How do I convert a binary string to hex using C?

Question

How do I convert an 8-bit binary string (e.g. \"10010011\") to hexadecimal using C?

Answer 1

void binaryToHex(const char *inStr, char *outStr) {
    // outStr must be at least strlen(inStr)/4 + 1 bytes.
    static char hex[] = "0123456789ABCDEF";
    int len = strlen(inStr) / 4;
    int i = strlen(inStr) % 4;
    char current = 0;
    if(i) { // handle not multiple of 4
        while(i--) {
            current = (current << 1) + (*inStr - '0');
            inStr++;
        }
        *outStr = hex[current];
        ++outStr;
    }
    while(len--) {
        current = 0;
        for(i = 0; i < 4; ++i) {
            current = (current << 1) + (*inStr - '0');
            inStr++;
        }
        *outStr = hex[current];
        ++outStr;
    }
    *outStr = 0; // null byte
}