Undefined.java revision 1805:7caf1f762f1d
1139823Simp/* 21541Srgrimes * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. 3166841Srwatson * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4166841Srwatson * 51541Srgrimes * This code is free software; you can redistribute it and/or modify it 61541Srgrimes * under the terms of the GNU General Public License version 2 only, as 71541Srgrimes * published by the Free Software Foundation. Oracle designates this 81541Srgrimes * particular file as subject to the "Classpath" exception as provided 91541Srgrimes * by Oracle in the LICENSE file that accompanied this code. 101541Srgrimes * 111541Srgrimes * This code is distributed in the hope that it will be useful, but WITHOUT 121541Srgrimes * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 131541Srgrimes * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 141541Srgrimes * version 2 for more details (a copy is included in the LICENSE file that 151541Srgrimes * accompanied this code). 161541Srgrimes * 171541Srgrimes * You should have received a copy of the GNU General Public License version 181541Srgrimes * 2 along with this work; if not, write to the Free Software Foundation, 191541Srgrimes * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 201541Srgrimes * 211541Srgrimes * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 221541Srgrimes * or visit www.oracle.com if you need additional information or have any 231541Srgrimes * questions. 241541Srgrimes */ 251541Srgrimes 261541Srgrimespackage jdk.nashorn.internal.runtime; 271541Srgrimes 281541Srgrimesimport static jdk.nashorn.internal.lookup.Lookup.MH; 291541Srgrimesimport static jdk.nashorn.internal.runtime.ECMAErrors.typeError; 301541Srgrimes 3150477Speterimport java.lang.invoke.MethodHandle; 321541Srgrimesimport java.lang.invoke.MethodHandles; 331541Srgrimesimport jdk.dynalink.CallSiteDescriptor; 342169Spaulimport jdk.dynalink.NamedOperation; 35166841Srwatsonimport jdk.dynalink.linker.GuardedInvocation; 362169Spaulimport jdk.dynalink.linker.support.Guards; 371541Srgrimesimport jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor; 381541Srgrimes 391541Srgrimes/** 40166841Srwatson * Unique instance of this class is used to represent JavaScript undefined. 41166841Srwatson */ 42166841Srwatsonpublic final class Undefined extends DefaultPropertyAccess { 431541Srgrimes 441541Srgrimes private Undefined() { 451541Srgrimes } 461541Srgrimes 471541Srgrimes private static final Undefined UNDEFINED = new Undefined(); 481541Srgrimes private static final Undefined EMPTY = new Undefined(); 491541Srgrimes 501541Srgrimes // Guard used for indexed property access/set on the Undefined instance 511541Srgrimes private static final MethodHandle UNDEFINED_GUARD = Guards.getIdentityGuard(UNDEFINED); 521541Srgrimes 531541Srgrimes /** 54192649Sbz * Get the value of {@code undefined}, this is represented as a global singleton 55192649Sbz * instance of this class. It can always be reference compared 56192649Sbz * 57192649Sbz * @return the undefined object 58192649Sbz */ 59192649Sbz public static Undefined getUndefined() { 60192649Sbz return UNDEFINED; 61192649Sbz } 62192649Sbz 63192649Sbz /** 64192649Sbz * Get the value of {@code empty}. This is represented as a global singleton 65192649Sbz * instanceof this class. It can always be reference compared. 66192649Sbz * <p> 67194062Svanhu * We need empty to differentiate behavior in things like array iterators 68194062Svanhu * <p> 69194062Svanhu * @return the empty object 70194062Svanhu */ 71194062Svanhu public static Undefined getEmpty() { 72194062Svanhu return EMPTY; 73166841Srwatson } 741541Srgrimes 751541Srgrimes /** 761541Srgrimes * Get the class name of Undefined 771541Srgrimes * @return "Undefined" 7852904Sshin */ 791541Srgrimes @SuppressWarnings("static-method") 801541Srgrimes public String getClassName() { 811541Srgrimes return "Undefined"; 821541Srgrimes } 831541Srgrimes 8416143Swollman @Override 851541Srgrimes public String toString() { 861541Srgrimes return "undefined"; 8728270Swollman } 8852904Sshin 8952904Sshin /** 90170613Sbms * Lookup the appropriate method for an invoke dynamic call. 911541Srgrimes * @param desc The invoke dynamic callsite descriptor. 921541Srgrimes * @return GuardedInvocation to be invoked at call site. 93190962Srwatson */ 94196039Srwatson public static GuardedInvocation lookup(final CallSiteDescriptor desc) { 95196039Srwatson switch (NashornCallSiteDescriptor.getStandardOperation(desc)) { 96196039Srwatson case CALL: 97196039Srwatson case NEW: 98190962Srwatson final String name = NashornCallSiteDescriptor.getOperand(desc); 99190962Srwatson final String msg = name != null? "not.a.function" : "cant.call.undefined"; 100196039Srwatson throw typeError(msg, name); 101196039Srwatson case GET: 102196039Srwatson // NOTE: we support GET:ELEMENT and SET:ELEMENT as JavaScript doesn't distinguish items from properties. Nashorn itself 103196039Srwatson // emits "GET:PROPERTY|ELEMENT|METHOD:identifier" for "<expr>.<identifier>" and "GET:ELEMENT|PROPERTY|METHOD" for "<expr>[<expr>]", but we are 104196039Srwatson // more flexible here and dispatch not on operation name (getProp vs. getElem), but rather on whether the 105196039Srwatson // operation has an associated name or not. 106196039Srwatson if (!(desc.getOperation() instanceof NamedOperation)) { 107190962Srwatson return findGetIndexMethod(desc); 108190962Srwatson } 1091541Srgrimes return findGetMethod(desc); 110166841Srwatson case SET: 1111541Srgrimes if (!(desc.getOperation() instanceof NamedOperation)) { 1121541Srgrimes return findSetIndexMethod(desc); 113166841Srwatson } 1146472Swollman return findSetMethod(desc); 1156472Swollman default: 11636079Swollman } 117166841Srwatson return null; 1181541Srgrimes } 119166841Srwatson 120166841Srwatson private static ECMAException lookupTypeError(final String msg, final CallSiteDescriptor desc) { 121166841Srwatson final String name = NashornCallSiteDescriptor.getOperand(desc); 122166841Srwatson return typeError(msg, name != null && !name.isEmpty()? name : null); 123166841Srwatson } 124166841Srwatson 125166841Srwatson private static final MethodHandle GET_METHOD = findOwnMH("get", Object.class, Object.class); 1261541Srgrimes private static final MethodHandle SET_METHOD = MH.insertArguments(findOwnMH("set", void.class, Object.class, Object.class, int.class), 3, NashornCallSiteDescriptor.CALLSITE_STRICT); 1271541Srgrimes 12855205Speter private static GuardedInvocation findGetMethod(final CallSiteDescriptor desc) { 12944078Sdfr return new GuardedInvocation(MH.insertArguments(GET_METHOD, 1, NashornCallSiteDescriptor.getOperand(desc)), UNDEFINED_GUARD).asType(desc); 13044078Sdfr } 131166841Srwatson 132195699Srwatson private static GuardedInvocation findGetIndexMethod(final CallSiteDescriptor desc) { 133195699Srwatson return new GuardedInvocation(GET_METHOD, UNDEFINED_GUARD).asType(desc); 134195727Srwatson } 135195727Srwatson 136195699Srwatson private static GuardedInvocation findSetMethod(final CallSiteDescriptor desc) { 137166841Srwatson return new GuardedInvocation(MH.insertArguments(SET_METHOD, 1, NashornCallSiteDescriptor.getOperand(desc)), UNDEFINED_GUARD).asType(desc); 138166841Srwatson } 139207369Sbz 140207369Sbz private static GuardedInvocation findSetIndexMethod(final CallSiteDescriptor desc) { 141207369Sbz return new GuardedInvocation(SET_METHOD, UNDEFINED_GUARD).asType(desc); 142207369Sbz } 143166842Srwatson 1441541Srgrimes @Override 145192649Sbz public Object get(final Object key) { 146192649Sbz throw typeError("cant.read.property.of.undefined", ScriptRuntime.safeToString(key)); 147192649Sbz } 148166841Srwatson 149217126Sjhb @Override 150166841Srwatson public void set(final Object key, final Object value, final int flags) { 151193731Szec throw typeError("cant.set.property.of.undefined", ScriptRuntime.safeToString(key)); 152193731Szec } 153193731Szec 154166841Srwatson @Override 155166841Srwatson public boolean delete(final Object key, final boolean strict) { 156166841Srwatson throw typeError("cant.delete.property.of.undefined", ScriptRuntime.safeToString(key)); 157186813Srrs } 158186813Srrs 1591541Srgrimes @Override 1602169Spaul public boolean has(final Object key) { 1612169Spaul return false; 162 } 163 164 @Override 165 public boolean hasOwnProperty(final Object key) { 166 return false; 167 } 168 169 private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class<?>... types) { 170 return MH.findVirtual(MethodHandles.lookup(), Undefined.class, name, MH.type(rtype, types)); 171 } 172} 173