1 /*
2 * Copyright (c) 2014, 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 java.lang.invoke;
27
28 import java.util.Arrays;
29 import static java.lang.invoke.LambdaForm.*;
30 import static java.lang.invoke.LambdaForm.Kind.*;
31 import static java.lang.invoke.MethodHandleNatives.Constants.REF_invokeVirtual;
32 import static java.lang.invoke.MethodHandleStatics.*;
33
34 /**
35 * A method handle whose invocation behavior is determined by a target.
36 * The delegating MH itself can hold extra "intentions" beyond the simple behavior.
37 * @author jrose
38 */
39 /*non-public*/
40 abstract class DelegatingMethodHandle extends MethodHandle {
41 protected DelegatingMethodHandle(MethodHandle target) {
42 this(target.type(), target);
43 }
44
45 protected DelegatingMethodHandle(MethodType type, MethodHandle target) {
46 super(type, chooseDelegatingForm(target));
47 }
48
49 protected DelegatingMethodHandle(MethodType type, LambdaForm form) {
50 super(type, form);
51 }
52
53 /** Define this to extract the delegated target which supplies the invocation behavior. */
54 protected abstract MethodHandle getTarget();
55
56 @Override
57 abstract MethodHandle asTypeUncached(MethodType newType);
58
59 @Override
60 MemberName internalMemberName() {
61 return getTarget().internalMemberName();
62 }
63
64 @Override
65 boolean isInvokeSpecial() {
66 return getTarget().isInvokeSpecial();
67 }
68
69 @Override
70 Class<?> internalCallerClass() {
71 return getTarget().internalCallerClass();
72 }
73
74 @Override
75 MethodHandle copyWith(MethodType mt, LambdaForm lf) {
76 // FIXME: rethink 'copyWith' protocol; it is too low-level for use on all MHs
77 throw newIllegalArgumentException("do not use this");
78 }
79
80 @Override
81 String internalProperties() {
82 return "\n& Class="+getClass().getSimpleName()+
83 "\n& Target="+getTarget().debugString();
84 }
85
86 @Override
87 BoundMethodHandle rebind() {
88 return getTarget().rebind();
89 }
90
91 private static LambdaForm chooseDelegatingForm(MethodHandle target) {
92 if (target instanceof SimpleMethodHandle)
93 return target.internalForm(); // no need for an indirection
94 return makeReinvokerForm(target, MethodTypeForm.LF_DELEGATE, DelegatingMethodHandle.class, NF_getTarget);
95 }
96
97 static LambdaForm makeReinvokerForm(MethodHandle target,
98 int whichCache,
99 Object constraint,
100 NamedFunction getTargetFn) {
101 // No pre-action needed.
102 return makeReinvokerForm(target, whichCache, constraint, true, getTargetFn, null);
103 }
104 /** Create a LF which simply reinvokes a target of the given basic type. */
105 static LambdaForm makeReinvokerForm(MethodHandle target,
106 int whichCache,
107 Object constraint,
108 boolean forceInline,
109 NamedFunction getTargetFn,
110 NamedFunction preActionFn) {
111 MethodType mtype = target.type().basicType();
112 Kind kind = whichKind(whichCache);
113 boolean customized = (whichCache < 0 ||
114 mtype.parameterSlotCount() > MethodType.MAX_MH_INVOKER_ARITY);
115 boolean hasPreAction = (preActionFn != null);
116 LambdaForm form;
117 if (!customized) {
118 form = mtype.form().cachedLambdaForm(whichCache);
119 if (form != null) return form;
120 }
121 final int THIS_DMH = 0;
122 final int ARG_BASE = 1;
123 final int ARG_LIMIT = ARG_BASE + mtype.parameterCount();
124 int nameCursor = ARG_LIMIT;
125 final int PRE_ACTION = hasPreAction ? nameCursor++ : -1;
126 final int NEXT_MH = customized ? -1 : nameCursor++;
127 final int REINVOKE = nameCursor++;
128 LambdaForm.Name[] names = LambdaForm.arguments(nameCursor - ARG_LIMIT, mtype.invokerType());
129 assert(names.length == nameCursor);
130 names[THIS_DMH] = names[THIS_DMH].withConstraint(constraint);
131 Object[] targetArgs;
132 if (hasPreAction) {
133 names[PRE_ACTION] = new LambdaForm.Name(preActionFn, names[THIS_DMH]);
134 }
135 if (customized) {
136 targetArgs = Arrays.copyOfRange(names, ARG_BASE, ARG_LIMIT, Object[].class);
137 names[REINVOKE] = new LambdaForm.Name(target, targetArgs); // the invoker is the target itself
138 } else {
139 names[NEXT_MH] = new LambdaForm.Name(getTargetFn, names[THIS_DMH]);
140 targetArgs = Arrays.copyOfRange(names, THIS_DMH, ARG_LIMIT, Object[].class);
141 targetArgs[0] = names[NEXT_MH]; // overwrite this MH with next MH
142 names[REINVOKE] = new LambdaForm.Name(mtype, targetArgs);
143 }
144 form = new LambdaForm(ARG_LIMIT, names, forceInline, kind);
145 if (!customized) {
146 form = mtype.form().setCachedLambdaForm(whichCache, form);
147 }
148 return form;
149 }
150
151 private static Kind whichKind(int whichCache) {
152 switch(whichCache) {
153 case MethodTypeForm.LF_REBIND: return BOUND_REINVOKER;
154 case MethodTypeForm.LF_DELEGATE: return DELEGATE;
155 default: return REINVOKER;
156 }
157 }
158
159 static final NamedFunction NF_getTarget;
160 static {
161 try {
162 MemberName member = new MemberName(DelegatingMethodHandle.class, "getTarget",
163 MethodType.methodType(MethodHandle.class), REF_invokeVirtual);
164 NF_getTarget = new NamedFunction(
165 MemberName.getFactory()
166 .resolveOrFail(REF_invokeVirtual, member, DelegatingMethodHandle.class, NoSuchMethodException.class));
167 } catch (ReflectiveOperationException ex) {
168 throw newInternalError(ex);
169 }
170 // The Holder class will contain pre-generated DelegatingMethodHandles resolved
171 // speculatively using MemberName.getFactory().resolveOrNull. However, that
172 // doesn't initialize the class, which subtly breaks inlining etc. By forcing
173 // initialization of the Holder class we avoid these issues.
174 UNSAFE.ensureClassInitialized(Holder.class);
175 }
176
177 /* Placeholder class for DelegatingMethodHandles generated ahead of time */
178 final class Holder {}
179 }