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