-
Notifications
You must be signed in to change notification settings - Fork 9
/
syncbuffer.go
131 lines (104 loc) · 2.43 KB
/
syncbuffer.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
// Copyright 2022 Namespace Labs Inc; All rights reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
package syncbuffer
import (
"bytes"
"io"
"sync"
"golang.org/x/exp/slices"
"namespacelabs.dev/foundation/internal/fnerrors"
)
type ByteBuffer struct {
mu sync.RWMutex
cond *sync.Cond
buf bytes.Buffer
}
type byteBufferReader struct {
sb *ByteBuffer
off int // The reader is not thread-safe.
}
var Discard = discard{io.Discard}
func Seal(b []byte) *Sealed {
return &Sealed{b}
}
func NewByteBuffer() *ByteBuffer {
x := &ByteBuffer{}
x.cond = sync.NewCond(x.mu.RLocker())
return x
}
func (sb *ByteBuffer) Writer() io.Writer {
return sb
}
func (sb *ByteBuffer) Reader() io.ReadCloser {
return &byteBufferReader{sb: sb, off: 0}
}
func (sb *ByteBuffer) Snapshot(copyBytes bool) []byte {
sb.mu.Lock()
defer sb.mu.Unlock()
if copyBytes {
input := sb.buf.Bytes()
c := make([]byte, len(input))
copy(input, c)
return c
}
return slices.Clone(sb.buf.Bytes())
}
func (sb *ByteBuffer) Seal() *Sealed {
sb.mu.Lock()
defer sb.mu.Unlock()
return &Sealed{sb.buf.Bytes()}
}
func (sb *ByteBuffer) Write(p []byte) (int, error) {
sb.mu.Lock()
n, err := sb.buf.Write(p)
sb.cond.Broadcast()
sb.mu.Unlock()
return n, err
}
func (sb *ByteBuffer) readAt(off int, p []byte) (int, error) {
sb.mu.RLock()
defer sb.mu.RUnlock()
for {
// If there are any bytes available to read, read those immediately.
b := sb.buf.Bytes()
if off < len(b) {
n := len(b) - off
if n > len(p) {
n = len(p)
}
copy(p[:n], b[off:(off+n)])
return n, nil
} else {
sb.cond.Wait()
}
}
}
func (r *byteBufferReader) Read(p []byte) (int, error) {
n, err := r.sb.readAt(r.off, p)
r.off += n
return n, err
}
func (r *byteBufferReader) Close() error { return nil }
type Sealed struct {
finalized []byte
}
func (s *Sealed) Writer() io.Writer {
return failedWriter{}
}
func (s *Sealed) Reader() io.ReadCloser {
return io.NopCloser(bytes.NewReader(s.finalized))
}
func (s *Sealed) Snapshot(_ bool) []byte {
return s.finalized
}
func (s *Sealed) Bytes() []byte { return s.finalized }
type failedWriter struct{}
func (failedWriter) GuaranteedWrite(p []byte) {
// XXX increment metric.
}
func (failedWriter) Write(p []byte) (int, error) {
return 0, fnerrors.New("already sealed")
}
type discard struct{ io.Writer }
func (discard) GuaranteedWrite(p []byte) {}