clash/common/pool/alloc.go
2022-03-16 12:10:13 +08:00

64 lines
1.5 KiB
Go

package pool
// Inspired by https://github.com/xtaci/smux/blob/master/alloc.go
import (
"errors"
"math/bits"
"sync"
)
var 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() any {
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]
}
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")
}
//lint:ignore SA6002 ignore temporarily
//nolint
alloc.buffers[bits].Put(buf)
return nil
}
// msb return the pos of most significant bit
func msb(size int) uint16 {
return uint16(bits.Len32(uint32(size)) - 1)
}