github.com/ethersphere/bee/v2@v2.2.0/pkg/file/buffer.go (about)

     1  // Copyright 2020 The Swarm Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package file
     6  
     7  import (
     8  	"io"
     9  
    10  	"github.com/ethersphere/bee/v2/pkg/swarm"
    11  )
    12  
    13  const (
    14  	maxBufferSize = swarm.ChunkSize * 2
    15  )
    16  
    17  // ChunkPipe ensures that only the last read is smaller than the chunk size,
    18  // regardless of size of individual writes.
    19  type ChunkPipe struct {
    20  	io.ReadCloser
    21  	writer io.WriteCloser
    22  	data   []byte
    23  	cursor int
    24  }
    25  
    26  // Creates a new ChunkPipe
    27  func NewChunkPipe() io.ReadWriteCloser {
    28  	r, w := io.Pipe()
    29  	return &ChunkPipe{
    30  		ReadCloser: r,
    31  		writer:     w,
    32  		data:       make([]byte, maxBufferSize),
    33  	}
    34  }
    35  
    36  // Read implements io.Reader
    37  func (c *ChunkPipe) Read(b []byte) (int, error) {
    38  	return c.ReadCloser.Read(b)
    39  }
    40  
    41  // Writer implements io.Writer
    42  func (c *ChunkPipe) Write(b []byte) (int, error) {
    43  	nw := 0
    44  
    45  	for {
    46  		if nw >= len(b) {
    47  			break
    48  		}
    49  
    50  		copied := copy(c.data[c.cursor:], b[nw:])
    51  		c.cursor += copied
    52  		nw += copied
    53  
    54  		if c.cursor >= swarm.ChunkSize {
    55  			// NOTE: the Write method contract requires all sent data to be
    56  			// written before returning (without error)
    57  			written, err := c.writer.Write(c.data[:swarm.ChunkSize])
    58  			if err != nil {
    59  				return nw, err
    60  			}
    61  			if swarm.ChunkSize != written {
    62  				return nw, io.ErrShortWrite
    63  			}
    64  
    65  			c.cursor -= swarm.ChunkSize
    66  
    67  			copy(c.data, c.data[swarm.ChunkSize:])
    68  		}
    69  	}
    70  
    71  	return nw, nil
    72  }
    73  
    74  // Close implements io.Closer
    75  func (c *ChunkPipe) Close() error {
    76  	if c.cursor > 0 {
    77  		written, err := c.writer.Write(c.data[:c.cursor])
    78  		if err != nil {
    79  			return err
    80  		}
    81  		if c.cursor != written {
    82  			return io.ErrShortWrite
    83  		}
    84  	}
    85  	return c.writer.Close()
    86  }