bool to_number(char const* beg, int sz, int& num)
	{
		char* end = 0;
		int tmp_num = ::strtol(beg, &end, 10);
		if(end != beg + sz)
		{
			return false;
		}
		num = tmp_num;
		return true;
	}

std::string value;
int num;
if (!to_number(value.c_str(), value.size(), num))
         return false;