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