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llvm-project/libcxx/include/__random/independent_bits_engine.h

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//===----------------------------------------------------------------------===//
//
// 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_INDEPENDENT_BITS_ENGINE_H
#define _LIBCPP___RANDOM_INDEPENDENT_BITS_ENGINE_H
#include <__config>
#include <__random/is_seed_sequence.h>
#include <__random/log2.h>
#include <__utility/move.h>
#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 _Engine, size_t __w, class _UIntType>
class _LIBCPP_TEMPLATE_VIS independent_bits_engine
{
template <class _UInt, _UInt _R0, size_t _Wp, size_t _Mp>
class __get_n
{
static _LIBCPP_CONSTEXPR const size_t _Dt = numeric_limits<_UInt>::digits;
static _LIBCPP_CONSTEXPR const size_t _Np = _Wp / _Mp + (_Wp % _Mp != 0);
static _LIBCPP_CONSTEXPR const size_t _W0 = _Wp / _Np;
static _LIBCPP_CONSTEXPR const _UInt _Y0 = _W0 >= _Dt ? 0 : (_R0 >> _W0) << _W0;
public:
static _LIBCPP_CONSTEXPR const size_t value = _R0 - _Y0 > _Y0 / _Np ? _Np + 1 : _Np;
};
public:
// types
typedef _UIntType result_type;
private:
_Engine __e_;
static _LIBCPP_CONSTEXPR const result_type _Dt = numeric_limits<result_type>::digits;
static_assert( 0 < __w, "independent_bits_engine invalid parameters");
static_assert(__w <= _Dt, "independent_bits_engine invalid parameters");
typedef typename _Engine::result_type _Engine_result_type;
typedef typename conditional
<
sizeof(_Engine_result_type) <= sizeof(result_type),
result_type,
_Engine_result_type
>::type _Working_result_type;
#ifdef _LIBCPP_CXX03_LANG
static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min
+ _Working_result_type(1);
#else
static _LIBCPP_CONSTEXPR const _Working_result_type _Rp = _Engine::max() - _Engine::min()
+ _Working_result_type(1);
#endif
static _LIBCPP_CONSTEXPR const size_t __m = __log2<_Working_result_type, _Rp>::value;
static _LIBCPP_CONSTEXPR const size_t __n = __get_n<_Working_result_type, _Rp, __w, __m>::value;
static _LIBCPP_CONSTEXPR const size_t __w0 = __w / __n;
static _LIBCPP_CONSTEXPR const size_t __n0 = __n - __w % __n;
static _LIBCPP_CONSTEXPR const size_t _WDt = numeric_limits<_Working_result_type>::digits;
static _LIBCPP_CONSTEXPR const size_t _EDt = numeric_limits<_Engine_result_type>::digits;
static _LIBCPP_CONSTEXPR const _Working_result_type __y0 = __w0 >= _WDt ? 0 :
(_Rp >> __w0) << __w0;
static _LIBCPP_CONSTEXPR const _Working_result_type __y1 = __w0 >= _WDt - 1 ? 0 :
(_Rp >> (__w0+1)) << (__w0+1);
static _LIBCPP_CONSTEXPR const _Engine_result_type __mask0 = __w0 > 0 ?
_Engine_result_type(~0) >> (_EDt - __w0) :
_Engine_result_type(0);
static _LIBCPP_CONSTEXPR const _Engine_result_type __mask1 = __w0 < _EDt - 1 ?
_Engine_result_type(~0) >> (_EDt - (__w0 + 1)) :
_Engine_result_type(~0);
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, "independent_bits_engine invalid parameters");
// engine characteristics
_LIBCPP_INLINE_VISIBILITY
static _LIBCPP_CONSTEXPR result_type min() { return _Min; }
_LIBCPP_INLINE_VISIBILITY
static _LIBCPP_CONSTEXPR result_type max() { return _Max; }
// constructors and seeding functions
_LIBCPP_INLINE_VISIBILITY
independent_bits_engine() {}
_LIBCPP_INLINE_VISIBILITY
explicit independent_bits_engine(const _Engine& __e)
: __e_(__e) {}
#ifndef _LIBCPP_CXX03_LANG
_LIBCPP_INLINE_VISIBILITY
explicit independent_bits_engine(_Engine&& __e)
: __e_(_VSTD::move(__e)) {}
#endif // _LIBCPP_CXX03_LANG
_LIBCPP_INLINE_VISIBILITY
explicit independent_bits_engine(result_type __sd) : __e_(__sd) {}
template<class _Sseq>
_LIBCPP_INLINE_VISIBILITY
explicit independent_bits_engine(_Sseq& __q,
typename enable_if<__is_seed_sequence<_Sseq, independent_bits_engine>::value &&
!is_convertible<_Sseq, _Engine>::value>::type* = 0)
: __e_(__q) {}
_LIBCPP_INLINE_VISIBILITY
void seed() {__e_.seed();}
_LIBCPP_INLINE_VISIBILITY
void seed(result_type __sd) {__e_.seed(__sd);}
template<class _Sseq>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
__is_seed_sequence<_Sseq, independent_bits_engine>::value,
void
>::type
seed(_Sseq& __q) {__e_.seed(__q);}
// generating functions
_LIBCPP_INLINE_VISIBILITY
result_type operator()() {return __eval(integral_constant<bool, _Rp != 0>());}
_LIBCPP_INLINE_VISIBILITY
void discard(unsigned long long __z) {for (; __z; --__z) operator()();}
// property functions
_LIBCPP_INLINE_VISIBILITY
const _Engine& base() const _NOEXCEPT {return __e_;}
template<class _Eng, size_t _Wp, class _UInt>
friend
bool
operator==(
const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
template<class _Eng, size_t _Wp, class _UInt>
friend
bool
operator!=(
const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
template <class _CharT, class _Traits,
class _Eng, size_t _Wp, class _UInt>
friend
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const independent_bits_engine<_Eng, _Wp, _UInt>& __x);
template <class _CharT, class _Traits,
class _Eng, size_t _Wp, class _UInt>
friend
basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is,
independent_bits_engine<_Eng, _Wp, _UInt>& __x);
private:
_LIBCPP_INLINE_VISIBILITY
result_type __eval(false_type);
result_type __eval(true_type);
template <size_t __count>
_LIBCPP_INLINE_VISIBILITY
static
typename enable_if
<
__count < _Dt,
result_type
>::type
__lshift(result_type __x) {return __x << __count;}
template <size_t __count>
_LIBCPP_INLINE_VISIBILITY
static
typename enable_if
<
(__count >= _Dt),
result_type
>::type
__lshift(result_type) {return result_type(0);}
};
template<class _Engine, size_t __w, class _UIntType>
inline
_UIntType
independent_bits_engine<_Engine, __w, _UIntType>::__eval(false_type)
{
return static_cast<result_type>(__e_() & __mask0);
}
template<class _Engine, size_t __w, class _UIntType>
_UIntType
independent_bits_engine<_Engine, __w, _UIntType>::__eval(true_type)
{
result_type _Sp = 0;
for (size_t __k = 0; __k < __n0; ++__k)
{
_Engine_result_type __u;
do
{
__u = __e_() - _Engine::min();
} while (__u >= __y0);
_Sp = static_cast<result_type>(__lshift<__w0>(_Sp) + (__u & __mask0));
}
for (size_t __k = __n0; __k < __n; ++__k)
{
_Engine_result_type __u;
do
{
__u = __e_() - _Engine::min();
} while (__u >= __y1);
_Sp = static_cast<result_type>(__lshift<__w0+1>(_Sp) + (__u & __mask1));
}
return _Sp;
}
template<class _Eng, size_t _Wp, class _UInt>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(
const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
const independent_bits_engine<_Eng, _Wp, _UInt>& __y)
{
return __x.base() == __y.base();
}
template<class _Eng, size_t _Wp, class _UInt>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(
const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
const independent_bits_engine<_Eng, _Wp, _UInt>& __y)
{
return !(__x == __y);
}
template <class _CharT, class _Traits,
class _Eng, size_t _Wp, class _UInt>
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const independent_bits_engine<_Eng, _Wp, _UInt>& __x)
{
return __os << __x.base();
}
template <class _CharT, class _Traits,
class _Eng, size_t _Wp, class _UInt>
basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is,
independent_bits_engine<_Eng, _Wp, _UInt>& __x)
{
_Eng __e;
__is >> __e;
if (!__is.fail())
__x.__e_ = __e;
return __is;
}
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___RANDOM_INDEPENDENT_BITS_ENGINE_H
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