Source
#include <cstddef>
#include <string>
#include <typeinfo>
//#include <boost/config.hpp>
#include <boost/limits.hpp>
#include <boost/throw_exception.hpp>
#include <boost/type_traits/is_pointer.hpp>
#include <sstream>
//
namespace kimi_boost
{
// exception used to indicate runtime lexical_cast failure
class bad_lexical_cast : public std::bad_cast
{
public:
bad_lexical_cast() :
source(&typeid(void)), target(&typeid(void))
{
}
bad_lexical_cast(
const std::type_info &source_type,
const std::type_info &target_type) :
source(&source_type), target(&target_type)
{
}
const std::type_info &source_type() const
{
return *source;
}
const std::type_info &target_type() const
{
return *target;
}
virtual const char *what() const throw()
{
return "bad lexical cast: "
"source type value could not be interpreted as target";
}
virtual ~bad_lexical_cast() throw()
{
}
private:
const std::type_info *source;
const std::type_info *target;
};
namespace detail // stream wrapper for handling lexical conversions
{
template<typename Target, typename Source>
class lexical_stream
{
private:
typedef char char_type;
std::basic_stringstream<char_type> stream;
public:
lexical_stream()
{
stream.unsetf(std::ios::skipws);
if(std::numeric_limits<Target>::is_specialized)
stream.precision(std::numeric_limits<Target>::digits10 + 1);
else if(std::numeric_limits<Source>::is_specialized)
stream.precision(std::numeric_limits<Source>::digits10 + 1);
}
~lexical_stream()
{
}
//把Source類型輸入到流中
bool operator<<(const Source &input)
{
return !(stream << input).fail();
}
//把流轉換為Target類型輸出
template<typename InputStreamable>
bool operator>>(InputStreamable &output)
{
return !boost::is_pointer<InputStreamable>::value &&
stream >> output &&
stream.get() ==
std::char_traits<char_type>::eof();
}
//string特化
template<>
bool operator>>(std::string &output)
{
output = stream.str();
return true;
}
};//class lexical_stream
}//namespace detail
namespace detail
{
template<class T>
struct array_to_pointer_decay
{
typedef T type;
};
template<class T, std::size_t N>
struct array_to_pointer_decay<T[N]>
{
typedef const T * type;
};
}
template<typename Target, typename Source>
Target lexical_cast(const Source &arg)
{
typedef typename detail::array_to_pointer_decay<Source>::type NewSource;
detail::lexical_stream<Target, NewSource> interpreter;
Target result;
if(!(interpreter << arg && interpreter >> result))
boost::throw_exception(bad_lexical_cast(typeid(NewSource), typeid(Target)));
return result;
}
}
Test code
void kimi_lexical_cast_test()
{
try
{
int i=kimi_boost::lexical_cast<int>("4365");
float f=kimi_boost::lexical_cast<float>("234.546");
double d=kimi_boost::lexical_cast<double>("24534.546345");
std::string s=kimi_boost::lexical_cast<std::string>(24534.546345);
}
catch(kimi_boost::bad_lexical_cast& e)
{
cout<<e.what()<<endl;
}
try{
int i2=kimi_boost::lexical_cast<int>("0.335");
}
catch(kimi_boost::bad_lexical_cast& e)
{
cout<<"source type: "<<e.source_type().name()<<endl;
cout<<"target type: "<<e.target_type().name()<<endl;
cout<<e.what()<<endl;
}
}
Output
source type: char const *
target type: int
bad lexical cast: source type value could not be interpreted as target
posted on 2010-05-27 10:37
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