1 /*
2 * Copyright (c) 2011, 2020, 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 *
23 */
24
25 #ifndef SHARE_OOPS_FIELDINFO_HPP
26 #define SHARE_OOPS_FIELDINFO_HPP
27
28 #include "oops/constantPool.hpp"
29 #include "oops/symbol.hpp"
30 #include "oops/typeArrayOop.hpp"
31 #include "utilities/vmEnums.hpp"
32
33 // This class represents the field information contained in the fields
34 // array of an InstanceKlass. Currently it's laid on top an array of
35 // Java shorts but in the future it could simply be used as a real
36 // array type. FieldInfo generally shouldn't be used directly.
37 // Fields should be queried either through InstanceKlass or through
38 // the various FieldStreams.
39 class FieldInfo {
40 friend class fieldDescriptor;
41 friend class JavaFieldStream;
42 friend class ClassFileParser;
43
44 public:
45 // fields
46 // Field info extracted from the class file and stored
47 // as an array of 6 shorts.
48
49 #define FIELDINFO_TAG_SIZE 2
50 #define FIELDINFO_TAG_OFFSET 1 << 0
51 #define FIELDINFO_TAG_CONTENDED 1 << 1
52
53 // Packed field has the tag, and can be either of:
54 // hi bits <--------------------------- lo bits
55 // |---------high---------|---------low---------|
56 // ..........................................CO
57 // ..........................................00 - non-contended field
58 // [--contention_group--]....................10 - contended field with contention group
59 // [------------------offset----------------]01 - real field offset
60
61 // Bit O indicates if the packed field contains an offset (O=1) or not (O=0)
62 // Bit C indicates if the field is contended (C=1) or not (C=0)
63 // (if it is contended, the high packed field contains the contention group)
64
65 enum FieldOffset {
66 access_flags_offset = 0,
67 name_index_offset = 1,
68 signature_index_offset = 2,
69 initval_index_offset = 3,
70 low_packed_offset = 4,
71 high_packed_offset = 5,
72 field_slots = 6
73 };
74
75 private:
76 u2 _shorts[field_slots];
77
78 void set_name_index(u2 val) { _shorts[name_index_offset] = val; }
79 void set_signature_index(u2 val) { _shorts[signature_index_offset] = val; }
80 void set_initval_index(u2 val) { _shorts[initval_index_offset] = val; }
81
82 u2 name_index() const { return _shorts[name_index_offset]; }
83 u2 signature_index() const { return _shorts[signature_index_offset]; }
84 u2 initval_index() const { return _shorts[initval_index_offset]; }
85
86 public:
87 static FieldInfo* from_field_array(Array<u2>* fields, int index) {
88 return ((FieldInfo*)fields->adr_at(index * field_slots));
89 }
90 static FieldInfo* from_field_array(u2* fields, int index) {
91 return ((FieldInfo*)(fields + index * field_slots));
92 }
93
94 void initialize(u2 access_flags,
95 u2 name_index,
96 u2 signature_index,
97 u2 initval_index) {
98 _shorts[access_flags_offset] = access_flags;
99 _shorts[name_index_offset] = name_index;
100 _shorts[signature_index_offset] = signature_index;
101 _shorts[initval_index_offset] = initval_index;
102 _shorts[low_packed_offset] = 0;
103 _shorts[high_packed_offset] = 0;
104 }
105
106 u2 access_flags() const { return _shorts[access_flags_offset]; }
107 u4 offset() const {
108 assert((_shorts[low_packed_offset] & FIELDINFO_TAG_OFFSET) != 0, "Offset must have been set");
109 return build_int_from_shorts(_shorts[low_packed_offset], _shorts[high_packed_offset]) >> FIELDINFO_TAG_SIZE;
110 }
111
112 bool is_contended() const {
113 return (_shorts[low_packed_offset] & FIELDINFO_TAG_CONTENDED) != 0;
114 }
115
116 u2 contended_group() const {
117 assert((_shorts[low_packed_offset] & FIELDINFO_TAG_OFFSET) == 0, "Offset must not have been set");
118 assert((_shorts[low_packed_offset] & FIELDINFO_TAG_CONTENDED) != 0, "Field must be contended");
119 return _shorts[high_packed_offset];
120 }
121
122 bool is_offset_set() const {
123 return (_shorts[low_packed_offset] & FIELDINFO_TAG_OFFSET)!= 0;
124 }
125
126 Symbol* name(ConstantPool* cp) const {
127 int index = name_index();
128 if (is_internal()) {
129 return lookup_symbol(index);
130 }
131 return cp->symbol_at(index);
132 }
133
134 Symbol* signature(ConstantPool* cp) const {
135 int index = signature_index();
136 if (is_internal()) {
137 return lookup_symbol(index);
138 }
139 return cp->symbol_at(index);
140 }
141
142 void set_access_flags(u2 val) { _shorts[access_flags_offset] = val; }
143 void set_offset(u4 val) {
144 val = val << FIELDINFO_TAG_SIZE; // make room for tag
145 _shorts[low_packed_offset] = extract_low_short_from_int(val) | FIELDINFO_TAG_OFFSET;
146 _shorts[high_packed_offset] = extract_high_short_from_int(val);
147 }
148
149 void set_contended_group(u2 val) {
150 assert((_shorts[low_packed_offset] & FIELDINFO_TAG_OFFSET) == 0, "Offset must not have been set");
151 assert((_shorts[low_packed_offset] & FIELDINFO_TAG_CONTENDED) == 0, "Overwritting contended group");
152 _shorts[low_packed_offset] |= FIELDINFO_TAG_CONTENDED;
153 _shorts[high_packed_offset] = val;
154 }
155
156 bool is_internal() const {
157 return (access_flags() & JVM_ACC_FIELD_INTERNAL) != 0;
158 }
159
160 bool is_stable() const {
161 return (access_flags() & JVM_ACC_FIELD_STABLE) != 0;
162 }
163 void set_stable(bool z) {
164 if (z) _shorts[access_flags_offset] |= JVM_ACC_FIELD_STABLE;
165 else _shorts[access_flags_offset] &= ~JVM_ACC_FIELD_STABLE;
166 }
167
168 Symbol* lookup_symbol(int symbol_index) const {
169 assert(is_internal(), "only internal fields");
170 return Symbol::vm_symbol_at(static_cast<vmSymbolID>(symbol_index));
171 }
172 };
173
174 #endif // SHARE_OOPS_FIELDINFO_HPP