Convert NSString that represents HEX value to hex (@"0d" to 0x0d)

Question

I want to convert ObjectiveC NSString, that contains for example string "0d" to hex value 0x0d. What's the easiest way to achieve that?

Example:

NSString *str = @"50";
unsigned char mac[1];
mac[0] = 0x50; //<- how to set mac[0] to 0x50 from "str" string?

Answer 1

- (NSData *)dataFromHexString {
    const char *chars = [self UTF8String];
    int i = 0, len = self.length;

    NSMutableData *data = [NSMutableData dataWithCapacity:len/2];
    char byteChars[3] = {chars[0],chars[1],'\0'};
    unsigned long wholeByte = strtoul(byteChars, NULL, 16);
    [data appendBytes:&wholeByte length:1];

    return data;
}