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hotspot/src/share/vm/memory/iterator.hpp

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+/*
+ * Copyright 1997-2006 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// The following classes are C++ `closures` for iterating over objects, roots and spaces
+
+class ReferenceProcessor;
+
+// OopClosure is used for iterating through roots (oop*)
+
+class OopClosure : public StackObj {
+ public:
+  ReferenceProcessor* _ref_processor;
+  OopClosure(ReferenceProcessor* rp) : _ref_processor(rp) { }
+  OopClosure() : _ref_processor(NULL) { }
+  virtual void do_oop(oop* o) = 0;
+  virtual void do_oop_v(oop* o) { do_oop(o); }
+
+  // In support of post-processing of weak links of KlassKlass objects;
+  // see KlassKlass::oop_oop_iterate().
+  virtual const bool should_remember_klasses() const { return false;    }
+  virtual void remember_klass(Klass* k) { /* do nothing */ }
+
+  // If "true", invoke on nmethods (when scanning compiled frames).
+  virtual const bool do_nmethods() const { return false; }
+
+  // The methods below control how object iterations invoking this closure
+  // should be performed:
+
+  // If "true", invoke on header klass field.
+  bool do_header() { return true; } // Note that this is non-virtual.
+  // Controls how prefetching is done for invocations of this closure.
+  Prefetch::style prefetch_style() { // Note that this is non-virtual.
+    return Prefetch::do_none;
+  }
+};
+
+// ObjectClosure is used for iterating through an object space
+
+class ObjectClosure : public StackObj {
+ public:
+  // Called for each object.
+  virtual void do_object(oop obj) = 0;
+};
+
+
+class BoolObjectClosure : public ObjectClosure {
+ public:
+  virtual bool do_object_b(oop obj) = 0;
+};
+
+// Applies an oop closure to all ref fields in objects iterated over in an
+// object iteration.
+class ObjectToOopClosure: public ObjectClosure {
+  OopClosure* _cl;
+public:
+  void do_object(oop obj);
+  ObjectToOopClosure(OopClosure* cl) : _cl(cl) {}
+};
+
+// A version of ObjectClosure with "memory" (see _previous_address below)
+class UpwardsObjectClosure: public BoolObjectClosure {
+  HeapWord* _previous_address;
+ public:
+  UpwardsObjectClosure() : _previous_address(NULL) { }
+  void set_previous(HeapWord* addr) { _previous_address = addr; }
+  HeapWord* previous()              { return _previous_address; }
+  // A return value of "true" can be used by the caller to decide
+  // if this object's end should *NOT* be recorded in
+  // _previous_address above.
+  virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
+};
+
+// A version of ObjectClosure that is expected to be robust
+// in the face of possibly uninitialized objects.
+class ObjectClosureCareful : public ObjectClosure {
+ public:
+  virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
+  virtual size_t do_object_careful(oop p) = 0;
+};
+
+// The following are used in CompactibleFreeListSpace and
+// ConcurrentMarkSweepGeneration.
+
+// Blk closure (abstract class)
+class BlkClosure : public StackObj {
+ public:
+  virtual size_t do_blk(HeapWord* addr) = 0;
+};
+
+// A version of BlkClosure that is expected to be robust
+// in the face of possibly uninitialized objects.
+class BlkClosureCareful : public BlkClosure {
+ public:
+  size_t do_blk(HeapWord* addr) {
+    guarantee(false, "call do_blk_careful instead");
+    return 0;
+  }
+  virtual size_t do_blk_careful(HeapWord* addr) = 0;
+};
+
+// SpaceClosure is used for iterating over spaces
+
+class Space;
+class CompactibleSpace;
+
+class SpaceClosure : public StackObj {
+ public:
+  // Called for each space
+  virtual void do_space(Space* s) = 0;
+};
+
+class CompactibleSpaceClosure : public StackObj {
+ public:
+  // Called for each compactible space
+  virtual void do_space(CompactibleSpace* s) = 0;
+};
+
+
+
+// MonitorClosure is used for iterating over monitors in the monitors cache
+
+class ObjectMonitor;
+
+class MonitorClosure : public StackObj {
+ public:
+  // called for each monitor in cache
+  virtual void do_monitor(ObjectMonitor* m) = 0;
+};
+
+// A closure that is applied without any arguments.
+class VoidClosure : public StackObj {
+ public:
+  // I would have liked to declare this a pure virtual, but that breaks
+  // in mysterious ways, for unknown reasons.
+  virtual void do_void();
+};
+
+
+// YieldClosure is intended for use by iteration loops
+// to incrementalize their work, allowing interleaving
+// of an interruptable task so as to allow other
+// threads to run (which may not otherwise be able to access
+// exclusive resources, for instance). Additionally, the
+// closure also allows for aborting an ongoing iteration
+// by means of checking the return value from the polling
+// call.
+class YieldClosure : public StackObj {
+  public:
+   virtual bool should_return() = 0;
+};
+
+// Abstract closure for serializing data (read or write).
+
+class SerializeOopClosure : public OopClosure {
+public:
+  // Return bool indicating whether closure implements read or write.
+  virtual bool reading() const = 0;
+
+  // Read/write the int pointed to by i.
+  virtual void do_int(int* i) = 0;
+
+  // Read/write the size_t pointed to by i.
+  virtual void do_size_t(size_t* i) = 0;
+
+  // Read/write the void pointer pointed to by p.
+  virtual void do_ptr(void** p) = 0;
+
+  // Read/write the HeapWord pointer pointed to be p.
+  virtual void do_ptr(HeapWord** p) = 0;
+
+  // Read/write the region specified.
+  virtual void do_region(u_char* start, size_t size) = 0;
+
+  // Check/write the tag.  If reading, then compare the tag against
+  // the passed in value and fail is they don't match.  This allows
+  // for verification that sections of the serialized data are of the
+  // correct length.
+  virtual void do_tag(int tag) = 0;
+};