# napi_sym
A proc_macro for Deno's Node-API implementation. It does the following things:
- Marks the symbol as `#[no_mangle]` and rewrites it as
`unsafe extern "C" $name`.
- Asserts that the function symbol is present in
[`symbol_exports.json`](./symbol_exports.json).
- Maps `deno_napi::Result` to raw `napi_result`.
```rust
use deno_napi::napi_value;
use deno_napi::Env;
use deno_napi::Error;
use deno_napi::Result;
#[napi_sym::napi_sym]
fn napi_get_boolean(
env: *mut Env,
value: bool,
result: *mut napi_value,
) -> Result {
let _env: &mut Env = env.as_mut().ok_or(Error::InvalidArg)?;
// *result = ...
Ok(())
}
```
### `symbol_exports.json`
A file containing the symbols that need to be put into the executable's dynamic
symbol table at link-time.
This is done using `/DEF:` on Windows, `-exported_symbol,_` on macOS and
`--export-dynamic-symbol=` on Linux. See [`cli/build.rs`](../build.rs).
On Windows, you need to generate the `.def` file by running
[`tools/napi/generate_symbols_lists.js`](../../tools/napi/generate_symbols_lists.js).