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/*
*
* Copyright (c) 2020 Project CHIP Authors
*
* Licensed 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.
*/
/**
* @file
* This file defines the classes corresponding to CHIP Exchange Context Delegate.
*
*/
#pragma once
#include <lib/support/CHIPMem.h>
#include <messaging/ApplicationExchangeDispatch.h>
#include <messaging/ExchangeMessageDispatch.h>
#include <system/SystemPacketBuffer.h>
#include <transport/SessionManager.h>
#include <transport/raw/MessageHeader.h>
namespace chip {
namespace Messaging {
class ExchangeContext;
/**
* @brief
* This class provides a skeleton for the callback functions. The functions will be
* called by ExchangeContext object on specific events. If the user of ExchangeContext
* is interested in receiving these callbacks, they can specialize this class and handle
* each trigger in their implementation of this class.
*
* For consumers who use an ExchangeContext to send/receive protocol messages, there are specific
* expectations around who manages the exchange w.r.t clean-up and destruction:
* 1. When you allocate an exchange, you own the exchange. Until you send a message successfully, it's on you
* to release that ownership by calling Close or Abort on the exchange.
*
* 2. If you send a message successfully that doesn't require a response, the ownership transfers to
* the ExchangeMgr, and it will close the exchange for you automatically.
*
* 3. If you send a message successfully that does require a response and desire to close it before
* you get any notifications on that exchange from the ExchangeMgr, you should call Close or Abort on that exchange.
*
* 4. On reception of a message on an exchange, the ownership transfers to the OnMessageReceived callee.
* If you return from OnMessageReceived and no messages were sent on that exchange, the exchange will transfer back
* to the ExchangeMgr and it will automatically close it.
*
* 5. If you call WillSendMessage on the exchange in OnMessageReceived indicating a desire to send a message later
* on the exchange, then the exchange remains with you, and it's your responsibility to either send a message on it,
* or Close/Abort if you no longer wish to have the exchange around.
*
* 6. If you get a call to OnExchangeClosing, you should give up your reference to the exchange
* by 'nulling' out your reference to the exchange. The exchange will be automatically closed by the ExchangeMgr.
*
* 6. If you get a call to OnResponseTimeout, you should give up your reference to the exchange
* by 'nulling' out your reference to the exchange UNLESS you intend to do further work on the exchange. If so,
* rules 2, 3 and 5 apply. Otherwise, the exchange will be automatically closed by the ExchangeMgr. Note that
* if the cause of the call is the release of the underlying session, attempts to send a message will result in failure.
*
*/
class DLL_EXPORT ExchangeDelegate
{
public:
virtual ~ExchangeDelegate() {}
/**
* @brief
* This function is the protocol callback for handling a received CHIP
* message.
*
* After calling this method an exchange will close itself unless one of
* two things happens:
*
* 1) A call to SendMessage on the exchange with the kExpectResponse flag
* set.
* 2) A call to WillSendMessage on the exchange.
*
* Consumers that don't do one of those things MUST NOT retain a pointer
* to the exchange.
*
* @param[in] ec A pointer to the ExchangeContext object.
* @param[in] payloadHeader A reference to the PayloadHeader object.
* @param[in] payload A handle to the PacketBuffer object holding the message payload.
*/
virtual CHIP_ERROR OnMessageReceived(ExchangeContext * ec, const PayloadHeader & payloadHeader,
System::PacketBufferHandle && payload) = 0;
/**
* @brief
* This function is the protocol callback to invoke when the timeout for the receipt
* of a response message has expired.
*
* After calling this method an exchange will close itself unless one of
* two things happens:
*
* 1) A call to SendMessage on the exchange with the kExpectResponse flag
* set.
* 2) A call to WillSendMessage on the exchange.
*
* Consumers that don't do one of those things MUST NOT retain a pointer
* to the exchange.
*
* @param[in] ec A pointer to the ExchangeContext object.
*/
virtual void OnResponseTimeout(ExchangeContext * ec) = 0;
/**
* @brief
* This function is the protocol callback to invoke when the associated
* exchange context is being closed.
*
* If the exchange was in a state where it was expecting a message to be
* sent due to an earlier WillSendMessage call or because the exchange has
* just been created as an initiator, the consumer is holding a reference
* to the exchange and it's the consumer's responsibility to call
* Release() on the exchange at some point. The usual way this happens is
* that the consumer tries to send its message, that fails, and the
* consumer calls Close() on the exchange. Calling Close() after an
* OnExchangeClosing() notification is allowed in this situation.
*
* @param[in] ec A pointer to the ExchangeContext object.
*/
virtual void OnExchangeClosing(ExchangeContext * ec) {}
virtual ExchangeMessageDispatch & GetMessageDispatch() { return ApplicationExchangeDispatch::Instance(); }
};
/**
* @brief
* This class handles unsolicited messages. The implementation can select an exchange delegate to use based on the payload header
* of the incoming message.
*/
class DLL_EXPORT UnsolicitedMessageHandler
{
public:
virtual ~UnsolicitedMessageHandler() {}
/**
* @brief
* This function handles an unsolicited CHIP message.
*
* If the implementation returns CHIP_NO_ERROR, it is expected to set newDelegate to the delegate to use for the exchange
* handling the message. The message layer will handle creating the exchange with this delegate.
*
* If the implementation returns an error, message processing will be aborted for this message.
*
* @param[in] payloadHeader A reference to the PayloadHeader object for the unsolicited message. The protocol and message
* type of this header match the UnsolicitedMessageHandler.
* @param[out] newDelegate A new exchange delegate to be used by the new exchange created to handle the message.
*/
virtual CHIP_ERROR OnUnsolicitedMessageReceived(const PayloadHeader & payloadHeader, ExchangeDelegate *& newDelegate) = 0;
/**
* @brief
* This function is called when OnUnsolicitedMessageReceived successfully returns a new delegate, but the session manager
* fails to assign the delegate to a new exchange. It can be used to free the delegate as needed.
*
* Once an exchange is created with the delegate, the OnExchangeClosing notification can be used to free the delegate as
* needed.
*
* @param[in] delegate The exchange delegate to be released.
*/
virtual void OnExchangeCreationFailed(ExchangeDelegate * delegate) {}
};
} // namespace Messaging
} // namespace chip