src.it.unimi.dsi.compression.CodeWordCoder Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of dsiutils Show documentation

The DSI utilities are a mishmash of classes accumulated during the last twenty years in projects developed at the DSI (Dipartimento di Scienze dell'Informazione, i.e., Information Sciences Department), now DI (Dipartimento di Informatica, i.e., Informatics Department), of the Universita` degli Studi di Milano.

There is a newer version: 2.7.3

Show newest version

/*
 * DSI utilities
 *
 * Copyright (C) 2005-2020 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 .
 *
 */

package it.unimi.dsi.compression;

import java.io.IOException;
import java.io.Serializable;

import it.unimi.dsi.bits.BitVector;
import it.unimi.dsi.fastutil.booleans.BooleanIterator;
import it.unimi.dsi.fastutil.booleans.BooleanIterators;
import it.unimi.dsi.io.OutputBitStream;

/** A coder based on a set of codewords. */

public class CodeWordCoder implements PrefixCoder, Serializable {
	private static final long serialVersionUID = 1L;
	/** The array of codewords of this coder. */
	protected final BitVector[] codeWord;

	/** 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.
	 */
	public CodeWordCoder(final BitVector[] codeWord) {
		this.codeWord = codeWord;
	}

	@Override
	public BooleanIterator encode(final int symbol) {
		return codeWord[symbol].iterator();
	}

	@Override
	public int encode(final int symbol, final OutputBitStream obs) throws IOException {
		final BitVector w = codeWord[symbol];
		final int length = (int) w.length();
		for(int i = 0; i < length; i++) obs.writeBit(w.getBoolean(i));
		return length;
	}

	@Override
	public int flush(final OutputBitStream unused) { return 0; }

	@Override
	public BooleanIterator flush() { return BooleanIterators.EMPTY_ITERATOR; }

	@Override
	public BitVector[] codeWords() { return codeWord; }
}