    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 *   https://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019
    020package org.apache.commons.io.channels;
    021
    022import java.io.ByteArrayInputStream;
    023import java.io.ByteArrayOutputStream;
    024import java.io.IOException;
    025import java.nio.ByteBuffer;
    026import java.nio.channels.ClosedChannelException;
    027import java.nio.channels.NonWritableChannelException;
    028import java.nio.channels.SeekableByteChannel;
    029import java.nio.file.OpenOption;
    030import java.nio.file.StandardOpenOption;
    031import java.util.Arrays;
    032import java.util.Objects;
    033import java.util.concurrent.locks.ReentrantLock;
    034
    035import org.apache.commons.io.IOUtils;
    036import org.apache.commons.io.build.AbstractStreamBuilder;
    037
    038/**
    039 * A {@link SeekableByteChannel} implementation backed by a byte array.
    040 * <p>
    041 * When used for writing, the internal buffer grows to accommodate incoming data. The natural size limit is the value of {@link IOUtils#SOFT_MAX_ARRAY_LENGTH}
    042 * and it's not possible to {@link #position(long) set the position} or {@link #truncate(long) truncate} to a value bigger than that. The raw internal buffer is
    043 * accessed via {@link ByteArraySeekableByteChannel#array()}.
    044 * </p>
    045 * <p>
    046 * Building a read-only channel from an existing byte array is supported with:
    047 * </p>
    048 * <pre>{@code
    049 * try (ByteArraySeekableByteChannel channel = ByteArraySeekableByteChannel.builder()
    050 *               .setByteArray(...)
    051 *               .setOpenOptions(StandardOpenOption.READ)
    052 *               .get()) {
    053 *               // read from channel
    054 * }
    055 * }</pre>
    056 *
    057 * @since 2.21.0
    058 */
    059public class ByteArraySeekableByteChannel implements SeekableByteChannel {
    060
    061    /**
    062     * Builds for {@link ByteArraySeekableByteChannel}.
    063     * <p>
    064     * Building a read-only channel from an existing byte array is supported with:
    065     * </p>
    066     * <pre>{@code
    067     * try (ByteArraySeekableByteChannel channel = ByteArraySeekableByteChannel.builder()
    068     *               .setByteArray(...)
    069     *               .setOpenOptions(StandardOpenOption.READ)
    070     *               .get()) {
    071     *               // read from channel
    072     * }
    073     * }</pre>
    074     *
    075     * @since 2.22.0
    076     */
    077    public static class Builder extends AbstractStreamBuilder<ByteArraySeekableByteChannel, Builder> {
    078
    079        /**
    080         * Constructs a new builder for {@link ByteArraySeekableByteChannel}.
    081         */
    082        public Builder() {
    083            setByteArray(IOUtils.EMPTY_BYTE_ARRAY);
    084        }
    085
    086        @Override
    087        public ByteArraySeekableByteChannel get() throws IOException {
    088            return new ByteArraySeekableByteChannel(this);
    089        }
    090    }
    091
    092    private static final int RESIZE_LIMIT = Integer.MAX_VALUE >> 1;
    093
    094    /**
    095     * Constructs a new builder for {@link ByteArraySeekableByteChannel}.
    096     *
    097     * @return a new builder for {@link ByteArraySeekableByteChannel}.
    098     * @since 2.22.0
    099     */
    100    public static Builder builder() {
    101        return new Builder();
    102    }
    103
    104    /**
    105     * Constructs a new channel backed directly by the given byte array.
    106     *
    107     * <p>
    108     * The channel initially contains the full contents of the array, with its size set to {@code bytes.length} and its position set to {@code 0}.
    109     * </p>
    110     *
    111     * <p>
    112     * Reads and writes operate on the shared array. If a write operation extends beyond the current capacity, the channel will automatically allocate a larger
    113     * backing array and copy the existing contents.
    114     * </p>
    115     *
    116     * @param bytes The byte array to wrap, must not be {@code null}
    117     * @return A new channel that uses the given array as its initial backing store.
    118     * @throws NullPointerException If {@code bytes} is {@code null}
    119     * @see #array()
    120     * @see ByteArrayInputStream#ByteArrayInputStream(byte[])
    121     */
    122    public static ByteArraySeekableByteChannel wrap(final byte[] bytes) {
    123        Objects.requireNonNull(bytes, "bytes");
    124        return new ByteArraySeekableByteChannel(bytes);
    125    }
    126    private byte[] data;
    127    private volatile boolean closed;
    128    private long position;
    129    private int size;
    130    private final boolean isWritable;
    131    private final ReentrantLock lock = new ReentrantLock();
    132
    133    /**
    134     * Constructs a new instance, with a default internal buffer capacity.
    135     * <p>
    136     * The initial size and position of the channel are 0.
    137     * </p>
    138     *
    139     * @see ByteArrayOutputStream#ByteArrayOutputStream()
    140     */
    141    public ByteArraySeekableByteChannel() {
    142        this(IOUtils.DEFAULT_BUFFER_SIZE);
    143    }
    144
    145    private ByteArraySeekableByteChannel(final Builder builder) throws IOException {
    146        this.data = builder.getByteArray();
    147        this.size = data.length;
    148        final OpenOption[] openOptions = builder.getOpenOptions();
    149        Arrays.sort(openOptions);
    150        this.isWritable = openOptions.length == 0 || Arrays.binarySearch(openOptions, StandardOpenOption.WRITE) >= 0
    151                || Arrays.binarySearch(openOptions, StandardOpenOption.APPEND) >= 0;
    152    }
    153
    154    private ByteArraySeekableByteChannel(final byte[] data) {
    155        this.data = data;
    156        this.size = data.length;
    157        this.isWritable = true;
    158    }
    159
    160    /**
    161     * Constructs a new instance, with an internal buffer of the given capacity, in bytes.
    162     * <p>
    163     * The initial size and position of the channel are 0.
    164     * </p>
    165     *
    166     * @param size Capacity of the internal buffer to allocate, in bytes.
    167     * @see ByteArrayOutputStream#ByteArrayOutputStream(int)
    168     */
    169    public ByteArraySeekableByteChannel(final int size) {
    170        if (size < 0) {
    171            throw new IllegalArgumentException("Size must be non-negative");
    172        }
    173        this.data = new byte[size];
    174        this.isWritable = true;
    175    }
    176
    177    /**
    178     * Gets the raw byte array backing this channel, <em>this is not a copy</em>.
    179     * <p>
    180     * NOTE: The returned buffer is not aligned with containing data, use {@link #size()} to obtain the size of data stored in the buffer.
    181     * </p>
    182     *
    183     * @return internal byte array.
    184     */
    185    public byte[] array() {
    186        return data;
    187    }
    188
    189    private void checkOpen() throws ClosedChannelException {
    190        if (!isOpen()) {
    191            throw new ClosedChannelException();
    192        }
    193    }
    194
    195    private void checkRange(final long newSize, final String method) {
    196        if (newSize < 0L) {
    197            throw new IllegalArgumentException(String.format("%s must be positive: %,d", method, newSize));
    198        }
    199    }
    200
    201    private void checkWritable() {
    202        if (!isWritable) {
    203            throw new NonWritableChannelException();
    204        }
    205    }
    206
    207    @Override
    208    public void close() {
    209        closed = true;
    210    }
    211
    212    /**
    213     * Like {@link #size()} but never throws {@link ClosedChannelException}.
    214     *
    215     * @return See {@link #size()}.
    216     */
    217    public long getSize() {
    218        return size;
    219    }
    220
    221    @Override
    222    public boolean isOpen() {
    223        return !closed;
    224    }
    225
    226    @Override
    227    public long position() throws ClosedChannelException {
    228        checkOpen();
    229        lock.lock();
    230        try {
    231            return position;
    232        } finally {
    233            lock.unlock();
    234        }
    235    }
    236
    237    @Override
    238    public SeekableByteChannel position(final long newPosition) throws IOException {
    239        checkOpen();
    240        checkRange(newPosition, "position()");
    241        lock.lock();
    242        try {
    243            position = newPosition;
    244        } finally {
    245            lock.unlock();
    246        }
    247        return this;
    248    }
    249
    250    @Override
    251    public int read(final ByteBuffer buf) throws IOException {
    252        checkOpen();
    253        lock.lock();
    254        try {
    255            if (position > Integer.MAX_VALUE) {
    256                return IOUtils.EOF;
    257            }
    258            int wanted = buf.remaining();
    259            final int possible = size - (int) position;
    260            if (possible <= 0) {
    261                return IOUtils.EOF;
    262            }
    263            if (wanted > possible) {
    264                wanted = possible;
    265            }
    266            buf.put(data, (int) position, wanted);
    267            position += wanted;
    268            return wanted;
    269        } finally {
    270            lock.unlock();
    271        }
    272    }
    273
    274    private void resize(final int newLength) {
    275        int len = data.length;
    276        if (len == 0) {
    277            len = 1;
    278        }
    279        if (newLength < RESIZE_LIMIT) {
    280            while (len < newLength) {
    281                len <<= 1;
    282            }
    283        } else { // avoid overflow
    284            len = newLength;
    285        }
    286        data = Arrays.copyOf(data, len);
    287    }
    288
    289    @Override
    290    public long size() throws ClosedChannelException {
    291        checkOpen();
    292        lock.lock();
    293        try {
    294            return size;
    295        } finally {
    296            lock.unlock();
    297        }
    298    }
    299
    300    /**
    301     * Gets a copy of the data stored in this channel.
    302     * <p>
    303     * The returned array is a copy of the internal buffer, sized to the actual data stored in this channel.
    304     * </p>
    305     *
    306     * @return a new byte array containing the data stored in this channel.
    307     */
    308    public byte[] toByteArray() {
    309        return Arrays.copyOf(data, size);
    310    }
    311
    312    @Override
    313    public SeekableByteChannel truncate(final long newSize) throws ClosedChannelException {
    314        checkOpen();
    315        checkWritable();
    316        checkRange(newSize, "truncate()");
    317        lock.lock();
    318        try {
    319            if (size > newSize) {
    320                size = (int) newSize;
    321            }
    322            if (position > newSize) {
    323                position = newSize;
    324            }
    325        } finally {
    326            lock.unlock();
    327        }
    328        return this;
    329    }
    330
    331    @Override
    332    public int write(final ByteBuffer b) throws IOException {
    333        checkOpen();
    334        checkWritable();
    335        //
    336        if (position > Integer.MAX_VALUE) {
    337            throw new IOException("position > Integer.MAX_VALUE");
    338        }
    339        lock.lock();
    340        try {
    341            final int wanted = b.remaining();
    342            // intPos <= Integer.MAX_VALUE
    343            final int intPos = (int) position;
    344            final long newPosition = position + wanted;
    345            if (newPosition > IOUtils.SOFT_MAX_ARRAY_LENGTH) {
    346                throw new IOException(String.format("Requested array size %,d is too large.", newPosition));
    347            }
    348            if (newPosition > size) {
    349                final int newPositionInt = (int) newPosition;
    350                // Ensure that newPositionInt ≤ data.length
    351                resize(newPositionInt);
    352                size = newPositionInt;
    353            }
    354            b.get(data, intPos, wanted);
    355            position = newPosition;
    356            if (size < intPos) {
    357                size = intPos;
    358            }
    359            return wanted;
    360        } finally {
    361            lock.unlock();
    362        }
    363    }
    364}