objArrayOop.hpp

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#ifndef SHARE_VM_OOPS_OBJARRAYOOP_HPP
#define SHARE_VM_OOPS_OBJARRAYOOP_HPP

#include "oops/arrayOop.hpp"

// An objArrayOop is an array containing oops.
// Evaluating "String arg[10]" will create an objArrayOop.

class objArrayOopDesc : public arrayOopDesc {
  friend class ObjArrayKlass;
  friend class Runtime1;
  friend class psPromotionManager;
  friend class CSetMarkOopClosure;
  friend class G1ParScanPartialArrayClosure;

  template <class T> T* obj_at_addr(int index) const {
    assert(is_within_bounds(index), "index out of bounds");
    return &((T*)base())[index];
  }

private:
  // Give size of objArrayOop in HeapWords minus the header
  static int array_size(int length) {
    const int OopsPerHeapWord = HeapWordSize/heapOopSize;
    assert(OopsPerHeapWord >= 1 && (HeapWordSize % heapOopSize == 0),
           "Else the following (new) computation would be in error");
#ifdef ASSERT
    // The old code is left in for sanity-checking; it'll
    // go away pretty soon. XXX
    // Without UseCompressedOops, this is simply:
    // oop->length() * HeapWordsPerOop;
    // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
    // The oop elements are aligned up to wordSize
    const int HeapWordsPerOop = heapOopSize/HeapWordSize;
    int old_res;
    if (HeapWordsPerOop > 0) {
      old_res = length * HeapWordsPerOop;
    } else {
      old_res = align_size_up(length, OopsPerHeapWord)/OopsPerHeapWord;
    }
#endif  // ASSERT
    int res = ((uint)length + OopsPerHeapWord - 1)/OopsPerHeapWord;
    assert(res == old_res, "Inconsistency between old and new.");
    return res;
  }

 public:
  // Returns the offset of the first element.
  static int base_offset_in_bytes() {
    return arrayOopDesc::base_offset_in_bytes(T_OBJECT);
  }

  // base is the address following the header.
  HeapWord* base() const      { return (HeapWord*) arrayOopDesc::base(T_OBJECT); }

  // Accessing
  oop obj_at(int index) const {
    // With UseCompressedOops decode the narrow oop in the objArray to an
    // uncompressed oop.  Otherwise this is simply a "*" operator.
    if (UseCompressedOops) {
      return load_decode_heap_oop(obj_at_addr<narrowOop>(index));
    } else {
      return load_decode_heap_oop(obj_at_addr<oop>(index));
    }
  }

  void obj_at_put(int index, oop value) {
    if (UseCompressedOops) {
      oop_store(obj_at_addr<narrowOop>(index), value);
    } else {
      oop_store(obj_at_addr<oop>(index), value);
    }
  }
  // Sizing
  static int header_size()    { return arrayOopDesc::header_size(T_OBJECT); }
  int object_size()           { return object_size(length()); }

  static int object_size(int length) {
    // This returns the object size in HeapWords.
    uint asz = array_size(length);
    uint osz = align_object_size(header_size() + asz);
    assert(osz >= asz,   "no overflow");
    assert((int)osz > 0, "no overflow");
    return (int)osz;
  }

  // special iterators for index ranges, returns size of object
#define ObjArrayOop_OOP_ITERATE_DECL(OopClosureType, nv_suffix)     \
  int oop_iterate_range(OopClosureType* blk, int start, int end);

  ALL_OOP_OOP_ITERATE_CLOSURES_1(ObjArrayOop_OOP_ITERATE_DECL)
  ALL_OOP_OOP_ITERATE_CLOSURES_2(ObjArrayOop_OOP_ITERATE_DECL)
};

#endif // SHARE_VM_OOPS_OBJARRAYOOP_HPP