Creating Bit Array in Powershell/C# from integers

Question

I'm trying to reverse engineer a game database and have come to a roadblock.

I can load all the tables/fields/records , however I'm stuck when it comes to converting the record values to hex or bits

the values (in game) are as follows: (15 bits) 192 - (10 bits) 20 - (5 bits) 19 - (5 bits) 2

In the db file , it shows 00 C0 - 00 0A - A6 - 00

This is strange , because only the first value (00 C0) is the same in Hex (192)

The other values are different , I'm guessing this is because they are not full bytes (10 and 5 bits respectively) so it must be using a bit array.

This guess is further proven when I change the final value from 2 , to 31. The last 2 values in the db are changed, and the hex string becomes 00 C0 - 00 0A - E6 - 07

So what's the best way to get these 4 integers in to a bit array in PowerShell so I can try to determine what's going on here ? If it is not obvious to any more experienced programmers what is at play here. If required I could also use C# however I'm less experienced.

Thanks

iRon · Accepted Answer · 2021-07-31 12:37:55Z

3

I am not sure what you want to achieve. 5bits words are literally odd. It could be that there is no clear conversion here but something like a hash. Anyways, you could technically count from 0 to 2^35 - 1 and poke that in your game and lookup the result in your database.

Let me give you a few conversion methods:

To bit array:

$Bits = 
    [convert]::ToString(192, 2).PadLeft(15, '0') +
    [convert]::ToString( 20, 2).PadLeft(10, '0') +
    [convert]::ToString( 19, 2).PadLeft( 5, '0') +
    [convert]::ToString(  2, 2).PadLeft( 5, '0')

$Bits
00000001100000000000101001001100010

And back:

if ($Bits -Match '(.{15})(.{10})(.{5})(.{5})') {
    $Matches[1..4].Foreach{ [convert]::ToByte($_, 2) }
}
192
20
19
2

To Int64:

$Int64 = [convert]::ToInt64($Bits, 2)

$Int64
201347682

To bytes:

$Bytes = [BitConverter]::GetBytes($Int64)

[System.BitConverter]::ToString($Bytes)
62-52-00-0C-00-00-00-00

Note that the bytes list is reverse order:

[convert]::ToString(0x62, 2)
1100010

edited Jul 31, 2021 at 12:37

answered Jul 31, 2021 at 10:58

iRon

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1 Comment

Pretend Mower Over a year ago

I'm pretty sure they aren't a hash , however you've given me the commands I was after. Should be able to do some trial and error and work it out. Thanks mate

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