monero/src/common/sfinae_helpers.h
2018-01-26 10:03:20 -05:00

147 lines
5 KiB
C++

// Copyright (c) 2016-2018, The Monero Project
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#pragma once
// the loose definitions of types in this file are, well, loose.
//
// these helpers aren't here for absolute type certainty at compile-time,
// but rather to help with templated functions telling types apart.
namespace sfinae
{
typedef char true_type;
struct false_type { true_type a[2]; };
template <typename T>
struct is_not_container
{
private:
// does not have const iterator
template <typename C> static false_type c_iter(typename C::const_iterator*);
template <typename C> static true_type c_iter(...);
// does not have value_type
template <typename C> static false_type v_type(typename C::value_type*);
template <typename C> static true_type v_type(...);
// does not have key_type
template <typename C> static false_type k_type(typename C::key_type*);
template <typename C> static true_type k_type(...);
// does not have mapped_type
template <typename C> static false_type m_type(typename C::mapped_type*);
template <typename C> static true_type m_type(...);
public:
static const bool value = (
(
sizeof(c_iter<T>(0)) == sizeof(true_type) &&
sizeof(v_type<T>(0)) == sizeof(true_type) &&
sizeof(k_type<T>(0)) == sizeof(true_type) &&
sizeof(m_type<T>(0)) == sizeof(true_type)
)
|| std::is_same<T, std::string>::value
);
typedef T type;
};
template <typename T>
struct is_vector_like
{
private:
// has const iterator
template <typename C> static true_type c_iter(typename C::const_iterator*);
template <typename C> static false_type c_iter(...);
// has value_type
template <typename C> static true_type v_type(typename C::value_type*);
template <typename C> static false_type v_type(...);
// does not have key_type
template <typename C> static false_type k_type(typename C::key_type*);
template <typename C> static true_type k_type(...);
// does not have mapped_type
template <typename C> static false_type m_type(typename C::mapped_type*);
template <typename C> static true_type m_type(...);
public:
static const bool value = (
sizeof(c_iter<T>(0)) == sizeof(true_type) &&
sizeof(v_type<T>(0)) == sizeof(true_type) &&
sizeof(k_type<T>(0)) == sizeof(true_type) &&
sizeof(m_type<T>(0)) == sizeof(true_type) &&
!std::is_same<T, std::string>::value
);
typedef T type;
};
template <typename T>
struct is_map_like
{
private:
// has const iterator
template <typename C> static true_type c_iter(typename C::const_iterator*);
template <typename C> static false_type c_iter(...);
// has value_type
template <typename C> static true_type v_type(typename C::value_type*);
template <typename C> static false_type v_type(...);
// has key_type
template <typename C> static true_type k_type(typename C::key_type*);
template <typename C> static false_type k_type(...);
// has mapped_type
template <typename C> static true_type m_type(typename C::mapped_type*);
template <typename C> static false_type m_type(...);
public:
static const bool value = (
sizeof(c_iter<T>(0)) == sizeof(true_type) &&
sizeof(v_type<T>(0)) == sizeof(true_type) &&
sizeof(k_type<T>(0)) == sizeof(true_type) &&
sizeof(m_type<T>(0)) == sizeof(true_type) &&
!std::is_same<T, std::string>::value
);
typedef T type;
};
} // namespace sfinae