ReC98/th02/math/randring.hpp

#define RANDRING_SIZE 256

extern uint8_t randring[RANDRING_SIZE];

void near randring_fill(void);

#if GAME == 2
	extern uint8_t randring_p;

	uint8_t near randring1_next8(void);
	uint8_t pascal near randring1_next8_and(uint8_t mask);
	uint16_t near randring1_next16(void);
	uint8_t near randring2_next8(void);
	uint8_t pascal near randring2_next8_and(uint8_t mask);
#endif

uint16_t near randring2_next16(void);

/// Constrained random numbers
/// --------------------------
/// These limit the next random number between [min] inclusive and [max]
/// exclusive, via either AND or MOD.

template <class T> inline bool is_range_a_power_of_two(T min, T max) {
	return (((max - min) & ((max - min) - 1)) == 0);
}

#if (GAME == 2)
	inline uint8_t randring1_next8_ge_lt(uint8_t min, uint8_t max) {
		if(is_range_a_power_of_two(min, max)) {
			return (min + randring1_next8_and((max - min) - 1));
		}
		return (min + (randring1_next8() % (max - min)));
	}

	inline uint16_t randring1_next16_ge_lt(uint16_t min, uint16_t max) {
		if(is_range_a_power_of_two(min, max)) {
			return (min + (randring1_next16() & ((max - min) - 1)));
		}
		return (min + (randring1_next16() % (max - min)));
	}
#endif
/// --------------------------