2022-03-14 13:44:15 -04:00
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# deno_ops
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`proc_macro` for generating highly optimized V8 functions from Deno ops.
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```rust
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// Declare an op.
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#[op]
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pub fn op_add(_: &mut OpState, a: i32, b: i32) -> Result<i32, AnyError> {
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Ok(a + b)
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}
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// Register with an extension.
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Extension::builder()
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.ops(vec![op_add::decl()])
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.build();
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```
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2022-07-22 08:24:22 -04:00
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## Peformance
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The macro can optimize away code, short circuit fast paths and generate a Fast
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API impl.
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Cases where code is optimized away:
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- `-> ()` skips serde_v8 and `rv.set` calls.
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- `-> Result<(), E>` skips serde_v8 and `rv.set` calls for `Ok()` branch.
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- `-> ResourceId` or `-> [int]` types will use specialized method like
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`v8::ReturnValue::set_uint32`. A fast path for SMI.
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- `-> Result<ResourceId, E>` or `-> Result<[int], E>` types will be optimized
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like above for the `Ok()` branch.
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### Fast calls
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The macro will infer and try to auto generate V8 fast API call trait impl for
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`sync` ops with:
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- arguments: integers / `&mut OpState`
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- return_type: integers
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The `#[op(fast)]` attribute can be used to enforce fast call generation at
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compile time.
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Trait gen for `async` ops & a ZeroCopyBuf equivalent type is planned and will be
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added soon.
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