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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.
67 lines
1.9 KiB
Rust
67 lines
1.9 KiB
Rust
// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
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use deno_core::op;
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use deno_core::Extension;
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use deno_core::JsRuntime;
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use deno_core::RuntimeOptions;
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use std::mem::transmute;
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use std::ptr::NonNull;
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// This is a hack to make the `#[op]` macro work with
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// deno_core examples.
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// You can remove this:
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use deno_core::*;
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struct WasmMemory(NonNull<v8::WasmMemoryObject>);
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fn wasm_memory_unchecked(state: &mut OpState) -> &mut [u8] {
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let WasmMemory(global) = state.borrow::<WasmMemory>();
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// SAFETY: `v8::Local` is always non-null pointer; the `HandleScope` is
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// already on the stack, but we don't have access to it.
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let memory_object = unsafe {
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transmute::<NonNull<v8::WasmMemoryObject>, v8::Local<v8::WasmMemoryObject>>(
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*global,
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)
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};
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let backing_store = memory_object.buffer().get_backing_store();
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let ptr = backing_store.data().unwrap().as_ptr() as *mut u8;
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let len = backing_store.byte_length();
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// SAFETY: `ptr` is a valid pointer to `len` bytes.
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unsafe { std::slice::from_raw_parts_mut(ptr, len) }
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}
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#[op(wasm)]
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fn op_wasm(state: &mut OpState, memory: Option<&mut [u8]>) {
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let memory = memory.unwrap_or_else(|| wasm_memory_unchecked(state));
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memory[0] = 69;
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}
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#[op(v8)]
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fn op_set_wasm_mem(
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scope: &mut v8::HandleScope,
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state: &mut OpState,
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memory: serde_v8::Value,
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) {
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let memory =
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v8::Local::<v8::WasmMemoryObject>::try_from(memory.v8_value).unwrap();
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let global = v8::Global::new(scope, memory);
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state.put(WasmMemory(global.into_raw()));
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}
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fn main() {
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// Build a deno_core::Extension providing custom ops
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let ext = Extension::builder("my_ext")
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.ops(vec![op_wasm::decl(), op_set_wasm_mem::decl()])
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.build();
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// Initialize a runtime instance
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let mut runtime = JsRuntime::new(RuntimeOptions {
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extensions: vec![ext],
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..Default::default()
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});
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runtime
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.execute_script("<usage>", include_ascii_string!("wasm.js"))
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.unwrap();
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}
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