#[unsafe(no_mangle)]
extern "C" fn panic() -> ! {
    panic!("Called panic from external code.");
}

#[repr(C)]
struct FFISlice {
    ptr: *const u8,
    len: usize,
}

impl FFISlice {
    fn as_slice(&self) -> &[u8] {
        unsafe { core::slice::from_raw_parts(self.ptr, self.len) }
    }
    fn as_str(&self) -> &str {
        unsafe { core::str::from_utf8_unchecked(self.as_slice()) }
    }
}

unsafe extern "C" {
    unsafe fn int_to_str2(value: usize, buffer: *mut u8, buffer_len: usize) -> FFISlice;
}

fn main() {
    let value = 1234567890usize;
    let mut buffer = [0u8; 32];
    unsafe {
        let slice = int_to_str2(value, buffer.as_mut_ptr(), buffer.len());
        let s = slice.as_str();
        println!("Integer: {}, String: {}", value, s);
        assert_eq!(s, value.to_string());
    }
}