- Simple to use API
- Allows sending Rust functions & closures through FFI boundary
no-stdcompatible- Supports multiple calling conventions (defaults to C calling convention)
- Simplifies usage and interaction with FFI closure-like functions
- Closures can have destructors
- Can specify closure's thread-safety level (None,
Send,SyncorSend + Sync)
Export closure
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);
}
}Exported closure w/ system calling convention
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);
}
}Imported closure
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);
}
}Imported, thread-safe closure
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);
}
});
}Note
ForClosureto implementFnOnceandFnMut, the 'nightly' feature must be enabled (and thus, the program must be built with nightly Rust). For a non-nightly version, useClosure::call