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// 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"
)
const buffer32K = 32 * 1024
var (
// BufioReader32KPool is a pool which returns bufio.Reader with a 32K buffer.
BufioReader32KPool = newBufioReaderPoolWithSize(buffer32K)
// BufioWriter32KPool is a pool which returns bufio.Writer with a 32K buffer.
BufioWriter32KPool = newBufioWriterPoolWithSize(buffer32K)
buffer32KPool = newBufferPoolWithSize(buffer32K)
)
// BufioReaderPool is a bufio reader that uses sync.Pool.
type BufioReaderPool struct {
pool sync.Pool
}
// newBufioReaderPoolWithSize is unexported because new pools should be
// added here to be shared where required.
func newBufioReaderPoolWithSize(size int) *BufioReaderPool {
return &BufioReaderPool{
pool: sync.Pool{
New: func() interface{} { return bufio.NewReaderSize(nil, size) },
},
}
}
// 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)
}
type bufferPool struct {
pool sync.Pool
}
func newBufferPoolWithSize(size int) *bufferPool {
return &bufferPool{
pool: sync.Pool{
New: func() interface{} { return make([]byte, size) },
},
}
}
func (bp *bufferPool) Get() []byte {
return bp.pool.Get().([]byte)
}
func (bp *bufferPool) Put(b []byte) {
bp.pool.Put(b)
}
// Copy is a convenience wrapper which uses a buffer to avoid allocation in io.Copy.
func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
buf := buffer32KPool.Get()
written, err = io.CopyBuffer(dst, src, buf)
buffer32KPool.Put(buf)
return
}
// 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
})
}
// BufioWriterPool is a bufio writer that uses sync.Pool.
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 {
return &BufioWriterPool{
pool: sync.Pool{
New: func() interface{} { return bufio.NewWriterSize(nil, size) },
},
}
}
// 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
})
}
|
