--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/parallelScavenge/adjoiningVirtualSpaces.hpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,108 @@
+/*
+ * Copyright 2003 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.
+ *
+ */
+
+
+// Contains two virtual spaces that each can individually span
+// most of the reserved region but committed parts of which
+// cannot overlap.
+//
+//      +-------+ <--- high_boundary for H
+//      |       |
+//      |   H   |
+//      |       |
+//      |       |
+//      |       |
+//      --------- <--- low for H
+//      |       |
+//      ========= <--- low_boundary for H, high_boundary for L
+//      |       |
+//      |       |
+//      |       |
+//      --------- <--- high for L
+//      |       |
+//      |   L   |
+//      |       |
+//      |       |
+//      |       |
+//      +-------+ <--- low_boundary for L
+//
+// Each virtual space in the AdjoiningVirtualSpaces grows and shrink
+// within its reserved region (between the low_boundary and the
+// boundary) independently.  If L want to grow above its high_boundary,
+// then the high_boundary of L and the low_boundary of H must be
+// moved up consistently.  AdjoiningVirtualSpaces provide the
+// interfaces for moving the this boundary.
+
+class AdjoiningVirtualSpaces {
+  // space at the high end and the low end, respectively
+  PSVirtualSpace*    _high;
+  PSVirtualSpace*    _low;
+
+  // The reserved space spanned by the two spaces.
+  ReservedSpace      _reserved_space;
+
+  // The minimum byte size for the low space.  It will not
+  // be shrunk below this value.
+  size_t _min_low_byte_size;
+  // Same for the high space
+  size_t _min_high_byte_size;
+
+  const size_t _alignment;
+
+ public:
+  // Allocates two virtual spaces that will be located at the
+  // high and low ends.  Does no initialization.
+  AdjoiningVirtualSpaces(ReservedSpace rs,
+                         size_t min_low_byte_size,
+                         size_t min_high_byte_size,
+                         size_t alignment);
+
+  // accessors
+  PSVirtualSpace* high() { return _high; }
+  PSVirtualSpace* low()  { return _low; }
+  ReservedSpace reserved_space() { return _reserved_space; }
+  size_t min_low_byte_size() { return _min_low_byte_size; }
+  size_t min_high_byte_size() { return _min_high_byte_size; }
+  size_t alignment() const { return _alignment; }
+
+  // move boundary between the two spaces up
+  bool adjust_boundary_up(size_t size_in_bytes);
+  // and down
+  bool adjust_boundary_down(size_t size_in_bytes);
+
+  // Maximum byte size for the high space.
+  size_t high_byte_size_limit() {
+    return _reserved_space.size() - _min_low_byte_size;
+  }
+  // Maximum byte size for the low space.
+  size_t low_byte_size_limit() {
+    return _reserved_space.size() - _min_high_byte_size;
+  }
+
+  // Sets the boundaries for the virtual spaces and commits and
+  // initial size;
+  void initialize(size_t max_low_byte_size,
+                  size_t init_low_byte_size,
+                  size_t init_high_byte_size);
+};