ByteArraySeekableByteChannel.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.io.channels;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
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.Objects;
import java.util.concurrent.locks.ReentrantLock;
import org.apache.commons.io.IOUtils;
/**
* A {@link SeekableByteChannel} implementation backed by a byte array.
* <p>
* 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}
* 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
* accessed via {@link ByteArraySeekableByteChannel#array()}.
* </p>
*
* @since 2.21.0
*/
public class ByteArraySeekableByteChannel implements SeekableByteChannel {
private static final int RESIZE_LIMIT = Integer.MAX_VALUE >> 1;
/**
* Constructs a new channel backed directly by the given byte array.
*
* <p>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}.</p>
*
* <p>Reads and writes operate on the shared array.
* If a write operation extends beyond the current capacity, the channel will
* automatically allocate a larger backing array and copy the existing contents.</p>
*
* @param bytes The byte array to wrap, must not be {@code null}
* @return A new channel that uses the given array as its initial backing store.
* @throws NullPointerException If {@code bytes} is {@code null}
* @see #array()
* @see ByteArrayInputStream#ByteArrayInputStream(byte[])
*/
public static ByteArraySeekableByteChannel wrap(final byte[] bytes) {
Objects.requireNonNull(bytes, "bytes");
return new ByteArraySeekableByteChannel(bytes);
}
private byte[] data;
private volatile boolean closed;
private long position;
private int size;
private final ReentrantLock lock = new ReentrantLock();
/**
* Constructs a new instance, with a default internal buffer capacity.
* <p>
* The initial size and position of the channel are 0.
* </p>
*
* @see ByteArrayOutputStream#ByteArrayOutputStream()
*/
public ByteArraySeekableByteChannel() {
this(IOUtils.DEFAULT_BUFFER_SIZE);
}
private ByteArraySeekableByteChannel(final byte[] data) {
this.data = data;
this.position = 0;
this.size = data.length;
}
/**
* Constructs a new instance, with an internal buffer of the given capacity, in bytes.
* <p>
* The initial size and position of the channel are 0.
* </p>
*
* @param size Capacity of the internal buffer to allocate, in bytes.
* @see ByteArrayOutputStream#ByteArrayOutputStream(int)
*/
public ByteArraySeekableByteChannel(final int size) {
if (size < 0) {
throw new IllegalArgumentException("Size must be non-negative");
}
this.data = new byte[size];
this.position = 0;
this.size = 0;
}
/**
* Gets the raw byte array backing this channel, <em>this is not a copy</em>.
* <p>
* NOTE: The returned buffer is not aligned with containing data, use {@link #size()} to obtain the size of data stored in the buffer.
* </p>
*
* @return internal byte array.
*/
public byte[] array() {
return data;
}
private void checkOpen() throws ClosedChannelException {
if (!isOpen()) {
throw new ClosedChannelException();
}
}
private void checkRange(final long newSize, final String method) {
if (newSize < 0L) {
throw new IllegalArgumentException(String.format("%s must be positive: %,d", method, newSize));
}
}
@Override
public void close() {
closed = true;
}
/**
* Like {@link #size()} but never throws {@link ClosedChannelException}.
*
* @return See {@link #size()}.
*/
public long getSize() {
return size;
}
@Override
public boolean isOpen() {
return !closed;
}
@Override
public long position() throws ClosedChannelException {
checkOpen();
lock.lock();
try {
return position;
} finally {
lock.unlock();
}
}
@Override
public SeekableByteChannel position(final long newPosition) throws IOException {
checkOpen();
checkRange(newPosition, "position()");
lock.lock();
try {
position = newPosition;
} finally {
lock.unlock();
}
return this;
}
@Override
public int read(final ByteBuffer buf) throws IOException {
checkOpen();
lock.lock();
try {
if (position > Integer.MAX_VALUE) {
return IOUtils.EOF;
}
int wanted = buf.remaining();
final int possible = size - (int) position;
if (possible <= 0) {
return IOUtils.EOF;
}
if (wanted > possible) {
wanted = possible;
}
buf.put(data, (int) position, wanted);
position += wanted;
return wanted;
} finally {
lock.unlock();
}
}
private void resize(final int newLength) {
int len = data.length;
if (len == 0) {
len = 1;
}
if (newLength < RESIZE_LIMIT) {
while (len < newLength) {
len <<= 1;
}
} else { // avoid overflow
len = newLength;
}
data = Arrays.copyOf(data, len);
}
@Override
public long size() throws ClosedChannelException {
checkOpen();
lock.lock();
try {
return size;
} finally {
lock.unlock();
}
}
/**
* Gets a copy of the data stored in this channel.
* <p>
* The returned array is a copy of the internal buffer, sized to the actual data stored in this channel.
* </p>
*
* @return a new byte array containing the data stored in this channel.
*/
public byte[] toByteArray() {
return Arrays.copyOf(data, size);
}
@Override
public SeekableByteChannel truncate(final long newSize) throws ClosedChannelException {
checkOpen();
checkRange(newSize, "truncate()");
lock.lock();
try {
if (size > newSize) {
size = (int) newSize;
}
if (position > newSize) {
position = newSize;
}
} finally {
lock.unlock();
}
return this;
}
@Override
public int write(final ByteBuffer b) throws IOException {
checkOpen();
if (position > Integer.MAX_VALUE) {
throw new IOException("position > Integer.MAX_VALUE");
}
lock.lock();
try {
final int wanted = b.remaining();
// intPos <= Integer.MAX_VALUE
final int intPos = (int) position;
final long newPosition = position + wanted;
if (newPosition > IOUtils.SOFT_MAX_ARRAY_LENGTH) {
throw new IOException(String.format("Requested array size %,d is too large.", newPosition));
}
if (newPosition > size) {
final int newPositionInt = (int) newPosition;
// Ensure that newPositionInt ��� data.length
resize(newPositionInt);
size = newPositionInt;
}
b.get(data, intPos, wanted);
position = newPosition;
if (size < intPos) {
size = intPos;
}
return wanted;
} finally {
lock.unlock();
}
}
}