libcruft-util/types/casts.hpp

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/*
* 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>
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//-----------------------------------------------------------------------------
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_GE (v, 0);
return static_cast<T> (v);
}
template <typename T, typename V>
T
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_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_LT (v, std::numeric_limits<V>::max () / 2);
return static_cast<T> (v);
}
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template <typename T, typename V>
T
_sign_cast (const typename std::enable_if<std::is_same<T, V>::value, V>::type v)
{ return 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); }
///----------------------------------------------------------------------------
/// assert if the value cannot be cast loslessly from U to T, else return the
/// converted value.Note: this is only a debug-time check and is compiled out
/// in optimised builds.
template <typename T, typename U>
T
trunc_cast (U u)
{
auto t = static_cast<T> (u);
if (u == u)
CHECK_EQ (t, u);
else
CHECK_NEQ (t, t);
return t;
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}
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///----------------------------------------------------------------------------
/// assert if the value is not a pointer to a subclass of T, else return the
/// converted value. Note: this is only a debug-time check and is compiled out
/// in optimised builds.
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template <typename T, typename V>
T*
known_cast (V *v) {
CHECK (dynamic_cast<T*> (v));
return static_cast<T*> (v);
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}
//-----------------------------------------------------------------------------
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template <typename T, typename V>
T&
known_cast (V &v) {
CHECK_NOTHROW (dynamic_cast<T> (v));
return static_cast<T> (v);
}
#endif