src.it.unimi.dsi.compression.Fast64CodeWordCoder Maven / Gradle / Ivy
package it.unimi.dsi.compression;
/*
* DSI utilities
*
* Copyright (C) 2007-2017 Sebastiano Vigna
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at your option)
* any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, see .
*
*/
import it.unimi.dsi.bits.BitVector;
import it.unimi.dsi.io.OutputBitStream;
import java.io.IOException;
/** A fast coder based on a set of codewords of length at most 64. */
public final class Fast64CodeWordCoder extends CodeWordCoder {
private static final long serialVersionUID = 1L;
/** An array parallel to {@link #codeWord} containing the codewords as longs (right aligned). */
private final long[] longCodeWord;
/** A cached array, parallel to {@link #longCodeWord}, of codewords length. */
private final int[] length;
/** Creates a new codeword-based coder using the given vector of codewords. The
* coder will be able to encode symbols numbered from 0 to codeWord.length-1
, included.
*
* @param codeWord a vector of codewords.
* @param longCodeWord the same codewords as those specified in codeWord
, but
* as right-aligned longs written in left-to-right fashion.
*/
public Fast64CodeWordCoder(final BitVector[] codeWord, final long[] longCodeWord) {
super(codeWord);
this.longCodeWord = longCodeWord;
length = new int[codeWord.length];
for(int i = length.length; i-- != 0;) length[i] = (int) codeWord[i].length();
}
@Override
public int encode(final int symbol, final OutputBitStream obs) throws IOException {
return obs.writeLong(longCodeWord[symbol], length[symbol]);
}
}