| /* |
| * 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.dynalink.CallSiteDescriptor; |
| import jdk.dynalink.NamedOperation; |
| import jdk.dynalink.linker.GuardedInvocation; |
| import jdk.dynalink.linker.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) { |
| switch (NashornCallSiteDescriptor.getStandardOperation(desc)) { |
| case CALL: |
| case NEW: |
| final String name = NashornCallSiteDescriptor.getOperand(desc); |
| final String msg = name != null? "not.a.function" : "cant.call.undefined"; |
| throw typeError(msg, name); |
| case GET: |
| // NOTE: we support GET:ELEMENT and SET:ELEMENT as JavaScript doesn't distinguish items from properties. Nashorn itself |
| // emits "GET:PROPERTY|ELEMENT|METHOD:identifier" for "<expr>.<identifier>" and "GET:ELEMENT|PROPERTY|METHOD" 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. |
| if (!(desc.getOperation() instanceof NamedOperation)) { |
| return findGetIndexMethod(desc); |
| } |
| return findGetMethod(desc); |
| case SET: |
| if (!(desc.getOperation() instanceof NamedOperation)) { |
| return findSetIndexMethod(desc); |
| } |
| return findSetMethod(desc); |
| default: |
| } |
| return null; |
| } |
| |
| private static ECMAException lookupTypeError(final String msg, final CallSiteDescriptor desc) { |
| final String name = NashornCallSiteDescriptor.getOperand(desc); |
| 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, NashornCallSiteDescriptor.getOperand(desc)), 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, NashornCallSiteDescriptor.getOperand(desc)), 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)); |
| } |
| } |