1 /*
2 * Copyright (c) 1997, 2013, 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 *
24
25 #ifndef SHARE_VM_OOPS_ARRAYOOP_HPP
26 #define SHARE_VM_OOPS_ARRAYOOP_HPP
27
28 #include "memory/universe.inline.hpp"
29 #include "oops/oop.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 // markOop
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
45 // Interpreter/Compiler offsets
46
47 // Header size computation.
48 // The header is considered the oop part of this type plus the length.
49 // Returns the aligned header_size_in_bytes. This is not equivalent to
50 // sizeof(arrayOopDesc) which should not appear in the code.
51 static int header_size_in_bytes() {
52 size_t hs = align_size_up(length_offset_in_bytes() + sizeof(int),
53 HeapWordSize);
54 #ifdef ASSERT
55 // make sure it isn't called before UseCompressedOops is initialized.
56 static size_t arrayoopdesc_hs = 0;
57 if (arrayoopdesc_hs == 0) arrayoopdesc_hs = hs;
58 assert(arrayoopdesc_hs == hs, "header size can't change");
59 #endif // ASSERT
60 return (int)hs;
61 }
62
63 public:
107 // overflow. We also need to make sure that this will not overflow a size_t on
108 // 32 bit platforms when we convert it to a byte size.
109 static int32_t max_array_length(BasicType type) {
110 assert(type >= 0 && type < T_CONFLICT, "wrong type");
111 assert(type2aelembytes(type) != 0, "wrong type");
112
113 const size_t max_element_words_per_size_t =
114 align_size_down((SIZE_MAX/HeapWordSize - header_size(type)), MinObjAlignment);
115 const size_t max_elements_per_size_t =
116 HeapWordSize * max_element_words_per_size_t / type2aelembytes(type);
117 if ((size_t)max_jint < max_elements_per_size_t) {
118 // It should be ok to return max_jint here, but parts of the code
119 // (CollectedHeap, Klass::oop_oop_iterate(), and more) uses an int for
120 // passing around the size (in words) of an object. So, we need to avoid
121 // overflowing an int when we add the header. See CRs 4718400 and 7110613.
122 return align_size_down(max_jint - header_size(type), MinObjAlignment);
123 }
124 return (int32_t)max_elements_per_size_t;
125 }
126
127 // for unit testing
128 #ifndef PRODUCT
129 static bool check_max_length_overflow(BasicType type);
130 #endif
131 };
132
133 #endif // SHARE_VM_OOPS_ARRAYOOP_HPP
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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 *
24
25 #ifndef SHARE_VM_OOPS_ARRAYOOP_HPP
26 #define SHARE_VM_OOPS_ARRAYOOP_HPP
27
28 #include "memory/universe.inline.hpp"
29 #include "oops/oop.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 // markOop
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_size_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 public:
108 // overflow. We also need to make sure that this will not overflow a size_t on
109 // 32 bit platforms when we convert it to a byte size.
110 static int32_t max_array_length(BasicType type) {
111 assert(type >= 0 && type < T_CONFLICT, "wrong type");
112 assert(type2aelembytes(type) != 0, "wrong type");
113
114 const size_t max_element_words_per_size_t =
115 align_size_down((SIZE_MAX/HeapWordSize - header_size(type)), MinObjAlignment);
116 const size_t max_elements_per_size_t =
117 HeapWordSize * max_element_words_per_size_t / type2aelembytes(type);
118 if ((size_t)max_jint < max_elements_per_size_t) {
119 // It should be ok to return max_jint here, but parts of the code
120 // (CollectedHeap, Klass::oop_oop_iterate(), and more) uses an int for
121 // passing around the size (in words) of an object. So, we need to avoid
122 // overflowing an int when we add the header. See CRs 4718400 and 7110613.
123 return align_size_down(max_jint - header_size(type), MinObjAlignment);
124 }
125 return (int32_t)max_elements_per_size_t;
126 }
127
128 };
129
130 #endif // SHARE_VM_OOPS_ARRAYOOP_HPP
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