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/*
* Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
import java.io.IOException;
import java.util.LinkedList;
import java.util.Objects;
import java.util.stream.Stream;
// Each stream has one of these for input. Each Http2Connection has one
// for output. Can be used blocking or asynchronously.
public class Queue<T> implements ExceptionallyCloseable {
private final LinkedList<T> q = new LinkedList<>();
private boolean closed = false;
private boolean closing = false;
private Throwable exception = null;
private int waiters; // true if someone waiting
private final T closeSentinel;
Queue(T closeSentinel) {
this.closeSentinel = Objects.requireNonNull(closeSentinel);
}
public synchronized int size() {
return q.size();
}
public synchronized boolean isClosed() {
return closed;
}
public synchronized boolean isClosing() {
return closing;
}
public synchronized void put(T obj) throws IOException {
Objects.requireNonNull(obj);
if (closed || closing) {
throw new IOException("stream closed");
}
q.add(obj);
if (waiters > 0) {
notifyAll();
}
}
// Other close() variants are immediate and abortive
// This allows whatever is on Q to be processed first.
public synchronized void orderlyClose() {
if (closing || closed)
return;
try {
put(closeSentinel);
} catch (IOException e) {
e.printStackTrace();
}
closing = true;
}
@Override
public synchronized void close() {
if (closed)
return;
closed = true;
notifyAll();
}
@Override
public synchronized void closeExceptionally(Throwable t) {
if (exception == null) exception = t;
else if (t != null && t != exception) {
if (!Stream.of(exception.getSuppressed())
.filter(x -> x == t)
.findFirst()
.isPresent())
{
exception.addSuppressed(t);
}
}
close();
}
public synchronized T take() throws IOException {
if (closed) {
throw newIOException("stream closed");
}
try {
while (q.size() == 0) {
waiters++;
wait();
if (closed) {
throw newIOException("Queue closed");
}
waiters--;
}
T item = q.removeFirst();
if (item.equals(closeSentinel)) {
closed = true;
assert q.isEmpty();
return null;
}
return item;
} catch (InterruptedException ex) {
throw new IOException(ex);
}
}
public synchronized T poll() throws IOException {
if (closed) {
throw newIOException("stream closed");
}
if (q.isEmpty()) {
return null;
}
return take();
}
private IOException newIOException(String msg) {
if (exception == null) {
return new IOException(msg);
} else {
return new IOException(msg, exception);
}
}
}
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