Java example source code file (RelinkableCallSite.java)

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callsitedescriptor, methodhandle, relinkablecallsite

The RelinkableCallSite.java Java example source code

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
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/*
 * 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
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       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

package jdk.internal.dynalink;

import java.lang.invoke.CallSite;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MutableCallSite;
import java.lang.invoke.VolatileCallSite;
import jdk.internal.dynalink.linker.GuardedInvocation;

/**
 * Interface for relinkable call sites. Language runtimes wishing to use this framework must use subclasses of
 * {@link CallSite} that also implement this interface as their call sites. There is a readily usable
 * {@link MonomorphicCallSite} subclass that implements monomorphic inline caching strategy as well as a
 * {@link ChainedCallSite} that retains a chain of already linked method handles. The reason this is defined as an
 * interface instead of a concrete, albeit abstract class is that it allows independent implementations to choose
 * between {@link MutableCallSite} and {@link VolatileCallSite} as they see fit.
 *
 * @author Attila Szegedi
 */
public interface RelinkableCallSite {
    /**
     * Initializes the relinkable call site by setting a relink-and-invoke method handle. The call site implementation
     * is supposed to set this method handle as its target.
     * @param relinkAndInvoke a relink-and-invoke method handle supplied by the {@link DynamicLinker}.
     */
    public void initialize(MethodHandle relinkAndInvoke);

    /**
     * Returns the descriptor for this call site.
     *
     * @return the descriptor for this call site.
     */
    public CallSiteDescriptor getDescriptor();

    /**
     * This method will be called by the dynamic linker every time the call site is normally relinked. It will be passed
     * a {@code GuardedInvocation} that the call site should incorporate into its target method handle. When this method
     * is called, the call site is allowed to keep other non-invalidated invocations around for implementation of
     * polymorphic inline caches and compose them with this invocation to form its final target.
     *
     * @param guardedInvocation the guarded invocation that the call site should incorporate into its target method
     * handle.
     * @param fallback the fallback method. This is a method matching the method type of the call site that is supplied
     * by the {@link DynamicLinker} to be used by this call site as a fallback when it can't invoke its target with the
     * passed arguments. The fallback method is such that when it's invoked, it'll try to discover the adequate target
     * for the invocation, subsequently invoke {@link #relink(GuardedInvocation, MethodHandle)} or
     * {@link #resetAndRelink(GuardedInvocation, MethodHandle)}, and finally invoke the target.
     */
    public void relink(GuardedInvocation guardedInvocation, MethodHandle fallback);

    /**
     * This method will be called by the dynamic linker every time the call site is relinked and the linker wishes the
     * call site to throw away any prior linkage state. It will be passed a {@code GuardedInvocation} that the call site
     * should use to build its target method handle. When this method is called, the call site is discouraged from
     * keeping previous state around, and is supposed to only link the current invocation.
     *
     * @param guardedInvocation the guarded invocation that the call site should use to build its target method handle.
     * @param fallback the fallback method. This is a method matching the method type of the call site that is supplied
     * by the {@link DynamicLinker} to be used by this call site as a fallback when it can't invoke its target with the
     * passed arguments. The fallback method is such that when it's invoked, it'll try to discover the adequate target
     * for the invocation, subsequently invoke {@link #relink(GuardedInvocation, MethodHandle)} or
     * {@link #resetAndRelink(GuardedInvocation, MethodHandle)}, and finally invoke the target.
     */
    public void resetAndRelink(GuardedInvocation guardedInvocation, MethodHandle fallback);
}