文盘Rust -- FFI 浅尝 | 京东云技术团队

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

1cargo new --bin ffi_sample
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Cargo.toml 配置

1[package]
2name = "ffi_sample"
3version = "0.1.0"
4edition = "2021"
5build = "build.rs"
6
7# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
8
9[build-dependencies]
10cc = "1.0.79"
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12[dependencies]
13libc = "0.2.146"
14libloading = "0.8.0"
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编写一个简单的c程序sample.c

1int add(int a,int b){
2    return a+b;
3}
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main.rs

1use std::os::raw::c_int;
2
3
4#[link(name = "sample")]
5extern "C" {
6    fn add(a: c_int, b: c_int) -> c_int;
7}
8
9fn main() {
10    let r = unsafe { add(2, 18) };
11    println!("{:?}", r);
12}
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build.rs

1
2fn main() {
3    cc::Build::new().file("sample.c").compile("sample");
4}
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代码目录树

1.
2├── Cargo.lock
3├── Cargo.toml
4├── build.rs
5├── sample.c
6└── src
7    └── main.rs
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1cargo run
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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

1[package]
2name = "ffi_sample"
3version = "0.1.0"
4edition = "2021"
5build = "build.rs"
6
7# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
8
9[build-dependencies]
10cc = "1.0.79"
11bindgen = "0.65.1"
12
13[dependencies]
14libc = "0.2.146"
15libloading = "0.8.0"
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新增 sample.h 头文件

1#ifndef ADD_H
2#define ADD_H
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4int add(int a, int b);
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6#endif
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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

1#include "sample.h";
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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

1use std::path::PathBuf;
2
3fn main() {
4    // 参考cc 文档
5    println!("cargo:rerun-if-changed=sample.c");
6    cc::Build::new()
7        .file("sample.c")
8        .shared_flag(true)
9        .compile("sample.so");
10    // 参考 https://doc.rust-lang.org/cargo/reference/build-scripts.html
11    println!("cargo:rustc-link-lib=sample.so");
12    println!("cargo:rerun-if-changed=sample.h");
13    let bindings = bindgen::Builder::default()
14        .header("wrapper.h")
15        .parse_callbacks(Box::new(bindgen::CargoCallbacks))
16        .generate()
17        .expect("Unable to generate bindings");
18
19    let out_path = PathBuf::from("bindings");
20    bindings
21        .write_to_file(out_path.join("sample_bindings.rs"))
22        .expect("Couldn't write bindings!");
23}
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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

1include!("../bindings/sample_bindings.rs");
2
3// #[link(name = "sample")]
4// extern "C" {
5//     fn add(a: c_int, b: c_int) -> c_int;
6// }
7
8fn main() {
9    let r = unsafe { add(2, 18) };
10    println!("{:?}", r);
11}
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代码目录树

1.
2├── Cargo.lock
3├── Cargo.toml
4├── bindings
5│   └── sample_bindings.rs
6├── build.rs
7├── sample.c
8├── sample.h
9├── src
10│   └── main.rs
11└── wrapper.h
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ffi_sample 工程的完整代码位置,读者可以clone https://github.com/jiashiwen/wenpanrust，直接运行即可

1cargo run -p ffi_sample
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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

1cargo new --lib wrapper_secp256k1
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cargo.toml

1[package]
2name = "wrapper_secp256k1"
3version = "0.1.0"
4edition = "2021"
5
6# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
7[build-dependencies]
8cc = "1.0.79"
9bindgen = "0.65.1"
10
11[dependencies]
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git 引入 submodule

1cd wrapper_secp256k1
2git submodule add https://github.com/bitcoin-core/secp256k1  wrapper_secp256k1/secp256k1_sys 
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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

1#include "secp256k1_sys/secp256k1/include/secp256k1.h"
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build.rs

1use std::path::PathBuf;
2
3fn main() {
4    println!("cargo:rustc-link-lib=secp256k1");
5    println!("cargo:rerun-if-changed=wrapper.h");
6    let bindings = bindgen::Builder::default()
7        .header("wrapper.h")
8        .parse_callbacks(Box::new(bindgen::CargoCallbacks))
9        .generate()
10        .expect("Unable to generate bindings");
11
12    let out_path = PathBuf::from("bindings");
13    bindings
14        .write_to_file(out_path.join("bindings.rs"))
15        .expect("Couldn't write bindings!");
16}
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cargo build 通过

编写测试 lib.rs

1include!("../bindings/secp256k1.rs");
2
3#[cfg(test)]
4mod tests {
5    use super::*;
6
7    #[test]
8    fn test_create_pubkey() {
9        // secp256k1返回公钥
10        let mut pubkey: secp256k1_pubkey = secp256k1_pubkey { data: [0; 64] };
11        let prikey: u8 = 1;
12
13        unsafe {
14            let context = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
15            assert!(!context.is_null());
16            let ret = secp256k1_ec_pubkey_create(&*context, &mut pubkey, &prikey);
17            assert_eq!(ret, 1);
18        }
19    }
20}
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运行测试 cargo test 报错

1warning: `wrapper_secp256k1` (lib) generated 5 warnings
2error: linking with `cc` failed: exit status: 1
3  |
4  = 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"
5  = note: ld: library not found for -lsecp256k1
6          clang: error: linker command failed with exit code 1 (use -v to see invocation)
7
8
9warning: `wrapper_secp256k1` (lib test) generated 5 warnings (5 duplicates)
10error: could not compile `wrapper_secp256k1` (lib test) due to previous error; 5 warnings emitted
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报错显示找不到编译 secp256k1 相对应的库。

手动编译secp256k1

1cd secp256k1_sys
2./autogen.sh
3./configure
4make
5make install
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编译完成后，测试通过

其实 secp256k1 有对应的 rust wrapper,我们这里只是展示一下封装的过程。

wrapper_secp256k1 工程的完整代码位置,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

1git clone https://github.com/jiashiwen/wenpanrust
2cd wenpanrust
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update submodule

1git submodule init
2git submodule update
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编译 secp256k1

1cd wrapper_secp256k1/secp256k1_sys 
2./autogen.sh
3./configure
4make
5make install  
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run test

1cargo test -p wrapper_secp256k1
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参考资料

Rust FFI (C vs Rust)学习杂记.pdf
bindgen官方文档
 Rust FFI 编程 - bindgen 使用示例

作者：京东科技贾世闻

来源：京东云开发者社区

文盘Rust -- FFI 浅尝 | 京东云技术团队

场景一调用C代码

场景二使用bindgen 通过头文件绑定c语言动态链接库

场景三封装一个c编写的库

评论区

相关推荐

文盘Rust -- FFI 浅尝 | 京东云技术团队

场景一 调用C代码

场景二 使用bindgen 通过头文件绑定c语言动态链接库

场景三 封装一个c编写的库

评论区

相关推荐

场景一调用C代码

场景二使用bindgen 通过头文件绑定c语言动态链接库

场景三封装一个c编写的库