Java example source code file (NashornGuards.java)

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Java - Java tags/keywords

class, is_instanceof_2, is_map, is_scriptfunction, is_scriptobject, methodhandle, nashornguards, object, propertymap, scriptobject, string, suppresswarnings

The NashornGuards.java Java example source code

/*
 * 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.
 */

package jdk.nashorn.internal.runtime.linker;

import static jdk.nashorn.internal.lookup.Lookup.MH;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import jdk.nashorn.internal.runtime.PropertyMap;
import jdk.nashorn.internal.runtime.ScriptFunction;
import jdk.nashorn.internal.runtime.ScriptObject;

/**
 * Constructor of method handles used to guard call sites.
 */
public final class NashornGuards {
    private static final MethodHandle IS_SCRIPTOBJECT          = findOwnMH("isScriptObject", boolean.class, Object.class);
    private static final MethodHandle IS_SCRIPTFUNCTION        = findOwnMH("isScriptFunction", boolean.class, Object.class);
    private static final MethodHandle IS_MAP                   = findOwnMH("isMap", boolean.class, Object.class, PropertyMap.class);
    private static final MethodHandle IS_INSTANCEOF_2          = findOwnMH("isInstanceOf2", boolean.class, Object.class, Class.class, Class.class);

    // don't create me!
    private NashornGuards() {
    }

    /**
     * Get the guard that checks if an item is a {@code ScriptObject}
     * @return method handle for guard
     */
    public static MethodHandle getScriptObjectGuard() {
        return IS_SCRIPTOBJECT;
    }

    /**
     * Get the guard that checks if an item is a {@code ScriptFunction}
     * @return method handle for guard
     */
    public static MethodHandle getScriptFunctionGuard() {
        return IS_SCRIPTFUNCTION;
    }

    /**
     * Get the guard that checks if a {@link PropertyMap} is equal to
     * a known map, using reference comparison
     *
     * @param map The map to check against. This will be bound to the guard method handle
     *
     * @return method handle for guard
     */
    public static MethodHandle getMapGuard(final PropertyMap map) {
        return MH.insertArguments(IS_MAP, 1, map);
    }

    /**
     * Get a guard that checks if in item is an instance of either of two classes.
     *
     * @param class1 the first class
     * @param class2 the second class
     * @return method handle for guard
     */
    public static MethodHandle getInstanceOf2Guard(final Class<?> class1, final Class class2) {
        return MH.insertArguments(IS_INSTANCEOF_2, 1, class1, class2);
    }

    @SuppressWarnings("unused")
    private static boolean isScriptObject(final Object self) {
        return self instanceof ScriptObject;
    }

    @SuppressWarnings("unused")
    private static boolean isScriptFunction(final Object self) {
        return self instanceof ScriptFunction;
    }

    @SuppressWarnings("unused")
    private static boolean isMap(final Object self, final PropertyMap map) {
        return self instanceof ScriptObject && ((ScriptObject)self).getMap() == map;
    }

    @SuppressWarnings("unused")
    private static boolean isInstanceOf2(final Object self, final Class<?> class1, final Class class2) {
        return class1.isInstance(self) || class2.isInstance(self);
    }

    private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class... types) {
        return MH.findStatic(MethodHandles.lookup(), NashornGuards.class, name, MH.type(rtype, types));
    }

}