split BufferPool from buffer.go

common/alloc/buffer_pool.go

@@ -0,0 +1,54 @@
+package alloc
+
+import (
+	"sync"
+)
+
+type BufferPool struct {
+	chain     chan []byte
+	allocator *sync.Pool
+}
+
+func NewBufferPool(bufferSize, poolSize int) *BufferPool {
+	pool := &BufferPool{
+		chain: make(chan []byte, poolSize),
+		allocator: &sync.Pool{
+			New: func() interface{} { return make([]byte, bufferSize) },
+		},
+	}
+	for i := 0; i < poolSize/2; i++ {
+		pool.chain <- make([]byte, bufferSize)
+	}
+	return pool
+}
+
+func (p *BufferPool) Allocate() *Buffer {
+	var b []byte
+	select {
+	case b = <-p.chain:
+	default:
+		b = p.allocator.Get().([]byte)
+	}
+	return &Buffer{
+		head:   b,
+		pool:   p,
+		Value:  b[defaultOffset:],
+		offset: defaultOffset,
+	}
+}
+
+func (p *BufferPool) Free(buffer *Buffer) {
+	rawBuffer := buffer.head
+	if rawBuffer == nil {
+		return
+	}
+	select {
+	case p.chain <- rawBuffer:
+	default:
+		p.allocator.Put(rawBuffer)
+	}
+}
+
+var smallPool = NewBufferPool(1024, 64)
+var mediumPool = NewBufferPool(8*1024, 128)
+var largePool = NewBufferPool(64*1024, 64)