org.apache.commons.compress.utils.SeekableInMemoryByteChannel Maven / Gradle / Ivy
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/*
* 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. The natural size limit is the value of {@link Integer#MAX_VALUE}
* and it is not possible to {@link #position(long) set the position} or {@link #truncate truncate} to a value bigger than that. 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;
/**
* Constructs a new instance using a default empty buffer.
*/
public SeekableInMemoryByteChannel() {
this(ByteUtils.EMPTY_BYTE_ARRAY);
}
/**
* Constructs a new instance from 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(final byte[] data) {
this.data = data;
this.size = data.length;
}
/**
* Constructs a new instance from 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(final int size) {
this(new byte[size]);
}
/**
* 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;
}
@Override
public void close() {
closed.set(true);
}
private void ensureOpen() throws ClosedChannelException {
if (!isOpen()) {
throw new ClosedChannelException();
}
}
@Override
public boolean isOpen() {
return !closed.get();
}
/**
* Returns this channel's position.
*
* This method violates the contract of {@link SeekableByteChannel#position()} as it will not throw any exception when invoked on a closed channel. Instead
* it will return the position the channel had when close has been called.
*
*/
@Override
public long position() {
return position;
}
@Override
public SeekableByteChannel position(final long newPosition) throws IOException {
ensureOpen();
if (newPosition < 0L || newPosition > Integer.MAX_VALUE) {
throw new IOException("Position has to be in range 0.. " + Integer.MAX_VALUE);
}
position = (int) newPosition;
return this;
}
@Override
public int read(final ByteBuffer buf) throws IOException {
ensureOpen();
int wanted = buf.remaining();
final int possible = size - position;
if (possible <= 0) {
return -1;
}
if (wanted > possible) {
wanted = possible;
}
buf.put(data, position, wanted);
position += wanted;
return wanted;
}
private void resize(final 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);
}
/**
* Returns the current size of entity to which this channel is connected.
*
* This method violates the contract of {@link SeekableByteChannel#size} as it will not throw any exception when invoked on a closed channel. Instead it
* will return the size the channel had when close has been called.
*
*/
@Override
public long size() {
return size;
}
/**
* Truncates the entity, to which this channel is connected, to the given size.
*
* This method violates the contract of {@link SeekableByteChannel#truncate} as it will not throw any exception when invoked on a closed channel.
*
*
* @throws IllegalArgumentException if size is negative or bigger than the maximum of a Java integer
*/
@Override
public SeekableByteChannel truncate(final long newSize) {
if (newSize < 0L || newSize > Integer.MAX_VALUE) {
throw new IllegalArgumentException("Size has to be in range 0.. " + Integer.MAX_VALUE);
}
if (size > newSize) {
size = (int) newSize;
}
if (position > newSize) {
position = (int) newSize;
}
return this;
}
@Override
public int write(final ByteBuffer b) throws IOException {
ensureOpen();
int wanted = b.remaining();
final int possibleWithoutResize = size - position;
if (wanted > possibleWithoutResize) {
final 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;
}
}