标准::环礁与 VC++

Question

I have been using std::atoll from cstdlib to convert a string to an int64_t with gcc. That function does not seem to be available on the Windows toolchain (using Visual Studio Express 2010). What is the best alternative?

I am also interested in converting strings to uint64_t . Integer definitions taken from cstdint .

Answer 1

MSVC have _atoi64 and similar functions, see here

For unsigned 64 bit types, see _strtoui64

Answer 2

• use stringstreams ( <sstream> )

   std::string numStr = "12344444423223"; std::istringstream iss(numStr); long long num; iss>>num;

• use boost lexical_cast ( boost/lexical_cast.hpp )

   std::string numStr = "12344444423223"; long long num = boost::lexical_cast<long long>(numStr);

Answer 3

If you have run a performance test and concluded that the conversion is your bottleneck and should be done really fast, and there's no ready function, I suggest you write your own. here's a sample that works really fast but has no error checking and deals with only positive numbers.

long long convert(const char* s)
{
    long long ret = 0;
    while(s != NULL)
    {
       ret*=10; //you can get perverted and write ret = (ret << 3) + (ret << 1) 
       ret += *s++ - '0';
    }
    return ret;
}

Answer 4

Visual Studio 2013 finally has std::atoll .

Answer 5

Do you have strtoull available in your <cstdlib> ? It's C99. And C++0x should also have stoull to work directly on strings.