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/**
* Boost Software License - Version 1.0 - August 17th, 2003
*
* Permission is hereby granted, free of charge, to any person or organization
* obtaining a copy of the software and accompanying documentation covered by
* this license (the "Software") to use, reproduce, display, distribute,
* execute, and transmit the Software, and to prepare derivative works of the
* Software, and to permit third-parties to whom the Software is furnished to
* do so, all subject to the following:
*
* The copyright notices in the Software and this entire statement, including
* the above license grant, this restriction and the following disclaimer,
* must be included in all copies of the Software, in whole or in part, and
* all derivative works of the Software, unless such copies or derivative
* works are solely in the form of machine-executable object code generated by
* a source language processor.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
* SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
* FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#ifndef COMMON_SAFE_BOOL_H
#define COMMON_SAFE_BOOL_H
namespace Common {
namespace impl {
template <typename T>
struct no_base {};
template <typename T>
struct safe_bool_impl {
typedef T *TP; // workaround to make parsing easier
TP stub;
typedef TP safe_bool_impl::*type;
};
}
/**
* @defgroup common_safe_bool Safe Boolean
* @ingroup common
*
* @brief Template for a SafeBool function.
*
* @{
*/
/**
* Prevents `operator bool` from implicitly converting to other types.
*/
template <typename DerivedT, typename BaseT = impl::no_base<DerivedT> >
struct SafeBool : BaseT {
private:
typedef impl::safe_bool_impl<DerivedT> impl_t;
typedef typename impl_t::type bool_type;
public:
operator bool_type() const {
return static_cast<const DerivedT *>(this)->operator_bool() ?
&impl_t::stub : nullptr;
}
operator bool_type() {
return static_cast<DerivedT *>(this)->operator_bool() ?
&impl_t::stub : 0;
}
};
/** @} */
} // End of namespace Common
#endif
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