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
205
206
207
|
// Package buffer implements a buffer for serialization, consisting of a chain of []byte-s to
// reduce copying and to allow reuse of individual chunks.
package buffer
import (
"io"
"sync"
)
// PoolConfig contains configuration for the allocation and reuse strategy.
type PoolConfig struct {
StartSize int // Minimum chunk size that is allocated.
PooledSize int // Minimum chunk size that is reused, reusing chunks too small will result in overhead.
MaxSize int // Maximum chunk size that will be allocated.
}
var config = PoolConfig{
StartSize: 128,
PooledSize: 512,
MaxSize: 32768,
}
// Reuse pool: chunk size -> pool.
var buffers = map[int]*sync.Pool{}
func initBuffers() {
for l := config.PooledSize; l <= config.MaxSize; l *= 2 {
buffers[l] = new(sync.Pool)
}
}
func init() {
initBuffers()
}
// Init sets up a non-default pooling and allocation strategy. Should be run before serialization is done.
func Init(cfg PoolConfig) {
config = cfg
initBuffers()
}
// putBuf puts a chunk to reuse pool if it can be reused.
func putBuf(buf []byte) {
size := cap(buf)
if size < config.PooledSize {
return
}
if c := buffers[size]; c != nil {
c.Put(buf[:0])
}
}
// getBuf gets a chunk from reuse pool or creates a new one if reuse failed.
func getBuf(size int) []byte {
if size < config.PooledSize {
return make([]byte, 0, size)
}
if c := buffers[size]; c != nil {
v := c.Get()
if v != nil {
return v.([]byte)
}
}
return make([]byte, 0, size)
}
// Buffer is a buffer optimized for serialization without extra copying.
type Buffer struct {
// Buf is the current chunk that can be used for serialization.
Buf []byte
toPool []byte
bufs [][]byte
}
// EnsureSpace makes sure that the current chunk contains at least s free bytes,
// possibly creating a new chunk.
func (b *Buffer) EnsureSpace(s int) {
if cap(b.Buf)-len(b.Buf) >= s {
return
}
l := len(b.Buf)
if l > 0 {
if cap(b.toPool) != cap(b.Buf) {
// Chunk was reallocated, toPool can be pooled.
putBuf(b.toPool)
}
if cap(b.bufs) == 0 {
b.bufs = make([][]byte, 0, 8)
}
b.bufs = append(b.bufs, b.Buf)
l = cap(b.toPool) * 2
} else {
l = config.StartSize
}
if l > config.MaxSize {
l = config.MaxSize
}
b.Buf = getBuf(l)
b.toPool = b.Buf
}
// AppendByte appends a single byte to buffer.
func (b *Buffer) AppendByte(data byte) {
if cap(b.Buf) == len(b.Buf) { // EnsureSpace won't be inlined.
b.EnsureSpace(1)
}
b.Buf = append(b.Buf, data)
}
// AppendBytes appends a byte slice to buffer.
func (b *Buffer) AppendBytes(data []byte) {
for len(data) > 0 {
if cap(b.Buf) == len(b.Buf) { // EnsureSpace won't be inlined.
b.EnsureSpace(1)
}
sz := cap(b.Buf) - len(b.Buf)
if sz > len(data) {
sz = len(data)
}
b.Buf = append(b.Buf, data[:sz]...)
data = data[sz:]
}
}
// AppendBytes appends a string to buffer.
func (b *Buffer) AppendString(data string) {
for len(data) > 0 {
if cap(b.Buf) == len(b.Buf) { // EnsureSpace won't be inlined.
b.EnsureSpace(1)
}
sz := cap(b.Buf) - len(b.Buf)
if sz > len(data) {
sz = len(data)
}
b.Buf = append(b.Buf, data[:sz]...)
data = data[sz:]
}
}
// Size computes the size of a buffer by adding sizes of every chunk.
func (b *Buffer) Size() int {
size := len(b.Buf)
for _, buf := range b.bufs {
size += len(buf)
}
return size
}
// DumpTo outputs the contents of a buffer to a writer and resets the buffer.
func (b *Buffer) DumpTo(w io.Writer) (written int, err error) {
var n int
for _, buf := range b.bufs {
if err == nil {
n, err = w.Write(buf)
written += n
}
putBuf(buf)
}
if err == nil {
n, err = w.Write(b.Buf)
written += n
}
putBuf(b.toPool)
b.bufs = nil
b.Buf = nil
b.toPool = nil
return
}
// BuildBytes creates a single byte slice with all the contents of the buffer. Data is
// copied if it does not fit in a single chunk.
func (b *Buffer) BuildBytes() []byte {
if len(b.bufs) == 0 {
ret := b.Buf
b.toPool = nil
b.Buf = nil
return ret
}
ret := make([]byte, 0, b.Size())
for _, buf := range b.bufs {
ret = append(ret, buf...)
putBuf(buf)
}
ret = append(ret, b.Buf...)
putBuf(b.toPool)
b.bufs = nil
b.toPool = nil
b.Buf = nil
return ret
}
|
