Hello MessageBox

Cargo.toml

[package]
name = "msgbox"
version = "0.1.0"
authors = ["kosta"]

[dependencies]
winapi = "*"
user32-sys = "*"
encoding = "*"

[profile.release]
opt-level = 3
debug = false
rpath = false
lto = true
debug-assertions = false
codegen-units = 1

main.rs

extern crate winapi;
extern crate user32;
extern crate encoding;

use std::slice;

use encoding::{Encoding, EncoderTrap};
use encoding::all::UTF_16LE;

fn to_utf16(s: &str) -> Vec<u8> {
    let mut result = UTF_16LE.encode(s, EncoderTrap::Ignore).unwrap_or(Vec::new());
    result.push(0);
    result.push(0);
    result
}

#[allow(non_snake_case)]
unsafe fn as_LPCWSTR(v: &Vec<u8>) -> winapi::winnt::LPCWSTR {
    let s : &[u16] = slice::from_raw_parts(v.as_ptr() as *const _, 
        v.len()/2);
    s.as_ptr()
}

fn message_box(title: &str, message: &str) {
     unsafe {
        user32::MessageBoxW(std::ptr::null_mut(), 
            as_LPCWSTR(&to_utf16(message)),
            as_LPCWSTR(&to_utf16(title)),  
            winapi::MB_ICONASTERISK);
    }
}

fn main() {
    message_box("Oh Hi!", "This is a very important message.");
}