1 /*
  2  * Copyright (c) 1997, 2020, 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.
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 23  */
 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 
 31 class Klass;
 32 
 33 // An objArrayOop is an array containing oops.
 34 // Evaluating "String arg[10]" will create an objArrayOop.
 35 
 36 class objArrayOopDesc : public arrayOopDesc {
 37   friend class ObjArrayKlass;
 38   friend class Runtime1;
 39   friend class psPromotionManager;
 40   friend class CSetMarkWordClosure;
 41 
 42   template <class T> T* obj_at_addr(int index) const;
 43 
 44   template <class T>
 45   static ptrdiff_t obj_at_offset(int index) {
 46     return base_offset_in_bytes() + sizeof(T) * index;
 47   }
 48 
 49 private:
 50   // Give size of objArrayOop in HeapWords minus the header
 51   static int array_size(int length) {
 52     const uint OopsPerHeapWord = HeapWordSize/heapOopSize;
 53     assert(OopsPerHeapWord >= 1 && (HeapWordSize % heapOopSize == 0),
 54            "Else the following (new) computation would be in error");
 55     uint res = ((uint)length + OopsPerHeapWord - 1)/OopsPerHeapWord;
 56 #ifdef ASSERT
 57     // The old code is left in for sanity-checking; it'll
 58     // go away pretty soon. XXX
 59     // Without UseCompressedOops, this is simply:
 60     // oop->length() * HeapWordsPerOop;
 61     // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
 62     // The oop elements are aligned up to wordSize
 63     const uint HeapWordsPerOop = heapOopSize/HeapWordSize;
 64     uint old_res;
 65     if (HeapWordsPerOop > 0) {
 66       old_res = length * HeapWordsPerOop;
 67     } else {
 68       old_res = align_up((uint)length, OopsPerHeapWord)/OopsPerHeapWord;
 69     }
 70     assert(res == old_res, "Inconsistency between old and new.");
 71 #endif  // ASSERT
 72     return res;
 73   }
 74 
 75  public:
 76   // Returns the offset of the first element.
 77   static int base_offset_in_bytes() {
 78     return arrayOopDesc::base_offset_in_bytes(T_OBJECT);
 79   }
 80 
 81   // base is the address following the header.
 82   HeapWord* base() const;
 83 
 84   // Accessing
 85   oop obj_at(int index) const;
 86 
 87   void obj_at_put(int index, oop value);
 88 
 89   oop atomic_compare_exchange_oop(int index, oop exchange_value, oop compare_value);
 90 
 91   // Sizing
 92   static int header_size()    { return arrayOopDesc::header_size(T_OBJECT); }
 93   int object_size()           { return object_size(length()); }
 94 
 95   static int object_size(int length) {
 96     // This returns the object size in HeapWords.
 97     uint asz = array_size(length);
 98     uint osz = align_object_size(header_size() + asz);
 99     assert(osz >= asz,   "no overflow");
100     assert((int)osz > 0, "no overflow");
101     return (int)osz;
102   }
103 
104   Klass* element_klass();
105 
106 public:
107   // special iterators for index ranges, returns size of object
108   template <typename OopClosureType>
109   void oop_iterate_range(OopClosureType* blk, int start, int end);
110 };
111 
112 #endif // SHARE_OOPS_OBJARRAYOOP_HPP
--- EOF ---