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<h1 class="menu-title">Real-Time Interrupt-driven Concurrency</h1>
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<h1 id="message-passing--capacity"><a class="header" href="#message-passing--capacity">Message passing &amp; capacity</a></h1>
<p>Software tasks support message passing, this means that software tasks can be spawned
with an argument: <code>foo::spawn(1)</code> which will run the task <code>foo</code> with the argument <code>1</code>.</p>
<p>Capacity sets the size of the spawn queue for the task, if not specified capacity defaults to 1.</p>
<p>In the example below, the capacity of task <code>foo</code> is <code>3</code>, allowing three simultaneous
pending spawns of <code>foo</code>. Exceeding this capacity is an <code>Error</code>.</p>
<p>The number of arguments to a task is not limited:</p>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>//! examples/message_passing.rs
#![deny(unsafe_code)]
#![deny(warnings)]
#![deny(missing_docs)]
#![no_main]
#![no_std]
use panic_semihosting as _;
#[rtic::app(device = lm3s6965, dispatchers = [SSI0])]
mod app {
use cortex_m_semihosting::{debug, hprintln};
#[shared]
struct Shared {}
#[local]
struct Local {}
#[init]
fn init(_: init::Context) -&gt; (Shared, Local, init::Monotonics) {
foo::spawn(1, 1).unwrap();
foo::spawn(1, 2).unwrap();
foo::spawn(2, 3).unwrap();
assert!(foo::spawn(1, 4).is_err()); // The capacity of `foo` is reached
(Shared {}, Local {}, init::Monotonics())
}
#[task(capacity = 3)]
fn foo(_c: foo::Context, x: i32, y: u32) {
hprintln!("foo {}, {}", x, y);
if x == 2 {
debug::exit(debug::EXIT_SUCCESS); // Exit QEMU simulator
}
}
}
<span class="boring">}</span></code></pre></pre>
<pre><code class="language-console">$ cargo run --target thumbv7m-none-eabi --example message_passing
foo 1, 1
foo 1, 2
foo 2, 3
</code></pre>
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