verdnatura-chat/ios/Pods/Folly/folly/Random-inl.h

87 lines
2.6 KiB
C++

/*
* Copyright 2014-present Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef FOLLY_RANDOM_H_
#error This file may only be included from folly/Random.h
#endif
namespace folly {
namespace detail {
// Return the state size needed by RNG, expressed as a number of uint32_t
// integers. Specialized for all templates specified in the C++11 standard.
// For some (mersenne_twister_engine), this is exported as a state_size static
// data member; for others, the standard shows formulas.
template <class RNG, typename = void>
struct StateSize {
// A sane default.
using type = std::integral_constant<size_t, 512>;
};
template <class RNG>
struct StateSize<RNG, void_t<decltype(RNG::state_size)>> {
using type = std::integral_constant<size_t, RNG::state_size>;
};
template <class UIntType, UIntType a, UIntType c, UIntType m>
struct StateSize<std::linear_congruential_engine<UIntType, a, c, m>> {
// From the standard [rand.eng.lcong], this is ceil(log2(m) / 32) + 3,
// which is the same as ceil(ceil(log2(m) / 32) + 3, and
// ceil(log2(m)) <= std::numeric_limits<UIntType>::digits
using type = std::integral_constant<
size_t,
(std::numeric_limits<UIntType>::digits + 31) / 32 + 3>;
};
template <class UIntType, size_t w, size_t s, size_t r>
struct StateSize<std::subtract_with_carry_engine<UIntType, w, s, r>> {
// [rand.eng.sub]: r * ceil(w / 32)
using type = std::integral_constant<size_t, r*((w + 31) / 32)>;
};
template <typename RNG>
using StateSizeT = _t<StateSize<RNG>>;
template <class RNG>
struct SeedData {
SeedData() {
Random::secureRandom(seedData.data(), seedData.size() * sizeof(uint32_t));
}
static constexpr size_t stateSize = StateSizeT<RNG>::value;
std::array<uint32_t, stateSize> seedData;
};
} // namespace detail
template <class RNG, class /* EnableIf */>
void Random::seed(RNG& rng) {
detail::SeedData<RNG> sd;
std::seed_seq s(std::begin(sd.seedData), std::end(sd.seedData));
rng.seed(s);
}
template <class RNG, class /* EnableIf */>
auto Random::create() -> RNG {
detail::SeedData<RNG> sd;
std::seed_seq s(std::begin(sd.seedData), std::end(sd.seedData));
return RNG(s);
}
} // namespace folly