nerdcruft/libcruft-util
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Add sign_cast functions

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These safely cast between signed and unsigned numeric quantities,
aborting if the result cannot be safely converted (as opposed to size
expanding or throwing).
This commit is contained in:
Danny Robson 2011-06-15 22:38:58 +10:00
parent 16e4cde82d
commit 4891c6af0e
1 changed files with 40 additions and 0 deletions
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40
types.hpp
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@ -3,6 +3,7 @@
#include <cstdint> #include <cstdint>
#include <string> #include <string>
#include <limits>
template <int BITS> template <int BITS>
struct bits_type; struct bits_type;
@ -53,4 +54,43 @@ template <typename T>
std::string type_to_string (void); std::string type_to_string (void);
template <typename T>
struct sign_types;
template <> struct sign_types <signed int> {
typedef signed int with_sign;
typedef unsigned int without_sign;
};
template <> struct sign_types <unsigned int> {
typedef signed int with_sign;
typedef unsigned int without_sign;
};
/// Safely cast a numeric type to its signed comparison, aborting if the
/// result is not representable.
template <typename T>
typename sign_types<T>::with_sign
sign_cast (const typename sign_types<T>::without_sign v)
{
check_hard (v <= std::numeric_limits<typename sign_types<T>::without_sign>::max () >> 1);
return static_cast <typename sign_types<T>::with_sign> (v);
}
/// Safely cast a numeric type to its unsigned comparison, aborting if the
/// result is not representable.
template <typename T>
typename sign_types<T>::without_sign
sign_cast (const typename sign_types<T>::with_sign v)
{
check_hard (v >= 0);
return static_cast <typename sign_types<T>::without_sign> (v);
}
#endif // __TYPES_HPP #endif // __TYPES_HPP