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a1764f7690
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.
48 lines
1.4 KiB
Rust
48 lines
1.4 KiB
Rust
// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
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//! This example shows you how to evaluate JavaScript expression and deserialize
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//! return value into a Rust object.
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// NOTE:
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// Here we are deserializing to `serde_json::Value` but you can
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// deserialize to any other type that implementes the `Deserialize` trait.
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use deno_core::v8;
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use deno_core::JsRuntime;
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use deno_core::RuntimeOptions;
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fn main() {
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let mut runtime = JsRuntime::new(RuntimeOptions::default());
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// Evaluate some code
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let code = "let a = 1+4; a*2";
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let output: serde_json::Value =
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eval(&mut runtime, code).expect("Eval failed");
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println!("Output: {output:?}");
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let expected_output = serde_json::json!(10);
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assert_eq!(expected_output, output);
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}
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fn eval(
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context: &mut JsRuntime,
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code: &'static str,
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) -> Result<serde_json::Value, String> {
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let res = context.execute_script_static("<anon>", code);
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match res {
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Ok(global) => {
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let scope = &mut context.handle_scope();
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let local = v8::Local::new(scope, global);
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// Deserialize a `v8` object into a Rust type using `serde_v8`,
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// in this case deserialize to a JSON `Value`.
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let deserialized_value =
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serde_v8::from_v8::<serde_json::Value>(scope, local);
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match deserialized_value {
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Ok(value) => Ok(value),
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Err(err) => Err(format!("Cannot deserialize value: {err:?}")),
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}
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}
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Err(err) => Err(format!("Evaling error: {err:?}")),
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}
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}
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