windows_strings.rs

use std::ffi::OsString;
use std::os::windows::ffi::OsStrExt;

#[link(name = "user32")]
extern "stdcall" {
    fn MessageBoxW(hwnd: *mut (), message: *const u16, title: *const u16, kind: u32);
}

struct LPCWSTR {
    str: Vec<u16>
}

impl LPCWSTR {
    fn as_ptr(&self) -> *const u16 {
        self.str.as_ptr()
    }
}

impl<T: Into<OsString>> From<T> for LPCWSTR {
    fn from(source: T) -> LPCWSTR {
        LPCWSTR { str: source.into().as_os_str().encode_wide().chain(Some(0).into_iter()).collect::<Vec<_>>() }
    }
}

fn message_box<T: Into<LPCWSTR>>(message: T, title: T) { 
    unsafe { MessageBoxW(::std::ptr::null_mut(), message.into().as_ptr(), title.into().as_ptr(), 0) };
}

fn main() {
    message_box("Hello, world!", "Greetings");
}