--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/memory/metachunk.cpp	Thu Nov 29 10:09:04 2012 -0800
@@ -0,0 +1,117 @@
+/*
+ * 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.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "memory/allocation.hpp"
+#include "memory/metachunk.hpp"
+#include "utilities/copy.hpp"
+#include "utilities/debug.hpp"
+
+//
+// Future modification
+//
+// The Metachunk can conceivable be replaced by the Chunk in
+// allocation.hpp.  Note that the latter Chunk is the space for
+// allocation (allocations from the chunk are out of the space in
+// the Chunk after the header for the Chunk) where as Metachunks
+// point to space in a VirtualSpace.  To replace Metachunks with
+// Chunks, change Chunks so that they can be allocated out of a VirtualSpace.
+
+const size_t metadata_chunk_initialize = 0xf7f7f7f7;
+
+size_t Metachunk::_overhead =
+  Chunk::aligned_overhead_size(sizeof(Metachunk)) / BytesPerWord;
+
+// Metachunk methods
+
+Metachunk* Metachunk::initialize(MetaWord* ptr, size_t word_size) {
+  // Set bottom, top, and end.  Allow space for the Metachunk itself
+  Metachunk* chunk = (Metachunk*) ptr;
+
+  MetaWord* chunk_bottom = ptr + _overhead;
+  chunk->set_bottom(ptr);
+  chunk->set_top(chunk_bottom);
+  MetaWord* chunk_end = ptr + word_size;
+  assert(chunk_end > chunk_bottom, "Chunk must be too small");
+  chunk->set_end(chunk_end);
+  chunk->set_next(NULL);
+  chunk->set_word_size(word_size);
+#ifdef ASSERT
+  size_t data_word_size = pointer_delta(chunk_end, chunk_bottom, sizeof(MetaWord));
+  Copy::fill_to_words((HeapWord*) chunk_bottom, data_word_size, metadata_chunk_initialize);
+#endif
+  return chunk;
+}
+
+
+MetaWord* Metachunk::allocate(size_t word_size) {
+  MetaWord* result = NULL;
+  // If available, bump the pointer to allocate.
+  if (free_word_size() >= word_size) {
+    result = _top;
+    _top = _top + word_size;
+  }
+  return result;
+}
+
+// _bottom points to the start of the chunk including the overhead.
+size_t Metachunk::used_word_size() {
+  return pointer_delta(_top, _bottom, sizeof(MetaWord));
+}
+
+size_t Metachunk::free_word_size() {
+  return pointer_delta(_end, _top, sizeof(MetaWord));
+}
+
+size_t Metachunk::capacity_word_size() {
+  return pointer_delta(_end, _bottom, sizeof(MetaWord));
+}
+
+void Metachunk::print_on(outputStream* st) const {
+  st->print_cr("Metachunk:"
+               " bottom " PTR_FORMAT " top " PTR_FORMAT
+               " end " PTR_FORMAT " size " SIZE_FORMAT,
+               bottom(), top(), end(), word_size());
+}
+
+#ifndef PRODUCT
+void Metachunk::mangle() {
+  // Mangle the payload of the chunk and not the links that
+  // maintain list of chunks.
+  HeapWord* start = (HeapWord*)(bottom() + overhead());
+  size_t word_size = capacity_word_size() - overhead();
+  Copy::fill_to_words(start, word_size, metadata_chunk_initialize);
+}
+#endif // PRODUCT
+
+void Metachunk::verify() {
+#ifdef ASSERT
+  // Cannot walk through the blocks unless the blocks have
+  // headers with sizes.
+  assert(_bottom <= _top &&
+         _top <= _end,
+         "Chunk has been smashed");
+#endif
+  return;
+}