Mon, 18 Feb 2013 16:00:15 +0100
8008371: Fix Dynalink compiler warnings and whitespace
Reviewed-by: jlaskey, sundar
1 /*
2 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
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9 * by Oracle in the LICENSE file that accompanied this code.
10 *
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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).
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26 /*
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file, and Oracle licenses the original version of this file under the BSD
31 * license:
32 */
33 /*
34 Copyright 2009-2013 Attila Szegedi
36 Licensed under both the Apache License, Version 2.0 (the "Apache License")
37 and the BSD License (the "BSD License"), with licensee being free to
38 choose either of the two at their discretion.
40 You may not use this file except in compliance with either the Apache
41 License or the BSD License.
43 If you choose to use this file in compliance with the Apache License, the
44 following notice applies to you:
46 You may obtain a copy of the Apache License at
48 http://www.apache.org/licenses/LICENSE-2.0
50 Unless required by applicable law or agreed to in writing, software
51 distributed under the License is distributed on an "AS IS" BASIS,
52 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
53 implied. See the License for the specific language governing
54 permissions and limitations under the License.
56 If you choose to use this file in compliance with the BSD License, the
57 following notice applies to you:
59 Redistribution and use in source and binary forms, with or without
60 modification, are permitted provided that the following conditions are
61 met:
62 * Redistributions of source code must retain the above copyright
63 notice, this list of conditions and the following disclaimer.
64 * Redistributions in binary form must reproduce the above copyright
65 notice, this list of conditions and the following disclaimer in the
66 documentation and/or other materials provided with the distribution.
67 * Neither the name of the copyright holder nor the names of
68 contributors may be used to endorse or promote products derived from
69 this software without specific prior written permission.
71 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
72 IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
73 TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
74 PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
75 BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
76 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
77 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
78 BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
79 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
80 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
81 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
82 */
84 package jdk.internal.dynalink;
86 import java.lang.invoke.MethodHandle;
87 import java.lang.invoke.MethodHandles;
88 import java.lang.invoke.MethodType;
89 import java.lang.invoke.MutableCallSite;
90 import java.util.List;
91 import jdk.internal.dynalink.linker.GuardedInvocation;
92 import jdk.internal.dynalink.linker.GuardingDynamicLinker;
93 import jdk.internal.dynalink.linker.LinkRequest;
94 import jdk.internal.dynalink.linker.LinkerServices;
95 import jdk.internal.dynalink.support.CallSiteDescriptorFactory;
96 import jdk.internal.dynalink.support.LinkRequestImpl;
97 import jdk.internal.dynalink.support.Lookup;
98 import jdk.internal.dynalink.support.RuntimeContextLinkRequestImpl;
100 /**
101 * The linker for {@link RelinkableCallSite} objects. Users of it (scripting frameworks and language runtimes) have to
102 * create a linker using the {@link DynamicLinkerFactory} and invoke its link method from the invokedynamic bootstrap
103 * methods to set the target of all the call sites in the code they generate. Usual usage would be to create one class
104 * per language runtime to contain one linker instance as:
105 *
106 * <pre>
107 * class MyLanguageRuntime {
108 * private static final GuardingDynamicLinker myLanguageLinker = new MyLanguageLinker();
109 * private static final DynamicLinker dynamicLinker = createDynamicLinker();
110 *
111 * private static DynamicLinker createDynamicLinker() {
112 * final DynamicLinkerFactory factory = new DynamicLinkerFactory();
113 * factory.setPrioritizedLinker(myLanguageLinker);
114 * return factory.createLinker();
115 * }
116 *
117 * public static CallSite bootstrap(MethodHandles.Lookup caller, String name, MethodType type) {
118 * return dynamicLinker.link(new MonomorphicCallSite(CallSiteDescriptorFactory.create(lookup, name, type)));
119 * }
120 * }
121 * </pre>
122 *
123 * Note how there are three components you will need to provide here:
124 * <ul>
125 * <li>You're expected to provide a {@link GuardingDynamicLinker} for your own language. If your runtime doesn't
126 * have its own language and/or object model (i.e. it's a generic scripting shell), you don't need to implement a
127 * dynamic linker; you would simply not invoke the {@code setPrioritizedLinker} method on the factory, or even better,
128 * simply use {@link DefaultBootstrapper}.</li>
129 * <li>The performance of the programs can depend on your choice of the class to represent call sites. The above
130 * example used {@link MonomorphicCallSite}, but you might want to use {@link ChainedCallSite} instead. You'll need to
131 * experiment and decide what fits your language runtime the best. You can subclass either of these or roll your own if
132 * you need to.</li>
133 * <li>You also need to provide {@link CallSiteDescriptor}s to your call sites. They are immutable objects that contain
134 * all the information about the call site: the class performing the lookups, the name of the method being invoked, and
135 * the method signature. The library has a default {@link CallSiteDescriptorFactory} for descriptors that you can use,
136 * or you can create your own descriptor classes, especially if you need to add further information (values passed in
137 * additional parameters to the bootstrap method) to them.</li>
138 * </ul>
139 *
140 * @author Attila Szegedi
141 */
142 public class DynamicLinker {
144 private static final String CLASS_NAME = DynamicLinker.class.getName();
145 private static final String RELINK_METHOD_NAME = "relink";
147 private final LinkerServices linkerServices;
148 private final int runtimeContextArgCount;
149 private final boolean syncOnRelink;
150 private final int unstableRelinkThreshold;
152 /**
153 * Creates a new dynamic linker.
154 *
155 * @param linkerServices the linkerServices used by the linker, created by the factory.
156 * @param runtimeContextArgCount see {@link DynamicLinkerFactory#setRuntimeContextArgCount(int)}
157 */
158 DynamicLinker(LinkerServices linkerServices, int runtimeContextArgCount, boolean syncOnRelink,
159 int unstableRelinkThreshold) {
160 if(runtimeContextArgCount < 0) {
161 throw new IllegalArgumentException("runtimeContextArgCount < 0");
162 }
163 if(unstableRelinkThreshold < 0) {
164 throw new IllegalArgumentException("unstableRelinkThreshold < 0");
165 }
166 this.runtimeContextArgCount = runtimeContextArgCount;
167 this.linkerServices = linkerServices;
168 this.syncOnRelink = syncOnRelink;
169 this.unstableRelinkThreshold = unstableRelinkThreshold;
170 }
172 /**
173 * Links an invokedynamic call site. It will install a method handle into the call site that invokes the relinking
174 * mechanism of this linker. Next time the call site is invoked, it will be linked for the actual arguments it was
175 * invoked with.
176 *
177 * @param callSite the call site to link.
178 * @return the callSite, for easy call chaining.
179 */
180 public <T extends RelinkableCallSite> T link(final T callSite) {
181 callSite.initialize(createRelinkAndInvokeMethod(callSite, 0));
182 return callSite;
183 }
185 /**
186 * Returns the object representing the lower level linker services of this class that are normally exposed to
187 * individual language-specific linkers. While as a user of this class you normally only care about the
188 * {@link #link(RelinkableCallSite)} method, in certain circumstances you might want to use the lower level services
189 * directly; either to lookup specific method handles, to access the type converters, and so on.
190 * @return the object representing the linker services of this class.
191 */
192 public LinkerServices getLinkerServices() {
193 return linkerServices;
194 }
196 private static final MethodHandle RELINK = Lookup.findOwnSpecial(MethodHandles.lookup(), RELINK_METHOD_NAME,
197 MethodHandle.class, RelinkableCallSite.class, int.class, Object[].class);
199 private MethodHandle createRelinkAndInvokeMethod(final RelinkableCallSite callSite, int relinkCount) {
200 // Make a bound MH of invoke() for this linker and call site
201 final MethodHandle boundRelinker = MethodHandles.insertArguments(RELINK, 0, this, callSite, Integer.valueOf(
202 relinkCount));
203 // Make a MH that gathers all arguments to the invocation into an Object[]
204 final MethodType type = callSite.getDescriptor().getMethodType();
205 final MethodHandle collectingRelinker = boundRelinker.asCollector(Object[].class, type.parameterCount());
206 return MethodHandles.foldArguments(MethodHandles.exactInvoker(type), collectingRelinker.asType(
207 type.changeReturnType(MethodHandle.class)));
208 }
210 /**
211 * Relinks a call site conforming to the invocation arguments.
212 *
213 * @param callSite the call site itself
214 * @param arguments arguments to the invocation
215 * @return return the method handle for the invocation
216 * @throws Exception rethrows any exception thrown by the linkers
217 */
218 @SuppressWarnings("unused")
219 private MethodHandle relink(RelinkableCallSite callSite, int relinkCount, Object... arguments) throws Exception {
220 final CallSiteDescriptor callSiteDescriptor = callSite.getDescriptor();
221 final boolean unstableDetectionEnabled = unstableRelinkThreshold > 0;
222 final boolean callSiteUnstable = unstableDetectionEnabled && relinkCount >= unstableRelinkThreshold;
223 final LinkRequest linkRequest =
224 runtimeContextArgCount == 0 ? new LinkRequestImpl(callSiteDescriptor, callSiteUnstable, arguments)
225 : new RuntimeContextLinkRequestImpl(callSiteDescriptor, callSiteUnstable, arguments,
226 runtimeContextArgCount);
228 // Find a suitable method handle with a guard
229 GuardedInvocation guardedInvocation = linkerServices.getGuardedInvocation(linkRequest);
231 // None found - throw an exception
232 if(guardedInvocation == null) {
233 throw new NoSuchDynamicMethodException(callSiteDescriptor.toString());
234 }
236 // If our call sites have a runtime context, and the linker produced a context-stripped invocation, adapt the
237 // produced invocation into contextual invocation (by dropping the context...)
238 if(runtimeContextArgCount > 0) {
239 final MethodType origType = callSiteDescriptor.getMethodType();
240 final MethodHandle invocation = guardedInvocation.getInvocation();
241 if(invocation.type().parameterCount() == origType.parameterCount() - runtimeContextArgCount) {
242 final List<Class<?>> prefix = origType.parameterList().subList(1, runtimeContextArgCount + 1);
243 final MethodHandle guard = guardedInvocation.getGuard();
244 guardedInvocation = guardedInvocation.dropArguments(1, prefix);
245 }
246 }
248 int newRelinkCount = relinkCount;
249 // Note that the short-circuited "&&" evaluation below ensures we'll increment the relinkCount until
250 // threshold + 1 but not beyond that. Threshold + 1 is treated as a special value to signal that resetAndRelink
251 // has already executed once for the unstable call site; we only want the call site to throw away its current
252 // linkage once, when it transitions to unstable.
253 if(unstableDetectionEnabled && newRelinkCount <= unstableRelinkThreshold && newRelinkCount++ == unstableRelinkThreshold) {
254 callSite.resetAndRelink(guardedInvocation, createRelinkAndInvokeMethod(callSite, newRelinkCount));
255 } else {
256 callSite.relink(guardedInvocation, createRelinkAndInvokeMethod(callSite, newRelinkCount));
257 }
258 if(syncOnRelink) {
259 MutableCallSite.syncAll(new MutableCallSite[] { (MutableCallSite)callSite });
260 }
261 return guardedInvocation.getInvocation();
262 }
264 /**
265 * Returns a stack trace element describing the location of the call site currently being relinked on the current
266 * thread. The operation internally creates a Throwable object and inspects its stack trace, so it's potentially
267 * expensive. The recommended usage for it is in writing diagnostics code.
268 * @return a stack trace element describing the location of the call site currently being relinked, or null if it is
269 * not invoked while a call site is being relinked.
270 */
271 public static StackTraceElement getRelinkedCallSiteLocation() {
272 final StackTraceElement[] trace = new Throwable().getStackTrace();
273 for(int i = 0; i < trace.length - 1; ++i) {
274 final StackTraceElement frame = trace[i];
275 if(RELINK_METHOD_NAME.equals(frame.getMethodName()) && CLASS_NAME.equals(frame.getClassName())) {
276 return trace[i + 1];
277 }
278 }
279 return null;
280 }
281 }