[Solved] Registry read out signed integer

[Simpel]

Hi,

I wondered why negative integers I wrote into registry (e.g. negative x-coordinates of a gui if using two monitors and the right one is the main one) wouldn't return right when reading. Now I know: it is saved as an unsigned integer (without algebraic sign). So here is a snippet that is changing unsigned to signed integer:

Global Const $g_sRegKey = "HKEY_CURRENT_USER\Software\" & @ScriptName ; path to registry

RegWrite($g_sRegKey, "Value", "REG_DWORD", -2147483647) ; write some negative integer into registry; -2147483647 highest possible negative integer , 2147483648 highest possible positive integer if talking of 32bit

Local $sValue = RegRead($g_sRegKey, "Value") ; read out registry
ConsoleWrite("Value: " & $sValue & @CRLF) ; show real value in console

Local $sResult = _SignedInteger($sValue) ; change to signed value
ConsoleWrite("Result: " & $sResult & @CRLF) ; and show it in console


Func _SignedInteger($iUnsignedInteger)
    Local $iSignedInteger
    If $iUnsignedInteger > (2^31) Then ; then it means a negative integer
        $iSignedInteger = $iUnsignedInteger - (2^32)
    Else
        $iSignedInteger = $iUnsignedInteger
    EndIf
    Return $iSignedInteger
EndFunc

It took me some time to find out the problem and so I hope I can help somebody with this.

Regards, Conrad

Edited April 25, 2019 by Simpel
[Solved]

[jchd]

13 hours ago, Simpel said:

-2147483647 highest possible negative integer , 2147483648 highest possible positive integer if talking of 32bit

Wrong values: it's [-2147483648, 2147483647] for an Int32.

Besides, under x64, it indeed seems that while the registry correctly records the binary value of the DWORD, retrieving it yields an Int64 under AutoIt.

Things behave correctly if the value is a REG_QWORD (Int64).

[Simpel]

@jchd I have to disagree. When I try my example and change the value I write to registry to -2147483648 it will return +2147483648. Writing 2147483648 returns +2147483648.

Thanks for the other info. So next time I try REG_QWORD.

Regards, Conrad

[jchd]

I was just noting that the range of a 2's complement 32-bit integer is [-2147483648, 2147483647].

Since 2147483648 exceeds the signed 32-bit range, it's quite natural that it stores and retrieves a 64-bit value identical to the input. That's an indication that the registry datatype (e.g. DWORD vs QWORD) isn't as strict as one could imagine.