forked from xtaci/smux
-
Notifications
You must be signed in to change notification settings - Fork 0
/
alloc.go
69 lines (59 loc) · 1.47 KB
/
alloc.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
package smux
import (
"sync"
"github.com/pkg/errors"
)
var defaultAllocator *Allocator
func init() {
defaultAllocator = NewAllocator()
}
// Allocator for incoming frames, optimized to prevent overwriting after zeroing
type Allocator struct {
buffers []sync.Pool
}
// NewAllocator initiates a []byte allocator for frames 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
}
// Get a []byte from pool with most appropriate cap
func (alloc *Allocator) Get(size int) []byte {
if size <= 0 || size > 65536 {
return nil
}
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) error {
bits := msb(cap(buf))
if cap(buf) == 0 || cap(buf) > 65536 || cap(buf) != 1<<bits {
return errors.New("allocator Put() incorrect buffer size")
}
alloc.buffers[bits].Put(buf)
return nil
}
// msb return the pos of most significiant bit
func msb(size int) uint16 {
var pos uint16
size >>= 1
for size > 0 {
size >>= 1
pos++
}
return pos
}