test/hotspot/jtreg/vmTestbase/vm/mlvm/indy/share/CallSiteDekkerActor.java

/*
 * Copyright (c) 2014, 2018, 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.
 *
 * 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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 * questions.
 */

package vm.mlvm.indy.share;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.CallSite;
import vm.mlvm.share.DekkerTest;

/**
 * The class implements Actor for {@link vm.mlvm.share.DekkerTest}.
 * <p>
 * This Actor switches targets for CallSite objects supplied in constructor.
 * Targets are method handles, generated with MethodHandle.constant(), which return true or false.
 * CallSite.setTarget() is used for setting appropriate target.
 * CallSite.dynamicInvoker().invokeExact() is used to detect which target is currently set.
 * No synchronization is used between setter and getter (see {@link vm.mlvm.share.DekkerTest} for details).
 *
 * @see vm.mlvm.share.DekkerTest
 */
public class CallSiteDekkerActor implements DekkerTest.Actor {

    public static final MethodHandle MH_FALSE = MethodHandles.constant(Boolean.class, false);
    public static final MethodHandle MH_TRUE = MethodHandles.constant(Boolean.class, true);

    private final CallSite a;
    private final CallSite b;

    public CallSiteDekkerActor(CallSite csa, CallSite csb) {
        a = csa;
        b = csb;
    }

    @Override
    public void reset() {
        a.setTarget(MH_FALSE);
        b.setTarget(MH_FALSE);
    }

    @Override
    public boolean actorA() throws Throwable {
        a.setTarget(MH_TRUE);
        return (Boolean) b.dynamicInvoker().invokeExact();
    }

    @Override
    public boolean actorB() throws Throwable {
        b.setTarget(MH_TRUE);
        return (Boolean) a.dynamicInvoker().invokeExact();
    }
}