ffi-closure - 通过FFI发送和接收闭包

特性

• 简单的API
• 允许通过FFI边界发送Rust函数和闭包
• no-std 兼容
• 支持多种调用约定（默认为C调用约定）
• 简化了与FFI 闭包样 函数的交互
• 闭包可以有析构函数
• 可以指定闭包的线程安全级别（None，Send，Sync或Send + Sync）

示例

导出闭包

use ffi_closure::Closure;
use std::ffi::c_void;
# mod sys {
#     use core::ffi::c_void;
#     #[no_mangle]
#     unsafe extern "C" fn some_lib_fn(f: unsafe extern "C" fn(i8, *mut c_void), user_data: *mut c_void) { f(-1, user_data) }
# }

extern "C" {
    fn some_lib_fn(f: unsafe extern "C" fn(i8, *mut c_void), user_data: *mut c_void);
}

pub fn main() {
    let weight = std::env::args().len() as i8;
    let closure = Closure::<dyn FnMut(i8)>::new(move |x| println!("{}", x * weight));

    let (f, user_data): (unsafe extern "C" fn(i8, *mut c_void), *mut c_void) = closure.as_extern_parts();
    unsafe {
        some_lib_fn(f, user_data);
    }
}

具有系统调用约定的导出闭包

use ffi_closure::{Closure, cc::System};
use std::ffi::c_void;
# mod sys {
#     use core::ffi::c_void;
#     #[no_mangle]
#     unsafe extern "C" fn some_lib_fn(f: unsafe extern "C" fn(i8, *mut c_void), user_data: *mut c_void) { f(-1, user_data) }
# }

extern "C" {
    fn some_lib_fn(f: unsafe extern "system" fn(i8, *mut c_void), user_data: *mut c_void);
}

pub fn main() {
    let weight = std::env::args().len() as i8;
    let closure = Closure::<dyn FnMut(i8), System>::new(move |x| println!("{}", x * weight));

    let (f, user_data): (unsafe extern "system" fn(i8, *mut c_void), *mut c_void) = closure.as_extern_parts();
    unsafe {
        some_lib_fn(f, user_data);
    }
}

导入闭包

use ffi_closure::Closure;
use std::ffi::c_void;

#[no_mangle]
pub extern "C" fn some_lib_fn(
    f: unsafe extern "C" fn(i8, *mut c_void),
    user_data: *mut c_void,
) {
    let mut f = unsafe { Closure::<dyn FnMut(i8)>::from_extern(f, user_data, None) };
    for i in 0..10 {
        f(i);
    }
}

线程安全的导入闭包

use ffi_closure::{Closure};
use std::ffi::c_void;

#[no_mangle]
pub unsafe extern "C" fn some_lib_fn(
    f: unsafe extern "C" fn(i8, *mut c_void),
    user_data: *mut c_void,
) {
    // SAFETY: Caller must ensure the passed function pointer and user data are thread-safe.
    let mut f = unsafe { Closure::<dyn Send + FnMut(i8)>::from_extern(f, user_data, None) };

    std::thread::spawn(move || {
        for i in 0..10 {
            f(i);
        }
    });
}

注意
为了使Closure实现FnOnce和FnMut，必须启用'nightly'功能（因此，程序必须使用nightly Rust构建）。对于非nightly版本，请使用Closure::call