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Even if bootstrapping the JS runtime is low level, it's an abstraction leak of core to require users to call `Deno.core.ops()` in JS space. So instead we're introducing a `JsRuntime::sync_ops_cache()` method, once we have runtime extensions a new runtime will ensure the ops cache is setup (for the provided extensions) and then loading/unloading plugins should be the only operations that require op cache syncs
99 lines
2.7 KiB
Rust
99 lines
2.7 KiB
Rust
// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
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//! This example shows you how to define ops in Rust and then call them from
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//! JavaScript.
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use deno_core::op_sync;
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use deno_core::JsRuntime;
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use std::io::Write;
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fn main() {
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// Initialize a runtime instance
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let mut runtime = JsRuntime::new(Default::default());
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// The first thing we do is define two ops. They will be used to show how to
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// pass data to Rust and back to JavaScript.
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//
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// The first one is used to print data to stdout, because by default the
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// JavaScript console functions are just stubs (they don't do anything).
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//
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// The second one just transforms some input and returns it to JavaScript.
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// Register the op for outputting a string to stdout.
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// It can be invoked with Deno.core.opcall and the id this method returns
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// or Deno.core.opSync and the name provided.
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runtime.register_op(
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"op_print",
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// The op_fn callback takes a state object OpState,
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// a structured arg of type `T` and an optional ZeroCopyBuf,
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// a mutable reference to a JavaScript ArrayBuffer
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op_sync(|_state, msg: Option<String>, zero_copy| {
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let mut out = std::io::stdout();
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// Write msg to stdout
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if let Some(msg) = msg {
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out.write_all(msg.as_bytes()).unwrap();
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}
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// Write the contents of every buffer to stdout
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if let Some(buf) = zero_copy {
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out.write_all(&buf).unwrap();
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}
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Ok(()) // No meaningful result
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}),
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);
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// Register the JSON op for summing a number array.
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runtime.register_op(
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"op_sum",
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// The op_sync function automatically deserializes
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// the first ZeroCopyBuf and serializes the return value
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// to reduce boilerplate
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op_sync(|_state, nums: Vec<f64>, _| {
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// Sum inputs
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let sum = nums.iter().fold(0.0, |a, v| a + v);
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// return as a Result<f64, AnyError>
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Ok(sum)
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}),
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);
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runtime.sync_ops_cache();
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// Now we see how to invoke the ops we just defined. The runtime automatically
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// contains a Deno.core object with several functions for interacting with it.
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// You can find its definition in core.js.
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runtime
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.execute(
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"<init>",
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r#"
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// Define a print function that uses
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// our op_print op to display the stringified argument.
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const _newline = new Uint8Array([10]);
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function print(value) {
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Deno.core.opSync('op_print', value.toString(), _newline);
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}
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"#,
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)
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.unwrap();
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// Now we can finally use this in an example.
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runtime
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.execute(
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"<usage>",
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r#"
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const arr = [1, 2, 3];
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print("The sum of");
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print(arr);
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print("is");
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print(Deno.core.opSync('op_sum', arr));
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// And incorrect usage
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try {
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print(Deno.core.opSync('op_sum', 0));
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} catch(e) {
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print('Exception:');
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print(e);
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}
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"#,
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)
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.unwrap();
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}
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