interoptopus 0.13.0

[![Latest Version]][crates.io]
[![docs]][docs.rs]
![MIT]
[![Rust](https://img.shields.io/badge/rust-1.53%2B-blue.svg?maxAge=3600)](https://github.com/ralfbiedert/interoptopus)
[![Rust](https://github.com/ralfbiedert/interoptopus/actions/workflows/rust.yml/badge.svg?branch=master)](https://github.com/ralfbiedert/interoptopus/actions/workflows/rust.yml)

## Interoptopus 🐙


The polyglot bindings generator for your library.

Interoptopus allows _you_ to deliver high-quality system libraries
to your users, and enables _your users_ to easily consume those libraries from the
language of _their_ choice:

- Design a single `.dll` / `.so` in Rust, consume it from any language.
- Use patterns (e.g., classes, strings) in languages that have them.
- Always be fully C compatible.
- Painless workflow, no external tools required.

We strive to make our generated bindings _zero cost_. They should be as idiomatic
as you could have reasonably written them yourself, but never magic or hiding the interface
you actually wanted to expose.


### Code you write ...


```rust
use interoptopus::{ffi_function, ffi_type, inventory};

#[ffi_type]

#[repr(C)]

pub struct Vec2 {
    pub x: f32,
    pub y: f32,
}

#[ffi_function]

#[no_mangle]

pub extern "C" fn my_function(input: Vec2) {
    println!("{}", input.x);
}

// This defines our FFI interface as `ffi_inventory` containing
// no constants, a single function `my_function`, no additional
// types (types are usually inferred) and no codegen patterns.
inventory!(ffi_inventory, [], [my_function], [], []);

```


### ... Interoptopus generates


| Language | Crate | Sample Output |
| --- | --- | --- |
| C# | [**interoptopus_backend_csharp**](https://crates.io/crates/interoptopus_backend_csharp) | [Interop.cs](https://github.com/ralfbiedert/interoptopus/blob/master/backends/csharp/tests/output_safe/Interop.cs) |
| C | [**interoptopus_backend_c**](https://crates.io/crates/interoptopus_backend_c) | [my_header.h](https://github.com/ralfbiedert/interoptopus/blob/master/backends/c/tests/output/my_header.h) |
| Python | [**interoptopus_backend_cpython**](https://crates.io/crates/interoptopus_backend_cpython) | [reference.py](https://github.com/ralfbiedert/interoptopus/blob/master/backends/cpython/tests/output/reference_project.py) |
| Other | Write your own backend<sup>1</sup> | - |

<sup>1</sup> Create your own backend in just a few hours. No pull request needed. [Pinkie promise](https://github.com/ralfbiedert/interoptopus/blob/master/FAQ.md#new-backends).



### Getting Started 🍼


If you want to ...
- **create a new API** see the [**hello world**](https://github.com/ralfbiedert/interoptopus/tree/master/examples/hello_world),
- **understand what's possible**, see the [**reference project**](https://github.com/ralfbiedert/interoptopus/tree/master/reference_project/src),
- **support a new language**, [**copy the C backend**](https://github.com/ralfbiedert/interoptopus/tree/master/backends/c).


### Supported Rust Constructs


See the [**reference project**](https://github.com/ralfbiedert/interoptopus/tree/master/reference_project/src) for an overview:
- [functions](https://github.com/ralfbiedert/interoptopus/blob/master/reference_project/src/functions.rs) (`extern "C"` functions and delegates)
- [types](https://github.com/ralfbiedert/interoptopus/blob/master/reference_project/src/types.rs) (composites, enums, opaques, references, ...)
- [constants](https://github.com/ralfbiedert/interoptopus/blob/master/reference_project/src/constants.rs) (primitive constants; results of const evaluation)
- [patterns](https://github.com/ralfbiedert/interoptopus/tree/master/reference_project/src/patterns) (ASCII pointers, options, slices, classes, ...)


### Performance 🏁


Generated low-level bindings are _zero cost_ w.r.t. hand-crafted bindings for that language.

That said, even hand-crafted bindings encounter some target-specific overhead
at the FFI boundary (e.g., marshalling or pinning in managed languages). For C# that cost
is often nanoseconds, for Python CFFI it can be microseconds.

While there is nothing you can do about Being aware of the call cost
can help you design better APIs.

Detailed call cost tables can be found here: <sup>🔥</sup>

- [**C# call overhead**](https://github.com/ralfbiedert/interoptopus/blob/master/backends/csharp/benches/BENCHMARK_RESULTS.md)
- [**Python call overhead**](https://github.com/ralfbiedert/interoptopus/blob/master/backends/python/tests/output/BENCHMARK_RESULTS.md)

For quick ballpark figures this table lists the most common call types in _ns / call_:

| Construct | C# | Python |
| --- | --- | --- |
| `primitive_void()` | 7 | 272 |
| `primitive_u32(0)` | 8 | 392 |
| `many_args_5(0, 0, 0, 0, 0)` | 10 | 786 |
| `callback(x => x, 0)` | 43 | 1168 |

<br/>



### Feature Flags


Gated behind **feature flags**, these enable:

- `derive` - Proc macros such as `ffi_type`, ...
- `serde` - Serde attributes on internal types.
- `log` - Invoke [log](https://crates.io/crates/log) on FFI errors.


### Changelog


- **v0.13** - Python backend uses `ctypes` now.
- **v0.12** - Better compat using `#[ffi_service_method]`.
- **v0.11** - C# switch ctors to static methods.
- **v0.10** - C# flavors `DotNet` and `Unity` (incl. Burst).
- **v0.9** - 150x faster C# slices, Python type hints.
- **v0.8** - Moved testing functions to respective backends.
- **v0.7** - Make patterns proc macros for better FFI docs.
- **v0.6** - Renamed and clarified many patterns.
- **v0.5** - More ergonomic slice usage in Rust and FFI.
- **v0.4** - Enable logging support in auto-generated FFI calls.
- **v0.3** - Better compatibility with generics.
- **v0.2** - Introduced "patterns"; _working_ interop for C#.
- **v0.1** - First version.

Also see our [upgrade instructions](https://github.com/ralfbiedert/interoptopus/blob/master/UPGRADE_INSTRUCTIONS.md).


### FAQ


- [FAQ and Safety Guides](https://github.com/ralfbiedert/interoptopus/blob/master/FAQ.md).


### Contributing


PRs are welcome.

- Submit small bug fixes directly. Major changes should be issues first.
- Anything that makes previously working bindings change behavior or stop compiling
is a major change;
- This doesn't mean we're opposed to breaking stuff just that
we'd like to talk about it before it happens.
- New features or patterns must be materialized in the reference project and accompanied by
an interop test (i.e., a backend test running C# / Python against a DLL invoking that code)
in at least one included backend.

[Latest Version]: https://img.shields.io/crates/v/interoptopus.svg
[crates.io]: https://crates.io/crates/interoptopus
[MIT]: https://img.shields.io/badge/license-MIT-blue.svg
[docs]: https://docs.rs/interoptopus/badge.svg
[docs.rs]: https://docs.rs/interoptopus/