Data Type Problem unsigned short

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

for example if users type like

Code:

---

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

Code:

---


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

try to declare:

usInputBit, usOutputBit, usResult and usResult2

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

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!?

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?

Code:

---

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.

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?