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  *

     5  * This code is free software; you can redistribute it and/or modify it

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     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

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    25 

    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

    35 

    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.

    39 

    40    You may not use this file except in compliance with either the Apache

    41    License or the BSD License.

    42 

    43    If you choose to use this file in compliance with the Apache License, the

    44    following notice applies to you:

    45 

    46        You may obtain a copy of the Apache License at

    47 

    48            http://www.apache.org/licenses/LICENSE-2.0

    49 

    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.

    55 

    56    If you choose to use this file in compliance with the BSD License, the

    57    following notice applies to you:

    58 

    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.

    70 

    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 */

    83 

    84 package jdk.internal.dynalink;

    85 

    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;

    99 

   100 

   101 /**

   102  * The linker for {@link RelinkableCallSite} objects. Users of it (scripting frameworks and language runtimes) have to

   103  * create a linker using the {@link DynamicLinkerFactory} and invoke its link method from the invokedynamic bootstrap

   104  * methods to set the target of all the call sites in the code they generate. Usual usage would be to create one class

   105  * per language runtime to contain one linker instance as:

   106  *

   107  * <pre>

   108  * class MyLanguageRuntime {

   109  *     private static final GuardingDynamicLinker myLanguageLinker = new MyLanguageLinker();

   110  *     private static final DynamicLinker dynamicLinker = createDynamicLinker();

   111  *

   112  *     private static DynamicLinker createDynamicLinker() {

   113  *         final DynamicLinkerFactory factory = new DynamicLinkerFactory();

   114  *         factory.setPrioritizedLinker(myLanguageLinker);

   115  *         return factory.createLinker();

   116  *     }

   117  *

   118  *     public static CallSite bootstrap(MethodHandles.Lookup caller, String name, MethodType type) {

   119  *         return dynamicLinker.link(new MonomorphicCallSite(CallSiteDescriptorFactory.create(lookup, name, type)));

   120  *     }

   121  * }

   122  * </pre>

   123  *

   124  * Note how there are three components you will need to provide here:

   125  * <ul>

   126  * <li>You're expected to provide a {@link GuardingDynamicLinker} for your own language. If your runtime doesn't

   127  * have its own language and/or object model (i.e. it's a generic scripting shell), you don't need to implement a

   128  * dynamic linker; you would simply not invoke the {@code setPrioritizedLinker} method on the factory, or even better,

   129  * simply use {@link DefaultBootstrapper}.</li>

   130  * <li>The performance of the programs can depend on your choice of the class to represent call sites. The above

   131  * example used {@link MonomorphicCallSite}, but you might want to use {@link ChainedCallSite} instead. You'll need to

   132  * experiment and decide what fits your language runtime the best. You can subclass either of these or roll your own if

   133  * you need to.</li>

   134  * <li>You also need to provide {@link CallSiteDescriptor}s to your call sites. They are immutable objects that contain

   135  * all the information about the call site: the class performing the lookups, the name of the method being invoked, and

   136  * the method signature. The library has a default {@link CallSiteDescriptorFactory} for descriptors that you can use,

   137  * or you can create your own descriptor classes, especially if you need to add further information (values passed in

   138  * additional parameters to the bootstrap method) to them.</li>

   139  * </ul>

   140  *

   141  * @author Attila Szegedi

   142  */

   143 public class DynamicLinker {

   144 

   145     private static final String CLASS_NAME = DynamicLinker.class.getName();

   146     private static final String RELINK_METHOD_NAME = "relink";

   147 

   148     private final LinkerServices linkerServices;

   149     private final int runtimeContextArgCount;

   150     private final boolean syncOnRelink;

   151     private final int unstableRelinkThreshold;

   152 

   153     /**

   154      * Creates a new dynamic linker.

   155      *

   156      * @param linkerServices the linkerServices used by the linker, created by the factory.

   157      * @param runtimeContextArgCount see {@link DynamicLinkerFactory#setRuntimeContextArgCount(int)}

   158      */

   159     DynamicLinker(LinkerServices linkerServices, int runtimeContextArgCount, boolean syncOnRelink,

   160             int unstableRelinkThreshold) {

   161         if(runtimeContextArgCount < 0) {

   162             throw new IllegalArgumentException("runtimeContextArgCount < 0");

   163         }

   164         if(unstableRelinkThreshold < 0) {

   165             throw new IllegalArgumentException("unstableRelinkThreshold < 0");

   166         }

   167         this.runtimeContextArgCount = runtimeContextArgCount;

   168         this.linkerServices = linkerServices;

   169         this.syncOnRelink = syncOnRelink;

   170         this.unstableRelinkThreshold = unstableRelinkThreshold;

   171     }

   172 

   173     /**

   174      * Links an invokedynamic call site. It will install a method handle into the call site that invokes the relinking

   175      * mechanism of this linker. Next time the call site is invoked, it will be linked for the actual arguments it was

   176      * invoked with.

   177      *

   178      * @param callSite the call site to link.

   179      * @return the callSite, for easy call chaining.

   180      */

   181     public <T extends RelinkableCallSite> T link(final T callSite) {

   182         callSite.initialize(createRelinkAndInvokeMethod(callSite, 0));

   183         return callSite;

   184     }

   185 

   186     /**

   187      * Returns the object representing the lower level linker services of this class that are normally exposed to

   188      * individual language-specific linkers. While as a user of this class you normally only care about the

   189      * {@link #link(RelinkableCallSite)} method, in certain circumstances you might want to use the lower level services

   190      * directly; either to lookup specific method handles, to access the type converters, and so on.

   191      * @return the object representing the linker services of this class.

   192      */

   193     public LinkerServices getLinkerServices() {

   194         return linkerServices;

   195     }

   196 

   197     private static final MethodHandle RELINK = Lookup.findOwnSpecial(MethodHandles.lookup(), RELINK_METHOD_NAME,

   198             MethodHandle.class, RelinkableCallSite.class, int.class, Object[].class);

   199 

   200     private MethodHandle createRelinkAndInvokeMethod(final RelinkableCallSite callSite, int relinkCount) {

   201         // Make a bound MH of invoke() for this linker and call site

   202         final MethodHandle boundRelinker = MethodHandles.insertArguments(RELINK, 0, this, callSite, Integer.valueOf(

   203                 relinkCount));

   204         // Make a MH that gathers all arguments to the invocation into an Object[]

   205         final MethodType type = callSite.getDescriptor().getMethodType();

   206         final MethodHandle collectingRelinker = boundRelinker.asCollector(Object[].class, type.parameterCount());

   207         return MethodHandles.foldArguments(MethodHandles.exactInvoker(type), collectingRelinker.asType(

   208                 type.changeReturnType(MethodHandle.class)));

   209     }

   210 

   211     /**

   212      * Relinks a call site conforming to the invocation arguments.

   213      *

   214      * @param callSite the call site itself

   215      * @param arguments arguments to the invocation

   216      * @return return the method handle for the invocation

   217      * @throws Exception rethrows any exception thrown by the linkers

   218      */

   219     @SuppressWarnings("unused")

   220     private MethodHandle relink(RelinkableCallSite callSite, int relinkCount, Object... arguments) throws Exception {

   221         final CallSiteDescriptor callSiteDescriptor = callSite.getDescriptor();

   222         final boolean unstableDetectionEnabled = unstableRelinkThreshold > 0;

   223         final boolean callSiteUnstable = unstableDetectionEnabled && relinkCount >= unstableRelinkThreshold;

   224         final LinkRequest linkRequest =

   225                 runtimeContextArgCount == 0 ? new LinkRequestImpl(callSiteDescriptor, callSiteUnstable, arguments)

   226                         : new RuntimeContextLinkRequestImpl(callSiteDescriptor, callSiteUnstable, arguments,

   227                                 runtimeContextArgCount);

   228 

   229         // Find a suitable method handle with a guard

   230         GuardedInvocation guardedInvocation = linkerServices.getGuardedInvocation(linkRequest);

   231 

   232         // None found - throw an exception

   233         if(guardedInvocation == null) {

   234             throw new NoSuchDynamicMethodException(callSiteDescriptor.toString());

   235         }

   236 

   237         // If our call sites have a runtime context, and the linker produced a context-stripped invocation, adapt the

   238         // produced invocation into contextual invocation (by dropping the context...)

   239         if(runtimeContextArgCount > 0) {

   240             final MethodType origType = callSiteDescriptor.getMethodType();

   241             final MethodHandle invocation = guardedInvocation.getInvocation();

   242             if(invocation.type().parameterCount() == origType.parameterCount() - runtimeContextArgCount) {

   243                 final List<Class<?>> prefix = origType.parameterList().subList(1, runtimeContextArgCount + 1);

   244                 final MethodHandle guard = guardedInvocation.getGuard();

   245                 guardedInvocation = guardedInvocation.dropArguments(1, prefix);

   246             }

   247         }

   248 

   249         if(unstableDetectionEnabled && relinkCount <= unstableRelinkThreshold && relinkCount++ == unstableRelinkThreshold) {

   250             // Note that we'll increase the relinkCount until threshold+1 and not increase it beyond that. Threshold+1

   251             // is treated as a special value to signal that resetAndRelink has already executed once for the unstable

   252             // call site; we only want the call site to throw away its current linkage once, when it transitions to

   253             // unstable.

   254             callSite.resetAndRelink(guardedInvocation, createRelinkAndInvokeMethod(callSite, relinkCount));

   255         } else {

   256             callSite.relink(guardedInvocation, createRelinkAndInvokeMethod(callSite, relinkCount));

   257         }

   258         if(syncOnRelink) {

   259             MutableCallSite.syncAll(new MutableCallSite[] { (MutableCallSite)callSite });

   260         }

   261         return guardedInvocation.getInvocation();

   262     }

   263 

   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 }