expose function from rust

  1. #[repr(C)]
  2. pub struct NativeVec {
  3.     vec: *mut u32,
  4.     vec_len: usize,
  5.     vec_cap: usize,
  6. }
  8. #[no_mangle]
  9. pub extern "C" fn new_vec() -> *mut NativeVec {
  10.     let v = vec![1_u32,2,3];
  11.     // prevent running v's destructor so we are in complete control of the allocation
  12.     // this is important
  13.     let mut v = mem::ManuallyDrop::new(v);
  14.     let nv = Box::new(NativeVec {
  15.         vec: v.as_mut_ptr(),
  16.         vec_len: v.len(),
  17.         vec_cap: v.capacity(),
  18.     });
  19.     Box::into_raw(nv)
  20. }
  22. #[no_mangle]
  23. pub extern "C" fn mutate_vec(v: *mut NativeVec) {
  24.      unsafe {
  25.         let v = Box::from_raw(v);
  26.         let v2 = Vec::from_raw_parts(v.vec, v.vec_len, v.vec_cap);
  27.         println!("len {:?}", v2.len());
  28.         println!("cap {:?}", v2.capacity());
  29.         println!("first {:?}", v2[0]);
  30.         println!("second {:?}", v2[1]);
  31.         println!("third {:?}", v2[2]);
  32.         drop(v2);  // not nessery calling manually
  33.     };
  34. }
  1. [package]
  2. name = "c_to_rust"
  3. version = "0.1.0"
  4. authors = ["Sean <xujihui1985@gmail.com>"]
  5. edition = "2018"
  6. build = "build.rs"
  8. # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
  10. [build-dependencies]
  11. cbindgen = "0.13.1"
  14. [lib]
  15. crate-type=["cdylib", "staticlib"]

cbindgen 是用来生成c 头文件为c代码用的

build.rs

  1. extern crate cbindgen;
  3. use std::env;
  4. use cbindgen::Language;
  6. fn main() {
  7.     let crate_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
  9.     cbindgen::Builder::new()
  10.         .with_crate(crate_dir)
  11.         .with_language(Language::C)
  12.         .generate()
  13.         .expect("Unable to generate bindings")
  14.         .write_to_file("target/debug/my_library.h");
  15. }

calling from c

  1. #include "my_library.h"
  2. #include <stdio.h>
  4. int main() 
  5. {
  6.     NativeVec* v = new_vec();
  7.     printf("length of vec is %d\n", v->vec_len);
  8.     for (int i = 0; i < v->vec_len; i++) 
  9.     {
  10.         printf("vec value is is %d\n", *(v->vec + i));
  11.         *(v->vec + i) = 123;
  12.     }
  14.     printf("addr %p\n", v->vec);
  15.     mutate_vec(v);
  16.     return 0;
  17. }
  1. gcc -o main.out main.c -I./target/debug -L./target/debug -lc_to_rust