pkg/pool: add pools for bufio readers & writers

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)

pools/pools.go

@@ -0,0 +1,111 @@
+// +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
+	})
+}

pools/pools_nopool.go

@@ -0,0 +1,73 @@
+// +build !go1.3
+
+package pools
+
+import (
+	"bufio"
+	"io"
+
+	"github.com/docker/docker/pkg/ioutils"
+)
+
+var (
+	BufioReader32KPool *BufioReaderPool
+	BufioWriter32KPool *BufioWriterPool
+)
+
+const buffer32K = 32 * 1024
+
+type BufioReaderPool struct {
+	size int
+}
+
+func init() {
+	BufioReader32KPool = newBufioReaderPoolWithSize(buffer32K)
+	BufioWriter32KPool = newBufioWriterPoolWithSize(buffer32K)
+}
+
+func newBufioReaderPoolWithSize(size int) *BufioReaderPool {
+	return &BufioReaderPool{size: size}
+}
+
+func (bufPool *BufioReaderPool) Get(r io.Reader) *bufio.Reader {
+	return bufio.NewReaderSize(r, bufPool.size)
+}
+
+func (bufPool *BufioReaderPool) Put(b *bufio.Reader) {
+	b.Reset(nil)
+}
+
+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 {
+			return readCloser.Close()
+		}
+		return nil
+	})
+}
+
+type BufioWriterPool struct {
+	size int
+}
+
+func newBufioWriterPoolWithSize(size int) *BufioWriterPool {
+	return &BufioWriterPool{size: size}
+}
+
+func (bufPool *BufioWriterPool) Get(w io.Writer) *bufio.Writer {
+	return bufio.NewWriterSize(w, bufPool.size)
+}
+
+func (bufPool *BufioWriterPool) Put(b *bufio.Writer) {
+	b.Reset(nil)
+}
+
+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 {
+			return writeCloser.Close()
+		}
+		return nil
+	})
+}