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/*
* Copyright 2019-2021 Diligent Graphics LLC
* Copyright 2015-2019 Egor Yusov
*
* 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.
*
* In no event and under no legal theory, whether in tort (including negligence),
* contract, or otherwise, unless required by applicable law (such as deliberate
* and grossly negligent acts) or agreed to in writing, shall any Contributor be
* liable for any damages, including any direct, indirect, special, incidental,
* or consequential damages of any character arising as a result of this License or
* out of the use or inability to use the software (including but not limited to damages
* for loss of goodwill, work stoppage, computer failure or malfunction, or any and
* all other commercial damages or losses), even if such Contributor has been advised
* of the possibility of such damages.
*/
#pragma once
#include "../../Platforms/Basic/interface/DebugUtilities.hpp"
namespace Diligent
{
/// Fast random number generator.
///
/// \note You should probably not use it for your production-grade encryption.
class FastRand
{
public:
using StateType = unsigned int;
static constexpr StateType Max = 0x7FFF;
explicit FastRand(StateType Seed) noexcept :
State{Seed}
{
}
StateType operator()()
{
State = StateType{214013} * State + StateType{2531011};
return (State >> StateType{16}) & Max;
}
private:
StateType State;
};
/// Generates a real random number in [Min, Max] range
template <typename Type>
class FastRandReal : private FastRand
{
public:
explicit FastRandReal(FastRand::StateType Seed) noexcept :
FastRand{Seed}
{}
FastRandReal(FastRand::StateType Seed, Type _Min, Type _Max) noexcept :
FastRand{Seed},
Min{_Min},
Range{_Max - _Min}
{}
Type operator()()
{
return (static_cast<Type>(FastRand::operator()()) / static_cast<Type>(FastRand::Max)) * Range + Min;
}
private:
const Type Min = 0.f;
const Type Range = 1.f;
};
using FastRandFloat = FastRandReal<float>;
using FastRandDouble = FastRandReal<double>;
/// Generates an integer random number in [Min, Max] range
class FastRandInt : private FastRand
{
public:
FastRandInt(FastRand::StateType Seed, int _Min, int _Max) noexcept :
FastRand{Seed},
Min{_Min},
Range{_Max - _Min + 1}
{
VERIFY_EXPR(_Max > _Min);
VERIFY(Range <= static_cast<int>(FastRand::Max), "Range is too large");
}
int operator()()
{
return Min + static_cast<int>(FastRand::operator()()) % Range;
}
private:
const int Min;
const int Range;
};
} // namespace Diligent
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