Using tilde (~) error

I have seen a portion of code that looks like this:

public static short ReadEncryptedShort2(int ReputationAddress)

{

int bits = ReputationAddress & 15;

ushort num = (ushort)MainProcess.ReadShort(ReputationAddress);

num = (ushort)MainProcess.rol_short((uint)num, bits);

num = ~num;

num = (ushort)MainProcess.rol_short((uint)num, 12);

num = ~num;

num = (ushort)MainProcess.rol_short((uint)num, bits);

return (short)num;

}

I've never seen the use of "~" before so am not sure how to debug.

I've googled the usage and its something to do with flipping the bytes(?)

The error i am getting it:

Cannot implicitly convert type 'int' to 'ushort'. An explicit conversion exists (are you missing a cast?)

can someone help point me in the right direction whats going on and why the error. Do i need some special reference/assembly to use the "~"?

Thanks,

1 Reply

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Vulpes13y ago
Accepted answer
'~' is the bitwise NOT operator in C# and does, as you say, flip all the bits of the operand. No special steps are needed to use it.

Now, if the operand is not an int, it first of all converts it to an int before the bit flipping takes place. It then returns an int.

So, num is of type ushort but ~num is of type int.

Consequently, you get an conversion error when you attempt to assign it back to the ushort variable num because int is 'bigger than' ushort.

So, I'd use a cast to avoid the error:

num = (ushort)~num;