src/share/vm/oops/objArrayOop.hpp

Print this page




  28 #include "oops/arrayOop.hpp"
  29 
  30 // An objArrayOop is an array containing oops.
  31 // Evaluating "String arg[10]" will create an objArrayOop.
  32 
  33 class objArrayOopDesc : public arrayOopDesc {
  34   friend class objArrayKlass;
  35   friend class Runtime1;
  36   friend class psPromotionManager;
  37   friend class CSetMarkOopClosure;
  38   friend class G1ParScanPartialArrayClosure;
  39 
  40   template <class T> T* obj_at_addr(int index) const {
  41     assert(is_within_bounds(index), "index out of bounds");
  42     return &((T*)base())[index];
  43   }
  44 
  45 private:
  46   // Give size of objArrayOop in HeapWords minus the header
  47   static int array_size(int length) {
  48     const int OopsPerHeapWord = HeapWordSize/heapOopSize;
  49     assert(OopsPerHeapWord >= 1 && (HeapWordSize % heapOopSize == 0),
  50            "Else the following (new) computation would be in error");

  51 #ifdef ASSERT
  52     // The old code is left in for sanity-checking; it'll
  53     // go away pretty soon. XXX
  54     // Without UseCompressedOops, this is simply:
  55     // oop->length() * HeapWordsPerOop;
  56     // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
  57     // The oop elements are aligned up to wordSize
  58     const int HeapWordsPerOop = heapOopSize/HeapWordSize;
  59     int old_res;
  60     if (HeapWordsPerOop > 0) {
  61       old_res = length * HeapWordsPerOop;
  62     } else {
  63       old_res = align_size_up(length, OopsPerHeapWord)/OopsPerHeapWord;
  64     }
  65 #endif  // ASSERT
  66     int res = ((uint)length + OopsPerHeapWord - 1)/OopsPerHeapWord;
  67     assert(res == old_res, "Inconsistency between old and new.");

  68     return res;
  69   }
  70 
  71  public:
  72   // Returns the offset of the first element.
  73   static int base_offset_in_bytes() {
  74     return arrayOopDesc::base_offset_in_bytes(T_OBJECT);
  75   }
  76 
  77   // base is the address following the header.
  78   HeapWord* base() const      { return (HeapWord*) arrayOopDesc::base(T_OBJECT); }
  79 
  80   // Accessing
  81   oop obj_at(int index) const {
  82     // With UseCompressedOops decode the narrow oop in the objArray to an
  83     // uncompressed oop.  Otherwise this is simply a "*" operator.
  84     if (UseCompressedOops) {
  85       return load_decode_heap_oop(obj_at_addr<narrowOop>(index));
  86     } else {
  87       return load_decode_heap_oop(obj_at_addr<oop>(index));




  28 #include "oops/arrayOop.hpp"
  29 
  30 // An objArrayOop is an array containing oops.
  31 // Evaluating "String arg[10]" will create an objArrayOop.
  32 
  33 class objArrayOopDesc : public arrayOopDesc {
  34   friend class objArrayKlass;
  35   friend class Runtime1;
  36   friend class psPromotionManager;
  37   friend class CSetMarkOopClosure;
  38   friend class G1ParScanPartialArrayClosure;
  39 
  40   template <class T> T* obj_at_addr(int index) const {
  41     assert(is_within_bounds(index), "index out of bounds");
  42     return &((T*)base())[index];
  43   }
  44 
  45 private:
  46   // Give size of objArrayOop in HeapWords minus the header
  47   static int array_size(int length) {
  48     const uint OopsPerHeapWord = HeapWordSize/heapOopSize;
  49     assert(OopsPerHeapWord >= 1 && (HeapWordSize % heapOopSize == 0),
  50            "Else the following (new) computation would be in error");
  51     uint res = ((uint)length + OopsPerHeapWord - 1)/OopsPerHeapWord;
  52 #ifdef ASSERT
  53     // The old code is left in for sanity-checking; it'll
  54     // go away pretty soon. XXX
  55     // Without UseCompressedOops, this is simply:
  56     // oop->length() * HeapWordsPerOop;
  57     // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
  58     // The oop elements are aligned up to wordSize
  59     const uint HeapWordsPerOop = heapOopSize/HeapWordSize;
  60     uint old_res;
  61     if (HeapWordsPerOop > 0) {
  62       old_res = length * HeapWordsPerOop;
  63     } else {
  64       old_res = align_size_up((uint)length, OopsPerHeapWord)/OopsPerHeapWord;
  65     }


  66     assert(res == old_res, "Inconsistency between old and new.");
  67 #endif  // ASSERT
  68     return res;
  69   }
  70 
  71  public:
  72   // Returns the offset of the first element.
  73   static int base_offset_in_bytes() {
  74     return arrayOopDesc::base_offset_in_bytes(T_OBJECT);
  75   }
  76 
  77   // base is the address following the header.
  78   HeapWord* base() const      { return (HeapWord*) arrayOopDesc::base(T_OBJECT); }
  79 
  80   // Accessing
  81   oop obj_at(int index) const {
  82     // With UseCompressedOops decode the narrow oop in the objArray to an
  83     // uncompressed oop.  Otherwise this is simply a "*" operator.
  84     if (UseCompressedOops) {
  85       return load_decode_heap_oop(obj_at_addr<narrowOop>(index));
  86     } else {
  87       return load_decode_heap_oop(obj_at_addr<oop>(index));