mirror of
https://github.com/aphrody-labs/rusty_v8.git
synced 2026-10-14 04:19:09 +00:00
Nathan Whitaker
65fb5c1683
Before this change, `HandleScope`s (and other scope types) were stored in the heap and we did bookkeeping at runtime of the current stack of scopes. The reasons were primarily:
- raw handle scopes need to be pinned in memory once initialized
- we couldn't enforce at compile that a `Local` didn't outlive the scope it was created from
The latter lead us to need a workaround where scopes actually were not exited when they were dropped, rather they were exited the next time we activated another scope.
This change refactors the scope implementation to:
- make scopes stack allocated, to reduce overhead of using them
- remove the runtime bookkeeping
- use lifetimes to prevent scopes from being dropped, so we can remove the `zombie` scope workaround
The practical effect is that creating a handle scope changes from:
```rust
let mut scope = v8::HandleScope::new(&mut isolate);
let local = v8::Integer::new(&mut scope, 123);
```
to:
```rust
let scope = std::pin::pin!(v8::HandleScope::new(&mut isolate));
let scope = scope.init();
let local = v8::Integer::new(&scope, 123);
// or shorter
v8::scope!(let scope, &mut isolate);
let local = v8::Integer::new(scope, 123);
```
If you accept a `HandleScope` as a parameter in a function, you would change it from:
```rust
fn takes_scope(s: &mut v8::HandleScope) {}
```
to
```rust
fn takes_scope(s: &mut v8::PinScope) {}
```
(`v8::PinScope` is a type alias for a pinned handle scope).
56 lines
1.6 KiB
Rust
56 lines
1.6 KiB
Rust
// Tests from the same file run in a single process. That's why this test
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// is in its own file, because changing the entropy source affects the
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// whole process.
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use std::sync::atomic::AtomicUsize;
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use std::sync::atomic::Ordering;
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static CALLS: AtomicUsize = AtomicUsize::new(0);
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#[test]
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fn set_entropy_source() {
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const N: usize = 3;
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v8::V8::set_entropy_source(|buf| {
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CALLS.fetch_add(1, Ordering::SeqCst);
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for c in buf {
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*c = 42;
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}
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true
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});
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v8::V8::initialize_platform(
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v8::new_unprotected_default_platform(0, false).make_shared(),
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);
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v8::V8::initialize();
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// Assumes that every isolate creates a PRNG from scratch, which is currently true.
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let mut results = vec![];
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for _ in 0..N {
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let isolate = &mut v8::Isolate::new(Default::default());
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v8::scope!(let scope, isolate);
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let context = v8::Context::new(scope, Default::default());
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let scope = &mut v8::ContextScope::new(scope, context);
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let source = v8::String::new(scope, "Math.random()").unwrap();
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let script = v8::Script::compile(scope, source, None).unwrap();
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let result = script.run(scope).unwrap();
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let result = result.to_string(scope).unwrap();
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let result = result.to_rust_string_lossy(scope);
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results.push(result);
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}
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unsafe {
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v8::V8::dispose();
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}
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v8::V8::dispose_platform();
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// All runs should have produced the same value.
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assert_eq!(results.len(), N);
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results.dedup();
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assert_eq!(results.len(), 1);
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// Doesn't have to be exactly N because V8 also calls
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// the EntropySource for things like hash seeds and ASLR.
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assert!(CALLS.load(Ordering::SeqCst) >= N);
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}
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