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/*
This file is part of GNUnet.
(C) 2014 Christian Grothoff (and other contributing authors)
GNUnet is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published
by the Free Software Foundation; either version 3, or (at your
option) any later version.
GNUnet 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 for more details.
You should have received a copy of the GNU General Public License
along with GNUnet; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
*/
package org.gnunet.requests;
import org.gnunet.mq.MessageQueue;
import java.util.LinkedList;
/**
* Container for requests that are responded to in sequential order.
*/
public class SequentialRequestContainer<T extends Request> extends RequestContainer {
/**
* Allow overlapping requests.
*/
private boolean overlap;
/**
* Request in our queue with information about them.
*/
private LinkedList<Identifier> requests = new LinkedList<Identifier>();
/**
* Message queue that is used to send envelopes.
*/
private final MessageQueue mq;
/**
* Number of active requests.
*/
private int requestsActive = 0;
/**
* Create a sequential request container that sends messages with the given
* message queue.
*
* @param mq message queue to send messages with
* @param overlap allow sending requests while other request have not yet completed
*/
public SequentialRequestContainer(MessageQueue mq, boolean overlap) {
this.mq = mq;
this.overlap = overlap;
}
/**
* Create a sequential request container that sends messages with the given
* message queue. Do not allow other requests to be send while the current request
* is still active.
*
* @param mq message queue to send messages with
*/
public SequentialRequestContainer(MessageQueue mq) {
this(mq, false);
}
/**
* Get the current request's identifier.
*
* @return current request
*/
public RequestIdentifier<T> getRequestIdentifier() {
return requests.peekFirst();
}
/**
* Get the current request and retire it.
* If there is no current request, null will be returned.
*
* @return current request
*/
public T getAndRetireRequest() {
RequestIdentifier<T> i = getRequestIdentifier();
if (null == i)
return null;
i.retire();
return i.getRequest();
}
public Iterable<RequestIdentifier<T>> iter() {
return (Iterable) requests;
}
/**
* Get the current request.
*
* @return the current request.
*/
public T getRequest() {
RequestIdentifier<T> i = getRequestIdentifier();
if (null == i)
return null;
return i.getRequest();
}
/**
* A request identifier in a sequential request container.
*/
private class Identifier extends SimpleRequestIdentifier<T> {
public Identifier(T request) {
super(request);
}
@Override
public void retire() {
super.retire();
if (requestsActive == 0 || requests.isEmpty())
throw new AssertionError();
boolean found = requests.remove(this);
if (!found)
throw new AssertionError("request not in queue");
requestsActive--;
Identifier next = requests.peekFirst();
if (null == next || next.queued)
return;
if (requestsActive == 0 || overlap)
next.send(mq);
}
}
/**
* Add a request to the queue
*
* @param request the request to add
* @return a handle that represents the queued request
*/
public RequestIdentifier<T> addRequest(final T request) {
final Identifier identifier = new Identifier(request);
requests.addLast(identifier);
// only send immediately if we are allowed to
if (overlap || requestsActive == 0) {
identifier.send(mq);
requestsActive += 1;
}
return identifier;
}
/**
* Re-send all active requests.
*/
@Override
public void restart() {
LinkedList<Identifier> requestsOld = requests;
requests = new LinkedList<Identifier>();
for (Identifier r : requestsOld) {
addRequest(r.getRequest());
}
}
}
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