org.apache.commons.compress.utils.SeekableInMemoryByteChannel Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of commons-compress Show documentation
Apache Commons Compress defines an API for working with compression and archive formats. These include bzip2, gzip, pack200, LZMA, XZ, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4, Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.
There is a newer version: 1.27.1
Show newest version
/*
 * 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.utils;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.SeekableByteChannel;
import java.util.Arrays;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * A {@link SeekableByteChannel} implementation that wraps a byte[].
 *
 * When this channel is used for writing an internal buffer grows to accommodate
 * incoming data. A natural size limit is the value of {@link Integer#MAX_VALUE}.
 * Internal buffer can be accessed via {@link SeekableInMemoryByteChannel#array()}.
 *
 * @since 1.13
 * @NotThreadSafe
 */
public class SeekableInMemoryByteChannel implements SeekableByteChannel {

    private static final int NAIVE_RESIZE_LIMIT = Integer.MAX_VALUE >> 1;

    private byte[] data;
    private final AtomicBoolean closed = new AtomicBoolean();
    private int position, size;

    /**
     * Constructor taking a byte array.
     *
     * This constructor is intended to be used with pre-allocated buffer or when
     * reading from a given byte array.
     *
     * @param data input data or pre-allocated array.
     */
    public SeekableInMemoryByteChannel(byte[] data) {
        this.data = data;
        size = data.length;
    }

    /**
     * Parameterless constructor - allocates internal buffer by itself.
     */
    public SeekableInMemoryByteChannel() {
        this(new byte[0]);
    }

    /**
     * Constructor taking a size of storage to be allocated.
     *
     * Creates a channel and allocates internal storage of a given size.
     *
     * @param size size of internal buffer to allocate, in bytes.
     */
    public SeekableInMemoryByteChannel(int size) {
        this(new byte[size]);
    }

    @Override
    public long position() {
        return position;
    }

    @Override
    public SeekableByteChannel position(long newPosition) throws IOException {
        ensureOpen();
        if (newPosition < 0L || newPosition > Integer.MAX_VALUE) {
            throw new IllegalArgumentException("Position has to be in range 0.. " + Integer.MAX_VALUE);
        }
        position = (int) newPosition;
        return this;
    }

    @Override
    public long size() {
        return size;
    }

    @Override
    public SeekableByteChannel truncate(long newSize) {
        if (size > newSize) {
            size = (int) newSize;
        }
        repositionIfNecessary();
        return this;
    }

    @Override
    public int read(ByteBuffer buf) throws IOException {
        ensureOpen();
        repositionIfNecessary();
        int wanted = buf.remaining();
        int possible = size - position;
        if (possible <= 0) {
            return -1;
        }
        if (wanted > possible) {
            wanted = possible;
        }
        buf.put(data, position, wanted);
        position += wanted;
        return wanted;
    }

    @Override
    public void close() {
        closed.set(true);
    }

    @Override
    public boolean isOpen() {
        return !closed.get();
    }

    @Override
    public int write(ByteBuffer b) throws IOException {
        ensureOpen();
        int wanted = b.remaining();
        int possibleWithoutResize = size - position;
        if (wanted > possibleWithoutResize) {
            int newSize = position + wanted;
            if (newSize < 0) { // overflow
                resize(Integer.MAX_VALUE);
                wanted = Integer.MAX_VALUE - position;
            } else {
                resize(newSize);
            }
        }
        b.get(data, position, wanted);
        position += wanted;
        if (size < position) {
            size = position;
        }
        return wanted;
    }

    /**
     * Obtains the array backing this channel.
     *
     * NOTE:
     * The returned buffer is not aligned with containing data, use
     * {@link #size()} to obtain the size of data stored in the buffer.
     *
     * @return internal byte array.
     */
    public byte[] array() {
        return data;
    }

    private void resize(int newLength) {
        int len = data.length;
        if (len <= 0) {
            len = 1;
        }
        if (newLength < NAIVE_RESIZE_LIMIT) {
            while (len < newLength) {
                len <<= 1;
            }
        } else { // avoid overflow
            len = newLength;
        }
        data = Arrays.copyOf(data, len);
    }

    private void ensureOpen() throws ClosedChannelException {
        if (!isOpen()) {
            throw new ClosedChannelException();
        }
    }

    private void repositionIfNecessary() {
        if (position > size) {
            position = size;
        }
    }

}