Java tutorial
/* * ==================================================================== * 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. * ==================================================================== * * This software consists of voluntary contributions made by many * individuals on behalf of the Apache Software Foundation. For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * */ package org.apache.http.nio.util; import java.io.IOException; import java.io.InterruptedIOException; import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.ReentrantLock; import org.apache.http.nio.ContentEncoder; import org.apache.http.nio.IOControl; /** * Implementation of the {@link ContentOutputBuffer} interface that can be * shared by multiple threads, usually the I/O dispatch of an I/O reactor and * a worker thread. * <p> * The I/O dispatch thread is expected to transfer data from the buffer to * {@link ContentEncoder} by calling {@link #produceContent(ContentEncoder)}. * <p> * The worker thread is expected to write data to the buffer by calling * {@link #write(int)}, {@link #write(byte[], int, int)} or {@link #writeCompleted()} * <p> * In case of an abnormal situation or when no longer needed the buffer must be * shut down using {@link #shutdown()} method. * * @since 4.0 */ public class SharedOutputBuffer extends ExpandableBuffer implements ContentOutputBuffer { private final IOControl ioctrl; private final ReentrantLock lock; private final Condition condition; private volatile boolean shutdown = false; private volatile boolean endOfStream = false; public SharedOutputBuffer(int buffersize, final IOControl ioctrl, final ByteBufferAllocator allocator) { super(buffersize, allocator); if (ioctrl == null) { throw new IllegalArgumentException("I/O content control may not be null"); } this.ioctrl = ioctrl; this.lock = new ReentrantLock(); this.condition = this.lock.newCondition(); } public void reset() { if (this.shutdown) { return; } this.lock.lock(); try { clear(); this.endOfStream = false; } finally { this.lock.unlock(); } } @Override public boolean hasData() { this.lock.lock(); try { return super.hasData(); } finally { this.lock.unlock(); } } @Override public int available() { this.lock.lock(); try { return super.available(); } finally { this.lock.unlock(); } } @Override public int capacity() { this.lock.lock(); try { return super.capacity(); } finally { this.lock.unlock(); } } @Override public int length() { this.lock.lock(); try { return super.length(); } finally { this.lock.unlock(); } } public int produceContent(final ContentEncoder encoder) throws IOException { if (this.shutdown) { return -1; } this.lock.lock(); try { setOutputMode(); int bytesWritten = 0; if (super.hasData()) { bytesWritten = encoder.write(this.buffer); if (encoder.isCompleted()) { this.endOfStream = true; } } if (!super.hasData()) { // No more buffered content // If at the end of the stream, terminate if (this.endOfStream && !encoder.isCompleted()) { encoder.complete(); } if (!this.endOfStream) { // suspend output events this.ioctrl.suspendOutput(); } } this.condition.signalAll(); return bytesWritten; } finally { this.lock.unlock(); } } public void close() { shutdown(); } public void shutdown() { if (this.shutdown) { return; } this.shutdown = true; this.lock.lock(); try { this.condition.signalAll(); } finally { this.lock.unlock(); } } public void write(final byte[] b, int off, int len) throws IOException { if (b == null) { return; } this.lock.lock(); try { if (this.shutdown || this.endOfStream) { throw new IllegalStateException("Buffer already closed for writing"); } setInputMode(); int remaining = len; while (remaining > 0) { if (!this.buffer.hasRemaining()) { flushContent(); setInputMode(); } int chunk = Math.min(remaining, this.buffer.remaining()); this.buffer.put(b, off, chunk); remaining -= chunk; off += chunk; } } finally { this.lock.unlock(); } } public void write(final byte[] b) throws IOException { if (b == null) { return; } write(b, 0, b.length); } public void write(int b) throws IOException { this.lock.lock(); try { if (this.shutdown || this.endOfStream) { throw new IllegalStateException("Buffer already closed for writing"); } setInputMode(); if (!this.buffer.hasRemaining()) { flushContent(); setInputMode(); } this.buffer.put((byte) b); } finally { this.lock.unlock(); } } public void flush() throws IOException { } private void flushContent() throws IOException { this.lock.lock(); try { try { while (super.hasData()) { if (this.shutdown) { throw new InterruptedIOException("Output operation aborted"); } this.ioctrl.requestOutput(); this.condition.await(); } } catch (InterruptedException ex) { throw new IOException("Interrupted while flushing the content buffer"); } } finally { this.lock.unlock(); } } public void writeCompleted() throws IOException { this.lock.lock(); try { if (this.endOfStream) { return; } this.endOfStream = true; this.ioctrl.requestOutput(); } finally { this.lock.unlock(); } } }