1 /*
   2  * Copyright (c) 1997, 2016, 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 #include "utilities/align.hpp"
  31 
  32 // An objArrayOop is an array containing oops.
  33 // Evaluating "String arg[10]" will create an objArrayOop.
  34 
  35 class objArrayOopDesc : public arrayOopDesc {
  36   friend class ObjArrayKlass;
  37   friend class Runtime1;
  38   friend class psPromotionManager;
  39   friend class CSetMarkOopClosure;
  40   friend class G1ParScanPartialArrayClosure;
  41 
  42   template <class T> T* obj_at_addr(int index) const {
  43     assert(is_within_bounds(index), "index out of bounds");
  44     return &((T*)base())[index];
  45   }
  46 
  47 private:
  48   // Give size of objArrayOop in HeapWords minus the header
  49   static int array_size(int length) {
  50     const uint OopsPerHeapWord = HeapWordSize/heapOopSize;
  51     assert(OopsPerHeapWord >= 1 && (HeapWordSize % heapOopSize == 0),
  52            "Else the following (new) computation would be in error");
  53     uint res = ((uint)length + OopsPerHeapWord - 1)/OopsPerHeapWord;
  54 #ifdef ASSERT
  55     // The old code is left in for sanity-checking; it'll
  56     // go away pretty soon. XXX
  57     // Without UseCompressedOops, this is simply:
  58     // oop->length() * HeapWordsPerOop;
  59     // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
  60     // The oop elements are aligned up to wordSize
  61     const uint HeapWordsPerOop = heapOopSize/HeapWordSize;
  62     uint old_res;
  63     if (HeapWordsPerOop > 0) {
  64       old_res = length * HeapWordsPerOop;
  65     } else {
  66       old_res = align_up((uint)length, OopsPerHeapWord)/OopsPerHeapWord;
  67     }
  68     assert(res == old_res, "Inconsistency between old and new.");
  69 #endif  // ASSERT
  70     return res;
  71   }
  72 
  73  public:
  74   // Returns the offset of the first element.
  75   static int base_offset_in_bytes() {
  76     return arrayOopDesc::base_offset_in_bytes(T_OBJECT);
  77   }
  78 
  79   // base is the address following the header.
  80   HeapWord* base() const      { return (HeapWord*) arrayOopDesc::base(T_OBJECT); }
  81 
  82   // Accessing
  83   oop obj_at(int index) const;
  84 
  85   void inline obj_at_put(int index, oop value);
  86 
  87   oop atomic_compare_exchange_oop(int index, oop exchange_value, oop compare_value);
  88 
  89   // Sizing
  90   static int header_size()    { return arrayOopDesc::header_size(T_OBJECT); }
  91   int object_size()           { return object_size(length()); }
  92 
  93   static int object_size(int length) {
  94     // This returns the object size in HeapWords.
  95     uint asz = array_size(length);
  96     uint osz = align_object_size(header_size() + asz);
  97     assert(osz >= asz,   "no overflow");
  98     assert((int)osz > 0, "no overflow");
  99     return (int)osz;
 100   }
 101 
 102   // special iterators for index ranges, returns size of object
 103 #define ObjArrayOop_OOP_ITERATE_DECL(OopClosureType, nv_suffix)     \
 104   void oop_iterate_range(OopClosureType* blk, int start, int end);
 105 
 106   ALL_OOP_OOP_ITERATE_CLOSURES_1(ObjArrayOop_OOP_ITERATE_DECL)
 107   ALL_OOP_OOP_ITERATE_CLOSURES_2(ObjArrayOop_OOP_ITERATE_DECL)
 108 };
 109 
 110 #endif // SHARE_VM_OOPS_OBJARRAYOOP_HPP