1 /*
 2  * Copyright (c) 2001, 2021, 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.  Oracle designates this
 8  * particular file as subject to the "Classpath" exception as provided
 9  * by Oracle in the LICENSE file that accompanied this code.
10  *
11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
18  * 2 along with this work; if not, write to the Free Software Foundation,
19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20  *
21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22  * or visit www.oracle.com if you need additional information or have any
23  * questions.
24  */
25 
26 package jdk.internal.reflect;
27 
28 import java.lang.reflect.*;
29 import jdk.internal.misc.Unsafe;
30 
31 /** Used only for the first few invocations of a Method; afterward,
32     switches to bytecode-based implementation */
33 
34 class NativeMethodAccessorImpl extends MethodAccessorImpl {
35      private static final Unsafe U = Unsafe.getUnsafe();
36      private static final long GENERATED_OFFSET
37         = U.objectFieldOffset(NativeMethodAccessorImpl.class, "generated");
38 
39     private final Method method;
40     private final DelegatingMethodAccessorImpl parent;
41     private int numInvocations;
42     private volatile int generated;
43 
44     NativeMethodAccessorImpl(Method method) {
45         this.method = method;
46         this.parent = new DelegatingMethodAccessorImpl(this);
47     }
48 
49     public Object invoke(Object obj, Object[] args)
50         throws IllegalArgumentException, InvocationTargetException
51     {
52         // We can't inflate methods belonging to vm-anonymous classes because
53         // that kind of class can't be referred to by name, hence can't be
54         // found from the generated bytecode.
55         if (++numInvocations > ReflectionFactory.inflationThreshold()
56                 && !method.getDeclaringClass().isHidden()
57                 && generated == 0
58                 && U.compareAndSetInt(this, GENERATED_OFFSET, 0, 1)) {
59             try {
60                 MethodAccessorImpl acc = (MethodAccessorImpl)
61                     new MethodAccessorGenerator().
62                         generateMethod(method.getDeclaringClass(),
63                                        method.getName(),
64                                        method.getParameterTypes(),
65                                        method.getReturnType(),
66                                        method.getExceptionTypes(),
67                                        method.getModifiers());
68                 parent.setDelegate(acc);
69             } catch (Throwable t) {
70                 // Throwable happens in generateMethod, restore generated to 0
71                 generated = 0;
72                 throw t;
73             }
74         }
75 
76         return invoke0(method, obj, args);
77     }
78 
79     DelegatingMethodAccessorImpl getParent() {
80         return parent;
81     }
82 
83     private static native Object invoke0(Method m, Object obj, Object[] args);
84 }