rSet.hpp

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/* Copyright 1994 - 1996 LongView Technologies L.L.C. $Revision: 1.14 $ */
/* Copyright (c) 2006, Sun Microsystems, Inc.
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// remembered set for GC, implemented as a card marking byte array with one byte / card
// Card size is 512 bytes
// NB: Card size must be >= 512 because of the offset_array in oldspace

const int card_shift = 9;                       // wired in to scavenge_contents
const int card_size  = 1 << card_shift;
const int card_size_in_oops = card_size / oopSize;

class rSet: public CHeapObj {
  friend class oldSpace;
  friend class oldGeneration;
  friend class SetOopClosure;

 private:
  char*    low_boundary;        // duplicate of old_gen var so byte_for can be inlined
  char*    high_boundary;
  char     byte_map[1];         // size is a lie
  
  // friend void oldSpace::switch_pointers_by_card(oop, oop);
  char* byte_for(void *p) const { return (char*)&byte_map[int((char*)p - low_boundary) >> card_shift]; }
  oop*  oop_for(char* p) const  { return (oop*)(low_boundary  +  ((p - byte_map) <<  card_shift)); }

  friend oop*  card_for(oop* p) { return (oop*)(int(p) & ~(card_size - 1)); }
  
  inline char* byte_map_end() const;
 
 public:
  int byte_map_size() const     { return (high_boundary - low_boundary) / card_size; }
  rSet();
  void* operator new(size_t size);
  
  inline void clear();
  char* byte_map_base() const   { return byte_for(NULL); }
  void record_store(void* p)    { *byte_for(p) = 0; }
  bool is_dirty(void* p) const  { return *byte_for(p) == 0; }

  // Tells is any card for obj is dirty
  bool is_object_dirty(memOop obj);

  void  scavenge_contents(oldSpace* s);
  char* scavenge_contents(oldSpace* s, char* begin, char* limit);
  bool verify(bool postScavenge);

  void print_set_for_space(oldSpace* sp);
  void print_set_for_object(memOop obj);

  // Returns the number of dirty pages in an old segment
  int number_of_dirty_pages_in(oldSpace* sp);

  // Return the number of pages with dirty objects.
  int number_of_pages_with_dirty_objects_in(oldSpace* sp);

  // Operations used during garbage collection
  void set_size(memOop obj, int size);
  int  get_size(memOop obj);

 private:
  void fixup(char *start, char *end);
  void clear(char *start, char *end);
  rSet(rSet *old, char *start, char *end);
  bool has_page_dirty_objects(oldSpace* sp, char* page);
};

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