设计

示例 1

1. Rust 导出一个 so 库
2. main 函数在 C 这边，链接 Rust 的 so 库
3. C 中分配栈内存，交由 Rust 端填充
4. Rust 端打印
5. C 端打印

示例 2

1. 同样的示例，C 中分配堆内存，交由 Rust 端填充，并且两边分别打印。

示例 1 代码

// src/lib.rs

use std::os::raw::c_int;
use std::slice;

#[repr(C)]
#[derive(Debug)]
pub struct Student {
pub num: c_int,
pub total: c_int,
}

#[no_mangle]
pub extern "C" fn fill_students(p_stu: *mut Student, n: c_int) {
assert!(!p_stu.is_null());
let s: &mut [Student] = unsafe { slice::from_raw_parts_mut(p_stu, n as usize) };
for elem in s.iter_mut() {
// fill any valid values
        elem.num = 1 as c_int;
        elem.total = 100 as c_int;
    }
}

#[no_mangle]
pub extern "C" fn print_students(p_stu: *mut Student, n: c_int) {
assert!(!p_stu.is_null());
let s: &[Student] = unsafe { slice::from_raw_parts(p_stu, n as usize) };
for elem in s.iter() {
println!("print in rust side: {:?}", elem);
    }
}

[lib]
crate-type = ["cdylib"]

// csrc/cfoo1.c

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>


typedef struct Students {
int num;                // serial number
int total;              // total score
} Student;

extern void fill_students(Student *stu, int);
extern void print_students(Student *stu, int);

void print_students_c(Student *stu, int n) {
int i;
for (i=0; i<n; i++) {
printf("C side print: %d %d\n", stu[i].num, stu[i].total);
        }
}

void main() {
int len = 10;
        Student students[len];

// call rust fill and print functions
        fill_students(students, len);
        print_students(students, len);

// call c print function
        print_students_c(students, len);
}

gcc -o ./cfoo1 ./cfoo1.c -L ./  -lrustffi4

LD_LIBRARY_PATH=. ./cfoo1

print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100

示例2的代码

// csrc/cfoo2.c

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>

typedef struct Students {
int num;                // serial number
int total;              // total score
} Student;

extern void fill_students(Student *stu, int);
extern void print_students(Student *stu, int);

Student* create_students(int n) {
if (n <= 0) return NULL;

        Student *stu = NULL;
        stu = (Student*) malloc(sizeof(Student)*n);

return stu;
}

void release_students(Student *stu) {
if (stu != NULL)
free(stu);
}

void print_students_c(Student *stu, int n) {
int i;
for (i=0; i<n; i++) {
printf("C side print: %d %d\n", stu[i].num, stu[i].total);
        }
}

void main() {
int len = 10;
        Student* students = create_students(len);

// call rust fill and print functions
        fill_students(students, len);
        print_students(students, len);

// call c print function
        print_students_c(students, len);

        release_students(students);
}

gcc -o ./cfoo2 ./cfoo2.c -L ./  -lrustffi4

LD_LIBRARY_PATH=. ./cfoo2

print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
print in rust side: Student { num: 1, total: 100 }
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100
C side print: 1 100

结论