Package org.apache.commons.compress.compressors.snappy

Class SnappyCompressorOutputStream

java.lang.Object

java.io.OutputStream

org.apache.commons.compress.compressors.CompressorOutputStream

org.apache.commons.compress.compressors.snappy.SnappyCompressorOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

public class SnappyCompressorOutputStream
extends CompressorOutputStream

CompressorOutputStream for the raw Snappy format.

This implementation uses an internal buffer in order to handle the back-references that are at the heart of the LZ77 algorithm. The size of the buffer must be at least as big as the biggest offset used in the compressed stream. The current version of the Snappy algorithm as defined by Google works on 32k blocks and doesn't contain offsets bigger than 32k which is the default block size used by this class.

The raw Snappy format requires the uncompressed size to be written at the beginning of the stream using a varint representation, i.e. the number of bytes needed to write the information is not known before the uncompressed size is known. We've chosen to make the uncompressedSize a parameter of the constructor in favor of buffering the whole output until the size is known. When using the FramedSnappyCompressorOutputStream this limitation is taken care of by the warpping framing format.

Since:

1.14

See Also:

Snappy compressed format description

Constructor Summary

Constructors

Constructor	Description
SnappyCompressorOutputStream(OutputStream os, long uncompressedSize)	Constructor using the default block size of 32k.
SnappyCompressorOutputStream(OutputStream os, long uncompressedSize, int blockSize)	Constructor using a configurable block size.
SnappyCompressorOutputStream(OutputStream os, long uncompressedSize, Parameters params)	Constructor providing full control over the underlying LZ77 compressor.

Method Summary

Modifier and Type	Method	Description
void	close()
static Parameters.Builder	createParameterBuilder(int blockSize)	Returns a builder correctly configured for the Snappy algorithm using the gven block size.
void	finish()	Compresses all remaining data and writes it to the stream, doesn't close the underlying stream.
void	write(byte[] data, int off, int len)
void	write(int b)

Methods inherited from class java.io.OutputStream

flush, nullOutputStream, write

Methods inherited from class java.lang.Object

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

Constructor Detail

SnappyCompressorOutputStream

public SnappyCompressorOutputStream(OutputStream os,
                                    long uncompressedSize)
                             throws IOException

Constructor using the default block size of 32k.

Parameters:

os - the outputstream to write compressed data to

uncompressedSize - the uncompressed size of data

Throws:

IOException - if writing of the size fails

SnappyCompressorOutputStream

public SnappyCompressorOutputStream(OutputStream os,
                                    long uncompressedSize,
                                    int blockSize)
                             throws IOException

Constructor using a configurable block size.

Parameters:

os - the outputstream to write compressed data to

uncompressedSize - the uncompressed size of data

blockSize - the block size used - must be a power of two

Throws:

IOException - if writing of the size fails

SnappyCompressorOutputStream

public SnappyCompressorOutputStream(OutputStream os,
                                    long uncompressedSize,
                                    Parameters params)
                             throws IOException

Constructor providing full control over the underlying LZ77 compressor.

Parameters:

os - the outputstream to write compressed data to

uncompressedSize - the uncompressed size of data

params - the parameters to use by the compressor - note that the format itself imposes some limits like a maximum match length of 64 bytes

Throws:

IOException - if writing of the size fails

Method Detail

write

public void write(int b)
           throws IOException

Specified by:

write in class OutputStream

Throws:

IOException

write

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

Overrides:

write in class OutputStream

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class OutputStream

Throws:

IOException

finish

public void finish()
            throws IOException

Compresses all remaining data and writes it to the stream, doesn't close the underlying stream.

Throws:

IOException - if an error occurs

createParameterBuilder

public static Parameters.Builder createParameterBuilder(int blockSize)

Returns a builder correctly configured for the Snappy algorithm using the gven block size.

Parameters:

blockSize - the block size.

Returns:

a builder correctly configured for the Snappy algorithm using the gven block size