/*
 * 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 <http://www.gnu.org/licenses/>.
 *
 */

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 <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] = (int) codeWord[i].length();
	}

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