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hotspot/src/share/vm/gc_implementation/shared/mutableSpace.hpp

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+/*
+ * Copyright 2001-2007 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.
+ *
+ */
+
+// A MutableSpace is a subtype of ImmutableSpace that supports the
+// concept of allocation. This includes the concepts that a space may
+// be only partially full, and the querry methods that go with such
+// an assumption.
+//
+// Invariant: (ImmutableSpace +) bottom() <= top() <= end()
+// top() is inclusive and end() is exclusive.
+
+class MutableSpace: public ImmutableSpace {
+  friend class VMStructs;
+ protected:
+  HeapWord* _top;
+
+ public:
+  virtual ~MutableSpace()                  {}
+  MutableSpace()                           { _top = NULL;    }
+  // Accessors
+  HeapWord* top() const                    { return _top;    }
+  virtual void set_top(HeapWord* value)    { _top = value;   }
+
+  HeapWord** top_addr()                    { return &_top; }
+  HeapWord** end_addr()                    { return &_end; }
+
+  virtual void set_bottom(HeapWord* value) { _bottom = value; }
+  virtual void set_end(HeapWord* value)    { _end = value; }
+
+  // Returns a subregion containing all objects in this space.
+  MemRegion used_region() { return MemRegion(bottom(), top()); }
+
+  // Initialization
+  virtual void initialize(MemRegion mr, bool clear_space);
+  virtual void clear();
+  virtual void update() { }
+  virtual void accumulate_statistics() { }
+
+  // Overwrites the unused portion of this space. Note that some collectors
+  // may use this "scratch" space during collections.
+  virtual void mangle_unused_area() {
+    mangle_region(MemRegion(_top, _end));
+  }
+  virtual void ensure_parsability() { }
+
+  void mangle_region(MemRegion mr) {
+    debug_only(Copy::fill_to_words(mr.start(), mr.word_size(), badHeapWord));
+  }
+
+  // Boolean querries.
+  bool is_empty() const              { return used_in_words() == 0; }
+  bool not_empty() const             { return used_in_words() > 0; }
+  bool contains(const void* p) const { return _bottom <= p && p < _end; }
+
+  // Size computations.  Sizes are in bytes.
+  size_t used_in_bytes() const                { return used_in_words() * HeapWordSize; }
+  size_t free_in_bytes() const                { return free_in_words() * HeapWordSize; }
+
+  // Size computations.  Sizes are in heapwords.
+  virtual size_t used_in_words() const                    { return pointer_delta(top(), bottom()); }
+  virtual size_t free_in_words() const                    { return pointer_delta(end(),    top()); }
+  virtual size_t tlab_capacity(Thread* thr) const         { return capacity_in_bytes();            }
+  virtual size_t unsafe_max_tlab_alloc(Thread* thr) const { return free_in_bytes();                }
+
+  // Allocation (return NULL if full)
+  virtual HeapWord* allocate(size_t word_size);
+  virtual HeapWord* cas_allocate(size_t word_size);
+  // Optional deallocation. Used in NUMA-allocator.
+  bool cas_deallocate(HeapWord *obj, size_t size);
+
+  // Iteration.
+  void oop_iterate(OopClosure* cl);
+  void object_iterate(ObjectClosure* cl);
+
+  // Debugging
+  virtual void print() const;
+  virtual void print_on(outputStream* st) const;
+  virtual void print_short() const;
+  virtual void print_short_on(outputStream* st) const;
+  virtual void verify(bool allow_dirty) const;
+};