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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) 2010-2020 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 static org.junit.Assert.assertEquals;

import java.io.IOException;
import java.util.Random;

import org.junit.Test;

import it.unimi.dsi.bits.BitVector;
import it.unimi.dsi.bits.LongArrayBitVector;
import it.unimi.dsi.util.SplitMix64Random;

public class HuTuckerCodecTest extends CodecTestCase {
	@Test
	public void testOneSymbol() throws IOException {
		final HuTuckerCodec codec = new HuTuckerCodec(new int[] { 1 });
		assertEquals(1, codec.codeWords().length);
		assertEquals(LongArrayBitVector.ofLength(0), codec.codeWords()[0]);
		final Random r = new SplitMix64Random(0);
		checkPrefixCodec(codec, r);
	}

	@Test
	public void testTwoEquiprobableSymbols() throws IOException {
		final HuTuckerCodec codec = new HuTuckerCodec(new int[] { 1, 1 });
		assertEquals(2, codec.codeWords().length);
		assertEquals(LongArrayBitVector.ofLength(1), codec.codeWords()[0]);
		final BitVector v = LongArrayBitVector.ofLength(1);
		v.set(0);
		assertEquals(v, codec.codeWords()[1]);
		final Random r = new SplitMix64Random(0);
		checkPrefixCodec(codec, r);
	}

	@Test
	public void testThreeNonequiprobableSymbols() throws IOException {
		final HuTuckerCodec codec = new HuTuckerCodec(new int[] { 1, 2, 4 });
		assertEquals(3, codec.codeWords().length);
		BitVector v = LongArrayBitVector.ofLength(2);
		assertEquals(v, codec.codeWords()[0]);
		v.set(1);
		assertEquals(v, codec.codeWords()[1]);

		v = LongArrayBitVector.ofLength(1);
		v.set(0);
		assertEquals(v, codec.codeWords()[2]);
		final Random r = new SplitMix64Random(0);
		checkPrefixCodec(codec, r);
	}

	@Test
	public void testRandomFrequencies() throws IOException {
		final Random r = new SplitMix64Random(0);
		final int[] frequency = new int[100];
		for(int i = 0; i < frequency.length; i++) frequency[i] = r.nextInt(1000);
		final HuTuckerCodec codec = new HuTuckerCodec(frequency);
		checkPrefixCodec(codec, r);
	}

	@Test
	public void testRandomCodeLengths() throws IOException {
		final int[] frequency = { 805, 1335, 6401, 7156, 7333, 10613, 10951, 11708, 12710, 12948, 13237, 13976, 20355, 20909, 22398, 26303, 26400, 28380, 28865, 30152, 31693, };
		final int[] codeLength = { 7, 7, 6, 5, 5, 5, 5, 5, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 3, 3 };
		final HuTuckerCodec codec = new HuTuckerCodec(frequency);
		checkLengths(frequency, codeLength, codec.codeWords());
		checkPrefixCodec(codec, new SplitMix64Random(1));
	}

	@Test
	public void testExponentialCodeLengths() throws IOException {
		final int[] frequency = { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864, 134217728, 268435456, 536870912, 1073741824 };
		final int[] codeLength = { 30, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 };
		final HuTuckerCodec codec = new HuTuckerCodec(frequency);
		checkLengths(frequency, codeLength, codec.codeWords());
		checkPrefixCodec(codec, new SplitMix64Random(1));
	}

}