duke@435: /*
duke@435:  * Copyright 2003 Sun Microsystems, Inc.  All Rights Reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
duke@435:  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435:  * CA 95054 USA or visit www.sun.com if you need additional information or
duke@435:  * have any questions.
duke@435:  *
duke@435:  */
duke@435: 
duke@435: 
duke@435: // Contains two virtual spaces that each can individually span
duke@435: // most of the reserved region but committed parts of which
duke@435: // cannot overlap.
duke@435: //
duke@435: //      +-------+ <--- high_boundary for H
duke@435: //      |       |
duke@435: //      |   H   |
duke@435: //      |       |
duke@435: //      |       |
duke@435: //      |       |
duke@435: //      --------- <--- low for H
duke@435: //      |       |
duke@435: //      ========= <--- low_boundary for H, high_boundary for L
duke@435: //      |       |
duke@435: //      |       |
duke@435: //      |       |
duke@435: //      --------- <--- high for L
duke@435: //      |       |
duke@435: //      |   L   |
duke@435: //      |       |
duke@435: //      |       |
duke@435: //      |       |
duke@435: //      +-------+ <--- low_boundary for L
duke@435: //
duke@435: // Each virtual space in the AdjoiningVirtualSpaces grows and shrink
duke@435: // within its reserved region (between the low_boundary and the
duke@435: // boundary) independently.  If L want to grow above its high_boundary,
duke@435: // then the high_boundary of L and the low_boundary of H must be
duke@435: // moved up consistently.  AdjoiningVirtualSpaces provide the
duke@435: // interfaces for moving the this boundary.
duke@435: 
duke@435: class AdjoiningVirtualSpaces {
duke@435:   // space at the high end and the low end, respectively
duke@435:   PSVirtualSpace*    _high;
duke@435:   PSVirtualSpace*    _low;
duke@435: 
duke@435:   // The reserved space spanned by the two spaces.
duke@435:   ReservedSpace      _reserved_space;
duke@435: 
duke@435:   // The minimum byte size for the low space.  It will not
duke@435:   // be shrunk below this value.
duke@435:   size_t _min_low_byte_size;
duke@435:   // Same for the high space
duke@435:   size_t _min_high_byte_size;
duke@435: 
duke@435:   const size_t _alignment;
duke@435: 
duke@435:  public:
duke@435:   // Allocates two virtual spaces that will be located at the
duke@435:   // high and low ends.  Does no initialization.
duke@435:   AdjoiningVirtualSpaces(ReservedSpace rs,
duke@435:                          size_t min_low_byte_size,
duke@435:                          size_t min_high_byte_size,
duke@435:                          size_t alignment);
duke@435: 
duke@435:   // accessors
duke@435:   PSVirtualSpace* high() { return _high; }
duke@435:   PSVirtualSpace* low()  { return _low; }
duke@435:   ReservedSpace reserved_space() { return _reserved_space; }
duke@435:   size_t min_low_byte_size() { return _min_low_byte_size; }
duke@435:   size_t min_high_byte_size() { return _min_high_byte_size; }
duke@435:   size_t alignment() const { return _alignment; }
duke@435: 
duke@435:   // move boundary between the two spaces up
duke@435:   bool adjust_boundary_up(size_t size_in_bytes);
duke@435:   // and down
duke@435:   bool adjust_boundary_down(size_t size_in_bytes);
duke@435: 
duke@435:   // Maximum byte size for the high space.
duke@435:   size_t high_byte_size_limit() {
duke@435:     return _reserved_space.size() - _min_low_byte_size;
duke@435:   }
duke@435:   // Maximum byte size for the low space.
duke@435:   size_t low_byte_size_limit() {
duke@435:     return _reserved_space.size() - _min_high_byte_size;
duke@435:   }
duke@435: 
duke@435:   // Sets the boundaries for the virtual spaces and commits and
duke@435:   // initial size;
duke@435:   void initialize(size_t max_low_byte_size,
duke@435:                   size_t init_low_byte_size,
duke@435:                   size_t init_high_byte_size);
duke@435: };