org.apache.hadoop.io.compress
Class BlockCompressorStream

java.lang.Object
  java.io.OutputStream
      org.apache.hadoop.io.compress.CompressionOutputStream
          org.apache.hadoop.io.compress.CompressorStream
              org.apache.hadoop.io.compress.BlockCompressorStream

All Implemented Interfaces:

Closeable, Flushable

public class BlockCompressorStream
extends CompressorStream

A CompressorStream which works with 'block-based' based compression algorithms, as opposed to 'stream-based' compression algorithms. It should be noted that this wrapper does not guarantee that blocks will be sized for the compressor. If the Compressor requires buffering to effect meaningful compression, it is responsible for it.

Field Summary

Fields inherited from class org.apache.hadoop.io.compress.CompressorStream

buffer, closed, compressor

Fields inherited from class org.apache.hadoop.io.compress.CompressionOutputStream

out

Constructor Summary

BlockCompressorStream(OutputStream out, Compressor compressor)
Create a BlockCompressorStream with given output-stream and compressor.

BlockCompressorStream(OutputStream out, Compressor compressor, int bufferSize, int compressionOverhead)
Create a BlockCompressorStream.

Method Summary

protected void	compress()
void	finish() Finishes writing compressed data to the output stream without closing the underlying stream.
void	write(byte[] b, int off, int len) Write the data provided to the compression codec, compressing no more than the buffer size less the compression overhead as specified during construction for each block.

Methods inherited from class org.apache.hadoop.io.compress.CompressorStream

close, resetState, write

Methods inherited from class org.apache.hadoop.io.compress.CompressionOutputStream

flush

Methods inherited from class java.io.OutputStream

write

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BlockCompressorStream

public BlockCompressorStream(OutputStream out,
                             Compressor compressor,
                             int bufferSize,
                             int compressionOverhead)

Create a BlockCompressorStream.

Parameters:

out - stream

compressor - compressor to be used

bufferSize - size of buffer

compressionOverhead - maximum 'overhead' of the compression algorithm with given bufferSize

BlockCompressorStream

public BlockCompressorStream(OutputStream out,
                             Compressor compressor)

Create a BlockCompressorStream with given output-stream and compressor. Use default of 512 as bufferSize and compressionOverhead of (1% of bufferSize + 12 bytes) = 18 bytes (zlib algorithm).

Parameters:

out - stream

compressor - compressor to be used

Method Detail

write

public void write(byte[] b,
                  int off,
                  int len)
           throws IOException

Write the data provided to the compression codec, compressing no more than the buffer size less the compression overhead as specified during construction for each block. Each block contains the uncompressed length for the block, followed by one or more length-prefixed blocks of compressed data.

Overrides:

write in class CompressorStream

Throws:

IOException

finish

public void finish()
            throws IOException

Description copied from class: CompressionOutputStream

Finishes writing compressed data to the output stream without closing the underlying stream.

Overrides:

finish in class CompressorStream

Throws:

IOException

compress

protected void compress()
                 throws IOException

Overrides:

compress in class CompressorStream

Throws:

IOException