github.com/ph/moby@v1.13.1/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  	// BufioReader32KPool is a pool which returns bufio.Reader with a 32K buffer.
    22  	BufioReader32KPool = newBufioReaderPoolWithSize(buffer32K)
    23  	// BufioWriter32KPool is a pool which returns bufio.Writer with a 32K buffer.
    24  	BufioWriter32KPool = newBufioWriterPoolWithSize(buffer32K)
    25  )
    26  
    27  const buffer32K = 32 * 1024
    28  
    29  // BufioReaderPool is a bufio reader that uses sync.Pool.
    30  type BufioReaderPool struct {
    31  	pool sync.Pool
    32  }
    33  
    34  // newBufioReaderPoolWithSize is unexported because new pools should be
    35  // added here to be shared where required.
    36  func newBufioReaderPoolWithSize(size int) *BufioReaderPool {
    37  	return &BufioReaderPool{
    38  		pool: sync.Pool{
    39  			New: func() interface{} { return bufio.NewReaderSize(nil, size) },
    40  		},
    41  	}
    42  }
    43  
    44  // Get returns a bufio.Reader which reads from r. The buffer size is that of the pool.
    45  func (bufPool *BufioReaderPool) Get(r io.Reader) *bufio.Reader {
    46  	buf := bufPool.pool.Get().(*bufio.Reader)
    47  	buf.Reset(r)
    48  	return buf
    49  }
    50  
    51  // Put puts the bufio.Reader back into the pool.
    52  func (bufPool *BufioReaderPool) Put(b *bufio.Reader) {
    53  	b.Reset(nil)
    54  	bufPool.pool.Put(b)
    55  }
    56  
    57  // Copy is a convenience wrapper which uses a buffer to avoid allocation in io.Copy.
    58  func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
    59  	buf := BufioReader32KPool.Get(src)
    60  	written, err = io.Copy(dst, buf)
    61  	BufioReader32KPool.Put(buf)
    62  	return
    63  }
    64  
    65  // NewReadCloserWrapper returns a wrapper which puts the bufio.Reader back
    66  // into the pool and closes the reader if it's an io.ReadCloser.
    67  func (bufPool *BufioReaderPool) NewReadCloserWrapper(buf *bufio.Reader, r io.Reader) io.ReadCloser {
    68  	return ioutils.NewReadCloserWrapper(r, func() error {
    69  		if readCloser, ok := r.(io.ReadCloser); ok {
    70  			readCloser.Close()
    71  		}
    72  		bufPool.Put(buf)
    73  		return nil
    74  	})
    75  }
    76  
    77  // BufioWriterPool is a bufio writer that uses sync.Pool.
    78  type BufioWriterPool struct {
    79  	pool sync.Pool
    80  }
    81  
    82  // newBufioWriterPoolWithSize is unexported because new pools should be
    83  // added here to be shared where required.
    84  func newBufioWriterPoolWithSize(size int) *BufioWriterPool {
    85  	return &BufioWriterPool{
    86  		pool: sync.Pool{
    87  			New: func() interface{} { return bufio.NewWriterSize(nil, size) },
    88  		},
    89  	}
    90  }
    91  
    92  // Get returns a bufio.Writer which writes to w. The buffer size is that of the pool.
    93  func (bufPool *BufioWriterPool) Get(w io.Writer) *bufio.Writer {
    94  	buf := bufPool.pool.Get().(*bufio.Writer)
    95  	buf.Reset(w)
    96  	return buf
    97  }
    98  
    99  // Put puts the bufio.Writer back into the pool.
   100  func (bufPool *BufioWriterPool) Put(b *bufio.Writer) {
   101  	b.Reset(nil)
   102  	bufPool.pool.Put(b)
   103  }
   104  
   105  // NewWriteCloserWrapper returns a wrapper which puts the bufio.Writer back
   106  // into the pool and closes the writer if it's an io.Writecloser.
   107  func (bufPool *BufioWriterPool) NewWriteCloserWrapper(buf *bufio.Writer, w io.Writer) io.WriteCloser {
   108  	return ioutils.NewWriteCloserWrapper(w, func() error {
   109  		buf.Flush()
   110  		if writeCloser, ok := w.(io.WriteCloser); ok {
   111  			writeCloser.Close()
   112  		}
   113  		bufPool.Put(buf)
   114  		return nil
   115  	})
   116  }