skidd13@7935: /* $Id$ */
skidd13@7935: 
rubidium@9111: /** @file random_func.hpp Pseudo random number generator. */
skidd13@7935: 
skidd13@7935: #ifndef RANDOM_FUNC_HPP
skidd13@7935: #define RANDOM_FUNC_HPP
skidd13@7935: 
skidd13@8126: #if defined(__APPLE__)
skidd13@8126: 	/* Apple already has Random declared */
skidd13@8126: 	#define Random OTTD_Random
skidd13@8126: #endif /* __APPLE__ */
skidd13@8126: 
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: 
rubidium@8434: /**
rubidium@8434:  * Structure to encapsulate the pseudo random number generators.
rubidium@8434:  */
rubidium@8434: struct Randomizer {
rubidium@8434: 	/** The state of the randomizer */
rubidium@8434: 	uint32 state[2];
rubidium@8434: 
rubidium@8434: 	/**
rubidium@8434: 	 * Generate the next pseudo random number
rubidium@8434: 	 * @return the random number
rubidium@8434: 	 */
rubidium@8434: 	uint32 Next();
rubidium@8434: 
rubidium@8434: 	/**
rubidium@8434: 	 * Generate the next pseudo random number scaled to max
rubidium@8434: 	 * @param max the maximum value of the returned random number
rubidium@8434: 	 * @return the random number
rubidium@8434: 	 */
rubidium@8434: 	uint32 Next(uint16 max);
rubidium@8434: 
rubidium@8434: 	/**
rubidium@8434: 	 * (Re)set the state of the random number generator.
rubidium@8434: 	 * @param seed the new state
rubidium@8434: 	 */
rubidium@8434: 	void SetSeed(uint32 seed);
rubidium@8434: };
rubidium@8434: extern Randomizer _random; ///< Random used in the game state calculations
rubidium@8434: extern Randomizer _interactive_random; ///< Random used every else where is does not (directly) influence the game state
rubidium@8434: 
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
rubidium@8434: 	static inline uint32 Random() { return _random.Next(); }
rubidium@8434: 	static inline uint32 RandomRange(uint16 max) { return _random.Next(max); }
skidd13@7935: #endif
skidd13@7935: 
rubidium@8434: static inline uint32 InteractiveRandom() { return _interactive_random.Next(); }
rubidium@8434: static inline uint32 InteractiveRandomRange(uint16 max) { return _interactive_random.Next(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);
smatz@8575: 	return (uint16)r < (uint16)(((a << 16) + b / 2) / 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 */