gstring - Rust macros to make strings on stack

gstring.rs

/// A helper to build a string on the stack.
///
/// Given an array it makes a writeable cursor available to the passed code block.
///
/// Returns a &str slice pointing at memory between the array start and the cursor.
///
/// Example:
///
///     use std::io::Write;
///     let mut foobar: [u8; 128] = unsafe {std::mem::uninitialized()};
///     let foobar = gstring! (foobar, {
///         write! (foobar, "foo") .unwrap();
///         write! (foobar, "bar") .unwrap();
///     });
macro_rules! gstring {($array: ident, $code: block) => {{
    let end = {
        let mut $array = std::io::Cursor::new (&mut $array[..]);
        let $array = &mut $array;
        $code;
        $array.position() as usize
    };
    unsafe {std::str::from_utf8_unchecked (&$array[0..end])}}
}}


fn main() {
    use std::io::Write;
    let mut two_and_two: [u8; 32] = unsafe {std::mem::uninitialized()};
    let two_and_two = gstring! (two_and_two, {
        write! (two_and_two, "2 + 2 = {}", 2 + 2) .unwrap();
    });
    println! ("{}", two_and_two);
}