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pools.go
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pools.go
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// +build go1.3
// Package pools provides a collection of pools which provide various
// data types with buffers. These can be used to lower the number of
// memory allocations and reuse buffers.
//
// New pools should be added to this package to allow them to be
// shared across packages.
//
// Utility functions which operate on pools should be added to this
// package to allow them to be reused.
package pools
import (
"bufio"
"io"
"sync"
"github.com/docker/docker/pkg/ioutils"
)
var (
// Pool which returns bufio.Reader with a 32K buffer
BufioReader32KPool *BufioReaderPool
// Pool which returns bufio.Writer with a 32K buffer
BufioWriter32KPool *BufioWriterPool
)
const buffer32K = 32 * 1024
type BufioReaderPool struct {
pool sync.Pool
}
func init() {
BufioReader32KPool = newBufioReaderPoolWithSize(buffer32K)
BufioWriter32KPool = newBufioWriterPoolWithSize(buffer32K)
}
// newBufioReaderPoolWithSize is unexported because new pools should be
// added here to be shared where required.
func newBufioReaderPoolWithSize(size int) *BufioReaderPool {
pool := sync.Pool{
New: func() interface{} { return bufio.NewReaderSize(nil, size) },
}
return &BufioReaderPool{pool: pool}
}
// Get returns a bufio.Reader which reads from r. The buffer size is that of the pool.
func (bufPool *BufioReaderPool) Get(r io.Reader) *bufio.Reader {
buf := bufPool.pool.Get().(*bufio.Reader)
buf.Reset(r)
return buf
}
// Put puts the bufio.Reader back into the pool.
func (bufPool *BufioReaderPool) Put(b *bufio.Reader) {
b.Reset(nil)
bufPool.pool.Put(b)
}
// NewReadCloserWrapper returns a wrapper which puts the bufio.Reader back
// into the pool and closes the reader if it's an io.ReadCloser.
func (bufPool *BufioReaderPool) NewReadCloserWrapper(buf *bufio.Reader, r io.Reader) io.ReadCloser {
return ioutils.NewReadCloserWrapper(r, func() error {
if readCloser, ok := r.(io.ReadCloser); ok {
readCloser.Close()
}
bufPool.Put(buf)
return nil
})
}
type BufioWriterPool struct {
pool sync.Pool
}
// newBufioWriterPoolWithSize is unexported because new pools should be
// added here to be shared where required.
func newBufioWriterPoolWithSize(size int) *BufioWriterPool {
pool := sync.Pool{
New: func() interface{} { return bufio.NewWriterSize(nil, size) },
}
return &BufioWriterPool{pool: pool}
}
// Get returns a bufio.Writer which writes to w. The buffer size is that of the pool.
func (bufPool *BufioWriterPool) Get(w io.Writer) *bufio.Writer {
buf := bufPool.pool.Get().(*bufio.Writer)
buf.Reset(w)
return buf
}
// Put puts the bufio.Writer back into the pool.
func (bufPool *BufioWriterPool) Put(b *bufio.Writer) {
b.Reset(nil)
bufPool.pool.Put(b)
}
// NewWriteCloserWrapper returns a wrapper which puts the bufio.Writer back
// into the pool and closes the writer if it's an io.Writecloser.
func (bufPool *BufioWriterPool) NewWriteCloserWrapper(buf *bufio.Writer, w io.Writer) io.WriteCloser {
return ioutils.NewWriteCloserWrapper(w, func() error {
buf.Flush()
if writeCloser, ok := w.(io.WriteCloser); ok {
writeCloser.Close()
}
bufPool.Put(buf)
return nil
})
}