1 /*
   2  * Copyright (c) 1997, 2015, 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 
  25 #ifndef SHARE_VM_OOPS_OBJARRAYOOP_HPP
  26 #define SHARE_VM_OOPS_OBJARRAYOOP_HPP
  27 
  28 #include "gc/shared/specialized_oop_closures.hpp"
  29 #include "oops/arrayOop.hpp"
  30 
  31 // An objArrayOop is an array containing oops.
  32 // Evaluating "String arg[10]" will create an objArrayOop.
  33 
  34 class objArrayOopDesc : public arrayOopDesc {
  35   friend class ObjArrayKlass;
  36   friend class Runtime1;
  37   friend class psPromotionManager;
  38   friend class CSetMarkOopClosure;
  39   friend class G1ParScanPartialArrayClosure;
  40 
  41   template <class T> T* obj_at_addr(int index) const {
  42     assert(is_within_bounds(index), "index out of bounds");
  43     return &((T*)base())[index];
  44   }
  45 
  46 private:
  47   // Give size of objArrayOop in HeapWords minus the header
  48   static int array_size(int length) {
  49     const uint OopsPerHeapWord = HeapWordSize/heapOopSize;
  50     assert(OopsPerHeapWord >= 1 && (HeapWordSize % heapOopSize == 0),
  51            "Else the following (new) computation would be in error");
  52     uint res = ((uint)length + OopsPerHeapWord - 1)/OopsPerHeapWord;
  53 #ifdef ASSERT
  54     // The old code is left in for sanity-checking; it'll
  55     // go away pretty soon. XXX
  56     // Without UseCompressedOops, this is simply:
  57     // oop->length() * HeapWordsPerOop;
  58     // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
  59     // The oop elements are aligned up to wordSize
  60     const uint HeapWordsPerOop = heapOopSize/HeapWordSize;
  61     uint old_res;
  62     if (HeapWordsPerOop > 0) {
  63       old_res = length * HeapWordsPerOop;
  64     } else {
  65       old_res = align_size_up((uint)length, OopsPerHeapWord)/OopsPerHeapWord;
  66     }
  67     assert(res == old_res, "Inconsistency between old and new.");
  68 #endif  // ASSERT
  69     return res;
  70   }
  71 
  72  public:
  73   // Returns the offset of the first element.
  74   static int base_offset_in_bytes() {
  75     return arrayOopDesc::base_offset_in_bytes(T_OBJECT);
  76   }
  77 
  78   // base is the address following the header.
  79   HeapWord* base() const      { return (HeapWord*) arrayOopDesc::base(T_OBJECT); }
  80 
  81   // Accessing
  82   oop obj_at(int index) const;
  83 
  84   void obj_at_put(int index, oop value) {
  85     if (UseCompressedOops) {
  86       oop_store(obj_at_addr<narrowOop>(index), value);
  87     } else {
  88       oop_store(obj_at_addr<oop>(index), value);
  89     }
  90   }
  91 
  92   oop atomic_compare_exchange_oop(int index, oop exchange_value, oop compare_value);
  93 
  94   // Sizing
  95   static int header_size()    { return arrayOopDesc::header_size(T_OBJECT); }
  96   int object_size()           { return object_size(length()); }
  97 
  98   static int object_size(int length) {
  99     // This returns the object size in HeapWords.
 100     uint asz = array_size(length);
 101     uint osz = align_object_size(header_size() + asz);
 102     assert(osz >= asz,   "no overflow");
 103     assert((int)osz > 0, "no overflow");
 104     return (int)osz;
 105   }
 106 
 107   // special iterators for index ranges, returns size of object
 108 #define ObjArrayOop_OOP_ITERATE_DECL(OopClosureType, nv_suffix)     \
 109   void oop_iterate_range(OopClosureType* blk, int start, int end);
 110 
 111   ALL_OOP_OOP_ITERATE_CLOSURES_1(ObjArrayOop_OOP_ITERATE_DECL)
 112   ALL_OOP_OOP_ITERATE_CLOSURES_2(ObjArrayOop_OOP_ITERATE_DECL)
 113 };
 114 
 115 #endif // SHARE_VM_OOPS_OBJARRAYOOP_HPP