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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

 * 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

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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

*/

package jdk.dynalink;

import java.lang.invoke.CallSite;

import java.lang.invoke.MethodHandle;

import jdk.dynalink.linker.GuardedInvocation;

import jdk.dynalink.support.ChainedCallSite;

import jdk.dynalink.support.SimpleRelinkableCallSite;

/**

 * Interface for call sites managed by a {@link DynamicLinker}. Users of

 * Dynalink must use subclasses of {@link CallSite} that also implement this

 * interface as their call site implementations. There is a readily usable

 * {@link SimpleRelinkableCallSite} subclass that implements monomorphic inline

 * caching strategy as well as {@link ChainedCallSite} that implements a

 * polymorphic inline caching strategy and retains a chain of previously linked

 * method handles. A relinkable call site will be managed by a

 * {@link DynamicLinker} object after being associated with it using its

 * {@link DynamicLinker#link(RelinkableCallSite)} method.

 */

public interface RelinkableCallSite {

    /**

     * Invoked by dynamic linker to initialize 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 using

     * {@link CallSite#setTarget(MethodHandle)}. Relink-and-invoke is the

     * initial method handle set by

     * {@link DynamicLinker#link(RelinkableCallSite)} that will cause the call

     * site to be relinked to an appropriate target on its first invocation

     * based on its arguments, and that linked target will then be invoked

     * (hence the name). This linking protocol effectively delays linking until

     * the call site is invoked with actual arguments and thus ensures that

     * linkers can make nuanced linking decisions based on those arguments and

     * not just on the static method type of the call site.

     * @param relinkAndInvoke a relink-and-invoke method handle supplied by

     * Dynalink.

     */

    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 relinked (but see

     * {@link #resetAndRelink(GuardedInvocation, MethodHandle)} for an

     * exception). 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 relinkAndInvoke a relink-and-invoke method handle. This is a

     * method handle matching the method type of the call site that is supplied

     * by the {@link DynamicLinker} as a callback. It should be used by this

     * call site as the ultimate 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 obtain an adequate target {@link GuardedInvocation} for the

     * invocation, and subsequently invoke

     * {@link #relink(GuardedInvocation, MethodHandle)} or

     * {@link #resetAndRelink(GuardedInvocation, MethodHandle)}, and finally

     * invoke the target.

     */

    public void relink(GuardedInvocation guardedInvocation, MethodHandle relinkAndInvoke);

    /**

     * This method will be called by the dynamic linker every time the call site

     * is relinked <b>and</b> the linker wishes the call site to throw away any

     * prior linkage state (that is how it differs from

     * {@link #relink(GuardedInvocation, MethodHandle)}). It will be passed a

     * {@code GuardedInvocation} that the call site should use to build its new

     * target method handle. When this method is called, the call site is

     * discouraged from keeping any previous state, 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 relinkAndInvoke a relink-and-invoke method handle. This is a

     * method handle matching the method type of the call site that is supplied

     * by the {@link DynamicLinker} as a callback. It should be used by this

     * call site as the ultimate 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 obtain an adequate target {@link GuardedInvocation} for the

     * invocation, and subsequently invoke

     * {@link #relink(GuardedInvocation, MethodHandle)} or

     * {@link #resetAndRelink(GuardedInvocation, MethodHandle)}, and finally

     * invoke the target.

     */

    public void resetAndRelink(GuardedInvocation guardedInvocation, MethodHandle relinkAndInvoke);

}