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src/hotspot/share/oops/arrayOop.hpp

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 27 
 28 #include "oops/oop.hpp"
 29 #include "utilities/align.hpp"
 30 
 31 // arrayOopDesc is the abstract baseclass for all arrays.  It doesn't
 32 // declare pure virtual to enforce this because that would allocate a vtbl
 33 // in each instance, which we don't want.
 34 
 35 // The layout of array Oops is:
 36 //
 37 //  markWord
 38 //  Klass*    // 32 bits if compressed but declared 64 in LP64.
 39 //  length    // shares klass memory or allocated after declared fields.
 40 
 41 
 42 class arrayOopDesc : public oopDesc {
 43   friend class VMStructs;
 44   friend class arrayOopDescTest;
 45 
 46   // Interpreter/Compiler offsets
 47 
 48   // Header size computation.
 49   // The header is considered the oop part of this type plus the length.
 50   // Returns the aligned header_size_in_bytes.  This is not equivalent to
 51   // sizeof(arrayOopDesc) which should not appear in the code.
 52   static int header_size_in_bytes() {
 53     size_t hs = align_up(length_offset_in_bytes() + sizeof(int),
 54                               HeapWordSize);
 55 #ifdef ASSERT
 56     // make sure it isn't called before UseCompressedOops is initialized.
 57     static size_t arrayoopdesc_hs = 0;
 58     if (arrayoopdesc_hs == 0) arrayoopdesc_hs = hs;
 59     assert(arrayoopdesc_hs == hs, "header size can't change");
 60 #endif // ASSERT
 61     return (int)hs;
 62   }
 63 
 64   // Returns the address of the length "field".  See length_offset_in_bytes().
 65   static int* length_addr_impl(void* obj_ptr) {
 66     char* ptr = static_cast<char*>(obj_ptr);
 67     return reinterpret_cast<int*>(ptr + length_offset_in_bytes());
 68   }
 69 
 70   // Check whether an element of a typeArrayOop with the given type must be
 71   // aligned 0 mod 8.  The typeArrayOop itself must be aligned at least this
 72   // strongly.
 73   static bool element_type_should_be_aligned(BasicType type) {
 74     return type == T_DOUBLE || type == T_LONG;
 75   }
 76 
 77  public:
 78   // The _length field is not declared in C++.  It is allocated after the
 79   // declared nonstatic fields in arrayOopDesc if not compressed, otherwise
 80   // it occupies the second half of the _klass field in oopDesc.
 81   static int length_offset_in_bytes() {
 82     return UseCompressedClassPointers ? klass_gap_offset_in_bytes() :
 83                                sizeof(arrayOopDesc);
 84   }
 85 
 86   // Returns the offset of the first element.
 87   static int base_offset_in_bytes(BasicType type) {
 88     return header_size(type) * HeapWordSize;
 89   }
 90 
 91   // Returns the address of the first element. The elements in the array will not
 92   // relocate from this address until a subsequent thread transition.
 93   void* base(BasicType type) const {
 94     return reinterpret_cast<void*>(cast_from_oop<intptr_t>(as_oop()) + base_offset_in_bytes(type));

 27 
 28 #include "oops/oop.hpp"
 29 #include "utilities/align.hpp"
 30 
 31 // arrayOopDesc is the abstract baseclass for all arrays.  It doesn't
 32 // declare pure virtual to enforce this because that would allocate a vtbl
 33 // in each instance, which we don't want.
 34 
 35 // The layout of array Oops is:
 36 //
 37 //  markWord
 38 //  Klass*    // 32 bits if compressed but declared 64 in LP64.
 39 //  length    // shares klass memory or allocated after declared fields.
 40 
 41 
 42 class arrayOopDesc : public oopDesc {
 43   friend class VMStructs;
 44   friend class arrayOopDescTest;
 45 
 46   // Interpreter/Compiler offsets
 47 protected:
 48   // Header size computation.
 49   // The header is considered the oop part of this type plus the length.
 50   // Returns the aligned header_size_in_bytes.  This is not equivalent to
 51   // sizeof(arrayOopDesc) which should not appear in the code.
 52   static int header_size_in_bytes() {
 53     size_t hs = align_up(length_offset_in_bytes() + sizeof(int),
 54                               HeapWordSize);
 55 #ifdef ASSERT
 56     // make sure it isn't called before UseCompressedOops is initialized.
 57     static size_t arrayoopdesc_hs = 0;
 58     if (arrayoopdesc_hs == 0) arrayoopdesc_hs = hs;
 59     assert(arrayoopdesc_hs == hs, "header size can't change");
 60 #endif // ASSERT
 61     return (int)hs;
 62   }
 63 
 64   // Returns the address of the length "field".  See length_offset_in_bytes().
 65   static int* length_addr_impl(void* obj_ptr) {
 66     char* ptr = static_cast<char*>(obj_ptr);
 67     return reinterpret_cast<int*>(ptr + length_offset_in_bytes());
 68   }
 69 
 70   // Check whether an element of a typeArrayOop with the given type must be
 71   // aligned 0 mod 8.  The typeArrayOop itself must be aligned at least this
 72   // strongly.
 73   static bool element_type_should_be_aligned(BasicType type) {
 74     return type == T_DOUBLE || type == T_LONG || type == T_INLINE_TYPE;
 75   }
 76 
 77  public:
 78   // The _length field is not declared in C++.  It is allocated after the
 79   // declared nonstatic fields in arrayOopDesc if not compressed, otherwise
 80   // it occupies the second half of the _klass field in oopDesc.
 81   static int length_offset_in_bytes() {
 82     return UseCompressedClassPointers ? klass_gap_offset_in_bytes() :
 83                                sizeof(arrayOopDesc);
 84   }
 85 
 86   // Returns the offset of the first element.
 87   static int base_offset_in_bytes(BasicType type) {
 88     return header_size(type) * HeapWordSize;
 89   }
 90 
 91   // Returns the address of the first element. The elements in the array will not
 92   // relocate from this address until a subsequent thread transition.
 93   void* base(BasicType type) const {
 94     return reinterpret_cast<void*>(cast_from_oop<intptr_t>(as_oop()) + base_offset_in_bytes(type));
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