Wed, 06 Jan 2010 22:21:39 -0800
Merge
1 /*
2 * Copyright 1997-2009 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 // arrayOopDesc is the abstract baseclass for all arrays. It doesn't
26 // declare pure virtual to enforce this because that would allocate a vtbl
27 // in each instance, which we don't want.
29 // The layout of array Oops is:
30 //
31 // markOop
32 // klassOop // 32 bits if compressed but declared 64 in LP64.
33 // length // shares klass memory or allocated after declared fields.
36 class arrayOopDesc : public oopDesc {
37 friend class VMStructs;
39 // Interpreter/Compiler offsets
41 // Header size computation.
42 // The header is considered the oop part of this type plus the length.
43 // Returns the aligned header_size_in_bytes. This is not equivalent to
44 // sizeof(arrayOopDesc) which should not appear in the code.
45 static int header_size_in_bytes() {
46 size_t hs = align_size_up(length_offset_in_bytes() + sizeof(int),
47 HeapWordSize);
48 #ifdef ASSERT
49 // make sure it isn't called before UseCompressedOops is initialized.
50 static size_t arrayoopdesc_hs = 0;
51 if (arrayoopdesc_hs == 0) arrayoopdesc_hs = hs;
52 assert(arrayoopdesc_hs == hs, "header size can't change");
53 #endif // ASSERT
54 return (int)hs;
55 }
57 public:
58 // The _length field is not declared in C++. It is allocated after the
59 // declared nonstatic fields in arrayOopDesc if not compressed, otherwise
60 // it occupies the second half of the _klass field in oopDesc.
61 static int length_offset_in_bytes() {
62 return UseCompressedOops ? klass_gap_offset_in_bytes() :
63 sizeof(arrayOopDesc);
64 }
66 // Returns the offset of the first element.
67 static int base_offset_in_bytes(BasicType type) {
68 return header_size(type) * HeapWordSize;
69 }
71 // Returns the address of the first element.
72 void* base(BasicType type) const {
73 return (void*) (((intptr_t) this) + base_offset_in_bytes(type));
74 }
76 // Tells whether index is within bounds.
77 bool is_within_bounds(int index) const { return 0 <= index && index < length(); }
79 // Accessors for instance variable which is not a C++ declared nonstatic
80 // field.
81 int length() const {
82 return *(int*)(((intptr_t)this) + length_offset_in_bytes());
83 }
84 void set_length(int length) {
85 *(int*)(((intptr_t)this) + length_offset_in_bytes()) = length;
86 }
88 // Should only be called with constants as argument
89 // (will not constant fold otherwise)
90 // Returns the header size in words aligned to the requirements of the
91 // array object type.
92 static int header_size(BasicType type) {
93 size_t typesize_in_bytes = header_size_in_bytes();
94 return (int)(Universe::element_type_should_be_aligned(type)
95 ? align_object_size(typesize_in_bytes/HeapWordSize)
96 : typesize_in_bytes/HeapWordSize);
97 }
99 // Return the maximum length of an array of BasicType. The length can passed
100 // to typeArrayOop::object_size(scale, length, header_size) without causing an
101 // overflow.
102 static int32_t max_array_length(BasicType type) {
103 assert(type >= 0 && type < T_CONFLICT, "wrong type");
104 assert(type2aelembytes(type) != 0, "wrong type");
105 const int bytes_per_element = type2aelembytes(type);
106 if (bytes_per_element < HeapWordSize) {
107 return max_jint;
108 }
110 const int32_t max_words = align_size_down(max_jint, MinObjAlignment);
111 const int32_t max_element_words = max_words - header_size(type);
112 const int32_t words_per_element = bytes_per_element >> LogHeapWordSize;
113 return max_element_words / words_per_element;
114 }
115 };