What's the fastest way to convert hex to integer in C++?

Question

I\'m trying to convert a hex char to integer as fast as possible.

This is only one line: int x = atoi(hex.c_str);

Is there a faster way

Answer 1

This is my favorite hex-to-int code:

inline int htoi(int x) {
    return 9 * (x >> 6) + (x & 017);
}

It is case-insensitive for letter, i.e will return correct result for "a" and "A".