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45 lines
1.2 KiB
Markdown
45 lines
1.2 KiB
Markdown
# 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(fast)]
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pub fn op_add(_: &mut OpState, a: i32, b: i32) -> i32 {
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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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## Performance
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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, bool, `&mut OpState`, `&[u8]`, &mut [u8]`,`&[u32]`,`&mut
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[u32]`
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- return_type: integers, bool
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The `#[op(fast)]` attribute should 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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