axmol/cocos/base/ccRandom.h

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Copyright (c) 2017-2018 Xiamen Yaji Software Co., Ltd.

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#ifndef __ccRandom_H_
#define __ccRandom_H_

#include <random>
#include <cstdlib>

#include "platform/CCPlatformMacros.h"

/**
 * @addtogroup base
 * @{
 */
NS_CC_BEGIN

/**
 * @class RandomHelper
 * @brief A helper class for creating random number.
 */
class CC_DLL RandomHelper
{
public:
    template <typename T>
    static T random_real(T min, T max)
    {
        std::uniform_real_distribution<T> dist(min, max);
        auto& mt = RandomHelper::getEngine();
        return dist(mt);
    }

    template <typename T>
    static T random_int(T min, T max)
    {
        std::uniform_int_distribution<T> dist(min, max);
        auto& mt = RandomHelper::getEngine();
        return dist(mt);
    }

private:
    static std::mt19937& getEngine();
};

/**
 * Returns a random value between `min` and `max`.
 */
template <typename T>
inline T random(T min, T max)
{
    return RandomHelper::random_int<T>(min, max);
}

template <>
inline float random(float min, float max)
{
    return RandomHelper::random_real(min, max);
}

template <>
inline long double random(long double min, long double max)
{
    return RandomHelper::random_real(min, max);
}

template <>
inline double random(double min, double max)
{
    return RandomHelper::random_real(min, max);
}

/**
 * Returns a random int between 0 and RAND_MAX.
 */
inline int random()
{
    return cocos2d::random(0, RAND_MAX);
};

/**
 * Returns a random float between -1 and 1.
 * It can be seeded using std::srand(seed);
 */
inline float rand_minus1_1()
{
    // FIXME: using the new c++11 random engine generator
    // without a proper way to set a seed is not useful.
    // Resorting to the old random method since it can
    // be seeded using std::srand()
    return ((std::rand() / (float)RAND_MAX) * 2) - 1;

    //    return cocos2d::random(-1.f, 1.f);
};

/**
 * Returns a random float between 0 and 1.
 * It can be seeded using std::srand(seed);
 */
inline float rand_0_1()
{
    // FIXME: using the new c++11 random engine generator
    // without a proper way to set a seed is not useful.
    // Resorting to the old random method since it can
    // be seeded using std::srand()
    return std::rand() / (float)RAND_MAX;

    //    return cocos2d::random(0.f, 1.f);
};

NS_CC_END
// end group
/// @}
#endif  //__ccRandom_H_