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denoland-deno/core/examples/hello_world.rs
Matt Mastracci a1764f7690
refactor(core): Improve ergonomics of managing ASCII strings (#18498)
This is a follow-on to the earlier work in reducing string copies,
mainly focused on ensuring that ASCII strings are easy to provide to the
JS runtime.

While we are replacing a 16-byte reference in a number of places with a
24-byte structure (measured via `std::mem::size_of`), the reduction in
copies wins out over the additional size of the arguments passed into
functions.

Benchmarking shows approximately the same if not slightly less wallclock
time/instructions retired, but I believe this continues to open up
further refactoring opportunities.
2023-04-04 06:46:31 -06:00

68 lines
1.7 KiB
Rust

// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
//! This example shows you how to define ops in Rust and then call them from
//! JavaScript.
use deno_core::op;
use deno_core::Extension;
use deno_core::JsRuntime;
use deno_core::RuntimeOptions;
// This is a hack to make the `#[op]` macro work with
// deno_core examples.
// You can remove this:
use deno_core::*;
#[op]
fn op_sum(nums: Vec<f64>) -> Result<f64, deno_core::error::AnyError> {
// Sum inputs
let sum = nums.iter().fold(0.0, |a, v| a + v);
// return as a Result<f64, AnyError>
Ok(sum)
}
fn main() {
// Build a deno_core::Extension providing custom ops
let ext = Extension::builder("my_ext")
.ops(vec![
// An op for summing an array of numbers
// The op-layer automatically deserializes inputs
// and serializes the returned Result & value
op_sum::decl(),
])
.build();
// Initialize a runtime instance
let mut runtime = JsRuntime::new(RuntimeOptions {
extensions: vec![ext],
..Default::default()
});
// Now we see how to invoke the op we just defined. The runtime automatically
// contains a Deno.core object with several functions for interacting with it.
// You can find its definition in core.js.
runtime
.execute_script_static(
"<usage>",
r#"
// Print helper function, calling Deno.core.print()
function print(value) {
Deno.core.print(value.toString()+"\n");
}
const arr = [1, 2, 3];
print("The sum of");
print(arr);
print("is");
print(Deno.core.ops.op_sum(arr));
// And incorrect usage
try {
print(Deno.core.ops.op_sum(0));
} catch(e) {
print('Exception:');
print(e);
}
"#,
)
.unwrap();
}