I have the following:
char const* code = "3D";
I need to convert this 2-digit lexical hex into a std::string, which will be a string with length of 1 (not including null terminator). I have the boost library at my disposal as well. How can I do this?
In the example above, I should have a std::string that prints "=" if properly converted.
I think something on this order should work:
std::istringstream buffer("3D");
int x;
buffer >> std::hex >> x;
std::string result(1, (char)x);
std::cout << result; // should print "="
For example, using only standard C++03:
#include <cstdlib>
#include <string>
#include <iostream>
int main() {
char const* code = "3D";
std::string str(1, static_cast<char>(std::strtoul(code, 0, 16)));
std::cout << str << std::endl;
}
In a real application, you'd have to test whether the entire string has been converted (second argument to strtoul) and whether the conversion result is in the allowed range.
Here is a more elaborate example, using C++11 and Boost:
#include <string>
#include <cstddef>
#include <iostream>
#include <stdexcept>
#include <boost/numeric/conversion/cast.hpp>
template<typename T>
T parse_int(const std::string& str, int base) {
std::size_t index = 0;
unsigned long result = std::stoul(str, &index, base);
if (index != str.length()) throw std::invalid_argument("Invalid argument");
return boost::numeric_cast<T>(result);
}
int main() {
char const* code = "3D";
std::string str(1, parse_int<char>(code, 16));
std::cout << str << std::endl;
}
In Boost release 1.50 (coming this May), you would simply write
string s;
boost::algorithm::unhex ( code, std::back_inserter (s));
Works on std::string, std::wstring, QtString, CString, etc, etc.
It's not C++ but you can still use the good old scanf:
int d;
scanf("%x", &d);
Or from a string using sscanf:
int d;
sscanf(code, "%x", &d);
And using a std::string:
int d;
sscanf(code.c_str(), "%x", &d);
For some case the C format function (scanf & printf families) are easier to use than the object-oriented equivalent.
sscanf example?
std::string? You know, that uses c_str?