Permissions hell

[CryoEnix]

Hey guys, long time no speak - I've got a bit of an issue here, but I'm sure one of you will be able to help...

 

 

Lets say that I've got several applications with a number of permissions allowed for each, stored within a single long data type:

 

 

App A is worth 1

App B is worth 2

App C is worth 4

App D is worth 8

App E is worth 16

App F is worth 32

 

And so on, ad infinitum.

 

Now the problem is, say if I need to know if the user has an access code of 45, how can I calculate whether he has access to application C or not - I know there's an algorithm for it, I just can't put my finger on it...

[CryoEnix]

Sorry for not clarifying, but I'm working in C# for this one - although the algorithm itself shouldn't be too difficult to translate should it be in any other language (just no PERL please ^^)

[mandelbrot]

Hi Cryo,

 

 

Look up the <Flags()> attribute for enumerations - very very useful...

<Flags()> _
Public Enum Apps
   None = 0
   AppA = 1
   AppB = 2
   AppC = 4
   AppD = 8
End Enum

After this, you simply need to set the property to point to this enumeration and use logical operators to manage the checking...

Public Class MyApp
   ...
   Private _AppType As Apps
   ...
   Public Property AppType() As Apps
       Get
           Return _AppType
       End Get
       Set(ByVal value As Apps)
           _AppType = value
       End Set
   End Property
   ...
End Class
...
...
   If (thisApp.AppType And Apps.AppA) = Apps.AppA Then
       'Do your stuff...
       ...
   End If

Does that help?

 

 

Paul.

[CryoEnix]

Cheers paul, I have that in VB, but the C# port doesn't seem to like this - is disagrees with the double ampersand. Any ideas?

 

if ((thisApp.AppType && Apps.AppA) == Apps.AppA ){//'Do your stuff...        ...   
}

[mandelbrot]

I'm afraid I'm not sure on that. It may be a casting problem, but my C# isn't that hot...

 

Let me have a look and I'll get back to you.

 

 

Paul.

[CryoEnix]

It's alright Paul, I've figured it out. Turns out that the double ampersand is just for boolean comparisons - a single is for binary, which is why it didn't work. It seems that the Basic 'And' statement does either, depending on the situation.

 

Thanks anyway!

[mandelbrot]

You're quite welcome, Cryo, and thanks for highlighting that - I'll remember it for when I do (eventually) switch to C#.