--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/memory/metablock.hpp	Tue Sep 18 23:35:42 2012 -0700
@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2012, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+#ifndef SHARE_VM_MEMORY_METABLOCK_HPP
+#define SHARE_VM_MEMORY_METABLOCK_HPP
+
+// Metablock are the unit of allocation from a Chunk.  It is initialized
+// with the size of the requested allocation.  That size is overwritten
+// once the allocation returns.
+//
+// A Metablock may be reused by its SpaceManager but are never moved between
+// SpaceManagers.  There is no explicit link to the Metachunk
+// from which it was allocated.  Metablock may be deallocated and
+// put on a freelist but the space is never freed, rather
+// the Metachunk it is a part of will be deallocated when it's
+// associated class loader is collected.
+
+class Metablock VALUE_OBJ_CLASS_SPEC {
+  friend class VMStructs;
+ private:
+  // Used to align the allocation (see below).
+  union block_t {
+    void* _data[3];
+    struct header_t {
+      size_t _word_size;
+      Metablock* _next;
+      Metablock* _prev;
+    } _header;
+  } _block;
+  static size_t _min_block_byte_size;
+  static size_t _overhead;
+
+  typedef union block_t Block;
+  typedef struct header_t Header;
+  const Block* block() const { return &_block; }
+  const Block::header_t* header() const { return &(block()->_header); }
+ public:
+
+  static Metablock* initialize(MetaWord* p, size_t word_size);
+
+  // This places the body of the block at a 2 word boundary
+  // because every block starts on a 2 word boundary.  Work out
+  // how to make the body on a 2 word boundary if the block
+  // starts on a arbitrary boundary.  JJJ
+
+  size_t word_size() const  { return header()->_word_size; }
+  void set_word_size(size_t v) { _block._header._word_size = v; }
+  size_t size() const volatile { return _block._header._word_size; }
+  void set_size(size_t v) { _block._header._word_size = v; }
+  Metablock* next() const { return header()->_next; }
+  void set_next(Metablock* v) { _block._header._next = v; }
+  Metablock* prev() const { return header()->_prev; }
+  void set_prev(Metablock* v) { _block._header._prev = v; }
+
+  static size_t min_block_byte_size() { return _min_block_byte_size; }
+  static size_t overhead() { return _overhead; }
+
+  bool is_free()                 { return header()->_word_size != 0; }
+  void clear_next()              { set_next(NULL); }
+  void link_prev(Metablock* ptr) { set_prev(ptr); }
+  uintptr_t* end()              { return ((uintptr_t*) this) + size(); }
+  bool cantCoalesce() const     { return false; }
+  void link_next(Metablock* ptr) { set_next(ptr); }
+  void link_after(Metablock* ptr){
+    link_next(ptr);
+    if (ptr != NULL) ptr->link_prev(this);
+  }
+
+  // Should not be needed in a free list of Metablocks
+  void markNotFree()            { ShouldNotReachHere(); }
+
+  // Debug support
+#ifdef ASSERT
+  void* prev_addr() const { return (void*)&_block._header._prev; }
+  void* next_addr() const { return (void*)&_block._header._next; }
+  void* size_addr() const { return (void*)&_block._header._word_size; }
+#endif
+  bool verify_chunk_in_free_list(Metablock* tc) const { return true; }
+  bool verify_par_locked() { return true; }
+
+  void assert_is_mangled() const {/* Don't check "\*/}
+};
+#endif // SHARE_VM_MEMORY_METABLOCK_HPP