1 /*
   2  * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 #ifndef SHARE_GC_Z_ZPAGETABLEENTRY_HPP
  25 #define SHARE_GC_Z_ZPAGETABLEENTRY_HPP
  26 
  27 #include "gc/z/zBitField.hpp"
  28 #include "memory/allocation.hpp"
  29 
  30 //
  31 // Page table entry layout
  32 // -----------------------
  33 //
  34 //   6
  35 //   3                                                                    1 0
  36 //  +----------------------------------------------------------------------+-+
  37 //  |11111111 11111111 11111111 11111111 11111111 11111111 11111111 1111111|1|
  38 //  +----------------------------------------------------------------------+-+
  39 //  |                                                                      |
  40 //  |                                          0-0 Relocating Flag (1-bit) *
  41 //  |
  42 //  |
  43 //  |
  44 //  * 63-1 Page address (63-bits)
  45 //
  46 
  47 class ZPage;
  48 
  49 class ZPageTableEntry VALUE_OBJ_CLASS_SPEC {
  50 private:
  51   typedef ZBitField<uint64_t, bool,   0, 1>     field_relocating;
  52   typedef ZBitField<uint64_t, ZPage*, 1, 63, 1> field_page;
  53 
  54   uint64_t _entry;
  55 
  56 public:
  57   ZPageTableEntry() :
  58       _entry(0) {}
  59 
  60   ZPageTableEntry(ZPage* page, bool relocating) :
  61       _entry(field_page::encode(page) |
  62              field_relocating::encode(relocating)) {}
  63 
  64   bool relocating() const {
  65     return field_relocating::decode(_entry);
  66   }
  67 
  68   ZPage* page() const {
  69     return field_page::decode(_entry);
  70   }
  71 };
  72 
  73 #endif // SHARE_GC_Z_ZPAGETABLEENTRY_HPP