fast64codewordcoder.java

MG4J (Managing Gigabytes for Java) is a free full-text search engine for large document collections

package it.unimi.dsi.mg4j.compression;

/*		 
* MG4J: Managing Gigabytes for Java
*
* Copyright (C) 2007 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 2.1 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, write to the Free Software
*  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
*/

import it.unimi.dsi.io.OutputBitStream;

import java.io.IOException;

import cern.colt.bitvector.BitVector;

/** A fast coder based on a set of codewords of length at most 64. 
 * 
 * @deprecated Moved to <code>dsiutils</code>.
 */

@Deprecated
final public 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 <code>codeWord.length-1</code>, included.
	 * 
	 * @param codeWord a vector of codewords.
	 * @param longCodeWord the same codewords as those specified in <code>codeWord</code>, 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 ] = codeWord[ i ].size();
	}

	@Override
	public int encode( final int symbol, final OutputBitStream obs ) throws IOException {
		return obs.writeLong( longCodeWord[ symbol ], length[ symbol ] );
	}
}