objective c - NSString (hex) to bytes -

is there method in objective-c converts hex string bytes? example @"1156ffcd3430aa22" unsigned char array {0x11, 0x56, 0xff, ...}.

fastest nsstring category implementation think of (cocktail of examples):

- (nsdata *)datafromhexstring {     const char *chars = [self utf8string];     int = 0, len = self.length;      nsmutabledata *data = [nsmutabledata datawithcapacity:len / 2];     char bytechars[3] = {'\0','\0','\0'};     unsigned long wholebyte;      while (i < len) {         bytechars[0] = chars[i++];         bytechars[1] = chars[i++];         wholebyte = strtoul(bytechars, null, 16);         [data appendbytes:&wholebyte length:1];     }      return data; } 

it close 8 times faster wookay's solution. nsscanner quite slow.