reinvent-bitfield.cpp

#include <cstdio>
#include <stdint.h>
#include <iostream>
template <class T, class U>
void is(T got, U expected) {
	if (got == expected) {
		std::cout << "ok" << std::endl;
	} else {
		std::cout << "not ok " << got << " != " << expected << std::endl;
	}
}



template <class T, uint8_t s, uint8_t e = s>
struct bits {
	T ref;
	static constexpr T mask = (T)(~( (T)(~0) << (e - s + 1))) << s;
	void operator=(const T val) { ref = (ref & ~mask) | ((val & (mask >> s)) << s); }
	operator T() const { return (ref & mask) >> s; }
};

template <uint8_t s, uint8_t e = s>
using bits8 = bits<uint8_t, s, e>;

int main () {
	union {
		uint8_t raw = 0;
		bits8<0, 1> FAULT_QUEUE      ;
		bits8<2>    CT_PIN_POLARITY  ;
		bits8<3>    INT_PIN_POLARITY ;
		bits8<4>    INT_CT_MODE      ;
		bits8<5, 6> OPERATION_MODE   ;
		bits8<7>    RESOLUTION       ;
	} config;

	config.OPERATION_MODE = 0b11;
	is((uint)config.raw, 0b01100000);

	config.FAULT_QUEUE = 0b10;
	is((uint)config.raw, 0b01100010);

	config.RESOLUTION = 1;
	is((uint)config.raw, 0b11100010);

	config.OPERATION_MODE = 0;
	is((uint)config.raw, 0b10000010);

	config.raw = 0;
	is((uint)config.OPERATION_MODE, 0b00);

	config.raw = 0b01000000;
	is((uint)config.OPERATION_MODE, 0b10);

	config.FAULT_QUEUE = 0b111;
	is((uint)config.raw, 0b01000011);
	return 0;
}