nodereadimpl.h

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#ifndef NODEREADIMPL_H_62B23520_7C8E_11DE_8A39_0800200C9A66_PM
#define NODEREADIMPL_H_62B23520_7C8E_11DE_8A39_0800200C9A66_PM
 
#if defined(_MSC_VER) || (defined(__GNUC__) && (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4)) // GCC supports "pragma once" correctly since 3.4
#pragma once
#endif
 
 
namespace YAML_PM
{
        // implementation for Node::Read
        // (the goal is to call ConvertScalar if we can, and fall back to operator >> if not)
        // thanks to litb from stackoverflow.com
        // http://stackoverflow.com/questions/1386183/how-to-call-a-templated-function-if-it-exists-and-something-else-otherwise/1386390#1386390
 
        // Note: this doesn't work on gcc 3.2, but does on gcc 3.4 and above. I'm not sure about 3.3.
        
#if __GNUC__ && (__GNUC__ < 3 || (__GNUC__ == 3 && __GNUC_MINOR__ <= 3))
        // trick doesn't work? Just fall back to ConvertScalar.
        // This means that we can't use any user-defined types as keys in a map
        template <typename T>
        inline bool Node::Read(T& value) const {
                return ConvertScalar(*this, value);
        }
#else
        // usual case: the trick!
        template<bool>
        struct read_impl;
        
        // ConvertScalar available
        template<>
        struct read_impl<true> {
                template<typename T>
                static bool read(const Node& node, T& value) {
                        return ConvertScalar(node, value);
                }
        };
 
        // ConvertScalar not available
        template<>
        struct read_impl<false> {
                template<typename T>
                static bool read(const Node& node, T& value) {
                        try {
                                node >> value;
                        } catch(const Exception&) {
                                return false;
                        }
                        return true;
                }
        };
        
        namespace fallback {
                // sizeof > 1
                struct flag { char c[2]; };
                flag Convert(...);
                
                int operator,(flag, flag);
                
                template<typename T>
                char operator,(flag, T const&);
                
                char operator,(int, flag);
                int operator,(char, flag);
        }
 
        template <typename T>
        inline bool Node::Read(T& value) const {
                using namespace fallback;
 
                return read_impl<sizeof (fallback::flag(), Convert(std::string(), value), fallback::flag()) != 1>::read(*this, value);
        }
#endif // done with trick
        
        // the main conversion function
        template <typename T>
        inline bool ConvertScalar(const Node& node, T& value) {
                std::string scalar;
                if(!node.GetScalar(scalar))
                        return false;
                
                return Convert(scalar, value);
        }
}
 
#endif // NODEREADIMPL_H_62B23520_7C8E_11DE_8A39_0800200C9A66_PM