Module me.lemire.integercompression
Package me.lemire.integercompression.differential

Interface SkippableIntegratedIntegerCODEC

All Known Implementing Classes:
IntegratedBinaryPacking, IntegratedVariableByte, SkippableIntegratedComposition
public interface SkippableIntegratedIntegerCODEC
Interface describing a standard CODEC to compress integers. This is a variation on the IntegerCODEC interface meant to be used for random access and with integrated differential coding (i.e., given a large array, you can segment it and decode just the subarray you need). The main differences are that we must specify the number of integers we wish to decode as well as the initial value (for differential coding). This information might be stored elsewhere.
Author:
Daniel Lemire

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    headlessCompress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos, IntWrapper initvalue)
    Compress data from an array to another array.
    void
    headlessUncompress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos, int num, IntWrapper initvalue)
    Uncompress data from an array to another array.
    int
    maxHeadlessCompressedLength(IntWrapper compressedPositions, int inlength)
    Compute the maximum number of integers that might be required to store the compressed form of a given input array segment, without headers.

  • Method Details

    • headlessCompress

      void headlessCompress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos, IntWrapper initvalue)
      Compress data from an array to another array. Both inpos and outpos are modified to represent how much data was read and written to if 12 ints (inlength = 12) are compressed to 3 ints, then inpos will be incremented by 12 while outpos will be incremented by 3 we use IntWrapper to pass the values by reference.
      Parameters:
      in - input array
      inpos - location in the input array
      inlength - how many integers to compress
      out - output array
      outpos - where to write in the output array
      initvalue - initial value for the purpose of differential coding, the value is automatically updated

    • headlessUncompress

      void headlessUncompress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos, int num, IntWrapper initvalue)
      Uncompress data from an array to another array. Both inpos and outpos parameters are modified to indicate new positions after read/write.
      Parameters:
      in - array containing data in compressed form
      inpos - where to start reading in the array
      inlength - length of the compressed data (ignored by some schemes)
      out - array where to write the compressed output
      outpos - where to write the compressed output in out
      num - number of integers we want to decode, the actual number of integers decoded can be less
      initvalue - initial value for the purpose of differential coding, the value is automatically updated

    • maxHeadlessCompressedLength

      int maxHeadlessCompressedLength(IntWrapper compressedPositions, int inlength)
      Compute the maximum number of integers that might be required to store the compressed form of a given input array segment, without headers.

      This is useful to pre-allocate the output buffer before calling headlessCompress(int[], IntWrapper, int, int[], IntWrapper, IntWrapper).

      Parameters:
      compressedPositions - since not all schemes compress every input integer, this parameter returns how many input integers will actually be compressed. This is useful when composing multiple schemes.
      inlength - number of integers to be compressed
      Returns:
      the maximum number of integers needed in the output array