include/__random/shuffle_order_engine.h

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___RANDOM_SHUFFLE_ORDER_ENGINE_H
#define _LIBCPP___RANDOM_SHUFFLE_ORDER_ENGINE_H

#include <__algorithm/equal.h>
#include <__config>
#include <__random/is_seed_sequence.h>
#include <__type_traits/enable_if.h>
#include <__type_traits/integral_constant.h>
#include <__type_traits/is_convertible.h>
#include <__utility/move.h>
#include <cstddef>
#include <cstdint>
#include <iosfwd>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

template <uint64_t _Xp, uint64_t _Yp>
struct __ugcd {
  static _LIBCPP_CONSTEXPR const uint64_t value = __ugcd<_Yp, _Xp % _Yp>::value;
};

template <uint64_t _Xp>
struct __ugcd<_Xp, 0> {
  static _LIBCPP_CONSTEXPR const uint64_t value = _Xp;
};

template <uint64_t _Np, uint64_t _Dp>
class __uratio {
  static_assert(_Dp != 0, "__uratio divide by 0");
  static _LIBCPP_CONSTEXPR const uint64_t __gcd = __ugcd<_Np, _Dp>::value;

public:
  static _LIBCPP_CONSTEXPR const uint64_t num = _Np / __gcd;
  static _LIBCPP_CONSTEXPR const uint64_t den = _Dp / __gcd;

  typedef __uratio<num, den> type;
};

template <class _Engine, size_t __k>
class _LIBCPP_TEMPLATE_VIS shuffle_order_engine {
  static_assert(0 < __k, "shuffle_order_engine invalid parameters");

public:
  // types
  typedef typename _Engine::result_type result_type;

private:
  _Engine __e_;
  result_type __v_[__k];
  result_type __y_;

public:
  // engine characteristics
  static _LIBCPP_CONSTEXPR const size_t table_size = __k;

#ifdef _LIBCPP_CXX03_LANG
  static const result_type _Min = _Engine::_Min;
  static const result_type _Max = _Engine::_Max;
#else
  static _LIBCPP_CONSTEXPR const result_type _Min = _Engine::min();
  static _LIBCPP_CONSTEXPR const result_type _Max = _Engine::max();
#endif
  static_assert(_Min < _Max, "shuffle_order_engine invalid parameters");
  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type min() { return _Min; }
  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type max() { return _Max; }

  static _LIBCPP_CONSTEXPR const unsigned long long _Rp = _Max - _Min + 1ull;

  // constructors and seeding functions
  _LIBCPP_HIDE_FROM_ABI shuffle_order_engine() { __init(); }
  _LIBCPP_HIDE_FROM_ABI explicit shuffle_order_engine(const _Engine& __e) : __e_(__e) { __init(); }
#ifndef _LIBCPP_CXX03_LANG
  _LIBCPP_HIDE_FROM_ABI explicit shuffle_order_engine(_Engine&& __e) : __e_(std::move(__e)) { __init(); }
#endif // _LIBCPP_CXX03_LANG
  _LIBCPP_HIDE_FROM_ABI explicit shuffle_order_engine(result_type __sd) : __e_(__sd) { __init(); }
  template <
      class _Sseq,
      __enable_if_t<__is_seed_sequence<_Sseq, shuffle_order_engine>::value && !is_convertible<_Sseq, _Engine>::value,
                    int> = 0>
  _LIBCPP_HIDE_FROM_ABI explicit shuffle_order_engine(_Sseq& __q) : __e_(__q) {
    __init();
  }
  _LIBCPP_HIDE_FROM_ABI void seed() {
    __e_.seed();
    __init();
  }
  _LIBCPP_HIDE_FROM_ABI void seed(result_type __sd) {
    __e_.seed(__sd);
    __init();
  }
  template <class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, shuffle_order_engine>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI void seed(_Sseq& __q) {
    __e_.seed(__q);
    __init();
  }

  // generating functions
  _LIBCPP_HIDE_FROM_ABI result_type operator()() { return __eval(integral_constant<bool, _Rp != 0>()); }
  _LIBCPP_HIDE_FROM_ABI void discard(unsigned long long __z) {
    for (; __z; --__z)
      operator()();
  }

  // property functions
  _LIBCPP_HIDE_FROM_ABI const _Engine& base() const _NOEXCEPT { return __e_; }

private:
  template <class _Eng, size_t _Kp>
  friend bool operator==(const shuffle_order_engine<_Eng, _Kp>& __x, const shuffle_order_engine<_Eng, _Kp>& __y);

  template <class _Eng, size_t _Kp>
  friend bool operator!=(const shuffle_order_engine<_Eng, _Kp>& __x, const shuffle_order_engine<_Eng, _Kp>& __y);

  template <class _CharT, class _Traits, class _Eng, size_t _Kp>
  friend basic_ostream<_CharT, _Traits>&
  operator<<(basic_ostream<_CharT, _Traits>& __os, const shuffle_order_engine<_Eng, _Kp>& __x);

  template <class _CharT, class _Traits, class _Eng, size_t _Kp>
  friend basic_istream<_CharT, _Traits>&
  operator>>(basic_istream<_CharT, _Traits>& __is, shuffle_order_engine<_Eng, _Kp>& __x);

  _LIBCPP_HIDE_FROM_ABI void __init() {
    for (size_t __i = 0; __i < __k; ++__i)
      __v_[__i] = __e_();
    __y_ = __e_();
  }

  _LIBCPP_HIDE_FROM_ABI result_type __eval(false_type) { return __eval2(integral_constant<bool, __k & 1>()); }
  _LIBCPP_HIDE_FROM_ABI result_type __eval(true_type) { return __eval(__uratio<__k, _Rp>()); }

  _LIBCPP_HIDE_FROM_ABI result_type __eval2(false_type) { return __eval(__uratio<__k / 2, 0x8000000000000000ull>()); }
  _LIBCPP_HIDE_FROM_ABI result_type __eval2(true_type) { return __evalf<__k, 0>(); }

  template <uint64_t _Np,
            uint64_t _Dp,
            __enable_if_t<(__uratio<_Np, _Dp>::num > 0xFFFFFFFFFFFFFFFFull / (_Max - _Min)), int> = 0>
  _LIBCPP_HIDE_FROM_ABI result_type __eval(__uratio<_Np, _Dp>) {
    return __evalf<__uratio<_Np, _Dp>::num, __uratio<_Np, _Dp>::den>();
  }

  template <uint64_t _Np,
            uint64_t _Dp,
            __enable_if_t<__uratio<_Np, _Dp>::num <= 0xFFFFFFFFFFFFFFFFull / (_Max - _Min), int> = 0>
  _LIBCPP_HIDE_FROM_ABI result_type __eval(__uratio<_Np, _Dp>) {
    const size_t __j = static_cast<size_t>(__uratio<_Np, _Dp>::num * (__y_ - _Min) / __uratio<_Np, _Dp>::den);
    __y_             = __v_[__j];
    __v_[__j]        = __e_();
    return __y_;
  }

  template <uint64_t __n, uint64_t __d>
  _LIBCPP_HIDE_FROM_ABI result_type __evalf() {
    const double __fp = __d == 0 ? __n / (2. * 0x8000000000000000ull) : __n / (double)__d;
    const size_t __j  = static_cast<size_t>(__fp * (__y_ - _Min));
    __y_              = __v_[__j];
    __v_[__j]         = __e_();
    return __y_;
  }
};

template <class _Engine, size_t __k>
_LIBCPP_CONSTEXPR const size_t shuffle_order_engine<_Engine, __k>::table_size;

template <class _Eng, size_t _Kp>
_LIBCPP_HIDE_FROM_ABI bool
operator==(const shuffle_order_engine<_Eng, _Kp>& __x, const shuffle_order_engine<_Eng, _Kp>& __y) {
  return __x.__y_ == __y.__y_ && std::equal(__x.__v_, __x.__v_ + _Kp, __y.__v_) && __x.__e_ == __y.__e_;
}

template <class _Eng, size_t _Kp>
inline _LIBCPP_HIDE_FROM_ABI bool
operator!=(const shuffle_order_engine<_Eng, _Kp>& __x, const shuffle_order_engine<_Eng, _Kp>& __y) {
  return !(__x == __y);
}

template <class _CharT, class _Traits, class _Eng, size_t _Kp>
_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os, const shuffle_order_engine<_Eng, _Kp>& __x) {
  __save_flags<_CharT, _Traits> __lx(__os);
  typedef basic_ostream<_CharT, _Traits> _Ostream;
  __os.flags(_Ostream::dec | _Ostream::left);
  _CharT __sp = __os.widen(' ');
  __os.fill(__sp);
  __os << __x.__e_ << __sp << __x.__v_[0];
  for (size_t __i = 1; __i < _Kp; ++__i)
    __os << __sp << __x.__v_[__i];
  return __os << __sp << __x.__y_;
}

template <class _CharT, class _Traits, class _Eng, size_t _Kp>
_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is, shuffle_order_engine<_Eng, _Kp>& __x) {
  typedef typename shuffle_order_engine<_Eng, _Kp>::result_type result_type;
  __save_flags<_CharT, _Traits> __lx(__is);
  typedef basic_istream<_CharT, _Traits> _Istream;
  __is.flags(_Istream::dec | _Istream::skipws);
  _Eng __e;
  result_type __vp[_Kp + 1];
  __is >> __e;
  for (size_t __i = 0; __i < _Kp + 1; ++__i)
    __is >> __vp[__i];
  if (!__is.fail()) {
    __x.__e_ = __e;
    for (size_t __i = 0; __i < _Kp; ++__i)
      __x.__v_[__i] = __vp[__i];
    __x.__y_ = __vp[_Kp];
  }
  return __is;
}

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___RANDOM_SHUFFLE_ORDER_ENGINE_H