Class LZ4

java.lang.Object
org.apache.lucene.util.compress.LZ4

public final class LZ4 extends Object
LZ4 compression and decompression routines.

https://github.com/lz4/lz4/tree/dev/lib http://fastcompression.blogspot.fr/p/lz4.html

The high-compression option is a simpler version of the one of the original algorithm, and only retains a better hash table that remembers about more occurrences of a previous 4-bytes sequence, and removes all the logic about handling of the case when overlapping matches are found.

  • Field Details

  • Constructor Details

    • LZ4

      private LZ4()
  • Method Details

    • hash

      private static int hash(int i, int hashBits)
    • hashHC

      private static int hashHC(int i)
    • readInt

      private static int readInt(byte[] buf, int i)
    • commonBytes

      private static int commonBytes(byte[] b, int o1, int o2, int limit)
    • decompress

      public static int decompress(DataInput compressed, int decompressedLen, byte[] dest, int dOff) throws IOException
      Decompress at least decompressedLen bytes into dest[dOff:]. Please note that dest must be large enough to be able to hold all decompressed data (meaning that you need to know the total decompressed length). If the given bytes were compressed using a preset dictionary then the same dictionary must be provided in dest[dOff-dictLen:dOff].
      Throws:
      IOException
    • encodeLen

      private static void encodeLen(int l, DataOutput out) throws IOException
      Throws:
      IOException
    • encodeLiterals

      private static void encodeLiterals(byte[] bytes, int token, int anchor, int literalLen, DataOutput out) throws IOException
      Throws:
      IOException
    • encodeLastLiterals

      private static void encodeLastLiterals(byte[] bytes, int anchor, int literalLen, DataOutput out) throws IOException
      Throws:
      IOException
    • encodeSequence

      private static void encodeSequence(byte[] bytes, int anchor, int matchRef, int matchOff, int matchLen, DataOutput out) throws IOException
      Throws:
      IOException
    • compress

      public static void compress(byte[] bytes, int off, int len, DataOutput out, LZ4.HashTable ht) throws IOException
      Compress bytes[off:off+len] into out using at most 16kB of memory. ht shouldn't be shared across threads but can safely be reused.
      Throws:
      IOException
    • compressWithDictionary

      public static void compressWithDictionary(byte[] bytes, int dictOff, int dictLen, int len, DataOutput out, LZ4.HashTable ht) throws IOException
      Compress bytes[dictOff+dictLen:dictOff+dictLen+len] into out using at most 16kB of memory. bytes[dictOff:dictOff+dictLen] will be used as a dictionary. dictLen must not be greater than 64kB, the maximum window size.

      ht shouldn't be shared across threads but can safely be reused.

      Throws:
      IOException