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
|
package stackless
import (
"errors"
"fmt"
"io"
"sync"
"github.com/valyala/bytebufferpool"
)
// Writer is an interface stackless writer must conform to.
//
// The interface contains common subset for Writers from compress/* packages.
type Writer interface {
Write(p []byte) (int, error)
Flush() error
Close() error
Reset(w io.Writer)
}
// NewWriterFunc must return new writer that will be wrapped into
// stackless writer.
type NewWriterFunc func(w io.Writer) Writer
// NewWriter creates a stackless writer around a writer returned
// from newWriter.
//
// The returned writer writes data to dstW.
//
// Writers that use a lot of stack space may be wrapped into stackless writer,
// thus saving stack space for high number of concurrently running goroutines.
func NewWriter(dstW io.Writer, newWriter NewWriterFunc) Writer {
w := &writer{
dstW: dstW,
}
w.zw = newWriter(&w.xw)
return w
}
type writer struct {
dstW io.Writer
zw Writer
err error
xw xWriter
p []byte
n int
op op
}
type op int
const (
opWrite op = iota
opFlush
opClose
opReset
)
func (w *writer) Write(p []byte) (int, error) {
w.p = p
err := w.do(opWrite)
w.p = nil
return w.n, err
}
func (w *writer) Flush() error {
return w.do(opFlush)
}
func (w *writer) Close() error {
return w.do(opClose)
}
func (w *writer) Reset(dstW io.Writer) {
w.xw.Reset()
w.do(opReset) //nolint:errcheck
w.dstW = dstW
}
func (w *writer) do(op op) error {
w.op = op
if !stacklessWriterFunc(w) {
return errHighLoad
}
err := w.err
if err != nil {
return err
}
if w.xw.bb != nil && len(w.xw.bb.B) > 0 {
_, err = w.dstW.Write(w.xw.bb.B)
}
w.xw.Reset()
return err
}
var errHighLoad = errors.New("cannot compress data due to high load")
var (
stacklessWriterFuncOnce sync.Once
stacklessWriterFuncFunc func(ctx any) bool
)
func stacklessWriterFunc(ctx any) bool {
stacklessWriterFuncOnce.Do(func() {
stacklessWriterFuncFunc = NewFunc(writerFunc)
})
return stacklessWriterFuncFunc(ctx)
}
func writerFunc(ctx any) {
w := ctx.(*writer)
switch w.op {
case opWrite:
w.n, w.err = w.zw.Write(w.p)
case opFlush:
w.err = w.zw.Flush()
case opClose:
w.err = w.zw.Close()
case opReset:
w.zw.Reset(&w.xw)
w.err = nil
default:
panic(fmt.Sprintf("BUG: unexpected op: %d", w.op))
}
}
type xWriter struct {
bb *bytebufferpool.ByteBuffer
}
func (w *xWriter) Write(p []byte) (int, error) {
if w.bb == nil {
w.bb = bufferPool.Get()
}
return w.bb.Write(p)
}
func (w *xWriter) Reset() {
if w.bb != nil {
bufferPool.Put(w.bb)
w.bb = nil
}
}
var bufferPool bytebufferpool.Pool
|
