Data Type Problem unsigned short

[vcstarter]

I am using data type unsigned short on two functions. An input function and an output function.

for example if users type like

unsigned short x =100;
unsigned short y;

y = input(x);
y = output(x);
cout<<y;
//the output should be 100

the problem is, the function can only take 2^(15) -1 or 32767. I can't figure out the problem. For instance if your input is over 32767, it gives wrong result.

Here is the code for both function

unsigned short Input(unsigned short usData) 
{
	unsigned short usOutputBit	 = 0;
	static int nRegisterBitValue = 0;
	unsigned short usResult		 = 0;
	unsigned short usResult2	 = 0;
	unsigned short usInputBit;
	unsigned short usBit;
	int i;

	usInputBit = usData;

	for (i = 0; i < 16; i++)
	{
		usBit = (usInputBit & 0x8000) ? 1 : 0;
		usOutputBit = usBit ^ nRegisterBitValue;
		nRegisterBitValue = usOutputBit;
		usInputBit  = usInputBit << 1;
		usResult    = (usOutputBit | 0x8000) | usResult2; 
		usResult	= usResult << 1;
		usResult2	= usResult;
		if(usInputBit == 0)
		{
			usResult = usResult >> 1;
		}
	}

	return(usResult);	
}

unsigned short Output(unsigned short usData)
{
	unsigned short usOutputBit  = 0;
	unsigned short usResult2	= 0;
	static int nRegisterValue	= 0;
	unsigned short usResult		= 0;
	unsigned short usInputBit;
	unsigned short usBit;
	int i;

	usInputBit = usData;

	
	for (i = 0; i < 16; i++)
	{
		usBit = (usInputBit & 0x8000) ? 1 : 0;
		usOutputBit = usBit ^ nRegisterValue;
		nRegisterValue = usBit;
		usInputBit	= usInputBit << 1;
		usResult	= (usOutputBit | 0x8000) | usResult2; 
		usResult	= usResult << 1;
		usResult2	= usResult;
		if(usInputBit == 0)
		{
			usResult = usResult >> 1;
		}
	}

	return(usResult);
}

I think the problem may be in this line of code
usResult = (usOutputBit | 0x8000) | usResult2;
which I use to pack the bit together

[Pham Son Thuy]

try to declare:

usInputBit, usOutputBit, usResult and usResult2

as "unsigned int" instead of "unsigned short".

[ReorX]

What are the functions supposed to do? From the code, it's impossible to tell, as it does not make any sense to me.
E.g., in
usResult = (usOutputBit | 0x8000) | usResult2;
usResult = usResult << 1;
you set the high order bit (0x8000) but in the next line, you shift the bit you just set again out of usResult.
So I think, you should first tell us what input() and output() should do, before someone can really help!
BTW: The code does not compile!?

[vcstarter]

The way to look at the function. I suppose to rename them as encoder and decoder

for instance the first function encode a number, while the second function decode the number like

Encode(13) you get 9
now if you decode 9 you get 13 back.

for instance if x = 13

and you type y=input(x)
and next y=output(y)
you should get 13 back, so this is what the functions suppose to do. However the problem I have, the highest value it can take is 32767

now I think the value if unsigned int is 32 bit, but I don't want 32 bit I only want 16 bit. So how can I fix that?

[Pham Son Thuy]

usInputBit  = usInputBit << 1;

assume that usInputBit > 32767, after execute the above command, the value of usInputBit will be greater than 2^16.

Why dont you like to declare the temporary variables in input(), output() as "unsigned int"? You only re-declare they as "unsigned int" mean while the prototype of input(unsigned short), output(unsigned short) still has no change.

[vcstarter]

What do you mean, I should use unsigned int for usinput. usInput is the input data and they are given as unsigned short. So if I change it to unsigned int, how do I make sure the input value is not greater than 16b it. So assume that I typecast it which I haven't try yet. Will that solve the problem?