63e88f80
 Hu Chunming
提交三方库
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///////////////////////////////////////////////////////////////
// Copyright 2019 John Maddock. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt
#ifndef BOOST_MP_DETAIL_CONSTEXPR_HPP
#define BOOST_MP_DETAIL_CONSTEXPR_HPP
#include <cstring>
#include <boost/multiprecision/detail/standalone_config.hpp>
namespace boost {
namespace multiprecision {
namespace std_constexpr {
template <class T>
inline BOOST_CXX14_CONSTEXPR void swap(T& a, T& b)
{
T t(a);
a = b;
b = t;
}
template <class InputIterator, class OutputIterator>
inline BOOST_CXX14_CONSTEXPR OutputIterator copy(InputIterator first, InputIterator last, OutputIterator result)
{
//
// There are 3 branches here, only one of which is selected at compile time:
//
#ifndef BOOST_MP_NO_CONSTEXPR_DETECTION
if (BOOST_MP_IS_CONST_EVALUATED(*first))
{
// constexpr safe code, never generates runtime code:
while (first != last)
{
*result = *first;
++first;
++result;
}
return result;
}
else
#endif
{
#ifndef BOOST_NO_CXX17_IF_CONSTEXPR
if constexpr (std::is_pointer<InputIterator>::value && std::is_pointer<OutputIterator>::value && std::is_trivially_copyable<typename std::remove_reference<decltype(*first)>::type>::value)
{
// The normal runtime branch:
std::memcpy(result, first, static_cast<std::size_t>(static_cast<std::size_t>(last - first) * sizeof(*first)));
return result + (last - first);
}
else
#endif
{
// Alternate runtime branch:
while (first != last)
{
*result = *first;
++first;
++result;
}
return result;
}
}
}
template <class I>
inline BOOST_CXX14_CONSTEXPR bool equal(const I* first, const I* last, const I* other)
{
while (first != last)
{
if (*first != *other)
return false;
++first;
++other;
}
return true;
}
}
}
} // namespace boost::multiprecision::std_constexpr
#endif
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