Generates NSData instance for given hex String. Hex string is looked up from 0th index to nth index, for hex literals and accordingly NSData instance is generated.

NSDataFromHexString.m

-(NSData *) NSDataFromHexString:(NSString *) hexstr
{
    NSMutableData *data = [[NSMutableData alloc] init];
    NSString *inputStr = [hexstr uppercaseString];
    
    NSString *hexChars = @"0123456789ABCDEF";
    
    Byte b1,b2;
    b1 = 255;
    b2 = 255;
    for (int i=0; i<hexstr.length; i++) {
        NSString *subStr = [inputStr substringWithRange:NSMakeRange(i, 1)];
        NSRange loc = [hexChars rangeOfString:subStr];
        
        if (loc.location == NSNotFound) continue;
        
        if (255 == b1) {
            b1 = (Byte)loc.location;
        }else {
            b2 = (Byte)loc.location;
            
            //Appending the Byte to NSData
            Byte *bytes = malloc(sizeof(Byte) *1);
            bytes[0] = ((b1<<4) & 0xf0) | (b2 & 0x0f);
            [data appendBytes:bytes length:1];
            
            b1 = b2 = 255;
        }
    }
    
    return data;
}