libffi 0.5.3

# libffi-rs: Rust bindings for [libffi](https://sourceware.org/libffi/)

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The C libffi library provides two main facilities: assembling calls
to functions dynamically, and creating closures that can be called
as ordinary C functions. In Rust, the latter means that we can turn
a Rust lambda (or any object implementing `Fn`/`FnMut`) into an
ordinary C function pointer that we can pass as a callback to C.

## Usage

It’s [on crates.io](https://crates.io/crates/libffi), so you can add

```toml
[dependencies]
libffi = "0.5.3"
```

to your `Cargo.toml` and

```rust
extern crate libffi;
```

to your crate root.

# Examples

In this example, we convert a Rust lambda containing a free variable
into an ordinary C code pointer. The type of `fun` below is
`extern "C" fn(u64, u64) -> u64`.

```
use libffi::high::Closure2;

let x = 5u64;
let f = |y: u64, z: u64| x + y + z;

let closure = Closure2::new(&f);
let fun     = closure.code_ptr();

assert_eq!(18, fun(6, 7));
```