Occasionally it is necessary to invert the bits for a number. Most often, this is part of custom algorithms or checksum calculations. It raises the general question: what’s the easiest way to do this?
“Bit-Flipping” can be done with the -bnot operator like this:
$number = 76 [Convert]::ToString($number,2) $newnumber = -bnot $number [Convert]::ToString($newnumber,2)
The result shows one caveat, though:
1001100 11111111111111111111111110110011
The operator always acts on signed 64-bit numbers. A better approach may be to use the -bxor operator and provide your own bit mask that you want to flip. For a byte, the bit mask would be 0xFF, and for an Int32, it would be 0xFFFFFFFF. Here is an example to flip the bits for a byte. We padded the string representation to 8 characters to make leading zeroes visible:
$number = 76 [Convert]::ToString([byte]$number,2).PadLeft(8, '0') $newnumber = $number -bxor 0xFF [Convert]::ToString($newnumber,2).PadLeft(8, '0')
The result matches:
01001100 10110011
Your learning points:
- PowerShell comes with a rich set of binary operators that all start with -b…
- To invert (flip) bits, you can use -bnot. To flip only some bits, use -bxor with your bit mask
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