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/* SPDX-License-Identifier: BSL-1.0 OR BSD-3-Clause */
#ifndef MPT_RANDOM_RANDOM_HPP
#define MPT_RANDOM_RANDOM_HPP
#include "mpt/base/namespace.hpp"
#include "mpt/random/engine.hpp"
#include <type_traits>
namespace mpt {
inline namespace MPT_INLINE_NS {
template <typename T, typename Trng>
inline T random(Trng & rng) {
static_assert(std::numeric_limits<T>::is_integer);
typedef typename std::make_unsigned<T>::type unsigned_T;
const unsigned int rng_bits = mpt::engine_traits<Trng>::result_bits();
unsigned_T result = 0;
for (std::size_t entropy = 0; entropy < (sizeof(T) * 8); entropy += rng_bits) {
if constexpr (rng_bits < (sizeof(T) * 8)) {
constexpr unsigned int shift_bits = rng_bits % (sizeof(T) * 8); // silence utterly stupid MSVC and GCC warnings about shifting by too big amount (in which case this branch is not even taken however)
result = (result << shift_bits) ^ static_cast<unsigned_T>(rng());
} else {
result = static_cast<unsigned_T>(rng());
}
}
return static_cast<T>(result);
}
template <typename T, std::size_t required_entropy_bits, typename Trng>
inline T random(Trng & rng) {
static_assert(std::numeric_limits<T>::is_integer);
typedef typename std::make_unsigned<T>::type unsigned_T;
const unsigned int rng_bits = mpt::engine_traits<Trng>::result_bits();
unsigned_T result = 0;
for (std::size_t entropy = 0; entropy < std::min(required_entropy_bits, sizeof(T) * 8); entropy += rng_bits) {
if constexpr (rng_bits < (sizeof(T) * 8)) {
constexpr unsigned int shift_bits = rng_bits % (sizeof(T) * 8); // silence utterly stupid MSVC and GCC warnings about shifting by too big amount (in which case this branch is not even taken however)
result = (result << shift_bits) ^ static_cast<unsigned_T>(rng());
} else {
result = static_cast<unsigned_T>(rng());
}
}
if constexpr (required_entropy_bits >= (sizeof(T) * 8)) {
return static_cast<T>(result);
} else {
return static_cast<T>(result & ((static_cast<unsigned_T>(1) << required_entropy_bits) - static_cast<unsigned_T>(1)));
}
}
template <typename T, typename Trng>
inline T random(Trng & rng, std::size_t required_entropy_bits) {
static_assert(std::numeric_limits<T>::is_integer);
typedef typename std::make_unsigned<T>::type unsigned_T;
const unsigned int rng_bits = mpt::engine_traits<Trng>::result_bits();
unsigned_T result = 0;
for (std::size_t entropy = 0; entropy < std::min(required_entropy_bits, sizeof(T) * 8); entropy += rng_bits) {
if constexpr (rng_bits < (sizeof(T) * 8)) {
constexpr unsigned int shift_bits = rng_bits % (sizeof(T) * 8); // silence utterly stupid MSVC and GCC warnings about shifting by too big amount (in which case this branch is not even taken however)
result = (result << shift_bits) ^ static_cast<unsigned_T>(rng());
} else {
result = static_cast<unsigned_T>(rng());
}
}
if (required_entropy_bits >= (sizeof(T) * 8)) {
return static_cast<T>(result);
} else {
return static_cast<T>(result & ((static_cast<unsigned_T>(1) << required_entropy_bits) - static_cast<unsigned_T>(1)));
}
}
template <typename T>
struct uniform_real_distribution {
private:
T a;
T b;
public:
inline uniform_real_distribution(T a_, T b_)
: a(a_)
, b(b_) {
return;
}
template <typename Trng>
inline T operator()(Trng & rng) const {
const int mantissa_bits = std::numeric_limits<T>::digits;
return ((b - a) * static_cast<T>(mpt::random<uint64, mantissa_bits>(rng)) / static_cast<T>((static_cast<uint64>(1u) << mantissa_bits))) + a;
}
};
template <typename T, typename Trng>
inline T random(Trng & rng, T min, T max) {
static_assert(!std::numeric_limits<T>::is_integer);
typedef mpt::uniform_real_distribution<T> dis_type;
dis_type dis(min, max);
return static_cast<T>(dis(rng));
}
} // namespace MPT_INLINE_NS
} // namespace mpt
#endif // MPT_RANDOM_RANDOM_HPP
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