handle.hpp

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/* Copyright 1996 LongView Technologies L.L.C. $Revision: 1.1 $ */
/* Copyright (c) 2006, Sun Microsystems, Inc.
All rights reserved.

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// Interface for preserving memOops across scavenge/gc in primitives.
// ex.
//    HandleMark hm;
//    Handle saved_oop(obj);
//    // call that might cause scavenge/gc
//    saved_oop.as_klass()->foo();

class HandleMark;
class Handle;

class Handles : AllStatic {
  static int  _top;
  static int  _size;
  static oop  _array[];
  static oop  oop_at(int index);
  static int  push_oop(oop value);
  static int  top() { return _top; }
  static void set_top(int t);

  friend class HandleMark;
  friend class Handle;
 public:
  // Memory managment
  static void oops_do(void f(oop*));
};

class HandleMark {
  int top;
 public:
  HandleMark()  { top = Handles::top(); }
  ~HandleMark() { Handles::set_top(top);}
};

class Handle : StackObj {
  int index;
 public:
  Handle(oop value) {
    index = Handles::push_oop(value);
  }
  
  oop as_oop() {
    return Handles::oop_at(index);
  }

  objArrayOop as_objArray() {
    assert(Handles::oop_at(index)->is_objArray(), "type check");
    return objArrayOop(Handles::oop_at(index));
  }

  memOop as_memOop() {
    assert(Handles::oop_at(index)->is_mem(), "type check");
    return memOop(Handles::oop_at(index));
  }

  klassOop as_klass() {
    assert(Handles::oop_at(index)->is_mem(), "type check");
    return klassOop(Handles::oop_at(index));
  }
};

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