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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.

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/*
 * DSI utilities
 *
 * Copyright (C) 2007-2020 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 it.unimi.dsi.bits.BitVector;
import it.unimi.dsi.io.OutputBitStream;

/** 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]);
	}
}