Recently, I am reading source code in the repo parity-bridges-common. There are some rs files full of incomprehensibly asynchronous syntax that I am not familiar with. Especially about FusedFuture. Example file:
According to the futures::future::fuse, what I understand is that we can transfer a Future into FusedFuture and then poll it, again and again, for many times. Besides this, I find a function named terminated() in FuseFurture and example below.
Creates a new Fuse-wrapped future which is already terminated. This can be useful in combination with looping and the select! macro, which bypasses terminated futures.
let (sender, mut stream) = mpsc::unbounded();
// Send a few messages into the stream
sender.unbounded_send(()).unwrap();
sender.unbounded_send(()).unwrap();
drop(sender);
// Use `Fuse::terminated()` to create an already-terminated future
// which may be instantiated later.
// bear: We must terminated() here in order to use select!?
let foo_printer = Fuse::terminated();
pin_mut!(foo_printer);
loop {
select! {
_ = foo_printer => {},
() = stream.select_next_some() => {
if !foo_printer.is_terminated() {
println!("Foo is already being printed!");
} else {
// bear: here we reset the foo_printer pointed value?
foo_printer.set(async {
// do some other async operations
println!("Printing foo from `foo_printer` future");
}.fuse());
}
},
complete => break, // `foo_printer` is terminated and the stream is done
}
}
I cannot understand when to use this function and how to combine it with select!. Can anyone help me understand it more easily? Or are there better docs or examples about this usage?
Some posts i found, maybe useful: