CODEWITHSUNDEEP
iosobjective-chexaddition
Ogyme
Ogyme

Reputation: 13

iOS hex addition

i have an NSString with hex value

NSString* someString = @"AAB827EB5A6E225CAA

i want to extract from b (the second char) to 2 (-5 char)

make an addition of all extracted char and i have to find the 5C as result (-4 and -3 char)

i have tried this : 

NSMutableArray *hex = [[NSMutableArray alloc]init];
        unichar firstChar = [[someString uppercaseString] characterAtIndex:0];
        unichar seconChar = [[someString uppercaseString] characterAtIndex:1];
        unichar lastChar = [[someString uppercaseString] characterAtIndex:[print length]-1];
        unichar beforeLastChar = [[someString uppercaseString] characterAtIndex:[print length]-2];

        if (firstChar == 'A' && seconChar == 'A' && lastChar =='A' && beforeLastChar=='A') {



            for (int i=2;i< [print length]-4; i++) {
                NSString *decim =[NSString stringWithFormat:@"%hu",[someString characterAtIndex:i]];
                [hex addObject:decim];
            }
                NSLog(@"hex : %@",hex);
}

but the log is

hex : ( 98, 56, 50, 55, 101, 98, 53, 97, 54, 101, 50, 50, )

i've tried to covert it to string then int for calculation but if i can avoid conversion and continue with hex i would prefer

thanks for help

Upvotes: 1

Views: 358

Answers (1)

Sulthan
Sulthan

Reputation: 130092

The code could be probably simplifed even more but one possibility:

NSString *someString = @"AAB827EB5A6E225CAA";

// I have improved a bit your check for prefix and suffix
if ([someString hasPrefix:@"AA"] && [someString hasSuffix:@"AA"]) {
    NSMutableArray *hexNumbers = [[NSMutableArray alloc] init];

    for (int i = 2; i < [someString length] - 4; i++) {
        unichar digit = [someString characterAtIndex:i];

        NSUInteger value;

        // we have to convert the character into its numeric value
        // we could also use NSScanner for it but this is a simple way
        if (digit >= 'A') {
            value = digit - 'A' + 10;
        } else {
            value = digit - '0';
        }

        // add the value to the array
        [hexNumbers addObject:@(value)];
    }

    NSLog(@"hex : %@", hexNumbers);

    // a trick to get the sum of an array
    NSNumber *sum = [hexNumbers valueForKeyPath:@"@sum.self"];

    // print the sum in decadic and in hexadecimal
    NSLog(@"Sum: %@, in hexa: %X", sum, [sum integerValue]);
}

Upvotes: 1

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