Package org.h2.tools

Class CompressTool

java.lang.Object
org.h2.tools.CompressTool
public class CompressTool extends Object
A tool to losslessly compress data, and expand the compressed data again.

  • Method Details

    • getInstance

      public static CompressTool getInstance()
      Get a new instance. Each instance uses a separate buffer, so multiple instances can be used concurrently. However each instance alone is not multithreading safe.
      Returns:
      a new instance

    • compress

      public byte[] compress(byte[] in, String algorithm)
      Compressed the data using the specified algorithm. If no algorithm is supplied, LZF is used
      Parameters:
      in - the byte array with the original data
      algorithm - the algorithm (LZF, DEFLATE)
      Returns:
      the compressed data

    • expand

      public byte[] expand(byte[] in)
      Expands the compressed data.
      Parameters:
      in - the byte array with the compressed data
      Returns:
      the uncompressed data

    • expand

      public static void expand(byte[] in, byte[] out, int outPos)
      INTERNAL
      Parameters:
      in - compressed data
      out - uncompressed result
      outPos - the offset at the output array

    • readVariableInt

      public static int readVariableInt(byte[] buff, int pos)
      Read a variable size integer using Rice coding.
      Parameters:
      buff - the buffer
      pos - the position
      Returns:
      the integer

    • writeVariableInt

      public static int writeVariableInt(byte[] buff, int pos, int x)
      Write a variable size integer using Rice coding. Negative values need 5 bytes.
      Parameters:
      buff - the buffer
      pos - the position
      x - the value
      Returns:
      the number of bytes written (0-5)

    • getVariableIntLength

      public static int getVariableIntLength(int x)
      Get a variable size integer length using Rice coding. Negative values need 5 bytes.
      Parameters:
      x - the value
      Returns:
      the number of bytes needed (0-5)

    • wrapOutputStream

      public static OutputStream wrapOutputStream(OutputStream out, String compressionAlgorithm, String entryName)
      INTERNAL
      Parameters:
      out - stream
      compressionAlgorithm - to be used
      entryName - in a zip file
      Returns:
      compressed stream

    • wrapInputStream

      public static InputStream wrapInputStream(InputStream in, String compressionAlgorithm, String entryName)
      INTERNAL
      Parameters:
      in - stream
      compressionAlgorithm - to be used
      entryName - in a zip file
      Returns:
      in stream or null if there is no such entry