# deno_ops
`proc_macro` for generating highly optimized V8 functions from Deno ops.
```rust,ignore
// Declare an op.
#[op(fast)]
pub fn op_add(_: &mut OpState, a: i32, b: i32) -> i32 {
a + b
}
// Register with an extension.
Extension {
name: "math",
ops: Cow::Borrowed(&[op_add::DECL]),
..Default::default()
}
```
## Performance
The macro can optimize away code, short circuit fast paths and generate a Fast
API impl.
Cases where code is optimized away:
- `-> ()` skips serde_v8 and `rv.set` calls.
- `-> Result<(), E>` skips serde_v8 and `rv.set` calls for `Ok()` branch.
- `-> ResourceId` or `-> [int]` types will use specialized method like
`v8::ReturnValue::set_uint32`. A fast path for SMI.
- `-> Result<ResourceId, E>` or `-> Result<[int], E>` types will be optimized
like above for the `Ok()` branch.
### Fast calls
The macro will infer and try to auto generate V8 fast API call trait impl for
`sync` ops with:
- arguments: integers, bool, `&mut OpState`, `&[u8]`, `&mut [u8]`, `&[u32]`,
`&mut [u32]`
- return_type: integers, bool
The `#[op(fast)]` attribute should be used to enforce fast call generation at
compile time.
Trait gen for `async` ops & a ZeroCopyBuf equivalent type is planned and will be
added soon.
### Wasm calls
The `#[op(wasm)]` attribute should be used for calls expected to be called from
Wasm. This enables the fast call generation and allows seamless `WasmMemory`
integration for generic and fast calls.
```rust,ignore
#[op(wasm)]
pub fn op_args_get(
offset: i32,
buffer_offset: i32,
memory: Option<&[u8]>, // Must be last parameter. Some(..) when entered from Wasm.
) {
// ...
}
```