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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include "idiscardhandler.h"
#include "imessagehandler.h"
#include "ireplyhandler.h"
#include <vespa/vespalib/util/ref_counted.h>
#include <atomic>
namespace mbus {
/**
* A ReplyGate will forward replies until it is closed. After being closed, the
* gate will silently delete all replies. The ReplyGate class has external
* reference counting. This class is used by session objects to perform safe
* untangling from messagebus when being destructed while having pending
* messages. The reference counting is needed to ensure that the object is alive
* until all pending replies have been correctly ignored. Thread synchronization
* is handled outside this class. Note that this class is only intended for
* internal use.
*/
class ReplyGate : public vespalib::enable_ref_counted,
public IDiscardHandler,
public IMessageHandler,
public IReplyHandler
{
private:
IMessageHandler &_sender;
std::atomic<bool> _open;
public:
/**
* Create a new ReplyGate.
*
* @param sender The underlying IMessageHandler object.
*/
ReplyGate(IMessageHandler &sender);
/**
* Send a Message to the underlying IMessageHandler. This method will
* increase the reference counter to ensure that this object is alive until
* the matching Reply has been obtained. In order to obtain the matching
* Reply, this method will push this object on the CallStack of the Message.
*/
void handleMessage(std::unique_ptr<Message> msg) override;
/**
* Forward or discard Reply. If the gate is still open, it will forward the
* Reply to the next IReplyHandler on the CallStack. If the gate is closed,
* the Reply will be discarded. This method also decreases the reference
* counter of this object.
*/
void handleReply(std::unique_ptr<Reply> reply) override;
// Implements IDiscardHandler.
void handleDiscard(Context ctx) override;
/**
* Close this gate. After this has been invoked, the gate will start to
* discard Reply objects. A closed gate can never be re-opened.
*/
void close();
};
} // namespace mbus
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