bitfield.rs

macro_rules! extract_bits {
    ($val:expr, $low:expr => $hi:expr) => {{
        let max_bit = std::mem::size_of_val(&$val) * 8 - 1;
        assert!((($hi as usize) <= max_bit) && ($low >= 0));
        $val << (max_bit - $hi) >> (max_bit - $hi + $low)
    }};
}

macro_rules! create_bitfield {
    ($name:ident: $ty:ty, { $($var_name:ident: $var_low:expr => $var_hi:expr),* }) => {
        #[derive(Debug)]
        struct $name {
            val: $ty,
        }
        
        impl $name {
            fn new(val: $ty) -> $name {
                $name {
                    val: val,
                }
            }
            
            $(
            #[inline]
            fn $var_name(&self) -> $ty {
                extract_bits!(self.val, $var_low => $var_hi)
            }
            )*
        }
    };
}

create_bitfield!(RAND: u32, {
    foo: 0 => 6,
    bar: 7 => 24,
    foobar: 25 => 31
});

fn main() {
    let val = 0xABCDEF12;
    let val_bf = RAND::new(val);
    
    println!("{:#X}", val);
    println!("{:#b}", val);
    println!("{:#b}", val_bf.foo());
    println!("{:#b}", val_bf.bar());
    println!("{:#b}", val_bf.foobar());
}