//===----------------------------------------------------------------------===//
//
// 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_SUBTRACT_WITH_CARRY_ENGINE_H
#define _LIBCPP___RANDOM_SUBTRACT_WITH_CARRY_ENGINE_H

#include <__algorithm/equal.h>
#include <__algorithm/min.h>
#include <__config>
#include <__random/is_seed_sequence.h>
#include <__random/linear_congruential_engine.h>
#include <cstddef>
#include <cstdint>
#include <iosfwd>
#include <limits>
#include <type_traits>

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

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

template<class _UIntType, size_t __w, size_t __s, size_t __r>
class _LIBCPP_TEMPLATE_VIS subtract_with_carry_engine;

template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
bool
operator==(
    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y);

template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
_LIBCPP_INLINE_VISIBILITY
bool
operator!=(
    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y);

template <class _CharT, class _Traits,
          class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
           const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x);

template <class _CharT, class _Traits,
          class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is,
           subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x);

template<class _UIntType, size_t __w, size_t __s, size_t __r>
class _LIBCPP_TEMPLATE_VIS subtract_with_carry_engine
{
public:
    // types
    typedef _UIntType result_type;

private:
    result_type __x_[__r];
    result_type  __c_;
    size_t      __i_;

    static _LIBCPP_CONSTEXPR const result_type _Dt = numeric_limits<result_type>::digits;
    static_assert(  0 <  __w, "subtract_with_carry_engine invalid parameters");
    static_assert(__w <= _Dt, "subtract_with_carry_engine invalid parameters");
    static_assert(  0 <  __s, "subtract_with_carry_engine invalid parameters");
    static_assert(__s <  __r, "subtract_with_carry_engine invalid parameters");
public:
    static _LIBCPP_CONSTEXPR const result_type _Min = 0;
    static _LIBCPP_CONSTEXPR const result_type _Max = __w == _Dt ? result_type(~0) :
                                                      (result_type(1) << __w) - result_type(1);
    static_assert(_Min < _Max, "subtract_with_carry_engine invalid parameters");

    // engine characteristics
    static _LIBCPP_CONSTEXPR const size_t word_size = __w;
    static _LIBCPP_CONSTEXPR const size_t short_lag = __s;
    static _LIBCPP_CONSTEXPR const size_t long_lag = __r;
    _LIBCPP_INLINE_VISIBILITY
    static _LIBCPP_CONSTEXPR result_type min() { return _Min; }
    _LIBCPP_INLINE_VISIBILITY
    static _LIBCPP_CONSTEXPR result_type max() { return _Max; }
    static _LIBCPP_CONSTEXPR const result_type default_seed = 19780503u;

    // constructors and seeding functions
#ifndef _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    subtract_with_carry_engine() : subtract_with_carry_engine(default_seed) {}
    _LIBCPP_INLINE_VISIBILITY
    explicit subtract_with_carry_engine(result_type __sd) { seed(__sd); }
#else
    _LIBCPP_INLINE_VISIBILITY
    explicit subtract_with_carry_engine(result_type __sd = default_seed) {
      seed(__sd);
    }
#endif
    template<class _Sseq>
        _LIBCPP_INLINE_VISIBILITY
        explicit subtract_with_carry_engine(_Sseq& __q,
        typename enable_if<__is_seed_sequence<_Sseq, subtract_with_carry_engine>::value>::type* = 0)
        {seed(__q);}
    _LIBCPP_INLINE_VISIBILITY
    void seed(result_type __sd = default_seed)
        {seed(__sd, integral_constant<unsigned, 1 + (__w - 1) / 32>());}
    template<class _Sseq>
        _LIBCPP_INLINE_VISIBILITY
        typename enable_if
        <
            __is_seed_sequence<_Sseq, subtract_with_carry_engine>::value,
            void
        >::type
        seed(_Sseq& __q)
            {__seed(__q, integral_constant<unsigned, 1 + (__w - 1) / 32>());}

    // generating functions
    result_type operator()();
    _LIBCPP_INLINE_VISIBILITY
    void discard(unsigned long long __z) {for (; __z; --__z) operator()();}

    template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
    friend
    bool
    operator==(
        const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
        const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y);

    template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
    friend
    bool
    operator!=(
        const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
        const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y);

    template <class _CharT, class _Traits,
              class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
    friend
    basic_ostream<_CharT, _Traits>&
    operator<<(basic_ostream<_CharT, _Traits>& __os,
               const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x);

    template <class _CharT, class _Traits,
              class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
    friend
    basic_istream<_CharT, _Traits>&
    operator>>(basic_istream<_CharT, _Traits>& __is,
               subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x);

private:

    void seed(result_type __sd, integral_constant<unsigned, 1>);
    void seed(result_type __sd, integral_constant<unsigned, 2>);
    template<class _Sseq>
        void __seed(_Sseq& __q, integral_constant<unsigned, 1>);
    template<class _Sseq>
        void __seed(_Sseq& __q, integral_constant<unsigned, 2>);
};

template<class _UIntType, size_t __w, size_t __s, size_t __r>
    _LIBCPP_CONSTEXPR const size_t subtract_with_carry_engine<_UIntType, __w, __s, __r>::word_size;

template<class _UIntType, size_t __w, size_t __s, size_t __r>
    _LIBCPP_CONSTEXPR const size_t subtract_with_carry_engine<_UIntType, __w, __s, __r>::short_lag;

template<class _UIntType, size_t __w, size_t __s, size_t __r>
    _LIBCPP_CONSTEXPR const size_t subtract_with_carry_engine<_UIntType, __w, __s, __r>::long_lag;

template<class _UIntType, size_t __w, size_t __s, size_t __r>
    _LIBCPP_CONSTEXPR const typename subtract_with_carry_engine<_UIntType, __w, __s, __r>::result_type
    subtract_with_carry_engine<_UIntType, __w, __s, __r>::default_seed;

template<class _UIntType, size_t __w, size_t __s, size_t __r>
void
subtract_with_carry_engine<_UIntType, __w, __s, __r>::seed(result_type __sd,
        integral_constant<unsigned, 1>)
{
    linear_congruential_engine<result_type, 40014u, 0u, 2147483563u>
        __e(__sd == 0u ? default_seed : __sd);
    for (size_t __i = 0; __i < __r; ++__i)
        __x_[__i] = static_cast<result_type>(__e() & _Max);
    __c_ = __x_[__r-1] == 0;
    __i_ = 0;
}

template<class _UIntType, size_t __w, size_t __s, size_t __r>
void
subtract_with_carry_engine<_UIntType, __w, __s, __r>::seed(result_type __sd,
        integral_constant<unsigned, 2>)
{
    linear_congruential_engine<result_type, 40014u, 0u, 2147483563u>
        __e(__sd == 0u ? default_seed : __sd);
    for (size_t __i = 0; __i < __r; ++__i)
    {
        result_type __e0 = __e();
        __x_[__i] = static_cast<result_type>(
                                    (__e0 + ((uint64_t)__e() << 32)) & _Max);
    }
    __c_ = __x_[__r-1] == 0;
    __i_ = 0;
}

template<class _UIntType, size_t __w, size_t __s, size_t __r>
template<class _Sseq>
void
subtract_with_carry_engine<_UIntType, __w, __s, __r>::__seed(_Sseq& __q,
        integral_constant<unsigned, 1>)
{
    const unsigned __k = 1;
    uint32_t __ar[__r * __k];
    __q.generate(__ar, __ar + __r * __k);
    for (size_t __i = 0; __i < __r; ++__i)
        __x_[__i] = static_cast<result_type>(__ar[__i] & _Max);
    __c_ = __x_[__r-1] == 0;
    __i_ = 0;
}

template<class _UIntType, size_t __w, size_t __s, size_t __r>
template<class _Sseq>
void
subtract_with_carry_engine<_UIntType, __w, __s, __r>::__seed(_Sseq& __q,
        integral_constant<unsigned, 2>)
{
    const unsigned __k = 2;
    uint32_t __ar[__r * __k];
    __q.generate(__ar, __ar + __r * __k);
    for (size_t __i = 0; __i < __r; ++__i)
        __x_[__i] = static_cast<result_type>(
                  (__ar[2 * __i] + ((uint64_t)__ar[2 * __i + 1] << 32)) & _Max);
    __c_ = __x_[__r-1] == 0;
    __i_ = 0;
}

template<class _UIntType, size_t __w, size_t __s, size_t __r>
_UIntType
subtract_with_carry_engine<_UIntType, __w, __s, __r>::operator()()
{
    const result_type& __xs = __x_[(__i_ + (__r - __s)) % __r];
    result_type& __xr = __x_[__i_];
    result_type __new_c = __c_ == 0 ? __xs < __xr : __xs != 0 ? __xs <= __xr : 1;
    __xr = (__xs - __xr - __c_) & _Max;
    __c_ = __new_c;
    __i_ = (__i_ + 1) % __r;
    return __xr;
}

template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
bool
operator==(
    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y)
{
    if (__x.__c_ != __y.__c_)
        return false;
    if (__x.__i_ == __y.__i_)
        return _VSTD::equal(__x.__x_, __x.__x_ + _Rp, __y.__x_);
    if (__x.__i_ == 0 || __y.__i_ == 0)
    {
        size_t __j = _VSTD::min(_Rp - __x.__i_, _Rp - __y.__i_);
        if (!_VSTD::equal(__x.__x_ + __x.__i_, __x.__x_ + __x.__i_ + __j,
                         __y.__x_ + __y.__i_))
            return false;
        if (__x.__i_ == 0)
            return _VSTD::equal(__x.__x_ + __j, __x.__x_ + _Rp, __y.__x_);
        return _VSTD::equal(__x.__x_, __x.__x_ + (_Rp - __j), __y.__x_ + __j);
    }
    if (__x.__i_ < __y.__i_)
    {
        size_t __j = _Rp - __y.__i_;
        if (!_VSTD::equal(__x.__x_ + __x.__i_, __x.__x_ + (__x.__i_ + __j),
                         __y.__x_ + __y.__i_))
            return false;
        if (!_VSTD::equal(__x.__x_ + (__x.__i_ + __j), __x.__x_ + _Rp,
                         __y.__x_))
            return false;
        return _VSTD::equal(__x.__x_, __x.__x_ + __x.__i_,
                           __y.__x_ + (_Rp - (__x.__i_ + __j)));
    }
    size_t __j = _Rp - __x.__i_;
    if (!_VSTD::equal(__y.__x_ + __y.__i_, __y.__x_ + (__y.__i_ + __j),
                     __x.__x_ + __x.__i_))
        return false;
    if (!_VSTD::equal(__y.__x_ + (__y.__i_ + __j), __y.__x_ + _Rp,
                     __x.__x_))
        return false;
    return _VSTD::equal(__y.__x_, __y.__x_ + __y.__i_,
                       __x.__x_ + (_Rp - (__y.__i_ + __j)));
}

template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(
    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y)
{
    return !(__x == __y);
}

template <class _CharT, class _Traits,
          class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
           const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __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.__x_[__x.__i_];
    for (size_t __j = __x.__i_ + 1; __j < _Rp; ++__j)
        __os << __sp << __x.__x_[__j];
    for (size_t __j = 0; __j < __x.__i_; ++__j)
        __os << __sp << __x.__x_[__j];
    __os << __sp << __x.__c_;
    return __os;
}

template <class _CharT, class _Traits,
          class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is,
           subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x)
{
    __save_flags<_CharT, _Traits> __lx(__is);
    typedef basic_istream<_CharT, _Traits> _Istream;
    __is.flags(_Istream::dec | _Istream::skipws);
    _UInt __t[_Rp+1];
    for (size_t __i = 0; __i < _Rp+1; ++__i)
        __is >> __t[__i];
    if (!__is.fail())
    {
        for (size_t __i = 0; __i < _Rp; ++__i)
            __x.__x_[__i] = __t[__i];
        __x.__c_ = __t[_Rp];
        __x.__i_ = 0;
    }
    return __is;
}

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___RANDOM_SUBTRACT_WITH_CARRY_ENGINE_H