1 /*
2 * Copyright (c) 2003, 2005, 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 class jfieldIDWorkaround: AllStatic {
26 // This workaround is because JVMTI doesn't have distinct entry points
27 // for methods that use static jfieldIDs and instance jfieldIDs.
28 // The workaround is to steal a low-order bit:
29 // a 1 means the jfieldID is an instance jfieldID,
30 // and the rest of the word is the offset of the field.
31 // a 0 means the jfieldID is a static jfieldID,
32 // and the rest of the word is the JNIid*.
33 //
34 // Another low-order bit is used to mark if an instance field
35 // is accompanied by an indication of which class it applies to.
36 //
37 // Bit-format of a jfieldID (most significant first):
38 // address:30 instance=0:1 checked=0:1
39 // offset:30 instance=1:1 checked=0:1
40 // klass:23 offset:7 instance=1:1 checked=1:1
41 //
42 // If the offset does not fit in 7 bits, or if the fieldID is
43 // not checked, then the checked bit is zero and the rest of
44 // the word (30 bits) contains only the offset.
140 }
141
142 static JNIid* from_static_jfieldID(jfieldID id) {
143 assert(jfieldIDWorkaround::is_static_jfieldID(id),
144 "to_JNIid, but not static jfieldID");
145 JNIid* result = (JNIid*) id;
146 assert(result->is_static_field_id(), "to_JNIid, but not static field id");
147 return result;
148 }
149
150 static jfieldID to_jfieldID(instanceKlassHandle k, int offset, bool is_static) {
151 if (is_static) {
152 JNIid *id = k->jni_id_for(offset);
153 debug_only(id->set_is_static_field_id());
154 return jfieldIDWorkaround::to_static_jfieldID(id);
155 } else {
156 return jfieldIDWorkaround::to_instance_jfieldID(k(), offset);
157 }
158 }
159 };
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1 /*
2 * Copyright (c) 2003, 2010, 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_VM_RUNTIME_JFIELDIDWORKAROUND_HPP
26 #define SHARE_VM_RUNTIME_JFIELDIDWORKAROUND_HPP
27
28 class jfieldIDWorkaround: AllStatic {
29 // This workaround is because JVMTI doesn't have distinct entry points
30 // for methods that use static jfieldIDs and instance jfieldIDs.
31 // The workaround is to steal a low-order bit:
32 // a 1 means the jfieldID is an instance jfieldID,
33 // and the rest of the word is the offset of the field.
34 // a 0 means the jfieldID is a static jfieldID,
35 // and the rest of the word is the JNIid*.
36 //
37 // Another low-order bit is used to mark if an instance field
38 // is accompanied by an indication of which class it applies to.
39 //
40 // Bit-format of a jfieldID (most significant first):
41 // address:30 instance=0:1 checked=0:1
42 // offset:30 instance=1:1 checked=0:1
43 // klass:23 offset:7 instance=1:1 checked=1:1
44 //
45 // If the offset does not fit in 7 bits, or if the fieldID is
46 // not checked, then the checked bit is zero and the rest of
47 // the word (30 bits) contains only the offset.
143 }
144
145 static JNIid* from_static_jfieldID(jfieldID id) {
146 assert(jfieldIDWorkaround::is_static_jfieldID(id),
147 "to_JNIid, but not static jfieldID");
148 JNIid* result = (JNIid*) id;
149 assert(result->is_static_field_id(), "to_JNIid, but not static field id");
150 return result;
151 }
152
153 static jfieldID to_jfieldID(instanceKlassHandle k, int offset, bool is_static) {
154 if (is_static) {
155 JNIid *id = k->jni_id_for(offset);
156 debug_only(id->set_is_static_field_id());
157 return jfieldIDWorkaround::to_static_jfieldID(id);
158 } else {
159 return jfieldIDWorkaround::to_instance_jfieldID(k(), offset);
160 }
161 }
162 };
163
164 #endif // SHARE_VM_RUNTIME_JFIELDIDWORKAROUND_HPP
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