Mercurial > jdk8-mips64-public > nashorn / file revision

 /*

  * 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;

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

 import static jdk.nashorn.internal.runtime.ECMAErrors.typeError;

 import java.lang.invoke.MethodHandle;

 import java.lang.invoke.MethodHandles;

 import jdk.internal.dynalink.CallSiteDescriptor;

 import jdk.internal.dynalink.linker.GuardedInvocation;

 import jdk.internal.dynalink.support.CallSiteDescriptorFactory;

 import jdk.internal.dynalink.support.Guards;

 import jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor;

 /**

  * Unique instance of this class is used to represent JavaScript undefined.

  */

 public final class Undefined extends DefaultPropertyAccess {

     private Undefined() {

     }

     private static final Undefined UNDEFINED = new Undefined();

     private static final Undefined EMPTY     = new Undefined();

     // Guard used for indexed property access/set on the Undefined instance

     private static final MethodHandle UNDEFINED_GUARD = Guards.getIdentityGuard(UNDEFINED);

     /**

      * Get the value of {@code undefined}, this is represented as a global singleton

      * instance of this class. It can always be reference compared

      *

      * @return the undefined object

      */

     public static Undefined getUndefined() {

         return UNDEFINED;

     }

     /**

      * Get the value of {@code empty}. This is represented as a global singleton

      * instanceof this class. It can always be reference compared.

      * <p>

      * We need empty to differentiate behavior in things like array iterators

      * <p>

      * @return the empty object

      */

     public static Undefined getEmpty() {

         return EMPTY;

     }

     /**

      * Get the class name of Undefined

      * @return "Undefined"

      */

     @SuppressWarnings("static-method")

     public String getClassName() {

         return "Undefined";

     }

     @Override

     public String toString() {

         return "undefined";

     }

     /**

      * Lookup the appropriate method for an invoke dynamic call.

      * @param desc The invoke dynamic callsite descriptor.

      * @return GuardedInvocation to be invoked at call site.

      */

     public static GuardedInvocation lookup(final CallSiteDescriptor desc) {

         final String operator = CallSiteDescriptorFactory.tokenizeOperators(desc).get(0);

         switch (operator) {

         case "new":

         case "call": {

             final String name = NashornCallSiteDescriptor.getFunctionDescription(desc);

             final String msg = name != null? "not.a.function" : "cant.call.undefined";

             throw typeError(msg, name);

         }

         case "callMethod":

             throw lookupTypeError("cant.read.property.of.undefined", desc);

         // NOTE: we support getElem and setItem as JavaScript doesn't distinguish items from properties. Nashorn itself

         // emits "dyn:getProp:identifier" for "<expr>.<identifier>" and "dyn:getElem" for "<expr>[<expr>]", but we are

         // more flexible here and dispatch not on operation name (getProp vs. getElem), but rather on whether the

         // operation has an associated name or not.

         case "getProp":

         case "getElem":

         case "getMethod":

             if (desc.getNameTokenCount() < 3) {

                 return findGetIndexMethod(desc);

             }

             return findGetMethod(desc);

         case "setProp":

         case "setElem":

             if (desc.getNameTokenCount() < 3) {

                 return findSetIndexMethod(desc);

             }

             return findSetMethod(desc);

         default:

             break;

         }

         return null;

     }

     private static ECMAException lookupTypeError(final String msg, final CallSiteDescriptor desc) {

         final String name = desc.getNameToken(2);

         return typeError(msg, name != null && !name.isEmpty()? name : null);

     }

     private static final MethodHandle GET_METHOD = findOwnMH("get", Object.class, Object.class);

     private static final MethodHandle SET_METHOD = MH.insertArguments(findOwnMH("set", void.class, Object.class, Object.class, int.class), 3, NashornCallSiteDescriptor.CALLSITE_STRICT);

     private static GuardedInvocation findGetMethod(final CallSiteDescriptor desc) {

         return new GuardedInvocation(MH.insertArguments(GET_METHOD, 1, desc.getNameToken(2)), UNDEFINED_GUARD).asType(desc);

     }

     private static GuardedInvocation findGetIndexMethod(final CallSiteDescriptor desc) {

         return new GuardedInvocation(GET_METHOD, UNDEFINED_GUARD).asType(desc);

     }

     private static GuardedInvocation findSetMethod(final CallSiteDescriptor desc) {

         return new GuardedInvocation(MH.insertArguments(SET_METHOD, 1, desc.getNameToken(2)), UNDEFINED_GUARD).asType(desc);

     }

     private static GuardedInvocation findSetIndexMethod(final CallSiteDescriptor desc) {

         return new GuardedInvocation(SET_METHOD, UNDEFINED_GUARD).asType(desc);

     }

     @Override

     public Object get(final Object key) {

         throw typeError("cant.read.property.of.undefined", ScriptRuntime.safeToString(key));

     }

     @Override

     public void set(final Object key, final Object value, final int flags) {

         throw typeError("cant.set.property.of.undefined", ScriptRuntime.safeToString(key));

     }

     @Override

     public boolean delete(final Object key, final boolean strict) {

         throw typeError("cant.delete.property.of.undefined", ScriptRuntime.safeToString(key));

     }

     @Override

     public boolean has(final Object key) {

         return false;

     }

     @Override

     public boolean hasOwnProperty(final Object key) {

         return false;

     }

     private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class<?>... types) {

         return MH.findVirtual(MethodHandles.lookup(), Undefined.class, name, MH.type(rtype, types));

     }

 }