-
Notifications
You must be signed in to change notification settings - Fork 322
/
msg_buf.go
101 lines (88 loc) · 2.55 KB
/
msg_buf.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
// Copyright (C) 2020, IrineSistiana
//
// This file is part of mosdns.
//
// mosdns is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// mosdns is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
// This file is a modified version from github.com/xtaci/smux/blob/master/alloc.go f386d90
// license of smux: MIT https://github.com/xtaci/smux/blob/master/LICENSE
package utils
import (
"fmt"
"github.com/miekg/dns"
"sync"
)
var (
defaultAllocator = NewAllocator()
)
type Allocator struct {
buffers []sync.Pool
}
// NewAllocator initiates a []byte allocator for dns.Msg less than 65536 bytes,
// the waste(memory fragmentation) of space allocation is guaranteed to be
// no more than 50%.
func NewAllocator() *Allocator {
alloc := new(Allocator)
alloc.buffers = make([]sync.Pool, 17) // 1B -> 64K
for k := range alloc.buffers {
i := k
alloc.buffers[k].New = func() interface{} {
return make([]byte, 1<<uint32(i))
}
}
return alloc
}
func GetMsgBuf(size int) []byte {
return defaultAllocator.Get(size)
}
func GetMsgBufFor(m *dns.Msg) ([]byte, error) {
l := m.Len()
if l > dns.MaxMsgSize || l <= 0 {
return nil, fmt.Errorf("msg length %d is invalid", l)
}
return defaultAllocator.Get(l), nil
}
func ReleaseMsgBuf(buf []byte) {
defaultAllocator.Put(buf)
}
// Get a []byte from pool with most appropriate cap
func (alloc *Allocator) Get(size int) []byte {
if size <= 0 || size > 65536 {
panic("unexpected size")
}
bits := msb(size)
if size == 1<<bits {
return alloc.buffers[bits].Get().([]byte)[:size]
} else {
return alloc.buffers[bits+1].Get().([]byte)[:size]
}
}
// Put returns a []byte to pool for future use,
// which the cap must be exactly 2^n
func (alloc *Allocator) Put(buf []byte) {
bits := msb(cap(buf))
if cap(buf) == 0 || cap(buf) > 65536 || cap(buf) != 1<<bits {
panic("unexpected cap size")
}
alloc.buffers[bits].Put(buf)
}
// msb return the pos of most significant bit
func msb(size int) uint16 {
var pos uint16
size >>= 1
for size > 0 {
size >>= 1
pos++
}
return pos
}