mirror of
https://github.com/Sarsoo/csbindgen.git
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286 lines
8.7 KiB
Markdown
286 lines
8.7 KiB
Markdown
# csbindgen
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[](https://crates.io/crates/csbindgen) [](https://docs.rs/csbindgen)
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Generate C# FFI from Rust for automatically brings native code and C native library to .NET and Unity.
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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.
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[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.
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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.
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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#.
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Getting Started
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---
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Install on `Cargo.toml` as `build-dependencies` and set up `bindgen::Builder` on `build.rs`.
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```toml
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[build-dependencies]
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csbindgen = "0.1.1"
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```
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### C (to Rust) to C#
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For example, build [lz4](https://github.com/lz4/lz4) compression library.
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```rust
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// using bindgen, generate binding code
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bindgen::Builder::default()
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.header("c/lz4/lz4.h")
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.generate().unwrap()
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.write_to_file("lz4.rs").unwrap();
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// using cc, build and link c code
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cc::Build::new().file("lz4.c").compile("lz4");
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// csbindgen code, generate both rust ffi and C# dll import
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csbindgen::Builder::default()
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.input_bindgen_file("lz4.rs") // read from bindgen generated code
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.csharp_dll_name("liblz4")
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.generate_to_file("lz4_ffi.rs", "../dotnet/NativeMethods.lz4.g.cs")
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.unwrap();
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```
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It will generates like these code.
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```rust
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// lz4_ffi.rs
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#[allow(unused)]
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use ::std::os::raw::*;
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use super::lz4;
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#[no_mangle]
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pub extern "C" fn csbindgen_LZ4_compress_default(src: *const c_char, dst: *mut c_char, srcSize: c_int, dstCapacity: c_int) -> c_int
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{
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unsafe {
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return lz4::LZ4_compress_default(src, dst, srcSize, dstCapacity);
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}
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}
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```
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```csharp
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// NativeMethods.lz4.g.cs
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using System;
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using System.Runtime.InteropServices;
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namespace CsBindgen
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{
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internal static unsafe partial class NativeMethods
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{
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const string __DllName = "liblz4";
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[DllImport(__DllName, EntryPoint = "csbindgen_LZ4_compress_default", CallingConvention = CallingConvention.Cdecl)]
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public static extern int LZ4_compress_default(byte* src, byte* dst, int srcSize, int dstCapacity);
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}
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}
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```
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Finally import generated module on `lib.rs`.
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```rust
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// lib.rs, import generated codes.
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#[allow(dead_code)]
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#[allow(non_snake_case)]
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#[allow(non_camel_case_types)]
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#[allow(non_upper_case_globals)]
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mod lz4;
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#[allow(dead_code)]
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#[allow(non_snake_case)]
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#[allow(non_camel_case_types)]
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mod lz4_ffi;
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```
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### Rust to C#.
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You can bring simple Rust FFI code to C#.
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```rust
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// lib.rs, simple FFI code
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#[no_mangle]
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pub extern "C" fn my_add(x: i32, y: i32) -> i32 {
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x + y
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}
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```
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Setup csbindgen code to `build.rs`.
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```rust
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csbindgen::Builder::default()
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.input_extern_file("lib.rs")
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.csharp_dll_name("nativelib")
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.generate_csharp_file("../dotnet/NativeMethods.g.cs")
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.unwrap();
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```
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It will generate this C# code.
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```csharp
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// NativeMethods.g.cs
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using System;
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using System.Runtime.InteropServices;
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namespace CsBindgen
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{
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internal static unsafe partial class NativeMethods
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{
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const string __DllName = "nativelib";
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[DllImport(__DllName, EntryPoint = "my_add", CallingConvention = CallingConvention.Cdecl)]
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public static extern int my_add(int x, int y);
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}
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}
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```
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Builder options(configure template)
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---
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`input_bindgen_file` -> setup options -> `generate_to_file` to use C to C# workflow. Here are full option guide.
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```rust
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csbindgen::Builder::default()
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.input_bindgen_file("src/lz4.rs")
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.method_filter(|x| { x.starts_with("LZ4") } )
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.rust_method_prefix("csbindgen_")
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.rust_file_header("use super::lz4;")
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.rust_method_type_path("lz4")
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.csharp_class_name("LibLz4")
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.csharp_class_accessibility("public")
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.csharp_namespace("CsBindgen")
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.csharp_dll_name("csbindgen_tests")
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.csharp_dll_name_if("UNITY_IOS && !UNITY_EDITOR", "__Internal")
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.csharp_entry_point_prefix("csbindgen_")
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.csharp_method_prefix("")
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.csharp_c_long_convert("int")
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.csharp_c_ulong_convert("uint")
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.generate_to_file("src/lz4_ffi.rs", "../dotnet-sandbox/lz4_bindgen.cs")
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.unwrap();
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```
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It will be embedded in the placeholder of the output file.
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```rust
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#[allow(unused)]
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use ::std::os::raw::*;
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{rust_file_header}
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#[no_mangle]
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pub extern "C" fn {rust_method_prefix}LZ4_versionNumber() -> c_int
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{
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unsafe {
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return {rust_method_type_path}::LZ4_versionNumber()
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}
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}
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```
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```csharp
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using System;
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using System.Runtime.InteropServices;
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namespace {csharp_namespace}
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{
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{csharp_class_accessibility} static unsafe partial class {csharp_class_name}
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{
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#if {csharp_dll_name_if(if_symbol,...)}
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const string __DllName = "{csharp_dll_name_if(...,if_dll_name)}";
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#else
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const string __DllName = "{csharp_dll_name}";
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#endif
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}
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[DllImport(__DllName, EntryPoint = "{csharp_entry_point_prefix}LZ4_versionNumber", CallingConvention = CallingConvention.Cdecl)]
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public static extern int {csharp_method_prefix}LZ4_versionNumber();
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}
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```
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Adjust `rust_file_header` and `rust_method_type_path` to match your module configuration.
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`method_filter` allows you to specify which methods to exclude; if unspecified, methods prefixed with `_` are excluded by default.
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`rust_method_prefix` and `csharp_method_prefix` or `csharp_entry_point_prefix` must be adjusted to match the method name to be called.
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`csharp_dll_name_if` is optional. If specified, `#if` allows two DllName to be specified, which is useful if the name must be `__Internal` at iOS build.
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If the file path to be loaded needs to be changed depending on the operating system, the following load code can be used.
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```csharp
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internal static unsafe partial class NativeMethods
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{
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// https://docs.microsoft.com/en-us/dotnet/standard/native-interop/cross-platform
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// Library path will search
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// win => __DllName, __DllName.dll
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// linux, osx => __DllName.so, __DllName.dylib
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// __DllName
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static NativeMethods()
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{
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NativeLibrary.SetDllImportResolver(typeof(NativeMethods).Assembly, DllImportResolver);
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}
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static IntPtr DllImportResolver(string libraryName, Assembly assembly, DllImportSearchPath? searchPath)
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{
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if (libraryName == __DllName)
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{
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var path = "runtimes/";
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if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
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{
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path += "win-";
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}
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else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
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{
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path += "osx-";
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}
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else
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{
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path += "linux-";
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}
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if (RuntimeInformation.OSArchitecture == Architecture.X86)
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{
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path += "x86";
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}
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else if (RuntimeInformation.OSArchitecture == Architecture.X64)
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{
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path += "x64";
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}
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else if (RuntimeInformation.OSArchitecture == Architecture.Arm64)
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{
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path += "arm64";
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}
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path += "/native/" + __DllName;
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return NativeLibrary.Load(path, assembly, searchPath);
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}
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return IntPtr.Zero;
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}
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}
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```
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`csharp_c_long_convert` and `csharp_c_ulong_convert` configure how handles `c_long` and `c_ulong` to C# type. default is to `int` and `uint` because `LLP64` is 32bit representation but you can change it to 64bit or use [CLong](https://learn.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.clong)/CULong struct after .NET 6.
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## Builder options: Rust to C#
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Rust to C# is similar workflow as C to C#, use the `input_extern_file` -> setup options -> `generate_csharp_file`.
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```rust
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csbindgen::Builder::default()
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.input_extern_file("src/lib.rs")
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.csharp_class_name("LibRust")
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.csharp_dll_name("csbindgen_tests")
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.generate_csharp_file("../dotnet-sandbox/NativeMethods.cs")
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.unwrap();
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```
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`generate_csharp_file` does not generate Rust file so no need to use `rust_` option.
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License
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---
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This library is licensed under the MIT License.
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