pub type Type = u32;
pub const MASK: Type = 0xFFFFF;
pub const SPAN: Type = 0x100000;
pub fn add(a: Type, b: Type) -> Type {
a.wrapping_add(b) & MASK
}
pub fn sub(a: Type, b: Type) -> Type {
a.wrapping_sub(b) & MASK
}
pub fn is_valid(a: Type) -> bool {
a & MASK == a
}