csbindgen/README.md

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# csbindgen
2023-02-28 07:21:19 +00:00
[![Crates](https://img.shields.io/crates/v/csbindgen.svg)](https://crates.io/crates/csbindgen) [![Api Rustdoc](https://img.shields.io/badge/api-rustdoc-blue)](https://docs.rs/csbindgen)
2023-02-28 07:20:32 +00:00
Generate C# FFI from Rust for brings C native library to .NET and Unity easily.
2023-02-28 09:12:04 +00:00
There are usually many pains involved in using the C Library with C#. Not only is it difficult to create bindings, but cross-platform builds are very difficult. In this day and age, you have to build for multiple platforms and architectures, windows, osx, linux, android, ios, each with x64, x86, arm.
[Rust](https://www.rust-lang.org/) has an excellent toolchain for cross-platform builds, as well as [cc crate](https://crates.io/crates/cc), [cmake crate](https://crates.io/crates/cmake) allow C source code to be integrated into the build. And [rust-bindgen](https://crates.io/crates/bindgen), which generates bindings from `.h`, is highly functional and very stable.
csbindgen can easily bring native C libraries into C# through Rust. csbindgen generates Rust extern code and C# DllImport code to work with C# from code generated from C by bindgen. With cc crate or cmake crate, C code is linked to the single rust native library.
Of course, you can also output pure FFI Rust code (or a wrapper layer to make it easier to bring C, C++ libraries into C#) to C#.
Getting Started
---
Install on `Cargo.toml` as `build-dependencies` and set up `bindgen::Builder` on `build.rs`.
```toml
[build-dependencies]
csbindgen = "0.1.1"
```
### C (to Rust) to C#
For example, build [lz4](https://github.com/lz4/lz4) compression library.
```rust
// using bindgen, generate binding code
bindgen::Builder::default()
.header("c/lz4/lz4.h")
.generate().unwrap()
.write_to_file("lz4.rs").unwrap();
// using cc, build and link c code
cc::Build::new().file("lz4.c").compile("lz4");
// csbindgen code, generate both rust ffi and C# dll import
csbindgen::Builder::default()
.input_bindgen_file("lz4.rs") // read from bindgen generated code
.csharp_dll_name("liblz4")
.generate_to_file("lz4_ffi.rs", "../dotnet/NativeMethods.lz4.g.cs")
.unwrap();
```
It will generates like these code.
```rust
// lz4_ffi.rs
#[allow(unused)]
use ::std::os::raw::*;
use super::lz4;
#[no_mangle]
pub extern "C" fn csbindgen_LZ4_compress_default(src: *const c_char, dst: *mut c_char, srcSize: c_int, dstCapacity: c_int) -> c_int
{
unsafe {
return lz4::LZ4_compress_default(src, dst, srcSize, dstCapacity);
}
}
```
```csharp
// NativeMethods.lz4.g.cs
using System;
using System.Runtime.InteropServices;
namespace CsBindgen
{
public static unsafe partial class NativeMethods
{
const string __DllName = "liblz4";
[DllImport(__DllName, EntryPoint = "csbindgen_LZ4_compress_default", CallingConvention = CallingConvention.Cdecl)]
public static extern int LZ4_compress_default(byte* src, byte* dst, int srcSize, int dstCapacity);
}
}
```
Finally import generated module on `lib.rs`.
```rust
// lib.rs, import generated codes.
#[allow(dead_code)]
#[allow(non_snake_case)]
#[allow(non_camel_case_types)]
#[allow(non_upper_case_globals)]
mod lz4;
#[allow(dead_code)]
#[allow(non_snake_case)]
#[allow(non_camel_case_types)]
mod lz4_ffi;
```
### Rust to C#.
You can bring simple Rust FFI code to C#.
```rust
// lib.rs, simple FFI code
#[no_mangle]
pub extern "C" fn my_add(x: i32, y: i32) -> i32 {
x + y
}
```
Setup csbindgen code to `build.rs`.
```rust
csbindgen::Builder::default()
.input_extern_file("lib.rs")
.csharp_dll_name("nativelib")
.generate_csharp_file("../dotnet/NativeMethods.g.cs")
.unwrap();
```
It will generate this C# code.
```csharp
// NativeMethods.g.cs
using System;
using System.Runtime.InteropServices;
namespace CsBindgen
{
public static unsafe partial class NativeMethods
{
const string __DllName = "nativelib";
[DllImport(__DllName, EntryPoint = "my_add", CallingConvention = CallingConvention.Cdecl)]
public static extern int my_add(int x, int y);
}
}
```
Builder options(configure template)
---
`input_bindgen_file` -> setup options -> `generate_to_file` to use C to C# workflow. Here are full option guide.
```rust
csbindgen::Builder::default()
.input_bindgen_file("src/lz4.rs")
.method_filter(|x| { !x.starts_with("_") && !x.starts_with("XXH") } )
.rust_method_prefix("csbindgen_")
.rust_file_header("use super::lz4;")
.rust_method_type_path("lz4")
.csharp_class_name("LibLz4")
.csharp_namespace("CsBindgen")
.csharp_dll_name("csbindgen_tests")
.csharp_dll_name_if("UNITY_IOS && !UNITY_EDITOR", "__Internal")
.csharp_entry_point_prefix("csbindgen_")
.csharp_method_prefix("")
.csharp_c_long_convert("int")
.csharp_c_long_convert("uint")
.generate_to_file("src/lz4_ffi.rs", "../dotnet-sandbox/lz4_bindgen.cs")
.unwrap();
```
```rust
#[allow(unused)]
use ::std::os::raw::*;
{rust_file_header}
#[no_mangle]
pub extern "C" fn {rust_method_prefix}LZ4_versionNumber() -> c_int
{
unsafe {
return {rust_method_type_path}::LZ4_versionNumber()
}
}
```
```csharp
using System;
using System.Runtime.InteropServices;
namespace {csharp_namespace}
{
public static unsafe partial class {csharp_class_name}
{
#if {csharp_dll_name_if(if_symbol,...)}
const string __DllName = "{csharp_dll_name_if(...,if_dll_name)}";
#else
const string __DllName = "{csharp_dll_name}";
#endif
}
[DllImport(__DllName, EntryPoint = "{csharp_entry_point_prefix}LZ4_versionNumber", CallingConvention = CallingConvention.Cdecl)]
public static extern int {csharp_method_prefix}LZ4_versionNumber();
}
```
Builder options: Rust to C#
---
csbindgen::Builder::default()
.input_extern_file("src/lib.rs")
.csharp_class_name("LibRust")
.csharp_dll_name("csbindgen_tests")
.generate_csharp_file("../dotnet-sandbox/method_call.cs")
.unwrap();
License
---
This library is licensed under the MIT License.