src/test/java/org/apache/commons/compress/compressors/lz77support/ParametersTest.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.commons.compress.compressors.lz77support;

import org.junit.Test;

import static org.junit.Assert.assertEquals;

public class ParametersTest {

    @Test
    public void defaultConstructor() {
        Parameters p = newParameters(128);
        assertEquals(128, p.getWindowSize());
        assertEquals(3, p.getMinBackReferenceLength());
        assertEquals(127, p.getMaxBackReferenceLength());
        assertEquals(127, p.getMaxOffset());
        assertEquals(128, p.getMaxLiteralLength());
    }

    @Test
    public void minBackReferenceLengthIsAtLeastThree() {
        Parameters p = newParameters(128, 2, 3, 4, 5);
        assertEquals(3, p.getMinBackReferenceLength());
    }

    @Test
    public void maxBackReferenceLengthIsMinBackReferenceLengthWhenSmallerThanMinBackReferenceLength() {
        Parameters p = newParameters(128, 2, 2, 4, 5);
        assertEquals(3, p.getMaxBackReferenceLength());
    }

    @Test
    public void maxBackReferenceLengthIsMinBackReferenceLengthWhenSmallerThanMinBackReferenceLengthReversedInvocationOrder() {
        Parameters p = Parameters.builder(128)
            .withMaxBackReferenceLength(2)
            .withMinBackReferenceLength(2)
            .withMaxOffset(4)
            .withMaxLiteralLength(5)
            .build();
        assertEquals(3, p.getMaxBackReferenceLength());
    }

    @Test
    public void maxBackReferenceLengthIsMinBackReferenceLengthIfBothAreEqual() {
        Parameters p = newParameters(128, 2, 3, 4, 5);
        assertEquals(3, p.getMaxBackReferenceLength());
    }

    @Test
    public void maxOffsetIsWindowSizeMinus1IfSetTo0() {
        Parameters p = newParameters(128, 2, 3, 0, 5);
        assertEquals(127, p.getMaxOffset());
    }

    @Test
    public void maxOffsetIsWindowSizeMinus1IfSetToANegativeValue() {
        Parameters p = newParameters(128, 2, 3, -1, 5);
        assertEquals(127, p.getMaxOffset());
    }

    @Test
    public void maxOffsetIsWindowSizeMinus1IfBiggerThanWindowSize() {
        Parameters p = newParameters(128, 2, 3, 129, 5);
        assertEquals(127, p.getMaxOffset());
    }

    @Test
    public void maxLiteralLengthIsWindowSizeIfSetTo0() {
        Parameters p = newParameters(128, 2, 3, 4, 0);
        assertEquals(128, p.getMaxLiteralLength());
    }

    @Test
    public void maxLiteralLengthIsWindowSizeIfSetToANegativeValue() {
        Parameters p = newParameters(128, 2, 3, 0, -1);
        assertEquals(128, p.getMaxLiteralLength());
    }

    @Test
    public void maxLiteralLengthIsWindowSizeIfSetToAValueTooBigToHoldInSlidingWindow() {
        Parameters p = newParameters(128, 2, 3, 0, 259);
        assertEquals(128, p.getMaxLiteralLength());
    }

    @Test
    public void allParametersUsuallyTakeTheirSpecifiedValues() {
        Parameters p = newParameters(256, 4, 5, 6, 7);
        assertEquals(256, p.getWindowSize());
        assertEquals(4, p.getMinBackReferenceLength());
        assertEquals(5, p.getMaxBackReferenceLength());
        assertEquals(6, p.getMaxOffset());
        assertEquals(7, p.getMaxLiteralLength());
    }

    @Test(expected = IllegalArgumentException.class)
    public void windowSizeMustNotBeSmallerThanMinBackReferenceLength() {
        newParameters(128, 200, 300, 400, 500);
    }

    @Test(expected = IllegalArgumentException.class)
    public void windowSizeMustBeAPowerOfTwo() {
        newParameters(100, 200, 300, 400, 500);
    }

    private static Parameters newParameters(int windowSize) {
        return Parameters.builder(windowSize).build();
    }

    private static Parameters newParameters(int windowSize, int minBackReferenceLength, int maxBackReferenceLength,
        int maxOffset, int maxLiteralLength) {
        return Parameters.builder(windowSize)
            .withMinBackReferenceLength(minBackReferenceLength)
            .withMaxBackReferenceLength(maxBackReferenceLength)
            .withMaxOffset(maxOffset)
            .withMaxLiteralLength(maxLiteralLength)
            .build();
    }
}