Manipulate new in a class file using BCEL?

[Hans Søndergaard <hs...@VitusBering.dk>]

In the Ravenscar-Java Profile the garbage collector is disabled (Ravenscar-Java is a subset of RTSJ (Real-Time Specification of Java)).

Instead of using the heap when running, a periodic thread has attached some physical memory, called scoped memory, when allocating memory for new objects.

 

This scoped memory works like a stack.

 

I already have access to physical memory.

 

My question is:

 

Is it possible to use BCEL to malipulate the class file (new, newarray, ..) so that a new object is created on a particular address in this scoped memory?

 

A piece of code could look like this:

 

MemoryArea localMem = new Memory(1024);  // allocate 1024 bytes

 

Runnable localLogic = new Runnable()

  {

    public void run()

    {

      ...

      /* if new objects are created in this scope of the run method,

         they must be allocated in localMem

       */

      ...

    }

  };

 

 

for (;;)

{

  localMem.enter(localLogic);

  PeriodicThread.waitForNextPeriod();

}

 

When enter is called any objects created by new are created in localMem (not on the heap). 

When enter goes out of scope, the localMem is re-initialised to empty, - just as a stack works. 

 

Regards

Hans Sondergaard

http://www.cs.aau.dk/ravenscar/

 

Re: Manipulate new in a class file using BCEL?

[Martin Schoeberl <ma...@jopdesign.com>]

>Is it possible to use BCEL to malipulate the class file (new, newarray, ..) so >that a new object is created on a particular 
>address in this scoped memory?


You can substitute each new or newarray in BCEL with e.g., a invokation
of a static method where you implement your scoped memory version of
new.

The main issue is: Do you know the object layout of your target JVM?
The internal structure (handles or not)?

This is not a BCEL property, but it depends on your JVM.

Furthermore you need a low-level (native) function to directly
manupulate the memory (heap).


Martin 


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