    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.compress.utils;
    019
    020import java.io.File;
    021import java.io.IOException;
    022import java.nio.ByteBuffer;
    023import java.nio.channels.ClosedChannelException;
    024import java.nio.channels.NonWritableChannelException;
    025import java.nio.channels.SeekableByteChannel;
    026import java.nio.file.Files;
    027import java.nio.file.Path;
    028import java.nio.file.StandardOpenOption;
    029import java.util.ArrayList;
    030import java.util.Arrays;
    031import java.util.Collections;
    032import java.util.List;
    033import java.util.Objects;
    034
    035/**
    036 * Implements a read-only {@link SeekableByteChannel} that concatenates a collection of other {@link SeekableByteChannel}s.
    037 * <p>
    038 * This is a lose port of <a href=
    039 * "https://github.com/frugalmechanic/fm-common/blob/master/jvm/src/main/scala/fm/common/MultiReadOnlySeekableByteChannel.scala">
    040 * MultiReadOnlySeekableByteChannel</a>
    041 * by Tim Underwood.
    042 * </p>
    043 *
    044 * @since 1.19
    045 */
    046public class MultiReadOnlySeekableByteChannel implements SeekableByteChannel {
    047
    048    private static final Path[] EMPTY_PATH_ARRAY = {};
    049
    050    /**
    051     * Concatenates the given files.
    052     *
    053     * @param files the files to concatenate
    054     * @throws NullPointerException if files is null
    055     * @throws IOException          if opening a channel for one of the files fails
    056     * @return SeekableByteChannel that concatenates all provided files
    057     */
    058    public static SeekableByteChannel forFiles(final File... files) throws IOException {
    059        final List<Path> paths = new ArrayList<>();
    060        for (final File f : Objects.requireNonNull(files, "files")) {
    061            paths.add(f.toPath());
    062        }
    063        return forPaths(paths.toArray(EMPTY_PATH_ARRAY));
    064    }
    065
    066    /**
    067     * Concatenates the given file paths.
    068     *
    069     * @param paths the file paths to concatenate, note that the LAST FILE of files should be the LAST SEGMENT(.zip) and these files should be added in correct
    070     *              order (e.g.: .z01, .z02... .z99, .zip)
    071     * @return SeekableByteChannel that concatenates all provided files
    072     * @throws NullPointerException if files is null
    073     * @throws IOException          if opening a channel for one of the files fails
    074     * @throws IOException          if the first channel doesn't seem to hold the beginning of a split archive
    075     * @since 1.22
    076     */
    077    public static SeekableByteChannel forPaths(final Path... paths) throws IOException {
    078        final List<SeekableByteChannel> channels = new ArrayList<>();
    079        for (final Path path : Objects.requireNonNull(paths, "paths")) {
    080            channels.add(Files.newByteChannel(path, StandardOpenOption.READ));
    081        }
    082        if (channels.size() == 1) {
    083            return channels.get(0);
    084        }
    085        return new MultiReadOnlySeekableByteChannel(channels);
    086    }
    087
    088    /**
    089     * Concatenates the given channels.
    090     *
    091     * @param channels the channels to concatenate
    092     * @throws NullPointerException if channels is null
    093     * @return SeekableByteChannel that concatenates all provided channels
    094     */
    095    public static SeekableByteChannel forSeekableByteChannels(final SeekableByteChannel... channels) {
    096        if (Objects.requireNonNull(channels, "channels").length == 1) {
    097            return channels[0];
    098        }
    099        return new MultiReadOnlySeekableByteChannel(Arrays.asList(channels));
    100    }
    101
    102    private final List<SeekableByteChannel> channelList;
    103
    104    private long globalPosition;
    105
    106    private int currentChannelIdx;
    107
    108    /**
    109     * Concatenates the given channels.
    110     *
    111     * @param channels the channels to concatenate
    112     * @throws NullPointerException if channels is null
    113     */
    114    public MultiReadOnlySeekableByteChannel(final List<SeekableByteChannel> channels) {
    115        this.channelList = Collections.unmodifiableList(new ArrayList<>(Objects.requireNonNull(channels, "channels")));
    116    }
    117
    118    @Override
    119    public void close() throws IOException {
    120        IOException first = null;
    121        for (final SeekableByteChannel ch : channelList) {
    122            try {
    123                ch.close();
    124            } catch (final IOException ex) {
    125                if (first == null) {
    126                    first = ex;
    127                }
    128            }
    129        }
    130        if (first != null) {
    131            throw new IOException("failed to close wrapped channel", first);
    132        }
    133    }
    134
    135    @Override
    136    public boolean isOpen() {
    137        return channelList.stream().allMatch(SeekableByteChannel::isOpen);
    138    }
    139
    140    /**
    141     * Gets this channel's position.
    142     * <p>
    143     * This method violates the contract of {@link SeekableByteChannel#position()} as it will not throw any exception when invoked on a closed channel. Instead
    144     * it will return the position the channel had when close has been called.
    145     * </p>
    146     */
    147    @Override
    148    public long position() {
    149        return globalPosition;
    150    }
    151
    152    @Override
    153    public synchronized SeekableByteChannel position(final long newPosition) throws IOException {
    154        if (newPosition < 0) {
    155            throw new IllegalArgumentException("Negative position: " + newPosition);
    156        }
    157        if (!isOpen()) {
    158            throw new ClosedChannelException();
    159        }
    160        globalPosition = newPosition;
    161        long pos = newPosition;
    162        for (int i = 0; i < channelList.size(); i++) {
    163            final SeekableByteChannel currentChannel = channelList.get(i);
    164            final long size = currentChannel.size();
    165
    166            final long newChannelPos;
    167            if (pos == -1L) {
    168                // Position is already set for the correct channel,
    169                // the rest of the channels get reset to 0
    170                newChannelPos = 0;
    171            } else if (pos <= size) {
    172                // This channel is where we want to be
    173                currentChannelIdx = i;
    174                final long tmp = pos;
    175                pos = -1L; // Mark pos as already being set
    176                newChannelPos = tmp;
    177            } else {
    178                // newPosition is past this channel. Set channel
    179                // position to the end and substract channel size from
    180                // pos
    181                pos -= size;
    182                newChannelPos = size;
    183            }
    184            currentChannel.position(newChannelPos);
    185        }
    186        return this;
    187    }
    188
    189    /**
    190     * Sets the position based on the given channel number and relative offset
    191     *
    192     * @param channelNumber  the channel number
    193     * @param relativeOffset the relative offset in the corresponding channel
    194     * @return global position of all channels as if they are a single channel
    195     * @throws IOException if positioning fails
    196     */
    197    public synchronized SeekableByteChannel position(final long channelNumber, final long relativeOffset) throws IOException {
    198        if (!isOpen()) {
    199            throw new ClosedChannelException();
    200        }
    201        long globalPosition = relativeOffset;
    202        for (int i = 0; i < channelNumber; i++) {
    203            globalPosition += channelList.get(i).size();
    204        }
    205
    206        return position(globalPosition);
    207    }
    208
    209    @Override
    210    public synchronized int read(final ByteBuffer dst) throws IOException {
    211        if (!isOpen()) {
    212            throw new ClosedChannelException();
    213        }
    214        if (!dst.hasRemaining()) {
    215            return 0;
    216        }
    217
    218        int totalBytesRead = 0;
    219        while (dst.hasRemaining() && currentChannelIdx < channelList.size()) {
    220            final SeekableByteChannel currentChannel = channelList.get(currentChannelIdx);
    221            final int newBytesRead = currentChannel.read(dst);
    222            if (newBytesRead == -1) {
    223                // EOF for this channel -- advance to next channel idx
    224                currentChannelIdx += 1;
    225                continue;
    226            }
    227            if (currentChannel.position() >= currentChannel.size()) {
    228                // we are at the end of the current channel
    229                currentChannelIdx++;
    230            }
    231            totalBytesRead += newBytesRead;
    232        }
    233        if (totalBytesRead > 0) {
    234            globalPosition += totalBytesRead;
    235            return totalBytesRead;
    236        }
    237        return -1;
    238    }
    239
    240    @Override
    241    public long size() throws IOException {
    242        if (!isOpen()) {
    243            throw new ClosedChannelException();
    244        }
    245        long acc = 0;
    246        for (final SeekableByteChannel ch : channelList) {
    247            acc += ch.size();
    248        }
    249        return acc;
    250    }
    251
    252    /**
    253     * @throws NonWritableChannelException since this implementation is read-only.
    254     */
    255    @Override
    256    public SeekableByteChannel truncate(final long size) {
    257        throw new NonWritableChannelException();
    258    }
    259
    260    /**
    261     * @throws NonWritableChannelException since this implementation is read-only.
    262     */
    263    @Override
    264    public int write(final ByteBuffer src) {
    265        throw new NonWritableChannelException();
    266    }
    267
    268}