| /* |
| * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /* |
| * This file is available under and governed by the GNU General Public |
| * License version 2 only, as published by the Free Software Foundation. |
| * However, the following notice accompanied the original version of this |
| * file, and Oracle licenses the original version of this file under the BSD |
| * license: |
| */ |
| /* |
| Copyright 2009-2013 Attila Szegedi |
| |
| Licensed under both the Apache License, Version 2.0 (the "Apache License") |
| and the BSD License (the "BSD License"), with licensee being free to |
| choose either of the two at their discretion. |
| |
| You may not use this file except in compliance with either the Apache |
| License or the BSD License. |
| |
| If you choose to use this file in compliance with the Apache License, the |
| following notice applies to you: |
| |
| You may obtain a copy of the Apache License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, |
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or |
| implied. See the License for the specific language governing |
| permissions and limitations under the License. |
| |
| If you choose to use this file in compliance with the BSD License, the |
| following notice applies to you: |
| |
| Redistribution and use in source and binary forms, with or without |
| modification, are permitted provided that the following conditions are |
| met: |
| * Redistributions of source code must retain the above copyright |
| notice, this list of conditions and the following disclaimer. |
| * Redistributions in binary form must reproduce the above copyright |
| notice, this list of conditions and the following disclaimer in the |
| documentation and/or other materials provided with the distribution. |
| * Neither the name of the copyright holder nor the names of |
| contributors may be used to endorse or promote products derived from |
| this software without specific prior written permission. |
| |
| THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS |
| IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
| TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A |
| PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER |
| BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR |
| BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
| OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
| ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| package jdk.dynalink; |
| |
| import java.lang.invoke.MethodHandle; |
| import java.lang.invoke.MethodHandles; |
| import java.lang.invoke.MethodType; |
| import java.lang.invoke.MutableCallSite; |
| import java.util.Objects; |
| import jdk.dynalink.linker.GuardedInvocation; |
| import jdk.dynalink.linker.GuardedInvocationTransformer; |
| import jdk.dynalink.linker.GuardingDynamicLinker; |
| import jdk.dynalink.linker.LinkRequest; |
| import jdk.dynalink.linker.LinkerServices; |
| import jdk.dynalink.linker.support.Lookup; |
| import jdk.dynalink.linker.support.SimpleLinkRequest; |
| import jdk.dynalink.support.ChainedCallSite; |
| import jdk.dynalink.support.SimpleRelinkableCallSite; |
| |
| /** |
| * The linker for {@link RelinkableCallSite} objects. A dynamic linker is a main |
| * objects when using Dynalink, it coordinates linking of call sites with |
| * linkers of available language runtimes that are represented by |
| * {@link GuardingDynamicLinker} objects (you only need to deal with these if |
| * you are yourself implementing a language runtime with its own object model |
| * and/or type conversions). To use Dynalink, you have to create one or more |
| * dynamic linkers using a {@link DynamicLinkerFactory}. Subsequently, you need |
| * to invoke its {@link #link(RelinkableCallSite)} method from |
| * {@code invokedynamic} bootstrap methods to let it manage all the call sites |
| * they create. Usual usage would be to create at least one class per language |
| * runtime to contain one linker instance as: |
| * <pre> |
| * |
| * class MyLanguageRuntime { |
| * private static final GuardingDynamicLinker myLanguageLinker = new MyLanguageLinker(); |
| * private static final DynamicLinker dynamicLinker = createDynamicLinker(); |
| * |
| * private static DynamicLinker createDynamicLinker() { |
| * final DynamicLinkerFactory factory = new DynamicLinkerFactory(); |
| * factory.setPrioritizedLinker(myLanguageLinker); |
| * return factory.createLinker(); |
| * } |
| * |
| * public static CallSite bootstrap(MethodHandles.Lookup lookup, String name, MethodType type) { |
| * return dynamicLinker.link( |
| * new SimpleRelinkableCallSite( |
| * new CallSiteDescriptor(lookup, parseOperation(name), type))); |
| * } |
| * |
| * private static Operation parseOperation(String name) { |
| * ... |
| * } |
| * } |
| * </pre> |
| * The above setup of one static linker instance is often too simple. You will |
| * often have your language runtime have a concept of some kind of |
| * "context class loader" and you will want to create one dynamic linker per |
| * such class loader, to ensure it incorporates linkers for all other language |
| * runtimes visible to that class loader (see |
| * {@link DynamicLinkerFactory#setClassLoader(ClassLoader)}). |
| * <p> |
| * There are three components you need to provide in the above example: |
| * <ul> |
| * |
| * <li>You are expected to provide a {@link GuardingDynamicLinker} for your own |
| * language. If your runtime doesn't have its own object model or type |
| * conversions, you don't need to implement a {@code GuardingDynamicLinker}; you |
| * would simply not invoke the {@code setPrioritizedLinker} method on the factory.</li> |
| * |
| * <li>The performance of the programs can depend on your choice of the class to |
| * represent call sites. The above example used |
| * {@link SimpleRelinkableCallSite}, but you might want to use |
| * {@link ChainedCallSite} instead. You'll need to experiment and decide what |
| * fits your runtime the best. You can further subclass either of these or |
| * implement your own.</li> |
| * |
| * <li>You also need to provide {@link CallSiteDescriptor}s to your call sites. |
| * They are immutable objects that contain all the information about the call |
| * site: the class performing the lookups, the operation being invoked, and the |
| * method signature. You will have to supply your own scheme to encode and |
| * decode operations in the call site name or static parameters, that is why |
| * in the above example the {@code parseOperation} method is left unimplemented.</li> |
| * |
| * </ul> |
| */ |
| public final class DynamicLinker { |
| private static final String CLASS_NAME = DynamicLinker.class.getName(); |
| private static final String RELINK_METHOD_NAME = "relink"; |
| |
| private static final String INITIAL_LINK_CLASS_NAME = "java.lang.invoke.MethodHandleNatives"; |
| private static final String INITIAL_LINK_METHOD_NAME = "linkCallSite"; |
| private static final String INVOKE_PACKAGE_PREFIX = "java.lang.invoke."; |
| |
| private final LinkerServices linkerServices; |
| private final GuardedInvocationTransformer prelinkTransformer; |
| private final boolean syncOnRelink; |
| private final int unstableRelinkThreshold; |
| |
| /** |
| * Creates a new dynamic linker. |
| * |
| * @param linkerServices the linkerServices used by the linker, created by the factory. |
| * @param prelinkTransformer see {@link DynamicLinkerFactory#setPrelinkTransformer(GuardedInvocationTransformer)} |
| * @param syncOnRelink see {@link DynamicLinkerFactory#setSyncOnRelink(boolean)} |
| * @param unstableRelinkThreshold see {@link DynamicLinkerFactory#setUnstableRelinkThreshold(int)} |
| */ |
| DynamicLinker(final LinkerServices linkerServices, final GuardedInvocationTransformer prelinkTransformer, |
| final boolean syncOnRelink, final int unstableRelinkThreshold) { |
| if(unstableRelinkThreshold < 0) { |
| throw new IllegalArgumentException("unstableRelinkThreshold < 0"); |
| } |
| this.linkerServices = linkerServices; |
| this.prelinkTransformer = prelinkTransformer; |
| this.syncOnRelink = syncOnRelink; |
| this.unstableRelinkThreshold = unstableRelinkThreshold; |
| } |
| |
| /** |
| * Links an invokedynamic call site. It will install a method handle into |
| * the call site that invokes the relinking mechanism of this linker. Next |
| * time the call site is invoked, it will be linked for the actual arguments |
| * it was invoked with. |
| * |
| * @param <T> the particular subclass of {@link RelinkableCallSite} for |
| * which to create a link. |
| * @param callSite the call site to link. |
| * |
| * @return the callSite, for easy call chaining. |
| */ |
| public <T extends RelinkableCallSite> T link(final T callSite) { |
| callSite.initialize(createRelinkAndInvokeMethod(callSite, 0)); |
| return callSite; |
| } |
| |
| /** |
| * Returns the object representing the linker services of this class that |
| * are normally exposed to individual {@link GuardingDynamicLinker |
| * language-specific linkers}. While as a user of this class you normally |
| * only care about the {@link #link(RelinkableCallSite)} method, in certain |
| * circumstances you might want to use the lower level services directly; |
| * either to lookup specific method handles, to access the type converters, |
| * and so on. |
| * |
| * @return the object representing the linker services of this class. |
| */ |
| public LinkerServices getLinkerServices() { |
| return linkerServices; |
| } |
| |
| private static final MethodHandle RELINK = Lookup.findOwnSpecial(MethodHandles.lookup(), RELINK_METHOD_NAME, |
| MethodHandle.class, RelinkableCallSite.class, int.class, Object[].class); |
| |
| private MethodHandle createRelinkAndInvokeMethod(final RelinkableCallSite callSite, final int relinkCount) { |
| // Make a bound MH of invoke() for this linker and call site |
| final MethodHandle boundRelinker = MethodHandles.insertArguments(RELINK, 0, this, callSite, Integer.valueOf( |
| relinkCount)); |
| // Make a MH that gathers all arguments to the invocation into an Object[] |
| final MethodType type = callSite.getDescriptor().getMethodType(); |
| final MethodHandle collectingRelinker = boundRelinker.asCollector(Object[].class, type.parameterCount()); |
| return MethodHandles.foldArguments(MethodHandles.exactInvoker(type), collectingRelinker.asType( |
| type.changeReturnType(MethodHandle.class))); |
| } |
| |
| /** |
| * Relinks a call site conforming to the invocation arguments. |
| * |
| * @param callSite the call site itself |
| * @param arguments arguments to the invocation |
| * |
| * @return return the method handle for the invocation |
| * |
| * @throws Exception rethrows any exception thrown by the linkers |
| */ |
| @SuppressWarnings("unused") |
| private MethodHandle relink(final RelinkableCallSite callSite, final int relinkCount, final Object... arguments) throws Exception { |
| final CallSiteDescriptor callSiteDescriptor = callSite.getDescriptor(); |
| final boolean unstableDetectionEnabled = unstableRelinkThreshold > 0; |
| final boolean callSiteUnstable = unstableDetectionEnabled && relinkCount >= unstableRelinkThreshold; |
| final LinkRequest linkRequest = new SimpleLinkRequest(callSiteDescriptor, callSiteUnstable, arguments); |
| |
| GuardedInvocation guardedInvocation = linkerServices.getGuardedInvocation(linkRequest); |
| |
| // None found - throw an exception |
| if(guardedInvocation == null) { |
| throw new NoSuchDynamicMethodException(callSiteDescriptor.toString()); |
| } |
| |
| // Make sure we transform the invocation before linking it into the call site. This is typically used to match the |
| // return type of the invocation to the call site. |
| guardedInvocation = prelinkTransformer.filter(guardedInvocation, linkRequest, linkerServices); |
| Objects.requireNonNull(guardedInvocation); |
| |
| int newRelinkCount = relinkCount; |
| // Note that the short-circuited "&&" evaluation below ensures we'll increment the relinkCount until |
| // threshold + 1 but not beyond that. Threshold + 1 is treated as a special value to signal that resetAndRelink |
| // has already executed once for the unstable call site; we only want the call site to throw away its current |
| // linkage once, when it transitions to unstable. |
| if(unstableDetectionEnabled && newRelinkCount <= unstableRelinkThreshold && newRelinkCount++ == unstableRelinkThreshold) { |
| callSite.resetAndRelink(guardedInvocation, createRelinkAndInvokeMethod(callSite, newRelinkCount)); |
| } else { |
| callSite.relink(guardedInvocation, createRelinkAndInvokeMethod(callSite, newRelinkCount)); |
| } |
| if(syncOnRelink) { |
| MutableCallSite.syncAll(new MutableCallSite[] { (MutableCallSite)callSite }); |
| } |
| return guardedInvocation.getInvocation(); |
| } |
| |
| /** |
| * Returns a stack trace element describing the location of the |
| * {@code invokedynamic} call site currently being linked on the current |
| * thread. The operation is potentially expensive as it needs to generate a |
| * stack trace to inspect it and is intended for use in diagnostics code. |
| * For "free-floating" call sites (not associated with an |
| * {@code invokedynamic} instruction), the result is not well-defined. |
| * |
| * @return a stack trace element describing the location of the call site |
| * currently being linked, or null if it is not invoked while a call |
| * site is being linked. |
| */ |
| public static StackTraceElement getLinkedCallSiteLocation() { |
| final StackTraceElement[] trace = new Throwable().getStackTrace(); |
| for(int i = 0; i < trace.length - 1; ++i) { |
| final StackTraceElement frame = trace[i]; |
| // If we found any of our linking entry points on the stack... |
| if(isRelinkFrame(frame) || isInitialLinkFrame(frame)) { |
| // ... then look for the first thing calling it that isn't j.l.invoke |
| for (int j = i + 1; j < trace.length; ++j) { |
| final StackTraceElement frame2 = trace[j]; |
| if (!frame2.getClassName().startsWith(INVOKE_PACKAGE_PREFIX)) { |
| return frame2; |
| } |
| } |
| } |
| } |
| return null; |
| } |
| |
| /** |
| * Returns {@code true} if the frame represents {@code MethodHandleNatives.linkCallSite()}, |
| * the frame immediately on top of the call site frame when the call site is |
| * being linked for the first time. |
| * |
| * @param frame the frame |
| * |
| * @return {@code true} if this frame represents {@code MethodHandleNatives.linkCallSite()}. |
| */ |
| private static boolean isInitialLinkFrame(final StackTraceElement frame) { |
| return testFrame(frame, INITIAL_LINK_METHOD_NAME, INITIAL_LINK_CLASS_NAME); |
| } |
| |
| /** |
| * Returns {@code true} if the frame represents {@code DynamicLinker.relink()}, |
| * the frame immediately on top of the call site frame when the call site is |
| * being relinked (linked for second and subsequent times). |
| * |
| * @param frame the frame |
| * |
| * @return {@code true} if this frame represents {@code DynamicLinker.relink()}. |
| */ |
| private static boolean isRelinkFrame(final StackTraceElement frame) { |
| return testFrame(frame, RELINK_METHOD_NAME, CLASS_NAME); |
| } |
| |
| private static boolean testFrame(final StackTraceElement frame, final String methodName, final String className) { |
| return methodName.equals(frame.getMethodName()) && className.equals(frame.getClassName()); |
| } |
| } |