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Overflow Error with XOR operation

Posted on 2003-11-17
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Last Modified: 2013-12-25
Hi everybody,
I wanted to calculate CRC and for this, I had written following code, but it gives me Overflow error. The error come in the line...
mCrc = mCrc Xor mStr         where...
mCrc = "1111111111111111"    (binary of 65535) and
mStr = "10"  (binary of 2)

Could you please help me out of this.
My code is:

Public mCrc
Public mTmpPoly
Public mTmpAsc
Public mTmpBin
Public mtmp

Private Sub Command1_Click()
Text2 = CalcCrc(Text1)
End Sub

Public Function CalcCrc(mStr As String)

mCrc = DecimalToBinary(65535)
mTmpPoly = DecimalToBinary(40961)
mStr = DecimalToBinary(2)
mCrc = mCrc Xor mStr

For i = 0 To 7
    mtmp = Right(mCrc, 1)
    mCrc = "0" & Left(mCrc, Len(mCrc) - 1)
Next

CalcCrc = mCrc
End Function

Sorry, if I have posted question to wrong zone.

thanks alot
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Question by:hiren_d_in
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2 Comments
 
LVL 76

Accepted Solution

by:
GrahamSkan earned 300 total points
ID: 9764125
It looks as if you are unnecessarily converting your binary values to strings.
 2 xor 65535 will give 65533 as it stands
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LVL 15

Expert Comment

by:SRigney
ID: 9764988
By using setting
mCrc = "1111111111111111"    (binary of 65535) and
mStr = "10"  (binary of 2)

This sets the variant to a type of String, and internally it is represented as a string.  If you try using this string in a function that takes an int (such as XOR). Then behind the scenes an implicit CInt is called.

Thus the line
mCrc = mCrc Xor mStr

Is really
mCrc = CInt(mCrc) Xor CInt(mStr)
The Xor does not actually take 2 strings that represent a binary number, it takes 2 numbers and compares them bit by bit.

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