1 /*
   2  * Copyright (c) 2011, 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
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  24 
  25 #ifndef SHARE_VM_OOPS_INSTANCEMIRRORKLASS_HPP
  26 #define SHARE_VM_OOPS_INSTANCEMIRRORKLASS_HPP
  27 
  28 #include "classfile/systemDictionary.hpp"
  29 #include "oops/instanceKlass.hpp"
  30 #include "runtime/handles.hpp"
  31 #include "utilities/macros.hpp"
  32 
  33 class ClassFileParser;
  34 
  35 // An InstanceMirrorKlass is a specialized InstanceKlass for
  36 // java.lang.Class instances.  These instances are special because
  37 // they contain the static fields of the class in addition to the
  38 // normal fields of Class.  This means they are variable sized
  39 // instances and need special logic for computing their size and for
  40 // iteration of their oops.
  41 
  42 
  43 class InstanceMirrorKlass: public InstanceKlass {
  44   friend class VMStructs;
  45   friend class InstanceKlass;
  46 
  47  public:
  48   static const KlassID ID = InstanceMirrorKlassID;
  49 
  50  private:
  51   static int _offset_of_static_fields;
  52 
  53   InstanceMirrorKlass(const ClassFileParser& parser) : InstanceKlass(parser, InstanceKlass::_misc_kind_mirror, ID) {}
  54 
  55  public:
  56   InstanceMirrorKlass() { assert(DumpSharedSpaces || UseSharedSpaces, "only for CDS"); }
  57 
  58   // Casting from Klass*
  59   static InstanceMirrorKlass* cast(Klass* k) {
  60     assert(InstanceKlass::cast(k)->is_mirror_instance_klass(),
  61            "cast to InstanceMirrorKlass");
  62     return static_cast<InstanceMirrorKlass*>(k);
  63   }
  64 
  65   // Returns the size of the instance including the extra static fields.
  66   virtual int oop_size(oop obj) const;
  67 
  68   // Static field offset is an offset into the Heap, should be converted by
  69   // based on UseCompressedOop for traversal
  70   static HeapWord* start_of_static_fields(oop obj) {
  71     return (HeapWord*)(cast_from_oop<intptr_t>(obj) + offset_of_static_fields());
  72   }
  73 
  74   static void init_offset_of_static_fields() {
  75     // Cache the offset of the static fields in the Class instance
  76     assert(_offset_of_static_fields == 0, "once");
  77     _offset_of_static_fields = InstanceMirrorKlass::cast(SystemDictionary::Class_klass())->size_helper() << LogHeapWordSize;
  78   }
  79 
  80   static int offset_of_static_fields() {
  81     return _offset_of_static_fields;
  82   }
  83 
  84   int compute_static_oop_field_count(oop obj);
  85 
  86   // Given a Klass return the size of the instance
  87   int instance_size(Klass* k);
  88 
  89   // allocation
  90   instanceOop allocate_instance(Klass* k, TRAPS);
  91 
  92   // GC specific object visitors
  93   //
  94 #if INCLUDE_PARALLELGC
  95   // Parallel Scavenge
  96   void oop_ps_push_contents(  oop obj, PSPromotionManager* pm);
  97   // Parallel Compact
  98   void oop_pc_follow_contents(oop obj, ParCompactionManager* cm);
  99   void oop_pc_update_pointers(oop obj, ParCompactionManager* cm);
 100 #endif
 101 
 102   // Oop fields (and metadata) iterators
 103   //
 104   // The InstanceMirrorKlass iterators also visit the hidden Klass pointer.
 105 
 106   // Iterate over the static fields.
 107   template <typename T, class OopClosureType>
 108   inline void oop_oop_iterate_statics(oop obj, OopClosureType* closure);
 109 
 110   // Forward iteration
 111   // Iterate over the oop fields and metadata.
 112   template <typename T, class OopClosureType>
 113   inline void oop_oop_iterate(oop obj, OopClosureType* closure);
 114 
 115   // Reverse iteration
 116   // Iterate over the oop fields and metadata.
 117   template <typename T, class OopClosureType>
 118   inline void oop_oop_iterate_reverse(oop obj, OopClosureType* closure);
 119 
 120   // Bounded range iteration
 121   // Iterate over the oop fields and metadata.
 122   template <typename T, class OopClosureType>
 123   inline void oop_oop_iterate_bounded(oop obj, OopClosureType* closure, MemRegion mr);
 124 
 125  private:
 126 
 127   // Iterate over the static fields.
 128   template <typename T, class OopClosureType>
 129   inline void oop_oop_iterate_statics_bounded(oop obj, OopClosureType* closure, MemRegion mr);
 130 };
 131 
 132 #endif // SHARE_VM_OOPS_INSTANCEMIRRORKLASS_HPP