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// Copyright 2017 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package pool
import (
"fmt"
"reflect"
"sync"
)
// Pool is a bucketed pool for variably sized byte slices.
type Pool struct {
buckets []sync.Pool
sizes []int
// make is the function used to create an empty slice when none exist yet.
make func(int) interface{}
}
// New returns a new Pool with size buckets for minSize to maxSize
// increasing by the given factor.
func New(minSize, maxSize int, factor float64, makeFunc func(int) interface{}) *Pool {
if minSize < 1 {
panic("invalid minimum pool size")
}
if maxSize < 1 {
panic("invalid maximum pool size")
}
if factor < 1 {
panic("invalid factor")
}
var sizes []int
for s := minSize; s <= maxSize; s = int(float64(s) * factor) {
sizes = append(sizes, s)
}
p := &Pool{
buckets: make([]sync.Pool, len(sizes)),
sizes: sizes,
make: makeFunc,
}
return p
}
// Get returns a new byte slices that fits the given size.
func (p *Pool) Get(sz int) interface{} {
for i, bktSize := range p.sizes {
if sz > bktSize {
continue
}
b := p.buckets[i].Get()
if b == nil {
b = p.make(bktSize)
}
return b
}
return p.make(sz)
}
// Put adds a slice to the right bucket in the pool.
func (p *Pool) Put(s interface{}) {
slice := reflect.ValueOf(s)
if slice.Kind() != reflect.Slice {
panic(fmt.Sprintf("%+v is not a slice", slice))
}
for i, size := range p.sizes {
if slice.Cap() > size {
continue
}
p.buckets[i].Put(slice.Slice(0, 0).Interface())
return
}
}
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