src/transport/raw/Base.h

/*
 *
 *    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
 *    Defines base properties and constants valid across all transport
 *    classes (UDP, TCP, BLE, ....)
 */

#pragma once

#include <core/CHIPError.h>
#include <inet/IPAddress.h>
#include <inet/UDPEndPoint.h>
#include <system/SystemPacketBuffer.h>
#include <transport/raw/MessageHeader.h>
#include <transport/raw/PeerAddress.h>

namespace chip {
namespace Transport {

/**
 * Transport class base, defining common methods among transports (message
 * packing by encoding and decoding headers) and generic message transport
 * methods.
 */
class Base
{
public:
    virtual ~Base() {}

    /**
     * Sets the message receive handler and associated argument
     *
     * @param[in] handler The callback to call when a message is received
     * @param[in] param   The argument to pass in to the handler function
     *
     */
    template <class T>
    void SetMessageReceiveHandler(void (*handler)(const PacketHeader &, const PeerAddress &, System::PacketBuffer *, T *),
                                  T * param)
    {
        mMessageReceivedArgument = param;
        OnMessageReceived        = reinterpret_cast<MessageReceiveHandler>(handler);
    }

    /**
     * @brief Send a message to the specified target.
     *
     * On connection-oriented transports, sending a message implies connecting to the target first.
     *
     * @details
     *   This method calls <tt>chip::System::PacketBuffer::Free</tt> on
     *   behalf of the caller regardless of the return status.
     */
    virtual CHIP_ERROR SendMessage(const PacketHeader & header, Header::Flags payloadFlags, const PeerAddress & address,
                                   System::PacketBuffer * msgBuf) = 0;

    /**
     * Determine if this transport can SendMessage to the specified peer address.
     *
     * Generally it is expected that a transport can send to any peer from which it receives a message.
     */
    virtual bool CanSendToPeer(const PeerAddress & address) = 0;

    /**
     * Handle disconnection from the specified peer if currently connected to it.
     */
    virtual void Disconnect(const PeerAddress & address) {}

protected:
    /**
     * Method used by subclasses to notify that a packet has been received after
     * any associated headers have been decoded.
     */
    void HandleMessageReceived(const PacketHeader & header, const PeerAddress & source, System::PacketBuffer * buffer)
    {
        if (OnMessageReceived)
        {
            OnMessageReceived(header, source, buffer, mMessageReceivedArgument);
        }
        else
        {
            System::PacketBuffer::Free(buffer);
        }
    }

    /**
     * This function is the application callback that is invoked when a message is received over a
     * Chip connection.
     *
     * @param[in]    msgBuf        A pointer to the PacketBuffer object holding the message.
     *
     * Callback *MUST* free msgBuf as a result of handling.
     */
    typedef void (*MessageReceiveHandler)(const PacketHeader & header, const PeerAddress & source, System::PacketBuffer * msgBuf,
                                          void * param);

    MessageReceiveHandler OnMessageReceived = nullptr; ///< Callback on message receiving
    void * mMessageReceivedArgument         = nullptr; ///< Argument for callback
};

} // namespace Transport
} // namespace chip