Event Horizon - Asynchronous I/O for the J* language.
Event Horizon is a library that provides asynchronous I/O functionality to the J* language for writing
concurrent code using an async/await-like syntax.
Behind the scenes the library uses libuv to run a sungle-threaded event loop that handles listening
for file descriptor changes and scheduling callbacks when data is available.
You can find more examples in the examples folder, the following is a short snippet demonstrating
how to write an echo server using the async-await syntax (NOTE: this code deliberately skips error
handling to make the example simpler):
import event_horizon as evh
import event_horizon.async for async
import event_horizon.tcp for TCPStream
@async // This decorator enables our function to await for promises via `yield` statements
fun handleClient(client)
var data
// `client.readLine` and `client.write` return `Promise`s. A `Promise` represent a not-yet
// available result, and must be `await`ed in order for its value to be resolved at some point
// in the fututre
while data = yield client.readLine() // To `await` for a Promise, we `yield` it
yield client.write(data) // Same thing here
end
end
@async
fun main()
var server = TCPStream()
server.bind("0.0.0.0", 8080)
yield server.listen(handleClient)
end
// This is the entry point for asynchronous code. It runs the event loop untill all aynschronous
// operations are completed. If a promise is passed to it it will attach error handlers to gracefully
// handle any errors in case of the promise being rejected
evh.run(main())
While the async/await syntax is the default and preferred method to write asynchronous code using
Event Horizon, raw bindings are provided in the event_horizon.uv module that provide a
thin wrapper to libuv for writing async code with good ol' callbacks.
Ensure you have libuv installed on your system. Then, simply issue this on your terminal:
mkdir build;
cd build;
cmake ..;
make -j;
sudo make install;Then you can start using the library in your J* code:
import event_horizon as evh
You can choose to bundle libuv with the library by setting the EVH_VENDOR_LIBUV CMake option to
ON. This will download and compile libuv as part of the build process, not requiring you to have
it installed on your system.