?
Solved

Using powers of two (?) to determine various access levels

Posted on 2008-10-11
2
Medium Priority
?
259 Views
Last Modified: 2012-05-05
I think there is a way to use powers of two or something similar to determine different levels. For instance, I have different access (different parts of my site), that different people should be able to access. I believe that by using division or modulus division there is a way to have a unique number for each situation. For instance, if someone was able to access areas 1, 3, and 4, the numbers would be divisible by a certain number for each, but not others. Can anyone guide me in the right direction? thanks
0
Comment
Question by:bkaneweb
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 18

Accepted Solution

by:
Hube02 earned 2000 total points
ID: 22695972
I have used a somewhat binary system to determine things like this in the past. For instance, each item is 2 times the last item, so the numeric value of the items run:

1, 2, 4, 8, 16, 31, 64, 128, 256, 1024, etc... (you should recognize this pattern)

Now comes the part where you determine what "BITS" are on and which are off.

Let's call the variable that holds this value "permissions".

So, lets say that the value contained in $permissions is 9. this means that the permission with the value of 1 and the permission with the value of 8 are on.

this line will detect if the "1 BIT is on"

if ($permissions&1)

What it does is this. We do a binary AND of $permissions & 1. If the 1 Bit is on the expression will return an non zero value which evaluates as true. If the 1 Bit is off then 0 is returned and the expression evaluates as false.

The same can be done at any level

if ($permissions&8) will return true (actually 8) if the 4th bit is on and false (0) if it is off.

Hopefully that helps and is at least close to what you are looking for. Let me know if you have any questions.



0
 

Author Closing Comment

by:bkaneweb
ID: 31505381
That worked great...thanks so much for the explanation and example!!!!
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

When we want to run, execute or repeat a statement multiple times, a loop is necessary. This article covers the two types of loops in Python: the while loop and the for loop.
The SignAloud Glove is capable of translating American Sign Language signs into text and audio.
In this seventh video of the Xpdf series, we discuss and demonstrate the PDFfonts utility, which lists all the fonts used in a PDF file. It does this via a command line interface, making it suitable for use in programs, scripts, batch files — any pl…
Six Sigma Control Plans

718 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question