Miniature Message Passing IPC System (Single Header C++ File)
https://creativecommons.org/licenses/by/4.0/ I chose this licence, for it's strict requirement of attribution, while still being quite permissive.
PicoMsg is a single-header, thread-safe, simple and fast message-passing library.
PicoMsg uses the single-producer, single-consumer approach. PicoMsg is simpler and smaller than nanomsg and zeromq, at around 500 SLOC.
PicoMsg uses a worker thread behind the scenes, to read and write. PicoMsg will communicate with sockets across processes. But if you are using PicoMsg to communicate within a process, it uses direct memory sharing! Much faster! You can also configure PicoMsg, like having multiple worker-threads, or changing how much memory it uses.
PicoMsg is almost always non-blocking. The default buffer sizes are: Send=1MB, Receive=1MB, Queue <= 8MB (it grows). If your program is busy sending a lot of data, it probably won't block.
The other side, will have two worker-threads that slurp up all your data. One thing to remember, is that you can't send messages bigger than your buffers. That limits us to 1MB-4 bytes per message, by default. PicoMsg will send and get multiple messages per read/send event, if multiple are available.
PicoMsg is open source. If the default behaviour is not good enough for you, feel free to tweak it! It shouldn't be hard to make the buffer-size growable if you really need that... or default to lower-sizes if you prefer.
PicoMsg is best placed at /usr/local/include/PicoMsg/PicoMsg.h , but will work fine no matter where it is placed.
cd /usr/local/include/PicoMsg/
g++ PicoTest.cpp -o picotest -std=c++20 -Os
Then you can run the executable using "picotest 1" or "picotest 2" or "picotest 3".
The API is mostly described in PicoMsg.h itself. However, a quick explanation is here:
Start by calling PicoCreate, then call either PicoStartChild, PicoStartThread or PicoStartFork on your PicoComms*. Call PicoDestroy when you are finished.
To send, use PicoSend (sends blocks of data), or PicoSendStr (sends c-strings).
To receive, use PicoGet. Both calls are non-blocking by default, but you can ask to block within the function call itself.
If you are a C++ expert you might try to find the C++ Spiders I have left in the code for you to discover! 🕸️ Don't worry they are friendly spiders.
PicoMsg also has some util functions. These functions are not always needed, but available in case you need them.
PicoError is very nice, because it returns an error that forced comms to close. If the comms is still open, the error is 0. The errors are from errno, so you can use strerror on them. For example, a PicoComms that was newly created, will have an error of ENOTCONN, meaning that it is not (yet) connected :) This error will go to 0, once you connect the comms.
Other useful utils are: PicoClose (in case you want to close the comms from multiple points in your app), PicoStillSending (in case you want to give your app a chance to still send more data.), PicoSay is very informative and can help debug things.
PicoConfig is useful to configure things about PicoMsg, such as the timeout-value, maximum unread-message queue size, and some variables used to improve (or disable) error-reporting to stdout.
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