how to convert byte value into int in objective-c

Question

Please tell me how to convert bytes to NSInteger/int in objective-c in iPhone programming?

Solution 1

What do you mean by "Bytes"? If you want convert single byte representing integer value to int (or NSInteger) type, just use "=":

Byte b = 123;
NSInteger x;
x = b;

as Byte (the same as unsigned char - 1 byte unsigned integer) and NSInteger (the same as int - 4 bytes signed integer) are both of simple integer types and can be converted automatically. Your should read more about "c data types" and "conversion rules". for example http://www.exforsys.com/tutorials/c-language/c-programming-language-data-types.html

If you want to convert several bytes storing some value to int, then convertion depends on structure of these data: how many bytes per value, signed or unsigned.

Solution 2

If by byte, you mean an unsigned 8 bit value, the following will do.

uint8_t foo = 3;   // or unsigned char foo...
NSInteger bar = (NSInteger) foo;

or even

NSInteger bar = foo;

Solution 3

My guess:

unsigned char data[] = { 0x00, 0x02, 0x45, 0x28 };
NSInteger intData = *((NSInteger *)data);

NSLog(@"data:%d", intData); // data:675611136
NSLog(@"data:%08x", intData); // data:28450200

So, beware of byte-order.

Solution 4

NSInteger x = 3;
unsigned char y = x;
int z = x + y;

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Comments

[Jason Coco]

What do you mean exactly by convert bytes to int?

[bbum]

'bytes'? What kind of bytes? Data? string? something over the net? xml? huh?

[ohho]

@bbum, the "value" does not come with an "s" in the question title.

[suse]

Can u show me with a small example? i want to knw is there any inbuilt method to convert bytes to int.

[bbum]

because you got it backwards? Still not worthy of a downvote given the lack of quality of the question.

[ohho]

y is a byte. z is an integer. the question is "how to convert byte value into int in objective-c"... never mind. I'll get used to this... ;-)

[ohho]

this is an objective-c question. NSInteger is defined in NSObjCRuntime.h and the first #import in NSObjCRuntime.h is <objc/objc.h>, so I consider the objective-c tag is ok. (Just my guess), the rationale behind this question is: someone new to objective-c may not see the difference between a NSInteger and a NSNumber at first sight.

[NSResponder]

NSInteger is a typedef, not an objective-C keyword. It's still a plain C question.

[John Ballinger]

Awesome that work for me. Thanks heaps, I have been searching ages for how to do this with hex. e.g. Sing8 foo = 0xF4 converting that to an int