Package org.h2.tools

Class CompressTool

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

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      byte[] compress​(byte[] in, java.lang.String algorithm)
      Compressed the data using the specified algorithm.
      byte[] expand​(byte[] in)
      Expands the compressed data.
      static void expand​(byte[] in, byte[] out, int outPos)
      INTERNAL
      static CompressTool getInstance()
      Get a new instance.
      static int getVariableIntLength​(int x)
      Get a variable size integer length using Rice coding.
      static int readVariableInt​(byte[] buff, int pos)
      Read a variable size integer using Rice coding.
      static java.io.InputStream wrapInputStream​(java.io.InputStream in, java.lang.String compressionAlgorithm, java.lang.String entryName)
      INTERNAL
      static java.io.OutputStream wrapOutputStream​(java.io.OutputStream out, java.lang.String compressionAlgorithm, java.lang.String entryName)
      INTERNAL
      static int writeVariableInt​(byte[] buff, int pos, int x)
      Write a variable size integer using Rice coding.

      • Methods inherited from class java.lang.Object

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

    • Method Detail

      • 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,
                       java.lang.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 java.io.OutputStream wrapOutputStream​(java.io.OutputStream out,
                                                    java.lang.String compressionAlgorithm,
                                                    java.lang.String entryName)
        INTERNAL
        Parameters:
        out - stream
        compressionAlgorithm - to be used
        entryName - in a zip file
        Returns:
        compressed stream

      • wrapInputStream

        public static java.io.InputStream wrapInputStream​(java.io.InputStream in,
                                                  java.lang.String compressionAlgorithm,
                                                  java.lang.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