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cast: simplify sign_cast, remove identity case

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This commit is contained in:
Danny Robson 2015-11-17 16:37:51 +11:00
parent 424e6e8701
commit cfb5e13c28
1 changed files with 39 additions and 35 deletions
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74
cast.hpp
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@ -23,44 +23,48 @@
#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_GE (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_LT (v, std::numeric_limits<V>::max () / 2);
return static_cast<T> (v);
}
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); }
///
/// 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);
}
///----------------------------------------------------------------------------