# js_ffi
```toml
[dependencies]
js_ffi = "0.0.1"
```
A simple FFI library for calling javascript from web assembly with Rust
* low magic
* minimal
* no macros
* ready for [web references](https://github.com/WebAssembly/reference-types/blob/master/proposals/reference-types/Overview.md)
* compatible with async-await
* works with web assembly languages other than Rust
## Simple Example
```rust
use js_ffi::*;
use executor::Executor;
const FUNCTION_LOG: i32 = 0;
const FUNCTION_SET_TIMEOUT: i32 = 1;
const FUNCTION_ALERT: i32 = 2;
#[no_mangle]
pub fn main() -> () {
register(FUNCTION_LOG,"console.log");
register(FUNCTION_SET_TIMEOUT,"window.setTimeout");
register(FUNCTION_ALERT,"window.alert");
Executor::spawn(async {
console_log("hey");
window_set_timeout(1000).await;
window_alert("you");
});
}
pub fn console_log(msg: &str) {
call_1(UNDEFINED, FUNCTION_LOG, TYPE_STRING, to_string(msg));
}
pub fn window_alert(msg: &str) {
call_1(UNDEFINED, FUNCTION_ALERT, TYPE_STRING, to_string(msg));
}
pub fn window_set_timeout(millis: i32) -> CallbackFuture {
let (future, id) = CallbackFuture::create();
js_call_2(
UNDEFINED,
FUNCTION_SET_TIMEOUT,
TYPE_FUNCTION,
id,
TYPE_NUM,
millis as f32,
);
future
}
```
```html
<script src="https://cdn.jsdelivr.net/gh/richardanaya/js_ffi/js_ffi.js"></script>
<script>run_wasm("my_app.wasm");</script>
```
## How it works
The basic premise is that you `register` the JavaScript functions you want to have access to from Rust to a constant number function handle. Then you can use `call_*` to send execute the function with arguments depending on the argument count you want to send (e.g. `call_1`, `call_7`). The idea is you can quickly create wrapper functions for exactly what you need. When calling the function you specify the object to call the function of (or undefined if you just want to call the function), the function id to call you registered with, and pairs of argument type and arguments afer.
`call_*(<object handle>,<function id>,<arg type>,<arg>,<arg type>,<arg>,...)`
## Advanced
Wrap third party. Anything with its functions in global space should be able to be wrapped and invoked.
```rust
const FUNCTION_JQUERY: i32 = 0;
const FUNCTION_JQUERY_ON: i32 = 1;
const FUNCTION_SAY_LOUD: i32 = 2;
fn main() {
register(FUNCTION_JQUERY,"$");
register(FUNCTION_JQUERY_ON,"jQuery.prototype.on");
register(FUNCTION_SAY_LOUD,"say_loud");
let obj = call_1(UNDEFINED,FUNCTION_JQUERY,TYPE_STRING,to_string("body"));
call_2(obj,
FUNCTION_JQUERY_ON,
TYPE_STRING,
to_string("click"),
FUNCTION,
create_callback(Box::new(||{
call_1(UNDEFINED,
FUNCTION_SAY_LOUD,
TYPE_STRING,
to_string("I was clicked!"));
}));
}
```
```html
<script src="https://code.jquery.com/jquery-3.4.1.min.js"></script>
<script src="https://cdn.jsdelivr.net/gh/richardanaya/js_ffi/js_ffi.js"></script>
<script>
function say_loud(msg){
window.alert(msg);
}
</script>
<script>run_wasm("my_app.wasm");</script>
```
# Don't like Rust?
The script `js_ffi.js` has nothing Rust specific. Everything is only done through methods
* `jsfficall0(f32,i32)`
* `jsfficall1(f32,i32,i32,f32)`
* `jsfficall2(f32,i32,i32,f32,i32,f32)`
* ...
* `jsfficall10(f32,i32,i32,f32,i32,f32,i32,f32,i32,f32,i32,f32,i32,f32,i32,f32,i32,f32,i32,f32,i32,f32)`
* `jsffiregister(i32,i32)`
And one callback:
* `jsfficallback(i32)`
And an entry point function:
* `main()`
As long as your module adheres to this you can use js_ffi. Strings are simply cstrings that end in a `0` character.
# License
This project is licensed under either of
* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
http://www.apache.org/licenses/LICENSE-2.0)
* MIT license ([LICENSE-MIT](LICENSE-MIT) or
http://opensource.org/licenses/MIT)
at your option.
### Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in woke by you, as defined in the Apache-2.0 license, shall be
dual licensed as above, without any additional terms or conditions.