Using random values to define behavior

[Michael Stahl]

Hi - 

Is there any way to define a variable (via "actions" or any other way) to get a random value? 

Here is what I deal with:

- I have code that builds a binary file (a blob of bytes)

- The maximum size of the binary file is limited

- The content of the binary file is comprised of building blocks. 

For example: Say I have three building blocks: A, B, C

Sizeof(A) = 50

Sizeof(B) = 20

Sizeof(C) can be anywhere between 1 and 30

Max file size: 100

So the file can contain: 

AA

 

or BBBBB

or ABB

etc.

Of course it can also contain C, but then I need to have the size of C to know what else can go into the file. For example, if sizeof(C) = 30 then the file can contain (for example):

AC

CBC

ABC

CCC

But if size(C) = 10, then I can also have 

CCCCAC

BCBA

etc.

My goal is to use AltWalker to create many cases of the file content, so I can test the parser for this file. 

I do this by defining a model that goes through edges that "AddA", "AddB", "AddC".  I control the loop of generation by looking at the number of bytes left after each addition of a component. So for example in "AddA" I have a guard: leftover > 49. 

The problem is that in order to cover many cases of C's size, I need a way to randomly set the size of C to different values between 1-30.

 Any ideas? 

Thanks,

Michael 

[Michael Stahl]

Robert Dezmerean provided a solution that works with AltWalker. 

See: 

https://github.com/Robert-96/altwalker-graph-data-demo

Michael