meta.h

//------------------------------------------------------------------------------
/*
    This file is part of Beast: https://github.com/vinniefalco/Beast
    Copyright 2014, Howard Hinnant <howard.hinnant@gmail.com>
 
    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.
 
    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
 
#ifndef BEAST_HASH_META_H_INCLUDED
#define BEAST_HASH_META_H_INCLUDED
 
#include <type_traits>
 
namespace beast {
 
template <bool...>
struct static_and;
 
template <bool b0, bool... bN>
struct static_and<b0, bN...>
    : public std::integral_constant<bool, b0 && static_and<bN...>::value>
{
    explicit static_and() = default;
};
 
template <>
struct static_and<> : public std::true_type
{
    explicit static_and() = default;
};
 
#ifndef __INTELLISENSE__
static_assert(static_and<true, true, true>::value, "");
static_assert(!static_and<true, false, true>::value, "");
#endif
 
template <std::size_t...>
struct static_sum;
 
template <std::size_t s0, std::size_t... sN>
struct static_sum<s0, sN...>
    : public std::integral_constant<std::size_t, s0 + static_sum<sN...>::value>
{
    explicit static_sum() = default;
};
 
template <>
struct static_sum<> : public std::integral_constant<std::size_t, 0>
{
    explicit static_sum() = default;
};
 
#ifndef __INTELLISENSE__
static_assert(static_sum<5, 2, 17, 0>::value == 24, "");
#endif
 
template <class T, class U>
struct enable_if_lvalue : public std::enable_if<
                              std::is_same<std::decay_t<T>, U>::value &&
                              std::is_lvalue_reference<T>::value>
{
    explicit enable_if_lvalue() = default;
};
 
template <class T, class U>
using enable_if_lvalue_t = typename enable_if_lvalue<T, U>::type;
 
}  // namespace beast
 
#endif  // BEAST_UTILITY_META_H_INCLUDED