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//! Example of interrupting a WebAssembly function's runtime via epoch
//! changes ("epoch interruption") in a synchronous context. To see
//! an example of setup for asynchronous usage, see
//! `tests/all/epoch_interruption.rs`
use anyhow::Error;
use std::sync::Arc;
use wasmtime::{Config, Engine, Instance, Module, Store};
fn main() -> Result<(), Error> {
// Set up an engine configured with epoch interruption enabled.
let mut config = Config::new();
config.epoch_interruption(true);
let engine = Arc::new(Engine::new(&config)?);
let mut store = Store::new(&engine, ());
// Configure the store to trap on reaching the epoch deadline.
// This is the default, but we do it explicitly here to
// demonstrate.
store.epoch_deadline_trap();
// Configure the store to have an initial epoch deadline one tick
// in the future.
store.set_epoch_deadline(1);
// Reuse the fibonacci function from the Fuel example. This is a
// long-running function that we will want to interrupt.
let module = Module::from_file(store.engine(), "examples/fuel.wat")?;
let instance = Instance::new(&mut store, &module, &[])?;
// Start a thread that will bump the epoch after 1 second.
let engine_clone = engine.clone();
std::thread::spawn(move || {
std::thread::sleep(std::time::Duration::from_secs(1));
engine_clone.increment_epoch();
});
// Invoke `fibonacci` with a large argument such that a normal
// invocation would take many seconds to complete.
let fibonacci = instance.get_typed_func::<i32, i32>(&mut store, "fibonacci")?;
match fibonacci.call(&mut store, 100) {
Ok(_) => panic!("Somehow we computed recursive fib(100) in less than a second!"),
Err(_) => {
println!("Trapped out of fib(100) after epoch increment");
}
};
Ok(())
}
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