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buffer_store.go
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/
buffer_store.go
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package standard
import (
"errors"
"math/bits"
"sync"
)
/*
内存池
*/
var (
ErrSize = errors.New("max size can't be less than min size")
)
type sizedPool struct {
size int
pool sync.Pool
}
func newSizedPool(size int) *sizedPool {
return &sizedPool{
size: size,
pool: sync.Pool{
New: func() any { return makeSlicePointer(size) },
},
}
}
// Pool is actually multiple pools which store buffers of specific size.
// i.e. it can be three pools which return buffers 32K, 64K and 128K.
type Pool struct {
minSize int
maxSize int
pools []*sizedPool
}
// New returns Pool which has buckets from minSize to maxSize.
// Buckets increase with the power of two, i.e with multiplier 2: [2b, 4b, 16b, ... , 1024b]
// Last pool will always be capped to maxSize.
func NewBufferStore(minSize, maxSize int) (*Pool, error) {
if maxSize < minSize {
return nil, ErrSize
}
const multiplier = 2
pools := make([]*sizedPool, 0)
curSize := minSize
for curSize < maxSize {
pools = append(pools, newSizedPool(curSize))
curSize *= multiplier
}
pools = append(pools, newSizedPool(maxSize))
return &Pool{
minSize: minSize,
maxSize: maxSize,
pools: pools,
}, nil
}
func (p *Pool) findPool(size int) *sizedPool {
if size > p.maxSize {
return nil
}
div, rem := bits.Div64(0, uint64(size), uint64(p.minSize))
idx := bits.Len64(div)
if rem == 0 && div != 0 && (div&(div-1)) == 0 {
idx--
}
return p.pools[idx]
}
// Get returns pointer to []byte which has len size.
// If there is no bucket with buffers >= size, slice will be allocated.
func (p *Pool) Get(size int) *[]byte {
sp := p.findPool(size)
if sp == nil {
return makeSlicePointer(size)
}
buf, ok := sp.pool.Get().(*[]byte)
if !ok {
return makeSlicePointer(size)
}
*buf = (*buf)[:size]
return buf
}
// Put returns pointer to slice to some bucket. Discards slice for which there is no bucket
func (p *Pool) Put(b *[]byte) {
sp := p.findPool(cap(*b))
if sp == nil {
return
}
*b = (*b)[:cap(*b)]
sp.pool.Put(b)
}
func makeSlicePointer(size int) *[]byte {
data := make([]byte, size)
return &data
}