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74 lines
1.6 KiB
Go
74 lines
1.6 KiB
Go
package pool
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// Inspired by https://github.com/xtaci/smux/blob/master/alloc.go
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import (
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"errors"
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"math/bits"
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"sync"
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)
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var defaultAllocator = NewAllocator()
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// Allocator for incoming frames, optimized to prevent overwriting after zeroing
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type Allocator struct {
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buffers []sync.Pool
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}
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// NewAllocator initiates a []byte allocator for frames less than 65536 bytes,
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// the waste(memory fragmentation) of space allocation is guaranteed to be
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// no more than 50%.
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func NewAllocator() *Allocator {
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alloc := new(Allocator)
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alloc.buffers = make([]sync.Pool, 17) // 1B -> 64K
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for k := range alloc.buffers {
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i := k
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alloc.buffers[k].New = func() any {
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return make([]byte, 1<<uint32(i))
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}
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}
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return alloc
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}
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// Get a []byte from pool with most appropriate cap
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func (alloc *Allocator) Get(size int) []byte {
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switch {
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case size < 0:
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panic("alloc.Get: len out of range")
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case size == 0:
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return nil
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case size > 65536:
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return make([]byte, size)
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default:
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bits := msb(size)
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if size == 1<<bits {
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return alloc.buffers[bits].Get().([]byte)[:size]
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}
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return alloc.buffers[bits+1].Get().([]byte)[:size]
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}
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}
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// Put returns a []byte to pool for future use,
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// which the cap must be exactly 2^n
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func (alloc *Allocator) Put(buf []byte) error {
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if cap(buf) == 0 || cap(buf) > 65536 {
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return nil
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}
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bits := msb(cap(buf))
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if cap(buf) != 1<<bits {
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return errors.New("allocator Put() incorrect buffer size")
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}
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//nolint
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//lint:ignore SA6002 ignore temporarily
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alloc.buffers[bits].Put(buf)
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return nil
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}
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// msb return the pos of most significant bit
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func msb(size int) uint16 {
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return uint16(bits.Len32(uint32(size)) - 1)
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}
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