Danny Robson
0e29675ef5
trunc_cast should be between float/int/uint or to types of lesser precision. also restrict to fundamental types until we actually test with arbitrary types.
134 lines
3.7 KiB
C++
134 lines
3.7 KiB
C++
/*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*
|
|
* Copyright 2011 Danny Robson <danny@nerdcruft.net>
|
|
*/
|
|
|
|
#ifndef __UTIL_CAST_HPP
|
|
#define __UTIL_CAST_HPP
|
|
|
|
#include "./debug.hpp"
|
|
|
|
#include <type_traits>
|
|
#include <limits>
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
/// 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.
|
|
///
|
|
/// The signed/unsigned and unsigned/signed cases are split so we can simplify
|
|
/// the out of range tests.
|
|
///
|
|
/// The same-type case is not provided because we want to error out on
|
|
/// unnecessary casts.
|
|
template <
|
|
typename T,
|
|
typename U
|
|
>
|
|
std::enable_if_t<
|
|
sizeof(T) == sizeof(U) &&
|
|
std::is_unsigned<T>::value &&
|
|
std::is_signed<U>::value,
|
|
T
|
|
>
|
|
sign_cast (const U u)
|
|
{
|
|
CHECK_GE (u, 0);
|
|
return static_cast<T> (u);
|
|
}
|
|
|
|
//-----------------------------------------------------------------------------
|
|
template <
|
|
typename T,
|
|
typename U
|
|
>
|
|
std::enable_if_t<
|
|
sizeof(T) == sizeof (U) &&
|
|
std::is_signed<T>::value &&
|
|
std::is_unsigned<U>::value,
|
|
T
|
|
>
|
|
sign_cast (const U u)
|
|
{
|
|
CHECK_LT (u, std::numeric_limits<U>::max () / 2);
|
|
return static_cast<T> (u);
|
|
}
|
|
|
|
|
|
///----------------------------------------------------------------------------
|
|
/// 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.
|
|
///
|
|
/// relies on equality operators being present and behaving sanely. attempts
|
|
/// to preserve NaN values.
|
|
///
|
|
/// allows the identity cast (if only to make cross-platform porting easier)
|
|
template <
|
|
typename T,
|
|
typename U
|
|
>
|
|
std::enable_if_t<
|
|
// only enabled for builtin types. there's no reason this couldn't be
|
|
// extended, but we've only really tested on integers and floats.
|
|
std::is_fundamental<T>::value && std::is_fundamental<U>::value && (
|
|
// either we're casting between real and integer
|
|
std::is_floating_point<T>::value != std::is_floating_point<U>::value
|
|
// or we're reducing the size of the type
|
|
|| sizeof (T) <= sizeof (U)
|
|
),
|
|
T
|
|
>
|
|
trunc_cast (const U &u)
|
|
{
|
|
auto t = static_cast<T> (u);
|
|
|
|
// if we're not a NaN then check equality by casting U-to-T-to-U. we can't
|
|
// explicitly check isnan because that call isn't valid for arbitrary
|
|
// types and we'll cause a compile-time error.
|
|
if (u == u)
|
|
CHECK_EQ (static_cast<U> (t), u);
|
|
// we must be a NaN. test that t is a NaN too by self-equality.
|
|
else
|
|
CHECK_NEQ (t, t);
|
|
|
|
return t;
|
|
}
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
/// 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.
|
|
template <typename T, typename V>
|
|
T*
|
|
known_cast (V *v)
|
|
{
|
|
CHECK (dynamic_cast<T*> (v));
|
|
return static_cast<T*> (v);
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
template <typename T, typename V>
|
|
T&
|
|
known_cast (V &v)
|
|
{
|
|
CHECK_NOTHROW (dynamic_cast<T> (v));
|
|
return static_cast<T> (v);
|
|
}
|
|
|
|
#endif
|