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package bpool
import (
"bytes"
)
// SizedBufferPool implements a pool of bytes.Buffers in the form of a bounded
// channel. Buffers are pre-allocated to the requested size.
type SizedBufferPool struct {
c chan *bytes.Buffer
a int
}
// SizedBufferPool creates a new BufferPool bounded to the given size.
// size defines the number of buffers to be retained in the pool and alloc sets
// the initial capacity of new buffers to minimize calls to make().
//
// The value of alloc should seek to provide a buffer that is representative of
// most data written to the the buffer (i.e. 95th percentile) without being
// overly large (which will increase static memory consumption). You may wish to
// track the capacity of your last N buffers (i.e. using an []int) prior to
// returning them to the pool as input into calculating a suitable alloc value.
func NewSizedBufferPool(size int, alloc int) (bp *SizedBufferPool) {
return &SizedBufferPool{
c: make(chan *bytes.Buffer, size),
a: alloc,
}
}
// Get gets a Buffer from the SizedBufferPool, or creates a new one if none are
// available in the pool. Buffers have a pre-allocated capacity.
func (bp *SizedBufferPool) Get() (b *bytes.Buffer) {
select {
case b = <-bp.c:
// reuse existing buffer
default:
// create new buffer
b = bytes.NewBuffer(make([]byte, 0, bp.a))
}
return
}
// Put returns the given Buffer to the SizedBufferPool.
func (bp *SizedBufferPool) Put(b *bytes.Buffer) {
b.Reset()
// Release buffers over our maximum capacity and re-create a pre-sized
// buffer to replace it.
// Note that the cap(b.Bytes()) provides the capacity from the read off-set
// only, but as we've called b.Reset() the full capacity of the underlying
// byte slice is returned.
if cap(b.Bytes()) > bp.a {
b = bytes.NewBuffer(make([]byte, 0, bp.a))
}
select {
case bp.c <- b:
default: // Discard the buffer if the pool is full.
}
}
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