blob: a021c57cf402850d49eea14b6f19cfffa517c971 (
plain)
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
|
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build go1.3
package v1
// Allocation pools for Buffers.
import "sync"
var pools [14]sync.Pool
var pool64 *sync.Pool
func init() {
var i uint
// TODO(pquerna): add science here around actual pool sizes.
for i = 6; i < 20; i++ {
n := 1 << i
pools[poolNum(n)].New = func() interface{} { return make([]byte, 0, n) }
}
pool64 = &pools[0]
}
// This returns the pool number that will give a buffer of
// at least 'i' bytes.
func poolNum(i int) int {
// TODO(pquerna): convert to log2 w/ bsr asm instruction:
// <https://groups.google.com/forum/#!topic/golang-nuts/uAb5J1_y7ns>
if i <= 64 {
return 0
} else if i <= 128 {
return 1
} else if i <= 256 {
return 2
} else if i <= 512 {
return 3
} else if i <= 1024 {
return 4
} else if i <= 2048 {
return 5
} else if i <= 4096 {
return 6
} else if i <= 8192 {
return 7
} else if i <= 16384 {
return 8
} else if i <= 32768 {
return 9
} else if i <= 65536 {
return 10
} else if i <= 131072 {
return 11
} else if i <= 262144 {
return 12
} else if i <= 524288 {
return 13
} else {
return -1
}
}
// Send a buffer to the Pool to reuse for other instances.
// You may no longer utilize the content of the buffer, since it may be used
// by other goroutines.
func Pool(b []byte) {
if b == nil {
return
}
c := cap(b)
// Our smallest buffer is 64 bytes, so we discard smaller buffers.
if c < 64 {
return
}
// We need to put the incoming buffer into the NEXT buffer,
// since a buffer guarantees AT LEAST the number of bytes available
// that is the top of this buffer.
// That is the reason for dividing the cap by 2, so it gets into the NEXT bucket.
// We add 2 to avoid rounding down if size is exactly power of 2.
pn := poolNum((c + 2) >> 1)
if pn != -1 {
pools[pn].Put(b[0:0])
}
// if we didn't have a slot for this []byte, we just drop it and let the GC
// take care of it.
}
// makeSlice allocates a slice of size n -- it will attempt to use a pool'ed
// instance whenever possible.
func makeSlice(n int) []byte {
if n <= 64 {
return pool64.Get().([]byte)[0:n]
}
pn := poolNum(n)
if pn != -1 {
return pools[pn].Get().([]byte)[0:n]
} else {
return make([]byte, n)
}
}
|
