聊聊Rust与C语言交互的具体步骤

rust FFI 是rust与其他语言互调的桥梁，通过FFI rust 可以有效继承 C 语言的历史资产。本期通过几个例子来聊聊rust与 C 语言交互的具体步骤。

场景一 调用C代码

创建工程

 

cargo new --bin ffi_sample

 

Cargo.toml 配置

 

[package]
name = "ffi_sample"
version = "0.1.0"
edition = "2021"
build = "build.rs"


# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html


[build-dependencies]
cc = "1.0.79"


[dependencies]
libc = "0.2.146"
libloading = "0.8.0"

 

编写一个简单的c程序sample.c

 

int add(int a,int b){
    return a+b;
}

 

main.rs

 

use std::c_int;




#[link(name = "sample")]
extern "C" {
    fn add(a: c_int, b: c_int) -> c_int;
}


fn main() {
    let r = unsafe { add(2, 18) };
    println!("{:?}", r);
}

 

build.rs

 

fn main() {
    cc::new().file("sample.c").compile("sample");
}

 

代码目录树

 

.
├── Cargo.lock
├── Cargo.toml
├── build.rs
├── sample.c
└── src
    └── main.rs

cargo run

 

场景二  使用bindgen 通过头文件绑定c语言动态链接库

修改Cargo.toml,新增bindgen依赖

 

[package]
name = "ffi_sample"
version = "0.1.0"
edition = "2021"
build = "build.rs"


# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html


[build-dependencies]
cc = "1.0.79"
bindgen = "0.65.1"


[dependencies]
libc = "0.2.146"
libloading = "0.8.0"

 

新增 sample.h 头文件

 

#ifndef ADD_H
#define ADD_H


int add(int a, int b);


#endif

 

新增 wrapper.h 头文件

wrapper.h 文件将包括所有各种头文件，这些头文件包含我们想要绑定的结构和函数的声明

 

#include "sample.h";

 

改写build.rs

编译 sample.c 生成动态链接库sample.so;通过bindgen生成rust binding c 的代码并输出到 bindings 目录

 

use std::PathBuf;


fn main() {
    // 参考cc 文档
    println!("cargo:rerun-if-changed=sample.c");
    cc::new()
        .file("sample.c")
        .shared_flag(true)
        .compile("sample.so");
    // 参考 https://doc.rust-lang.org/cargo/reference/build-scripts.html
    println!("cargo:rustc-link-lib=sample.so");
    println!("cargo:rerun-if-changed=sample.h");
    let bindings = bindgen::default()
        .header("wrapper.h")
        .parse_callbacks(Box::CargoCallbacks))
        .generate()
        .expect("Unable to generate bindings");


    let out_path = PathBuf::from("bindings");
    bindings
        .write_to_file(out_path.join("sample_bindings.rs"))
        .expect("Couldn't write bindings!");
}

 

修改main.rs

include 宏引入sample 动态链接库的binding。以前我们自己手写的C函数绑定就不需要了，看看bindings/sample_bindings.rs 的内容与我们手写的函数绑定是等效的

 

include!("../bindings/sample_bindings.rs");


// #[link(name = "sample")]
// extern "C" {
//     fn add(a: c_int, b: c_int) -> c_int;
// }


fn main() {
    let r = unsafe { add(2, 18) };
    println!("{:?}", r);
}

 

代码目录树

 

.
├── Cargo.lock
├── Cargo.toml
├── bindings
│   └── sample_bindings.rs
├── build.rs
├── sample.c
├── sample.h
├── src
│   └── main.rs
└── wrapper.h

 

ffi_sample 工程的完整代码：https://github.com/jiashiwen/wenpanrust/tree/main/ffi_sample,读者可以clone https://github.com/jiashiwen/wenpanrust，直接运行即可

 

cargo run -p ffi_sample

 

场景三 封装一个c编写的库

secp256k1是一个椭圆曲线计算的 clib，这玩意儿在密码学和隐私计算方面的常用算法，下面我们从工程方面看看封装secp256k1如何操作

 

cargo new --lib wrapper_secp256k1

 

cargo.toml

 

[package]
name = "wrapper_secp256k1"
version = "0.1.0"
edition = "2021"


# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[build-dependencies]
cc = "1.0.79"
bindgen = "0.65.1"


[dependencies]

 

git 引入 submodule

 

cd wrapper_secp256k1
git submodule add https://github.com/bitcoin-core/secp256k1  wrapper_secp256k1/secp256k1_sys

 

工程下新建bindings目录用来存放绑定文件，该目录与src平级

wrapper.h

 

#include "secp256k1_sys/secp256k1/include/secp256k1.h"

 

build.rs

 

use std::path::PathBuf;


fn main() {
    println!("cargo:rustc-link-lib=secp256k1");
    println!("cargo:rerun-if-changed=wrapper.h");
    let bindings = bindgen::default()
        .header("wrapper.h")
        .parse_callbacks(Box::CargoCallbacks))
        .generate()
        .expect("Unable to generate bindings");


    let out_path = PathBuf::from("bindings");
    bindings
        .write_to_file(out_path.join("bindings.rs"))
        .expect("Couldn't write bindings!");
}

 

cargo build 通过

编写测试 lib.rs

 

include!("../bindings/secp256k1.rs");


#[cfg(test)]
mod tests {
    use super::*;


    #[test]
    fn test_create_pubkey() {
        // secp256k1返回公钥
        let mut pubkey: secp256k1_pubkey = secp256k1_pubkey { data: [0; 64] };
        let prikey: u8 = 1;


        unsafe {
            let context = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
            assert!(!context.is_null());
            let ret = secp256k1_ec_pubkey_create(&*context, &mut pubkey, &prikey);
            assert_eq!(ret, 1);
        }
    }
}

 

运行测试 cargo test 报错

 

warning: `wrapper_secp256k1` (lib) generated 5 warnings
error: linking with `cc` failed: exit status: 1
  |
  = note: LC_ALL="C" PATH="/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/bin:/Users/jiashiwen/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libobject-6d1da0e5d7930106.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libmemchr-d6d74858e37ed726.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libaddr2line-d75e66c6c1b76fdd.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libgimli-546ea342344e3761.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/librustc_demangle-8ad10e36ca13f067.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libstd_detect-0543b8486ac00cf6.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libhashbrown-7f0d42017ce08763.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libminiz_oxide-65e6b9c4725e3b7f.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libadler-131157f72607aea7.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/librustc_std_workspace_alloc-f7d15060b16c135d.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libunwind-a52bfac5ae872be2.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libcfg_if-1762d9ac100ea3e7.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/liblibc-f8e0e4708f61f3f4.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/liballoc-af9a608dd9cb26b2.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/librustc_std_workspace_core-9777023438fd3d6a.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libcore-83ca6d61eb70e9b8.rlib" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib/libcompiler_builtins-ea2ca6e1df0449b8.rlib" "-lSystem" "-lc" "-lm" "-L" "/usr/local/Cellar/rust/1.70.0/lib/rustlib/x86_64-apple-darwin/lib" "-o" "/Users/jiashiwen/rustproject/wrapper_secp256k1/target/debug/deps/wrapper_secp256k1-4bf30c62ecfdf2a7" "-Wl,-dead_strip" "-nodefaultlibs"
  = note: ld: library not found for -lsecp256k1
          clang: error: linker command failed with exit code 1 (use -v to see invocation)




warning: `wrapper_secp256k1` (lib test) generated 5 warnings (5 duplicates)
error: could not compile `wrapper_secp256k1` (lib test) due to previous error; 5 warnings emitted

 

报错显示找不到编译 secp256k1 相对应的库。

手动编译secp256k1

 

cd secp256k1_sys
./autogen.sh
./configure
make
make install

 

编译完成后，测试通过

其实 secp256k1 有对应的 [rust wrapper](https://github.com/rust-bitcoin/rust-secp256k1),我们这里只是展示一下封装的过程。

wrapper_secp256k1 工程的完整代码：https://github.com/jiashiwen/wenpanrust/tree/main/wrapper_secp256k1,有兴趣的朋友可以clone https://github.com/jiashiwen/wenpanrust。通过以下操作查看运行结果：

clone 项目

 

  git clone https://github.com/jiashiwen/wenpanrust
  cd wenpanrust

 

update submodule

 

  git submodule init
  git submodule update

 

编译 secp256k1

 

  cd wrapper_secp256k1/secp256k1_sys 
  ./autogen.sh
  ./configure
  make
  make install

 

run test

 

  cargo test -p wrapper_secp256k1

 

　　审核编辑：汤梓红