github.com/squaremo/docker@v1.3.2-0.20150516120342-42cfc9554972/pkg/pools/pools.go (about)

     1  // Package pools provides a collection of pools which provide various
     2  // data types with buffers. These can be used to lower the number of
     3  // memory allocations and reuse buffers.
     4  //
     5  // New pools should be added to this package to allow them to be
     6  // shared across packages.
     7  //
     8  // Utility functions which operate on pools should be added to this
     9  // package to allow them to be reused.
    10  package pools
    11  
    12  import (
    13  	"bufio"
    14  	"io"
    15  	"sync"
    16  
    17  	"github.com/docker/docker/pkg/ioutils"
    18  )
    19  
    20  var (
    21  	// Pool which returns bufio.Reader with a 32K buffer
    22  	BufioReader32KPool *BufioReaderPool
    23  	// Pool which returns bufio.Writer with a 32K buffer
    24  	BufioWriter32KPool *BufioWriterPool
    25  )
    26  
    27  const buffer32K = 32 * 1024
    28  
    29  type BufioReaderPool struct {
    30  	pool sync.Pool
    31  }
    32  
    33  func init() {
    34  	BufioReader32KPool = newBufioReaderPoolWithSize(buffer32K)
    35  	BufioWriter32KPool = newBufioWriterPoolWithSize(buffer32K)
    36  }
    37  
    38  // newBufioReaderPoolWithSize is unexported because new pools should be
    39  // added here to be shared where required.
    40  func newBufioReaderPoolWithSize(size int) *BufioReaderPool {
    41  	pool := sync.Pool{
    42  		New: func() interface{} { return bufio.NewReaderSize(nil, size) },
    43  	}
    44  	return &BufioReaderPool{pool: pool}
    45  }
    46  
    47  // Get returns a bufio.Reader which reads from r. The buffer size is that of the pool.
    48  func (bufPool *BufioReaderPool) Get(r io.Reader) *bufio.Reader {
    49  	buf := bufPool.pool.Get().(*bufio.Reader)
    50  	buf.Reset(r)
    51  	return buf
    52  }
    53  
    54  // Put puts the bufio.Reader back into the pool.
    55  func (bufPool *BufioReaderPool) Put(b *bufio.Reader) {
    56  	b.Reset(nil)
    57  	bufPool.pool.Put(b)
    58  }
    59  
    60  // NewReadCloserWrapper returns a wrapper which puts the bufio.Reader back
    61  // into the pool and closes the reader if it's an io.ReadCloser.
    62  func (bufPool *BufioReaderPool) NewReadCloserWrapper(buf *bufio.Reader, r io.Reader) io.ReadCloser {
    63  	return ioutils.NewReadCloserWrapper(r, func() error {
    64  		if readCloser, ok := r.(io.ReadCloser); ok {
    65  			readCloser.Close()
    66  		}
    67  		bufPool.Put(buf)
    68  		return nil
    69  	})
    70  }
    71  
    72  type BufioWriterPool struct {
    73  	pool sync.Pool
    74  }
    75  
    76  // newBufioWriterPoolWithSize is unexported because new pools should be
    77  // added here to be shared where required.
    78  func newBufioWriterPoolWithSize(size int) *BufioWriterPool {
    79  	pool := sync.Pool{
    80  		New: func() interface{} { return bufio.NewWriterSize(nil, size) },
    81  	}
    82  	return &BufioWriterPool{pool: pool}
    83  }
    84  
    85  // Get returns a bufio.Writer which writes to w. The buffer size is that of the pool.
    86  func (bufPool *BufioWriterPool) Get(w io.Writer) *bufio.Writer {
    87  	buf := bufPool.pool.Get().(*bufio.Writer)
    88  	buf.Reset(w)
    89  	return buf
    90  }
    91  
    92  // Put puts the bufio.Writer back into the pool.
    93  func (bufPool *BufioWriterPool) Put(b *bufio.Writer) {
    94  	b.Reset(nil)
    95  	bufPool.pool.Put(b)
    96  }
    97  
    98  // NewWriteCloserWrapper returns a wrapper which puts the bufio.Writer back
    99  // into the pool and closes the writer if it's an io.Writecloser.
   100  func (bufPool *BufioWriterPool) NewWriteCloserWrapper(buf *bufio.Writer, w io.Writer) io.WriteCloser {
   101  	return ioutils.NewWriteCloserWrapper(w, func() error {
   102  		buf.Flush()
   103  		if writeCloser, ok := w.(io.WriteCloser); ok {
   104  			writeCloser.Close()
   105  		}
   106  		bufPool.Put(buf)
   107  		return nil
   108  	})
   109  }