[Function] htoi(const char s[]): convert hexdecimal string s to integer

/* htoi: convert hexdecimal string s to integer */ unsigned int htoi(const char s[]) { unsigned int i, n, temp; if ((s[0] != '0') || ((s[1] != 'x') && (s[1] != 'X'))) { return (-1); } i = 2; n = 0; while (1) { temp = s[i++]; if ((temp >= '0') && (temp <= '9')) { n = (n << 4) + (temp - '0'); } else if ((temp >= 'A') && (temp <= 'F')) { n = (n << 4) + (temp - 'A' + 10); } else if ((temp >= 'a') && (temp <= 'f')) { n = (n << 4) + (temp - 'a' + 10); } else { return (temp == '\0') ? n : (-1); } } }