In my latest personal project I have switched my asio networking code from callback functions to coroutines. It is such a big improvement! Repeated actions can be written as simple loops, error handling is done with exceptions and the code is generally much easier to follow. And here's the icing on the cake: most data can actually stay in local variables, which means I don't have to care about the lifetime!
Yeah, I have in mind handling network messages, mainly. Thinking about it, I have this problem at two layers:
- At the transport layer, I read in a header on a message (which may come in one byte at a time!), get a size for the serialized message, then read N bytes for the message. The simple way to do things is to use a thread per socket, but that results in a lot of wasted memory, depending on how many sockets there are. Instead I use epoll, but now I can't make the simple for loop reading in bytes for the message - I have to have a buffer + allocated size + current size + state enum, wrapped in a struct, then run a switch statement every time I get an epoll event for the socket.
- At half a level higher, there might be multiple messages or other negotiations that need to happen before we can start to stream messages to the owner of the connection. Once again - need to either use a thread or a state enum to keep track of where we are.
Even if you want the enum to be able to report state, you can still set it somewhere for debug purposes.
