Splitting megaphone_tcp

Previously...

• I made some plans about how to create megaphone_tcp.
• Determine if segment contains a complete header
• If not, then keep reading until you do have a complete header
• Parse out the connection ID and packet length, 
• If you have a complete header, then determine if you have a complete megaphone packet
• If not, then keep reading until you have a complete megaphone packet
• Send the megaphone process the completed packet.
• Wait for another packet to arrive.
• I created receive_loop, which takes care of controlling the process.
• I created the part that receives headers.

While writing the portion of megaphone_tcp that handles extracting the payload, it occurred to me that the name "megaphone_tcp" was something of a misnomer.  Rather than handling all things TCP, it really wanted to handle just those things relating to receiving a packet from TCP.  

Therefore, to further muddy the waters, I resolved to rename megaphone_tcp to megaphone_receiver.  At some point real soon now (ha!) I will create another module called megaphone_sender or megaphone_ecm to handle all things related to sending packets to ECM.

I modified the receive_header function so that it actually compiles.  It is basically the same, so I will not reprint it here.  Rather I will publish it along with the rest of the megaphone functionality on github.  Note that currently the megaphone-ejabberd account there does not have anything in it.

Here is the code for receiving the body of the message:

receive_packet_body (Socket, Data, Length) ->

    case byte_size(Data) of

        %%

        %% need more data to fill out the packet

        %%

        ContentLength when ContentLength < Length ->

            case gen_tcp:recv(Socket, 0) of

                {ok, NewData} ->

                    Data2 = Data ++ NewData,

                    receive_packet_body (Socket, Data2, Length)

            end;

        %%

        %% we have enough to fill out the packet

        %%

        true ->

            PacketData = binary_part(Data, 0, Length),

            %%

            %% Check for leftovers

            %%

            if

                byte_size(Data) == Length ->

                    { Data, undefined };

                true ->

                    LeftOvers = binary_part(Data, Length, byte_size(Data) - Length),

                    { PacketData, LeftOvers }

            end

    end.

For next time, the code that hands the packet off to the megaphone process.