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/*
* This file is part of OpenTTD.
* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
* OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
*/
/** @file random_func.hpp Pseudo random number generator. */
#ifndef RANDOM_FUNC_HPP
#define RANDOM_FUNC_HPP
#if defined(__APPLE__)
/* Apple already has Random declared */
# define Random OTTD_Random
#endif /* __APPLE__ */
/**
* Structure to encapsulate the pseudo random number generators.
*/
struct Randomizer {
/** The state of the randomizer */
uint32 state[2];
uint32 Next();
uint32 Next(uint32 limit);
void SetSeed(uint32 seed);
};
extern Randomizer _random; ///< Random used in the game state calculations
extern Randomizer _interactive_random; ///< Random used everywhere else, where it does not (directly) influence the game state
/** Stores the state of all random number generators */
struct SavedRandomSeeds {
Randomizer random;
Randomizer interactive_random;
};
/**
* Saves the current seeds
* @param storage Storage for saving
*/
static inline void SaveRandomSeeds(SavedRandomSeeds *storage)
{
storage->random = _random;
storage->interactive_random = _interactive_random;
}
/**
* Restores previously saved seeds
* @param storage Storage where SaveRandomSeeds() stored th seeds
*/
static inline void RestoreRandomSeeds(const SavedRandomSeeds &storage)
{
_random = storage.random;
_interactive_random = storage.interactive_random;
}
void SetRandomSeed(uint32 seed);
#ifdef RANDOM_DEBUG
# ifdef __APPLE__
# define OTTD_Random() DoRandom(__LINE__, __FILE__)
# else
# define Random() DoRandom(__LINE__, __FILE__)
# endif
uint32 DoRandom(int line, const char *file);
# define RandomRange(limit) DoRandomRange(limit, __LINE__, __FILE__)
uint32 DoRandomRange(uint32 limit, int line, const char *file);
#else
static inline uint32 Random()
{
return _random.Next();
}
/**
* Pick a random number between 0 and \a limit - 1, inclusive. That means 0
* can be returned and \a limit - 1 can be returned, but \a limit can not be
* returned.
* @param limit Limit for the range to be picked from.
* @return A random number in [0,\a limit).
*/
static inline uint32 RandomRange(uint32 limit)
{
return _random.Next(limit);
}
#endif
static inline uint32 InteractiveRandom()
{
return _interactive_random.Next();
}
static inline uint32 InteractiveRandomRange(uint32 limit)
{
return _interactive_random.Next(limit);
}
/**
* Checks if a given randomize-number is below a given probability.
*
* This function is used to check if the given probability by the fraction of (a/b)
* is greater than low 16 bits of the given randomize-number r.
*
* Do not use this function twice on the same random 16 bits as it will yield
* the same result. One can use a random number for two calls to Chance16I,
* where one call sends the low 16 bits and the other the high 16 bits.
*
* @param a The numerator of the fraction
* @param b The denominator of the fraction, must of course not be null
* @param r The given randomize-number
* @return True if the probability given by r is less or equal to (a/b)
*/
static inline bool Chance16I(const uint a, const uint b, const uint32 r)
{
assert(b != 0);
return (((uint16)r * b + b / 2) >> 16) < a;
}
/**
* Flips a coin with given probability.
*
* This function returns true with (a/b) probability.
*
* @see Chance16I()
* @param a The nominator of the fraction
* @param b The denominator of the fraction
* @return True with (a/b) probability
*/
#ifdef RANDOM_DEBUG
# define Chance16(a, b) Chance16I(a, b, DoRandom(__LINE__, __FILE__))
#else
static inline bool Chance16(const uint a, const uint b)
{
return Chance16I(a, b, Random());
}
#endif /* RANDOM_DEBUG */
/**
* Flips a coin with a given probability and saves the randomize-number in a variable.
*
* This function uses the same parameters as Chance16. The third parameter
* must be a variable the randomize-number from Random() is saved in.
*
* The low 16 bits of r will already be used and can therefore not be passed to
* Chance16I. One can only send the high 16 bits to Chance16I.
*
* @see Chance16I()
* @param a The numerator of the fraction
* @param b The denominator of the fraction
* @param r The variable to save the randomize-number from Random()
* @return True in (a/b) percent
*/
#ifdef RANDOM_DEBUG
# define Chance16R(a, b, r) (r = DoRandom(__LINE__, __FILE__), Chance16I(a, b, r))
#else
static inline bool Chance16R(const uint a, const uint b, uint32 &r)
{
r = Random();
return Chance16I(a, b, r);
}
#endif /* RANDOM_DEBUG */
#endif /* RANDOM_FUNC_HPP */
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