RexxActivationStack.hpp

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/******************************************************************************/
/* REXX Kernel                                       RexxActivationStack.hpp  */
/*                                                                            */
/* Primitive Activation Stack Frame Definitions                               */
/*                                                                            */
/******************************************************************************/
 
#ifndef Included_RexxActivationStack
#define Included_RexxActivationStack
 
 
class RexxActivationFrameBuffer : public RexxInternalObject {
    public:
     inline void *operator new(size_t size, void *ptr) { return ptr;};
     inline void  operator delete(void *) { ; }
     inline void  operator delete(void *, void *) { ; }
 
     RexxActivationFrameBuffer() { ; }
     inline RexxActivationFrameBuffer(RESTORETYPE restoreType) { ; }
     void live(size_t);
     void liveGeneral(int reason);
     void flatten(RexxEnvelope *);
 
     inline bool hasCapacity(size_t entries) { return size - next >= entries; }
     inline RexxObject **allocateFrame(size_t entries)
     {
         RexxObject **frame = &buffer[next];
         next += entries;
         return frame;
     }
 
     inline bool contains(RexxObject **frame)
     {
         return frame >= &buffer[0] && frame <= &buffer[size];
     }
 
     inline void releaseFrame(RexxObject **frame)
     {
         next = frame - &buffer[0];
     }
 
     inline void push(RexxActivationFrameBuffer *p)
     {
         previous = p;    // chain this up
     }
 
 
     inline void reset() { next = 0; }    // reset a cached frame buffer
 
     inline RexxActivationFrameBuffer *getPrevious() { return previous; }
 
     static RexxActivationFrameBuffer *newInstance(size_t);
 
protected:
 
 
     size_t size;                        /* size of the buffer (in slots) */
     size_t next;                        /* location of next allocation */
     RexxActivationFrameBuffer *previous;/* previous entry in the stack */
     RexxObject *buffer[1];              /* start of the buffer location */
};
 
 
class RexxActivationStack {
 public:
 
  enum { DefaultFrameBufferSize = 2048 };
 
  inline void *operator new(size_t size, void *ptr) { return ptr;};
  RexxActivationStack() { ; }
  void live(size_t);
  void liveGeneral(int reason);
 
  void init();
  void expandCapacity(size_t entries);
 
  inline void ensureCapacity(size_t entries) { if (!current->hasCapacity(entries)) { expandCapacity(entries); } }
  inline RexxObject **allocateFrame(size_t entries)
  {
      /* make sure we have space first */
      ensureCapacity(entries);
      /* now allocate from the current stack buffer */
      return current->allocateFrame(entries);
  }
  void releaseFrame(RexxObject **frame)
    {
        /* we may be popping back one or more buffers.  We deactivate */
        /* the newer ones */
        while (!current->contains(frame)) {
            /* we need to pop at least one buffer off of the stack */
            RexxActivationFrameBuffer *released = current;
            current = released->getPrevious();
            /* we'll keep at least one buffer around for reuse.  If */
            /* we've already got one in the cache, just let this one */
            /* get GCed. */
            if (unused == OREF_NULL) {
                unused = released;
                unused->reset();   // reset to clean state
            }
        }
 
        /* now back this up to the release point */
        current->releaseFrame(frame);
    }
 
protected:
 
  RexxActivationFrameBuffer *current;
  RexxActivationFrameBuffer *unused;
};
 
 
inline RexxActivationFrameBuffer *new_activationFrameBuffer(size_t s) { return RexxActivationFrameBuffer::newInstance(s); }
 
#endif