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:

  • Constructor Details

    • 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 Details

    • 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

    • 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

    • write

      public void write(byte[] data, int off, int len) throws IOException
      Overrides:
      write in class OutputStream
      Throws:
      IOException

    • write

      public void write(int b) throws IOException
      Specified by:
      write in class OutputStream
      Throws:
      IOException