CoCalc -- independent_bits

GitHub Repository: freebsd/freebsd-src
Path: blob/main/contrib/llvm-project/libcxx/include/__random/independent_bits_engine.h
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___RANDOM_INDEPENDENT_BITS_ENGINE_H
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#define _LIBCPP___RANDOM_INDEPENDENT_BITS_ENGINE_H
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#include <__config>
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#include <__fwd/istream.h>
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#include <__fwd/ostream.h>
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#include <__random/is_seed_sequence.h>
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#include <__random/log2.h>
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#include <__type_traits/conditional.h>
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#include <__type_traits/enable_if.h>
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#include <__type_traits/is_convertible.h>
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#include <__utility/move.h>
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#include <cstddef>
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#include <limits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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#  pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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template <class _Engine, size_t __w, class _UIntType>
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class _LIBCPP_TEMPLATE_VIS independent_bits_engine {
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  template <class _UInt, _UInt _R0, size_t _Wp, size_t _Mp>
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  class __get_n {
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    static _LIBCPP_CONSTEXPR const size_t _Dt = numeric_limits<_UInt>::digits;
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    static _LIBCPP_CONSTEXPR const size_t _Np = _Wp / _Mp + (_Wp % _Mp != 0);
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    static _LIBCPP_CONSTEXPR const size_t _W0 = _Wp / _Np;
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    static _LIBCPP_CONSTEXPR const _UInt _Y0  = _W0 >= _Dt ? 0 : (_R0 >> _W0) << _W0;
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  public:
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    static _LIBCPP_CONSTEXPR const size_t value = _R0 - _Y0 > _Y0 / _Np ? _Np + 1 : _Np;
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  };
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public:
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  // types
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  typedef _UIntType result_type;
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private:
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  _Engine __e_;
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  static _LIBCPP_CONSTEXPR const result_type _Dt = numeric_limits<result_type>::digits;
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  static_assert(0 < __w, "independent_bits_engine invalid parameters");
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  static_assert(__w <= _Dt, "independent_bits_engine invalid parameters");
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  typedef typename _Engine::result_type _Engine_result_type;
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  typedef __conditional_t<sizeof(_Engine_result_type) <= sizeof(result_type), result_type, _Engine_result_type>
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      _Working_result_type;
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#ifdef _LIBCPP_CXX03_LANG
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  static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min + _Working_result_type(1);
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#else
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  static _LIBCPP_CONSTEXPR const _Working_result_type _Rp = _Engine::max() - _Engine::min() + _Working_result_type(1);
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#endif
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  static _LIBCPP_CONSTEXPR const size_t __m                = __log2<_Working_result_type, _Rp>::value;
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  static _LIBCPP_CONSTEXPR const size_t __n                = __get_n<_Working_result_type, _Rp, __w, __m>::value;
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  static _LIBCPP_CONSTEXPR const size_t __w0               = __w / __n;
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  static _LIBCPP_CONSTEXPR const size_t __n0               = __n - __w % __n;
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  static _LIBCPP_CONSTEXPR const size_t _WDt               = numeric_limits<_Working_result_type>::digits;
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  static _LIBCPP_CONSTEXPR const size_t _EDt               = numeric_limits<_Engine_result_type>::digits;
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  static _LIBCPP_CONSTEXPR const _Working_result_type __y0 = __w0 >= _WDt ? 0 : (_Rp >> __w0) << __w0;
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  static _LIBCPP_CONSTEXPR const _Working_result_type __y1 = __w0 >= _WDt - 1 ? 0 : (_Rp >> (__w0 + 1)) << (__w0 + 1);
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  static _LIBCPP_CONSTEXPR const
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      _Engine_result_type __mask0 = __w0 > 0 ? _Engine_result_type(~0) >> (_EDt - __w0) : _Engine_result_type(0);
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  static _LIBCPP_CONSTEXPR const _Engine_result_type __mask1 =
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      __w0 < _EDt - 1 ? _Engine_result_type(~0) >> (_EDt - (__w0 + 1)) : _Engine_result_type(~0);
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public:
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  static _LIBCPP_CONSTEXPR const result_type _Min = 0;
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  static _LIBCPP_CONSTEXPR const result_type _Max =
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      __w == _Dt ? result_type(~0) : (result_type(1) << __w) - result_type(1);
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  static_assert(_Min < _Max, "independent_bits_engine invalid parameters");
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  // engine characteristics
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  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type min() { return _Min; }
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  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type max() { return _Max; }
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  // constructors and seeding functions
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  _LIBCPP_HIDE_FROM_ABI independent_bits_engine() {}
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  _LIBCPP_HIDE_FROM_ABI explicit independent_bits_engine(const _Engine& __e) : __e_(__e) {}
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#ifndef _LIBCPP_CXX03_LANG
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  _LIBCPP_HIDE_FROM_ABI explicit independent_bits_engine(_Engine&& __e) : __e_(std::move(__e)) {}
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#endif // _LIBCPP_CXX03_LANG
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  _LIBCPP_HIDE_FROM_ABI explicit independent_bits_engine(result_type __sd) : __e_(__sd) {}
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  template <
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      class _Sseq,
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      __enable_if_t<__is_seed_sequence<_Sseq, independent_bits_engine>::value && !is_convertible<_Sseq, _Engine>::value,
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                    int> = 0>
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  _LIBCPP_HIDE_FROM_ABI explicit independent_bits_engine(_Sseq& __q) : __e_(__q) {}
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  _LIBCPP_HIDE_FROM_ABI void seed() { __e_.seed(); }
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  _LIBCPP_HIDE_FROM_ABI void seed(result_type __sd) { __e_.seed(__sd); }
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  template <class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, independent_bits_engine>::value, int> = 0>
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  _LIBCPP_HIDE_FROM_ABI void seed(_Sseq& __q) {
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    __e_.seed(__q);
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  }
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  // generating functions
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  _LIBCPP_HIDE_FROM_ABI result_type operator()() { return __eval(integral_constant<bool, _Rp != 0>()); }
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  _LIBCPP_HIDE_FROM_ABI void discard(unsigned long long __z) {
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    for (; __z; --__z)
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      operator()();
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  }
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  // property functions
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  _LIBCPP_HIDE_FROM_ABI const _Engine& base() const _NOEXCEPT { return __e_; }
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  template <class _Eng, size_t _Wp, class _UInt>
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  friend bool operator==(const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
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                         const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
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  template <class _Eng, size_t _Wp, class _UInt>
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  friend bool operator!=(const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
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                         const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
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  template <class _CharT, class _Traits, class _Eng, size_t _Wp, class _UInt>
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  friend basic_ostream<_CharT, _Traits>&
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  operator<<(basic_ostream<_CharT, _Traits>& __os, const independent_bits_engine<_Eng, _Wp, _UInt>& __x);
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  template <class _CharT, class _Traits, class _Eng, size_t _Wp, class _UInt>
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  friend basic_istream<_CharT, _Traits>&
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  operator>>(basic_istream<_CharT, _Traits>& __is, independent_bits_engine<_Eng, _Wp, _UInt>& __x);
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private:
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  _LIBCPP_HIDE_FROM_ABI result_type __eval(false_type);
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  _LIBCPP_HIDE_FROM_ABI result_type __eval(true_type);
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  template <size_t __count,
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            __enable_if_t<__count< _Dt, int> = 0> _LIBCPP_HIDE_FROM_ABI static result_type __lshift(result_type __x) {
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    return __x << __count;
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  }
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  template <size_t __count, __enable_if_t<(__count >= _Dt), int> = 0>
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  _LIBCPP_HIDE_FROM_ABI static result_type __lshift(result_type) {
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    return result_type(0);
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  }
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};
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template <class _Engine, size_t __w, class _UIntType>
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inline _UIntType independent_bits_engine<_Engine, __w, _UIntType>::__eval(false_type) {
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  return static_cast<result_type>(__e_() & __mask0);
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}
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template <class _Engine, size_t __w, class _UIntType>
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_UIntType independent_bits_engine<_Engine, __w, _UIntType>::__eval(true_type) {
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  result_type __sp = 0;
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  for (size_t __k = 0; __k < __n0; ++__k) {
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    _Engine_result_type __u;
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    do {
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      __u = __e_() - _Engine::min();
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    } while (__u >= __y0);
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    __sp = static_cast<result_type>(__lshift<__w0>(__sp) + (__u & __mask0));
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  }
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  for (size_t __k = __n0; __k < __n; ++__k) {
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    _Engine_result_type __u;
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    do {
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      __u = __e_() - _Engine::min();
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    } while (__u >= __y1);
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    __sp = static_cast<result_type>(__lshift<__w0 + 1>(__sp) + (__u & __mask1));
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  }
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  return __sp;
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}
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template <class _Eng, size_t _Wp, class _UInt>
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inline _LIBCPP_HIDE_FROM_ABI bool
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operator==(const independent_bits_engine<_Eng, _Wp, _UInt>& __x, const independent_bits_engine<_Eng, _Wp, _UInt>& __y) {
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  return __x.base() == __y.base();
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}
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template <class _Eng, size_t _Wp, class _UInt>
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inline _LIBCPP_HIDE_FROM_ABI bool
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operator!=(const independent_bits_engine<_Eng, _Wp, _UInt>& __x, const independent_bits_engine<_Eng, _Wp, _UInt>& __y) {
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  return !(__x == __y);
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}
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template <class _CharT, class _Traits, class _Eng, size_t _Wp, class _UInt>
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_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
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operator<<(basic_ostream<_CharT, _Traits>& __os, const independent_bits_engine<_Eng, _Wp, _UInt>& __x) {
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  return __os << __x.base();
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}
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template <class _CharT, class _Traits, class _Eng, size_t _Wp, class _UInt>
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_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
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operator>>(basic_istream<_CharT, _Traits>& __is, independent_bits_engine<_Eng, _Wp, _UInt>& __x) {
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  _Eng __e;
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  __is >> __e;
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  if (!__is.fail())
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    __x.__e_ = __e;
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  return __is;
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}
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___RANDOM_INDEPENDENT_BITS_ENGINE_H
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