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use std::ffi::CStr;

use libc::{c_int, off_t};

#[cfg(not(any(target_os = "freebsd", all(target_os = "linux", feature = "memfd"))))]
pub fn create_shmem<T: AsRef<CStr>>(name: T, length: usize) -> c_int {
    unsafe {
        let fd = libc::shm_open(
            name.as_ref().as_ptr(),
            libc::O_CREAT | libc::O_RDWR | libc::O_EXCL,
            0o600,
        );
        assert!(fd >= 0);
        assert!(libc::shm_unlink(name.as_ref().as_ptr()) == 0);
        assert!(libc::ftruncate(fd, length as off_t) == 0);
        fd
    }
}

#[cfg(target_os = "freebsd")]
pub fn create_shmem<T: AsRef<CStr>>(_name: T, length: usize) -> c_int {
    unsafe {
        let fd = libc::shm_open(
            libc::SHM_ANON,
            libc::O_CREAT | libc::O_RDWR | libc::O_EXCL,
            0o600,
        );
        assert!(fd >= 0);
        assert!(libc::ftruncate(fd, length as off_t) == 0);
        fd
    }
}

#[cfg(all(feature = "memfd", target_os = "linux"))]
pub fn create_shmem<T: AsRef<CStr>>(name: T, length: usize) -> c_int {
    unsafe {
        let fd = memfd_create(name.as_ref().as_ptr(), 0);
        assert!(fd >= 0);
        assert!(libc::ftruncate(fd, length as off_t) == 0);
        fd
    }
}

#[cfg(all(feature = "memfd", target_os = "linux"))]
unsafe fn memfd_create(name: *const libc::c_char, flags: usize) -> c_int {
    libc::syscall(libc::SYS_memfd_create, name, flags) as c_int
}

#[cfg(test)]
mod tests {
    use std::ffi::CString;

    #[test]
    fn test_create_shmem() {
        super::create_shmem(CString::new("/helloworld").unwrap(), 1024);
    }
}