src/test/java/org/apache/commons/codec/digest/XXHash32OverflowTest.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
 *
 *      https://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.codec.digest;

import static org.junit.jupiter.api.Assertions.assertTrue;
import static org.junit.jupiter.api.Assumptions.assumeTrue;

import org.junit.jupiter.api.Test;

class XXHash32OverflowTest {

    /**
     * This test hits an edge case where a very large number of bytes is added to the incremental
     * hash. The data is constructed so that an integer counter of unprocessed bytes will
     * overflow. If this is not handled correctly then the code throws an exception when it
     * copies more data into the unprocessed bytes array.
     */
    @Test
    void testIncrementalHashWithUnprocessedBytesAndHugeLengthArray() {
        // Assert the test precondition that a large array added to unprocessed bytes
        // will overflow an integer counter. We use the smallest hugeLength possible
        // as some VMs cannot allocate maximum length arrays.
        final int bufferSize = 16;
        final int unprocessedSize = bufferSize - 1;
        final int hugeLength = Integer.MAX_VALUE - (unprocessedSize - 1);
        assertTrue(unprocessedSize + hugeLength < bufferSize, "This should overflow to negative");

        // Check the test can be run
        byte[] bytes = null;
        try {
            bytes = new byte[hugeLength];
        } catch (final OutOfMemoryError ignore) {
            // Some VMs cannot allocate an array this large.
            // Some test environments may not have enough available memory for this.
        }
        assumeTrue(bytes != null, "Cannot allocate array of length " + hugeLength);

        final XXHash32 inc = new XXHash32();
        // Add bytes that should be unprocessed
        inc.update(bytes, 0, unprocessedSize);
        // Add a huge number of bytes to overflow an integer counter of unprocessed bytes.
        inc.update(bytes, 0, hugeLength);
    }
}