skidd13@7935: /* $Id$ */
skidd13@7935: 
skidd13@7935: /** @file random_func.h */
skidd13@7935: 
skidd13@7935: #ifndef RANDOM_FUNC_HPP
skidd13@7935: #define RANDOM_FUNC_HPP
skidd13@7935: 
skidd13@7935: /**************
skidd13@7935:  * Warning: DO NOT enable this unless you understand what it does
skidd13@7935:  *
skidd13@7935:  * If enabled, in a network game all randoms will be dumped to the
skidd13@7935:  *  stdout if the first client joins (or if you are a client). This
skidd13@7935:  *  is to help finding desync problems.
skidd13@7935:  *
skidd13@7935:  * Warning: DO NOT enable this unless you understand what it does
skidd13@7935:  **************/
skidd13@7935: 
skidd13@7935: //#define RANDOM_DEBUG
skidd13@7935: 
skidd13@7935: 
skidd13@7935: // Enable this to produce higher quality random numbers.
skidd13@7935: // Doesn't work with network yet.
skidd13@7935: // #define MERSENNE_TWISTER
skidd13@7935: 
skidd13@7935: void SetRandomSeed(uint32 seed);
skidd13@7935: #ifdef RANDOM_DEBUG
skidd13@7935: 	#define Random() DoRandom(__LINE__, __FILE__)
skidd13@7935: 	uint32 DoRandom(int line, const char *file);
skidd13@7935: 	#define RandomRange(max) DoRandomRange(max, __LINE__, __FILE__)
skidd13@7935: 	uint DoRandomRange(uint max, int line, const char *file);
skidd13@7935: #else
skidd13@7935: 	uint32 Random();
skidd13@7935: 	uint RandomRange(uint max);
skidd13@7935: #endif
skidd13@7935: 
skidd13@7935: uint32 InteractiveRandom(); // Used for random sequences that are not the same on the other end of the multiplayer link
skidd13@7935: uint InteractiveRandomRange(uint max);
skidd13@7935: 
skidd13@7967: /**
skidd13@7967:  * Checks if a given randomize-number is below a given probability.
skidd13@7967:  *
skidd13@7967:  * This function is used to check if the given probability by the fraction of (a/b)
skidd13@7967:  * is greater than low 16 bits of the given randomize-number v.
skidd13@7967:  *
skidd13@7967:  * Do not use this function twice on the same random 16 bits as it will yield
skidd13@7967:  * the same result. One can use a random number for two calls to Chance16I,
skidd13@7967:  * where one call sends the low 16 bits and the other the high 16 bits.
skidd13@7967:  *
skidd13@7967:  * @param a The numerator of the fraction
skidd13@7967:  * @param b The denominator of the fraction, must of course not be null
skidd13@7967:  * @param r The given randomize-number
skidd13@7967:  * @return True if v is less or equals (a/b)
skidd13@7967:  */
skidd13@7967: static inline bool Chance16I(const uint a, const uint b, const uint32 r)
skidd13@7967: {
skidd13@7967: 	assert(b != 0);
skidd13@7967: 	return (uint16)r < (uint16)((a << 16) / b);
skidd13@7967: }
skidd13@7967: 
skidd13@7967: /**
skidd13@7967:  * Flips a coin with a given probability.
skidd13@7967:  *
skidd13@7967:  * This macro can be used to get true or false randomized according to a
skidd13@7967:  * given probability. The parameter a and b create a percent value with
skidd13@7967:  * (a/b). The macro returns true in (a/b) percent.
skidd13@7967:  *
skidd13@7967:  * @see Chance16I()
skidd13@7967:  * @param a The numerator of the fraction
skidd13@7967:  * @param b The denominator of the fraction
skidd13@7967:  * @return True in (a/b) percent
skidd13@7967:  */
skidd13@7967: static inline bool Chance16(const uint a, const uint b)
skidd13@7967: {
skidd13@7967: 	return Chance16I(a, b, Random());
skidd13@7967: }
skidd13@7967: 
skidd13@7967: /**
skidd13@7967:  * Flips a coin with a given probability and saves the randomize-number in a variable.
skidd13@7967:  *
skidd13@7967:  * This function uses the same parameters as Chance16. The third parameter
skidd13@7967:  * must be a variable the randomize-number from Random() is saved in.
skidd13@7967:  *
skidd13@7967:  * The low 16 bits of r will already be used and can therefor not be passed to
skidd13@7967:  * Chance16I. One can only send the high 16 bits to Chance16I.
skidd13@7967:  *
skidd13@7967:  * @see Chance16I()
skidd13@7967:  * @param a The numerator of the fraction
skidd13@7967:  * @param b The denominator of the fraction
skidd13@7967:  * @param r The variable to save the randomize-number from Random()
skidd13@7967:  * @return True in (a/b) percent
skidd13@7967:  */
skidd13@7967: static inline bool Chance16R(const uint a, const uint b, uint32 &r)
skidd13@7967: {
skidd13@7967: 	r = Random();
skidd13@7967: 	return Chance16I(a, b, r);
skidd13@7967: }
skidd13@7967: 
skidd13@7935: #endif /* RANDOM_FUNC_HPP */