// Copyright 2020 Phyronnaz #pragma once #include "CoreMinimal.h" #include #include // While random generators are standardized, samplers aren't // To avoid issues, we use the microsoft std version on all platforms // License: /* The Microsoft C++ Standard Library is under the Apache License v2.0 with LLVM Exception: Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. Definitions. "License" shall mean the terms and conditions for use, reproduction, and distribution as defined by Sections 1 through 9 of this document. "Licensor" shall mean the copyright owner or entity authorized by the copyright owner that is granting the License. "Legal Entity" shall mean the union of the acting entity and all other entities that control, are controlled by, or are under common control with that entity. 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See the License for the specific language governing permissions and limitations under the License. ---- LLVM Exceptions to the Apache 2.0 License ---- As an exception, if, as a result of your compiling your source code, portions of this Software are embedded into an Object form of such source code, you may redistribute such embedded portions in such Object form without complying with the conditions of Sections 4(a), 4(b) and 4(d) of the License. In addition, if you combine or link compiled forms of this Software with software that is licensed under the GPLv2 ("Combined Software") and if a court of competent jurisdiction determines that the patent provision (Section 3), the indemnity provision (Section 9) or other Section of the License conflicts with the conditions of the GPLv2, you may retroactively and prospectively choose to deem waived or otherwise exclude such Section(s) of the License, but only in their entirety and only with respect to the Combined Software. */ namespace cross_platform_std { // CLASS TEMPLATE _Rng_from_urng template class _Rng_from_urng { // wrap a URNG as an RNG public: using _Ty0 = std::make_unsigned_t<_Diff>; using _Ty1 = typename _Urng::result_type; using _Udiff = std::conditional_t < sizeof(_Ty1) < sizeof(_Ty0), _Ty0, _Ty1 > ; explicit _Rng_from_urng(_Urng& _Func) : _Ref(_Func), _Bits(8 * sizeof(_Udiff)), _Bmask(_Udiff(-1)) { for (; (_Urng::max)() - (_Urng::min)() < _Bmask; _Bmask >>= 1) { --_Bits; } } _Diff operator()(_Diff _Index) { // adapt _Urng closed range to [0, _Index) for (;;) { // try a sample random value _Udiff _Ret = 0; // random bits _Udiff _Mask = 0; // 2^N - 1, _Ret is within [0, _Mask] while (_Mask < _Udiff(_Index - 1)) { // need more random bits _Ret <<= _Bits - 1; // avoid full shift _Ret <<= 1; _Ret |= _Get_bits(); _Mask <<= _Bits - 1; // avoid full shift _Mask <<= 1; _Mask |= _Bmask; } // _Ret is [0, _Mask], _Index - 1 <= _Mask, return if unbiased if (_Ret / _Index < _Mask / _Index || _Mask % _Index == _Udiff(_Index - 1)) { return static_cast<_Diff>(_Ret % _Index); } } } _Udiff _Get_all_bits() { // return a random value _Udiff _Ret = 0; for (size_t _Num = 0; _Num < 8 * sizeof(_Udiff); _Num += _Bits) { // don't mask away any bits _Ret <<= _Bits - 1; // avoid full shift _Ret <<= 1; _Ret |= _Get_bits(); } return _Ret; } _Rng_from_urng(const _Rng_from_urng&) = delete; _Rng_from_urng& operator=(const _Rng_from_urng&) = delete; private: _Udiff _Get_bits() { // return a random value within [0, _Bmask] for (;;) { // repeat until random value is in range _Udiff _Val = _Ref() - (_Urng::min)(); if (_Val <= _Bmask) { return _Val; } } } _Urng& _Ref; // reference to URNG size_t _Bits; // number of random bits generated by _Get_bits() _Udiff _Bmask; // 2^_Bits - 1 }; // CLASS TEMPLATE uniform_int template class uniform_int { // uniform integer distribution public: using result_type = _Ty; struct param_type { // parameter package using distribution_type = uniform_int; explicit param_type(result_type _Min0 = 0, result_type _Max0 = 9) { // construct from parameters _Init(_Min0, _Max0); } bool operator==(const param_type& _Right) const { // test for equality return _Min == _Right._Min && _Max == _Right._Max; } bool operator!=(const param_type& _Right) const { // test for inequality return !(*this == _Right); } result_type a() const { // return a value return _Min; } result_type b() const { // return b value return _Max; } void _Init(_Ty _Min0, _Ty _Max0) { // set internal state _Min = _Min0; _Max = _Max0; } result_type _Min; result_type _Max; }; explicit uniform_int(_Ty _Min0 = 0, _Ty _Max0 = 9) : _Par(_Min0, _Max0) { // construct from parameters } explicit uniform_int(const param_type& _Par0) : _Par(_Par0) { // construct from parameter package } result_type a() const { // return a value return _Par.a(); } result_type b() const { // return b value return _Par.b(); } param_type param() const { // return parameter package return _Par; } void param(const param_type& _Par0) { // set parameter package _Par = _Par0; } result_type(min)() const { // return minimum possible generated value return _Par._Min; } result_type(max)() const { // return maximum possible generated value return _Par._Max; } void reset() { // clear internal state } template result_type operator()(_Engine& _Eng) const { // return next value return _Eval(_Eng, _Par._Min, _Par._Max); } template result_type operator()( _Engine& _Eng, const param_type& _Par0) const { // return next value, given parameter package return _Eval(_Eng, _Par0._Min, _Par0._Max); } template result_type operator()(_Engine& _Eng, result_type _Nx) const { // return next value return _Eval(_Eng, 0, _Nx - 1); } template std::basic_istream<_Elem, _Traits>& _Read(std::basic_istream<_Elem, _Traits>& _Istr) { // read state from _Istr _Ty _Min0; _Ty _Max0; _Istr >> _Min0 >> _Max0; _Par._Init(_Min0, _Max0); return _Istr; } template std::basic_ostream<_Elem, _Traits>& _Write(std::basic_ostream<_Elem, _Traits>& _Ostr) const { // write state to _Ostr return _Ostr << _Par._Min << ' ' << _Par._Max; } private: using _Uty = std::make_unsigned_t<_Ty>; template result_type _Eval(_Engine& _Eng, _Ty _Min, _Ty _Max) const { // compute next value in range [_Min, _Max] _Rng_from_urng<_Uty, _Engine> _Rng(_Eng); const _Uty _Umin = _Adjust(_Uty(_Min)); const _Uty _Umax = _Adjust(_Uty(_Max)); _Uty _Uret; if (_Umax - _Umin == _Uty(-1)) { _Uret = static_cast<_Uty>(_Rng._Get_all_bits()); } else { _Uret = static_cast<_Uty>(_Rng(static_cast<_Uty>(_Umax - _Umin + 1))); } return _Ty(_Adjust(static_cast<_Uty>(_Uret + _Umin))); } static _Uty _Adjust(_Uty _Uval) { // convert signed ranges to unsigned ranges and vice versa return _Adjust(_Uval, std::is_signed<_Ty>()); } static _Uty _Adjust(_Uty _Uval, std::true_type) { // convert signed ranges to unsigned ranges and vice versa const _Uty _Adjuster = (_Uty(-1) >> 1) + 1; // 2^(N-1) if (_Uval < _Adjuster) { return static_cast<_Uty>(_Uval + _Adjuster); } else { return static_cast<_Uty>(_Uval - _Adjuster); } } static _Uty _Adjust(_Uty _Uval, std::false_type) { // _Ty is already unsigned, do nothing return _Uval; } param_type _Par; }; template std::basic_istream<_Elem, _Traits>& operator>>(std::basic_istream<_Elem, _Traits>& _Istr, uniform_int<_Ty>& _Dist) { // read state from _Istr return _Dist._Read(_Istr); } template std::basic_ostream<_Elem, _Traits>& operator<<(std::basic_ostream<_Elem, _Traits>& _Ostr, const uniform_int<_Ty>& _Dist) { // write state to _Ostr return _Dist._Write(_Ostr); } // CLASS TEMPLATE uniform_int_distribution template class uniform_int_distribution : public uniform_int<_Ty> { // uniform integer distribution public: using _Mybase = uniform_int<_Ty>; using _Mypbase = typename _Mybase::param_type; using result_type = typename _Mybase::result_type; struct param_type : public _Mypbase { // parameter package using distribution_type = uniform_int_distribution; explicit param_type(result_type _Min0 = 0, result_type _Max0 = (std::numeric_limits<_Ty>::max)()) : _Mypbase(_Min0, _Max0) { // construct from parameters } param_type(const _Mypbase& _Right) : _Mypbase(_Right) { // construct from base } }; explicit uniform_int_distribution(_Ty _Min0 = 0, _Ty _Max0 = (std::numeric_limits<_Ty>::max)()) : _Mybase(_Min0, _Max0) { // construct from parameters } explicit uniform_int_distribution(const param_type& _Par0) : _Mybase(_Par0) { // construct from parameter package } }; template bool operator==(const uniform_int_distribution<_Ty>& _Left, const uniform_int_distribution<_Ty>& _Right) { // test for equality return _Left.param() == _Right.param(); } template bool operator!=(const uniform_int_distribution<_Ty>& _Left, const uniform_int_distribution<_Ty>& _Right) { // test for inequality return !(_Left == _Right); } }