71 lines
1.2 KiB
Go
71 lines
1.2 KiB
Go
// Package iobufpool implements a global segregated-fit pool of buffers for IO.
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//
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// It uses *[]byte instead of []byte to avoid the sync.Pool allocation with Put. Unfortunately, using a pointer to avoid
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// an allocation is purposely not documented. https://github.com/golang/go/issues/16323
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package iobufpool
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import "sync"
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const minPoolExpOf2 = 8
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var pools [18]*sync.Pool
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func init() {
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for i := range pools {
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bufLen := 1 << (minPoolExpOf2 + i)
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pools[i] = &sync.Pool{
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New: func() any {
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buf := make([]byte, bufLen)
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return &buf
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},
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}
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}
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}
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// Get gets a []byte of len size with cap <= size*2.
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func Get(size int) *[]byte {
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i := getPoolIdx(size)
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if i >= len(pools) {
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buf := make([]byte, size)
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return &buf
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}
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ptrBuf := (pools[i].Get().(*[]byte))
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*ptrBuf = (*ptrBuf)[:size]
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return ptrBuf
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}
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func getPoolIdx(size int) int {
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size--
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size >>= minPoolExpOf2
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i := 0
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for size > 0 {
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size >>= 1
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i++
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}
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return i
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}
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// Put returns buf to the pool.
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func Put(buf *[]byte) {
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i := putPoolIdx(cap(*buf))
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if i < 0 {
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return
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}
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pools[i].Put(buf)
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}
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func putPoolIdx(size int) int {
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minPoolSize := 1 << minPoolExpOf2
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for i := range pools {
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if size == minPoolSize<<i {
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return i
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}
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}
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return -1
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}
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