C++ convert hex string to signed integer

Question

I want to convert a hex string to a 32 bit signed integer in C++.

So, for example, I have the hex string \"fffefffe\". The binary representation of this is 111111

Answer 1

For a method that works with both C and C++, you might want to consider using the standard library function strtol().

#include 
#include 
using namespace std;

int main() {
    string s = "abcd";
    char * p;
    long n = strtol( s.c_str(), & p, 16 );
    if ( * p != 0 ) { //my bad edit was here
        cout << "not a number" << endl;
    }
    else {
        cout << n << endl;
    }
}