humpback-dds/src/bitmask_macro.rs

use core::mem::size_of;

/*
 * Macro builder for bit masks
 * $collection: Name for the bit mask collection
 * $unsigned_type: Unsigned type for the data that the bit mask will be applied onto
 * ($name: name of a bit mask, $shift: shift of the bit field, $width: no. of bits in the bit field)
 * Note: All bit masks must concern a set of contiguous bits
 */

macro_rules! construct_bitmask {
	($collection: ident; $unsigned_type: ty; $($name: ident, $shift: expr, $width: expr),+) => {
		#[derive(Debug, Copy, Clone)]
		pub enum $collection {
			$(
				$name,
			)*
		}

		impl $collection {
			pub(crate) fn get_width(self) -> u8 {
				match self {
					$(
						$collection::$name => $width,
					)*
				}
			}
			pub(crate) fn get_shift(self) -> u8 {
				match self {
					$(
						$collection::$name => $shift,
					)*
				}
			}
			pub(crate) fn get_bitmask(self) -> $unsigned_type {
				let mut mask: $unsigned_type = 0;
				for bit in 0..self.get_width() {
					mask |= (1 << (self.get_shift() + bit) % ((size_of::<$unsigned_type>() as u8) * 8));
				}
				mask
			}
			pub(crate) fn get_shifted_bits(self, arg: $unsigned_type) -> $unsigned_type {
				assert!(arg < (2 << self.get_width()));
				(arg << self.get_shift())
			}
			pub(crate) fn set_data_by_arg(self, data: &mut $unsigned_type, arg: $unsigned_type) {
				// Clear bits in field, then insert shifted argument
				*data &= (!self.get_bitmask());
				*data |= self.get_shifted_bits(arg);
			}
			pub(crate) fn get_filtered_content(self, data: $unsigned_type) -> $unsigned_type {
				// Filter everything then shift bits
				((data & self.get_bitmask()) >> (self.get_shift() % ((size_of::<$unsigned_type>() as u8) * 8)))
			}
		}
	}
}