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