if len(b) == 0 {
panic("unexpected empty output buffer")
}
if c.inEOF && c.finalHeaderBuffered && c.headerBuf.Len() == 0 { // all bufs empty and no more bytes to expect
return 0, io.EOF
}
n = 0
if c.headerBuf.Len() > 0 { // first drain the header buf
nh, err := c.headerBuf.Read(b[n:])
if nh > 0 {
n += nh
}
if nh == 0 || (err != nil && err != io.EOF) {
panic("unexpected behavior: in-memory buffer should not throw errors")
}
if c.headerBuf.Len() != 0 {
return n, nil // finish writing the header before we can proceed with payload
}
if c.finalHeaderBuffered {
// we just wrote the final header
return n, io.EOF
}
}
if c.remainingChunkBytes > 0 { // then drain the payload buf
npl := copy(b[n:], c.payloadBuf[c.payloadBufLen-c.remainingChunkBytes:c.payloadBufLen])
c.remainingChunkBytes -= npl
if c.remainingChunkBytes < 0 {
panic("unexpected behavior, copy() should not copy more than max(cap(), len())")
}
n += npl
}
if c.remainingChunkBytes == 0 && !c.inEOF { // fillup bufs
newPayloadLen, err := c.in.Read(c.payloadBuf)
if newPayloadLen > 0 {
c.payloadBufLen = newPayloadLen
c.remainingChunkBytes = newPayloadLen
}
if err == io.EOF {
c.inEOF = true
} else if err != nil {
return n, err
}
if newPayloadLen == 0 { // apparently, this happens with some Readers
c.finalHeaderBuffered = true
}
// Fill header buf
{
c.headerBuf.Reset()
nextChunkLen := uint32(newPayloadLen)
err := binary.Write(c.headerBuf, ChunkHeaderByteOrder, nextChunkLen)
if err != nil {
panic("unexpected error, write to in-memory buffer should not throw error")
}
}
if c.headerBuf.Len() == 0 {
panic("unexpected empty header buf")
}
} else if c.remainingChunkBytes == 0 && c.inEOF && !c.finalHeaderBuffered {
c.headerBuf.Reset()
err := binary.Write(c.headerBuf, ChunkHeaderByteOrder, uint32(0))
if err != nil {
panic("unexpected error, write to in-memory buffer should not throw error [2]")
}
c.finalHeaderBuffered = true
}
return
}