001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.io.channels;
019
020import java.io.IOException;
021import java.nio.ByteBuffer;
022import java.nio.channels.FileChannel;
023import java.util.Objects;
024
025import org.apache.commons.io.IOUtils;
026
027/**
028 * Works with {@link FileChannel}.
029 *
030 * @since 2.15.0
031 */
032public final class FileChannels {
033
034    /**
035     * Tests if two RandomAccessFiles contents are equal.
036     *
037     * @param channel1       A FileChannel.
038     * @param channel2       Another FileChannel.
039     * @param byteBufferSize The two internal buffer capacities, in bytes.
040     * @return true if the contents of both RandomAccessFiles are equal, false otherwise.
041     * @throws IOException if an I/O error occurs.
042     */
043    public static boolean contentEquals(final FileChannel channel1, final FileChannel channel2, final int byteBufferSize) throws IOException {
044        // Short-circuit test
045        if (Objects.equals(channel1, channel2)) {
046            return true;
047        }
048        // Short-circuit test
049        final long size1 = size(channel1);
050        final long size2 = size(channel2);
051        if (size1 != size2) {
052            return false;
053        }
054        if (size1 == 0 && size2 == 0) {
055            return true;
056        }
057        // Dig in and do the work
058        final ByteBuffer byteBuffer1 = ByteBuffer.allocateDirect(byteBufferSize);
059        final ByteBuffer byteBuffer2 = ByteBuffer.allocateDirect(byteBufferSize);
060        while (true) {
061            final int read1 = channel1.read(byteBuffer1);
062            final int read2 = channel2.read(byteBuffer2);
063            byteBuffer1.clear();
064            byteBuffer2.clear();
065            if (read1 == IOUtils.EOF && read2 == IOUtils.EOF) {
066                return byteBuffer1.equals(byteBuffer2);
067            }
068            if (read1 != read2) {
069                return false;
070            }
071            if (!byteBuffer1.equals(byteBuffer2)) {
072                return false;
073            }
074        }
075    }
076
077    private static long size(final FileChannel channel) throws IOException {
078        return channel != null ? channel.size() : 0;
079    }
080
081    /**
082     * Don't instantiate.
083     */
084    private FileChannels() {
085        // no-op
086    }
087}