Very poor boost::lexical_cast performance

Question

Windows XP SP3. Core 2 Duo 2.0 GHz. I\'m finding the boost::lexical_cast performance to be extremely slow. Wanted to find out ways to speed up the code. Using /O2 optimizati

Answer 1

You could specialize lexical_cast for int and double types. Use strtod and strtol in your's specializations.

namespace boost {
template<>
inline int lexical_cast(const std::string& arg)
{
    char* stop;
    int res = strtol( arg.c_str(), &stop, 10 );
    if ( *stop != 0 ) throw_exception(bad_lexical_cast(typeid(int), typeid(std::string)));
    return res;
}
template<>
inline std::string lexical_cast(const int& arg)
{
    char buffer[65]; // large enough for arg < 2^200
    ltoa( arg, buffer, 10 );
    return std::string( buffer ); // RVO will take place here
}
}//namespace boost

int main(int argc, char* argv[])
{
    std::string str = "22"; // SOME STRING
    int int_str = boost::lexical_cast( str );
    std::string str2 = boost::lexical_cast( str_int );

    return 0;
}

This variant will be faster than using default implementation, because in default implementation there is construction of heavy stream objects. And it is should be little faster than printf, because printf should parse format string.