libcruft-util/types/casts.hpp

88 lines
2.7 KiB
C++
Raw Normal View History

/*
* This file is part of libgim.
*
* libgim is free software: you can redistribute it and/or modify it under the
* terms of the GNU General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any later
* version.
*
* libgim is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with libgim. If not, see <http://www.gnu.org/licenses/>.
*
* Copyright 2011 Danny Robson <danny@nerdcruft.net>
*/
#ifndef __UTIL_TYPES_CASTS_HPP
#define __UTIL_TYPES_CASTS_HPP
#include "../debug.hpp"
#include <type_traits>
#include <limits>
namespace detail {
template <typename T, typename V>
T
_sign_cast (const typename std::enable_if<sizeof(T) == sizeof(V) &&
std::is_unsigned<T>::value &&
std::is_signed<V>::value, V>::type v)
{
CHECK_HARD (v >= 0);
return static_cast<T> (v);
}
template <typename T, typename V>
T
_sign_cast (const typename std::enable_if<sizeof(T) == sizeof(V) &&
std::is_signed<T>::value &&
std::is_unsigned<V>::value, V>::type v)
{
CHECK_HARD (v < std::numeric_limits<V>::max () / 2);
return static_cast<T> (v);
}
}
/// Safely cast a numeric type to its (un)signed counterpart, aborting if the
/// dynamically checked result is not representable. May be optimised out if
/// NDEBUG is defined.
template <typename T, typename V>
T
sign_cast (const V v)
{ return detail::_sign_cast<T,V>(v); }
namespace detail {
// Same sign, no possibility of truncation with larger target type
template <typename T, typename V>
T
_trunc_cast (const typename std::enable_if<sizeof (T) >= sizeof (V) &&
std::is_signed<T>::value == std::is_signed<V>::value, V>::type v)
{ return v; }
template <typename T, typename V>
T
_trunc_cast (const typename std::enable_if<sizeof (T) < sizeof (V) &&
std::is_signed<T>::value == std::is_signed<V>::value, V>::type v) {
CHECK_HARD (v <= std::numeric_limits<T>::max ());
checK_hard (v >= std::numeric_limits<T>::min ());
return static_cast<T> (v);
}
}
template <typename T, typename V>
T
trunc_cast (V v)
{ return detail::_trunc_cast<T, V> (v); }
#endif