改变 pool.NewBuffer 的行为，响应固定容量的BufferPool (#20)

Author: thinkeridea

pool/benchmark/buffer_test.go

@@ -5,27 +5,12 @@ package pool
 
 import (
 	"bytes"
-	"math/bits"
-	"sort"
 	"sync"
-	"sync/atomic"
 	"unsafe"
 
 	"github.com/thinkeridea/go-extend/exsync"
 )
 
-const (
-	bucketSize              = 22
-	minSizeBits             = 6
-	minSize                 = 1 << minSizeBits                    // 2^6=64
-	maxSize                 = 1 << (minSizeBits + bucketSize - 1) // 2^28=256MB
-	calibrateCallsThreshold = 10240
-)
-
-var (
-	buffBucket = [bucketSize]sync.Pool{}
-)
-
 // BufferPool bytes.Buffer 的 sync.Pool 接口
 // 可以直接 Get *bytes.Buffer 并 Reset Buffer
 type BufferPool interface {
@@ -36,77 +21,6 @@ type BufferPool interface {
 	Put(*bytes.Buffer)
 }
 
-type buffer struct {
-	index       uint32
-	calibrating uint32
-	release     uint32
-	calls       [bucketSize]uint32
-}
-
-// NewBuffer 创建一个动态评估需求容量的 BufferPool，它们共享一个底层 bytes.Buffer 区间池
-// Deprecated: 这是错误测试产生的结果，它并没有相较 sync.Pool 有明显优势，详细参看: https://github.com/thinkeridea/go-extend/issues/17
-func NewBuffer(size int) BufferPool {
-	b := &buffer{}
-	b.index = uint32(buffBucketIndex(size))
-	return b
-}
-
-// Get 从 Pool 中获取一个 *bytes.Buffer 实例, 该实例已经被 Reset
-func (p *buffer) Get() *bytes.Buffer {
-	idx := atomic.LoadUint32(&p.index)
-	v := buffBucket[idx].Get()
-	if v != nil {
-		b := v.(*bytes.Buffer)
-		b.Reset()
-		return b
-	}
-
-	return bytes.NewBuffer(make([]byte, 0, minSize<<idx))
-}
-
-// Put 把 *bytes.Buffer 放回 Pool 中
-func (p *buffer) Put(b *bytes.Buffer) {
-	if b.Cap() <= maxSize {
-		buffBucket[buffBucketIndex(b.Cap())].Put(b)
-	}
-
-	atomic.AddUint32(&p.calls[buffBucketIndex(bufferLen(b))], 1)
-	if atomic.AddUint32(&p.release, 1) > calibrateCallsThreshold {
-		p.calibrate()
-	}
-}
-
-func (p *buffer) calibrate() {
-	if !atomic.CompareAndSwapUint32(&p.calibrating, 0, 1) {
-		return
-	}
-
-	var callSize [bucketSize]uint64
-	for i := range callSize {
-		callSize[i] = uint64(atomic.SwapUint32(&p.calls[i], 0))<<32 | minSize<<i
-	}
-
-	sort.Slice(callSize[:], func(i, j int) bool {
-		return callSize[i] > callSize[j]
-	})
-
-	atomic.SwapUint32(&p.index, uint32(buffBucketIndex(int(callSize[0]<<32>>32))))
-	atomic.StoreUint32(&p.release, 0)
-	atomic.SwapUint32(&p.calibrating, 0)
-}
-
-func buffBucketIndex(n int) int {
-	if n == 0 {
-		return 0
-	}
-
-	idx := bits.Len32(uint32((n - 1) >> minSizeBits))
-	if idx >= bucketSize {
-		idx = bucketSize - 1
-	}
-	return idx
-}
-
 var (
 	buff64   exsync.OncePointer
 	buff128  exsync.OncePointer
@@ -121,6 +35,17 @@ type bufferPool struct {
 	sync.Pool
 }
 
+// NewBuffer 创建一个指定容量的 BufferPool，这将是一个独立的非共享的，每次调用都会返回新的BufferPool
+func NewBuffer(size int) BufferPool {
+	return &bufferPool{
+		Pool: sync.Pool{
+			New: func() interface{} {
+				return bytes.NewBuffer(make([]byte, size))
+			},
+		},
+	}
+}
+
 func newBufferPool(size int) unsafe.Pointer {
 	return unsafe.Pointer(&bufferPool{
 		Pool: sync.Pool{