1 /*
   2  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.nashorn.internal.runtime;
  27 
  28 import static jdk.nashorn.internal.codegen.CompilerConstants.staticCall;
  29 import static jdk.nashorn.internal.codegen.CompilerConstants.staticCallNoLookup;
  30 import static jdk.nashorn.internal.runtime.ECMAErrors.referenceError;
  31 import static jdk.nashorn.internal.runtime.ECMAErrors.syntaxError;
  32 import static jdk.nashorn.internal.runtime.ECMAErrors.typeError;
  33 import static jdk.nashorn.internal.runtime.JSType.isRepresentableAsInt;
  34 
  35 import java.lang.invoke.MethodHandle;
  36 import java.lang.reflect.Array;
  37 import java.util.Collections;
  38 import java.util.Iterator;
  39 import java.util.Locale;
  40 import java.util.NoSuchElementException;
  41 import java.util.Objects;
  42 import jdk.internal.dynalink.beans.StaticClass;
  43 import jdk.nashorn.api.scripting.ScriptObjectMirror;
  44 import jdk.nashorn.internal.codegen.CompilerConstants.Call;
  45 import jdk.nashorn.internal.ir.debug.JSONWriter;
  46 import jdk.nashorn.internal.parser.Lexer;
  47 import jdk.nashorn.internal.runtime.linker.Bootstrap;
  48 
  49 
  50 /**
  51  * Utilities to be called by JavaScript runtime API and generated classes.
  52  */
  53 
  54 public final class ScriptRuntime {
  55     private ScriptRuntime() {
  56     }
  57 
  58     /** Singleton representing the empty array object '[]' */
  59     public static final Object[] EMPTY_ARRAY = new Object[0];
  60 
  61     /** Unique instance of undefined. */
  62     public static final Undefined UNDEFINED = Undefined.getUndefined();
  63 
  64     /**
  65      * Unique instance of undefined used to mark empty array slots.
  66      * Can't escape the array.
  67      */
  68     public static final Undefined EMPTY = Undefined.getEmpty();
  69 
  70     /** Method handle to generic + operator, operating on objects */
  71     public static final Call ADD = staticCallNoLookup(ScriptRuntime.class, "ADD", Object.class, Object.class, Object.class);
  72 
  73     /** Method handle to generic === operator, operating on objects */
  74     public static final Call EQ_STRICT = staticCallNoLookup(ScriptRuntime.class, "EQ_STRICT", boolean.class, Object.class, Object.class);
  75 
  76     /** Method handle used to enter a {@code with} scope at runtime. */
  77     public static final Call OPEN_WITH = staticCallNoLookup(ScriptRuntime.class, "openWith", ScriptObject.class, ScriptObject.class, Object.class);
  78 
  79     /** Method handle used to exit a {@code with} scope at runtime. */
  80     public static final Call CLOSE_WITH = staticCallNoLookup(ScriptRuntime.class, "closeWith", ScriptObject.class, ScriptObject.class);
  81 
  82     /**
  83      * Method used to place a scope's variable into the Global scope, which has to be done for the
  84      * properties declared at outermost script level.
  85      */
  86     public static final Call MERGE_SCOPE = staticCallNoLookup(ScriptRuntime.class, "mergeScope", ScriptObject.class, ScriptObject.class);
  87 
  88     /**
  89      * Return an appropriate iterator for the elements in a for-in construct
  90      */
  91     public static final Call TO_PROPERTY_ITERATOR = staticCallNoLookup(ScriptRuntime.class, "toPropertyIterator", Iterator.class, Object.class);
  92 
  93     /**
  94      * Return an appropriate iterator for the elements in a for-each construct
  95      */
  96     public static final Call TO_VALUE_ITERATOR = staticCallNoLookup(ScriptRuntime.class, "toValueIterator", Iterator.class, Object.class);
  97 
  98     /**
  99       * Method handle for apply. Used from {@link ScriptFunction} for looking up calls to
 100       * call sites that are known to be megamorphic. Using an invoke dynamic here would
 101       * lead to the JVM deoptimizing itself to death
 102       */
 103     public static final Call APPLY = staticCall(ScriptRuntime.class, "apply", Object.class, ScriptFunction.class, Object.class, Object[].class);
 104 
 105     /**
 106      * Converts a switch tag value to a simple integer. deflt value if it can't.
 107      *
 108      * @param tag   Switch statement tag value.
 109      * @param deflt default to use if not convertible.
 110      * @return int tag value (or deflt.)
 111      */
 112     public static int switchTagAsInt(final Object tag, final int deflt) {
 113         if (tag instanceof Number) {
 114             final double d = ((Number)tag).doubleValue();
 115             if (isRepresentableAsInt(d)) {
 116                 return (int)d;
 117             }
 118         }
 119 
 120         return deflt;
 121     }
 122 
 123     /**
 124      * Converts a switch tag value to a simple integer. deflt value if it can't.
 125      *
 126      * @param tag   Switch statement tag value.
 127      * @param deflt default to use if not convertible.
 128      * @return int tag value (or deflt.)
 129      */
 130     public static int switchTagAsInt(final long tag, final int deflt) {
 131         return isRepresentableAsInt(tag) ? (int)tag : deflt;
 132     }
 133 
 134     /**
 135      * Converts a switch tag value to a simple integer. deflt value if it can't.
 136      *
 137      * @param tag   Switch statement tag value.
 138      * @param deflt default to use if not convertible.
 139      * @return int tag value (or deflt.)
 140      */
 141     public static int switchTagAsInt(final double tag, final int deflt) {
 142         return isRepresentableAsInt(tag) ? (int)tag : deflt;
 143     }
 144 
 145     /**
 146      * This is the builtin implementation of {@code Object.prototype.toString}
 147      * @param self reference
 148      * @return string representation as object
 149      */
 150     public static String builtinObjectToString(final Object self) {
 151         String className;
 152         // Spec tells us to convert primitives by ToObject..
 153         // But we don't need to -- all we need is the right class name
 154         // of the corresponding primitive wrapper type.
 155 
 156         final JSType type = JSType.of(self);
 157 
 158         switch (type) {
 159         case BOOLEAN:
 160             className = "Boolean";
 161             break;
 162         case NUMBER:
 163             className = "Number";
 164             break;
 165         case STRING:
 166             className = "String";
 167             break;
 168         // special case of null and undefined
 169         case NULL:
 170             className = "Null";
 171             break;
 172         case UNDEFINED:
 173             className = "Undefined";
 174             break;
 175         case OBJECT:
 176         case FUNCTION:
 177             if (self instanceof ScriptObject) {
 178                 className = ((ScriptObject)self).getClassName();
 179             } else {
 180                 className = self.getClass().getName();
 181             }
 182             break;
 183         default:
 184             // Nashorn extension: use Java class name
 185             className = self.getClass().getName();
 186             break;
 187         }
 188 
 189         final StringBuilder sb = new StringBuilder();
 190         sb.append("[object ");
 191         sb.append(className);
 192         sb.append(']');
 193 
 194         return sb.toString();
 195     }
 196 
 197     /**
 198      * This is called whenever runtime wants to throw an error and wants to provide
 199      * meaningful information about an object. We don't want to call toString which
 200      * ends up calling "toString" from script world which may itself throw error.
 201      * When we want to throw an error, we don't additional error from script land
 202      * -- which may sometimes lead to infinite recursion.
 203      *
 204      * @param obj Object to converted to String safely (without calling user script)
 205      * @return safe String representation of the given object
 206      */
 207     public static String safeToString(final Object obj) {
 208         return JSType.toStringImpl(obj, true);
 209     }
 210 
 211     /**
 212      * Used to determine property iterator used in for in.
 213      * @param obj Object to iterate on.
 214      * @return Iterator.
 215      */
 216     public static Iterator<String> toPropertyIterator(final Object obj) {
 217         if (obj instanceof ScriptObject) {
 218             return ((ScriptObject)obj).propertyIterator();
 219         }
 220 
 221         if (obj != null && obj.getClass().isArray()) {
 222             final int length = Array.getLength(obj);
 223 
 224             return new Iterator<String>() {
 225                 private int index = 0;
 226 
 227                 @Override
 228                 public boolean hasNext() {
 229                     return index < length;
 230                 }
 231 
 232                 @Override
 233                 public String next() {
 234                     return "" + index++; //TODO numeric property iterator?
 235                 }
 236 
 237                 @Override
 238                 public void remove() {
 239                     throw new UnsupportedOperationException();
 240                 }
 241             };
 242         }
 243 
 244         if (obj instanceof ScriptObjectMirror) {
 245             return ((ScriptObjectMirror)obj).keySet().iterator();
 246         }
 247 
 248         return Collections.emptyIterator();
 249     }
 250 
 251     /**
 252      * Used to determine property value iterator used in for each in.
 253      * @param obj Object to iterate on.
 254      * @return Iterator.
 255      */
 256     public static Iterator<?> toValueIterator(final Object obj) {
 257         if (obj instanceof ScriptObject) {
 258             return ((ScriptObject)obj).valueIterator();
 259         }
 260 
 261         if (obj != null && obj.getClass().isArray()) {
 262             final Object array  = obj;
 263             final int    length = Array.getLength(obj);
 264 
 265             return new Iterator<Object>() {
 266                 private int index = 0;
 267 
 268                 @Override
 269                 public boolean hasNext() {
 270                     return index < length;
 271                 }
 272 
 273                 @Override
 274                 public Object next() {
 275                     if (index >= length) {
 276                         throw new NoSuchElementException();
 277                     }
 278                     return Array.get(array, index++);
 279                 }
 280 
 281                 @Override
 282                 public void remove() {
 283                     throw new UnsupportedOperationException();
 284                 }
 285             };
 286         }
 287 
 288         if (obj instanceof ScriptObjectMirror) {
 289             return ((ScriptObjectMirror)obj).values().iterator();
 290         }
 291 
 292         if (obj instanceof Iterable) {
 293             return ((Iterable<?>)obj).iterator();
 294         }
 295 
 296         return Collections.emptyIterator();
 297     }
 298 
 299     /**
 300      * Merge a scope into its prototype's map.
 301      * Merge a scope into its prototype.
 302      *
 303      * @param scope Scope to merge.
 304      * @return prototype object after merge
 305      */
 306     public static ScriptObject mergeScope(final ScriptObject scope) {
 307         final ScriptObject global = scope.getProto();
 308         global.addBoundProperties(scope);
 309         return global;
 310     }
 311 
 312     /**
 313      * Check that the target function is associated with current Context. And also make sure that 'self', if
 314      * ScriptObject, is from current context.
 315      *
 316      * Call a function given self and args. If the number of the arguments is known in advance, you can likely achieve
 317      * better performance by {@link Bootstrap#createDynamicInvoker(String, Class, Class...) creating a dynamic invoker}
 318      * for operation {@code "dyn:call"}, then using its {@link MethodHandle#invokeExact(Object...)} method instead.
 319      *
 320      * @param target ScriptFunction object.
 321      * @param self   Receiver in call.
 322      * @param args   Call arguments.
 323      * @return Call result.
 324      */
 325     public static Object checkAndApply(final ScriptFunction target, final Object self, final Object... args) {
 326         final ScriptObject global = Context.getGlobalTrusted();
 327         if (! (global instanceof GlobalObject)) {
 328             throw new IllegalStateException("No current global set");
 329         }
 330 
 331         if (target.getContext() != global.getContext()) {
 332             throw new IllegalArgumentException("'target' function is not from current Context");
 333         }
 334 
 335         if (self instanceof ScriptObject && ((ScriptObject)self).getContext() != global.getContext()) {
 336             throw new IllegalArgumentException("'self' object is not from current Context");
 337         }
 338 
 339         // all in order - call real 'apply'
 340         return apply(target, self, args);
 341     }
 342 
 343     /**
 344      * Call a function given self and args. If the number of the arguments is known in advance, you can likely achieve
 345      * better performance by {@link Bootstrap#createDynamicInvoker(String, Class, Class...) creating a dynamic invoker}
 346      * for operation {@code "dyn:call"}, then using its {@link MethodHandle#invokeExact(Object...)} method instead.
 347      *
 348      * @param target ScriptFunction object.
 349      * @param self   Receiver in call.
 350      * @param args   Call arguments.
 351      * @return Call result.
 352      */
 353     public static Object apply(final ScriptFunction target, final Object self, final Object... args) {
 354         try {
 355             return target.invoke(self, args);
 356         } catch (final RuntimeException | Error e) {
 357             throw e;
 358         } catch (final Throwable t) {
 359             throw new RuntimeException(t);
 360         }
 361     }
 362 
 363     /**
 364      * Generic implementation of ECMA 9.12 - SameValue algorithm
 365      *
 366      * @param x first value to compare
 367      * @param y second value to compare
 368      *
 369      * @return true if both objects have the same value
 370      */
 371     public static boolean sameValue(final Object x, final Object y) {
 372         final JSType xType = JSType.of(x);
 373         final JSType yType = JSType.of(y);
 374 
 375         if (xType != yType) {
 376             return false;
 377         }
 378 
 379         if (xType == JSType.UNDEFINED || xType == JSType.NULL) {
 380             return true;
 381         }
 382 
 383         if (xType == JSType.NUMBER) {
 384             final double xVal = ((Number)x).doubleValue();
 385             final double yVal = ((Number)y).doubleValue();
 386 
 387             if (Double.isNaN(xVal) && Double.isNaN(yVal)) {
 388                 return true;
 389             }
 390 
 391             // checking for xVal == -0.0 and yVal == +0.0 or vice versa
 392             if (xVal == 0.0 && (Double.doubleToLongBits(xVal) != Double.doubleToLongBits(yVal))) {
 393                 return false;
 394             }
 395 
 396             return xVal == yVal;
 397         }
 398 
 399         if (xType == JSType.STRING || yType == JSType.BOOLEAN) {
 400             return x.equals(y);
 401         }
 402 
 403         return (x == y);
 404     }
 405 
 406     /**
 407      * Returns AST as JSON compatible string. This is used to
 408      * implement "parse" function in resources/parse.js script.
 409      *
 410      * @param code code to be parsed
 411      * @param name name of the code source (used for location)
 412      * @param includeLoc tells whether to include location information for nodes or not
 413      * @return JSON string representation of AST of the supplied code
 414      */
 415     public static String parse(final String code, final String name, final boolean includeLoc) {
 416         return JSONWriter.parse(Context.getContextTrusted().getEnv(), code, name, includeLoc);
 417     }
 418 
 419     /**
 420      * Test whether a char is valid JavaScript whitespace
 421      * @param ch a char
 422      * @return true if valid JavaScript whitespace
 423      */
 424     public static boolean isJSWhitespace(final char ch) {
 425         return Lexer.isJSWhitespace(ch);
 426     }
 427 
 428     /**
 429      * Entering a {@code with} node requires new scope. This is the implementation
 430      *
 431      * @param scope      existing scope
 432      * @param expression expression in with
 433      *
 434      * @return {@link WithObject} that is the new scope
 435      */
 436     public static ScriptObject openWith(final ScriptObject scope, final Object expression) {
 437         final ScriptObject global = Context.getGlobalTrusted();
 438         if (expression == UNDEFINED) {
 439             throw typeError(global, "cant.apply.with.to.undefined");
 440         } else if (expression == null) {
 441             throw typeError(global, "cant.apply.with.to.null");
 442         }
 443 
 444         final ScriptObject withObject = new WithObject(scope, JSType.toScriptObject(global, expression));
 445 
 446         return withObject;
 447     }
 448 
 449     /**
 450      * Exiting a {@code with} node requires restoring scope. This is the implementation
 451      *
 452      * @param scope existing scope
 453      *
 454      * @return restored scope
 455      */
 456     public static ScriptObject closeWith(final ScriptObject scope) {
 457         if (scope instanceof WithObject) {
 458             return scope.getProto();
 459         }
 460         return scope;
 461     }
 462 
 463     /**
 464      * ECMA 11.6.1 - The addition operator (+) - generic implementation
 465      * Compiler specializes using {@link jdk.nashorn.internal.codegen.RuntimeCallSite}
 466      * if any type information is available for any of the operands
 467      *
 468      * @param x  first term
 469      * @param y  second term
 470      *
 471      * @return result of addition
 472      */
 473     public static Object ADD(final Object x, final Object y) {
 474         // This prefix code to handle Number special is for optimization.
 475         final boolean xIsNumber = x instanceof Number;
 476         final boolean yIsNumber = y instanceof Number;
 477 
 478         if (xIsNumber && yIsNumber) {
 479              return ((Number)x).doubleValue() + ((Number)y).doubleValue();
 480         }
 481 
 482         final boolean xIsUndefined = x == UNDEFINED;
 483         final boolean yIsUndefined = y == UNDEFINED;
 484 
 485         if ((xIsNumber && yIsUndefined) || (xIsUndefined && yIsNumber) || (xIsUndefined && yIsUndefined)) {
 486             return Double.NaN;
 487         }
 488 
 489         // code below is as per the spec.
 490         final Object xPrim = JSType.toPrimitive(x);
 491         final Object yPrim = JSType.toPrimitive(y);
 492 
 493         if (xPrim instanceof String || yPrim instanceof String
 494                 || xPrim instanceof ConsString || yPrim instanceof ConsString) {
 495             return new ConsString(JSType.toCharSequence(xPrim), JSType.toCharSequence(yPrim));
 496         }
 497 
 498         return JSType.toNumber(xPrim) + JSType.toNumber(yPrim);
 499     }
 500 
 501     /**
 502      * Debugger hook.
 503      * TODO: currently unimplemented
 504      *
 505      * @return undefined
 506      */
 507     public static Object DEBUGGER() {
 508         return UNDEFINED;
 509     }
 510 
 511     /**
 512      * New hook
 513      *
 514      * @param clazz type for the clss
 515      * @param args  constructor arguments
 516      *
 517      * @return undefined
 518      */
 519     public static Object NEW(final Object clazz, final Object... args) {
 520         return UNDEFINED;
 521     }
 522 
 523     /**
 524      * ECMA 11.4.3 The typeof Operator - generic implementation
 525      *
 526      * @param object   the object from which to retrieve property to type check
 527      * @param property property in object to check
 528      *
 529      * @return type name
 530      */
 531     public static Object TYPEOF(final Object object, final Object property) {
 532         Object obj = object;
 533 
 534         if (property != null) {
 535             if (obj instanceof ScriptObject) {
 536                 obj = ((ScriptObject)obj).get(property);
 537             } else if (object instanceof Undefined) {
 538                 obj = ((Undefined)obj).get(property);
 539             } else if (object == null) {
 540                 throw typeError("cant.get.property", safeToString(property), "null");
 541             } else if (JSType.isPrimitive(obj)) {
 542                 obj = ((ScriptObject)JSType.toScriptObject(obj)).get(property);
 543             } else {
 544                 obj = UNDEFINED;
 545             }
 546         }
 547 
 548         return JSType.of(obj).typeName();
 549     }
 550 
 551     /**
 552      * ECMA 11.4.2 - void operator
 553      *
 554      * @param object object to evaluate
 555      *
 556      * @return Undefined as the object type
 557      */
 558     public static Object VOID(final Object object) {
 559         if (object instanceof Number) {
 560             if (Double.isNaN(((Number)object).doubleValue())) {
 561                 return Double.NaN;
 562             }
 563         }
 564 
 565         return UNDEFINED;
 566     }
 567 
 568     /**
 569      * Throw ReferenceError when LHS of assignment or increment/decrement
 570      * operator is not an assignable node (say a literal)
 571      *
 572      * @param lhs Evaluated LHS
 573      * @param rhs Evaluated RHS
 574      * @param msg Additional LHS info for error message
 575      * @return undefined
 576      */
 577     public static Object REFERENCE_ERROR(final Object lhs, final Object rhs, final Object msg) {
 578         throw referenceError("cant.be.used.as.lhs", Objects.toString(msg));
 579     }
 580 
 581     /**
 582      * ECMA 11.4.1 - delete operation, generic implementation
 583      *
 584      * @param obj       object with property to delete
 585      * @param property  property to delete
 586      * @param strict    are we in strict mode
 587      *
 588      * @return true if property was successfully found and deleted
 589      */
 590     public static boolean DELETE(final Object obj, final Object property, final Object strict) {
 591         if (obj instanceof ScriptObject) {
 592             return ((ScriptObject)obj).delete(property, Boolean.TRUE.equals(strict));
 593         }
 594 
 595         if (obj instanceof Undefined) {
 596             return ((Undefined)obj).delete(property, false);
 597         }
 598 
 599         if (obj == null) {
 600             throw typeError("cant.delete.property", safeToString(property), "null");
 601         }
 602 
 603         if (obj instanceof ScriptObjectMirror) {
 604             return ((ScriptObjectMirror)obj).delete(property);
 605         }
 606 
 607         if (JSType.isPrimitive(obj)) {
 608             return ((ScriptObject) JSType.toScriptObject(obj)).delete(property, Boolean.TRUE.equals(strict));
 609         }
 610 
 611         // if object is not reference type, vacuously delete is successful.
 612         return true;
 613     }
 614 
 615     /**
 616      * ECMA 11.4.1 - delete operator, special case
 617      *
 618      * This is 'delete' that always fails. We have to check strict mode and throw error.
 619      * That is why this is a runtime function. Or else we could have inlined 'false'.
 620      *
 621      * @param property  property to delete
 622      * @param strict    are we in strict mode
 623      *
 624      * @return false always
 625      */
 626     public static boolean FAIL_DELETE(final Object property, final Object strict) {
 627         if (Boolean.TRUE.equals(strict)) {
 628             throw syntaxError("strict.cant.delete", safeToString(property));
 629         }
 630         return false;
 631     }
 632 
 633     /**
 634      * ECMA 11.9.1 - The equals operator (==) - generic implementation
 635      *
 636      * @param x first object to compare
 637      * @param y second object to compare
 638      *
 639      * @return true if type coerced versions of objects are equal
 640      */
 641     public static boolean EQ(final Object x, final Object y) {
 642         return equals(x, y);
 643     }
 644 
 645     /**
 646      * ECMA 11.9.2 - The does-not-equal operator (==) - generic implementation
 647      *
 648      * @param x first object to compare
 649      * @param y second object to compare
 650      *
 651      * @return true if type coerced versions of objects are not equal
 652      */
 653     public static boolean NE(final Object x, final Object y) {
 654         return !EQ(x, y);
 655     }
 656 
 657     /** ECMA 11.9.3 The Abstract Equality Comparison Algorithm */
 658     private static boolean equals(final Object x, final Object y) {
 659         final JSType xType = JSType.of(x);
 660         final JSType yType = JSType.of(y);
 661 
 662         if (xType == yType) {
 663 
 664             if (xType == JSType.UNDEFINED || xType == JSType.NULL) {
 665                 return true;
 666             }
 667 
 668             if (xType == JSType.NUMBER) {
 669                 final double xVal = ((Number)x).doubleValue();
 670                 final double yVal = ((Number)y).doubleValue();
 671                 if (Double.isNaN(xVal) || Double.isNaN(yVal)) {
 672                     return false;
 673                 }
 674 
 675                 return xVal == yVal;
 676             }
 677 
 678             if (xType == JSType.STRING) {
 679                 // String may be represented by ConsString
 680                 return x.toString().equals(y.toString());
 681             }
 682 
 683             if (xType == JSType.BOOLEAN) {
 684                 // Boolean comparison
 685                 return x.equals(y);
 686             }
 687 
 688             return x == y;
 689         }
 690 
 691         if ((xType == JSType.UNDEFINED && yType == JSType.NULL) ||
 692             (xType == JSType.NULL && yType == JSType.UNDEFINED)) {
 693             return true;
 694         }
 695 
 696         if (xType == JSType.NUMBER && yType == JSType.STRING) {
 697             return EQ(x, JSType.toNumber(y));
 698         }
 699 
 700         if (xType == JSType.STRING && yType == JSType.NUMBER) {
 701             return EQ(JSType.toNumber(x), y);
 702         }
 703 
 704         if (xType == JSType.BOOLEAN) {
 705             return EQ(JSType.toNumber(x), y);
 706         }
 707 
 708         if (yType == JSType.BOOLEAN) {
 709             return EQ(x, JSType.toNumber(y));
 710         }
 711 
 712         if ((xType == JSType.STRING || xType == JSType.NUMBER) &&
 713              (y instanceof ScriptObject))  {
 714             return EQ(x, JSType.toPrimitive(y));
 715         }
 716 
 717         if ((x instanceof ScriptObject) &&
 718             (yType == JSType.STRING || yType == JSType.NUMBER)) {
 719             return EQ(JSType.toPrimitive(x), y);
 720         }
 721 
 722         return false;
 723     }
 724 
 725     /**
 726      * ECMA 11.9.4 - The strict equal operator (===) - generic implementation
 727      *
 728      * @param x first object to compare
 729      * @param y second object to compare
 730      *
 731      * @return true if objects are equal
 732      */
 733     public static boolean EQ_STRICT(final Object x, final Object y) {
 734         return strictEquals(x, y);
 735     }
 736 
 737     /**
 738      * ECMA 11.9.5 - The strict non equal operator (!==) - generic implementation
 739      *
 740      * @param x first object to compare
 741      * @param y second object to compare
 742      *
 743      * @return true if objects are not equal
 744      */
 745     public static boolean NE_STRICT(final Object x, final Object y) {
 746         return !EQ_STRICT(x, y);
 747     }
 748 
 749     /** ECMA 11.9.6 The Strict Equality Comparison Algorithm */
 750     private static boolean strictEquals(final Object x, final Object y) {
 751         final JSType xType = JSType.of(x);
 752         final JSType yType = JSType.of(y);
 753 
 754         if (xType != yType) {
 755             return false;
 756         }
 757 
 758         if (xType == JSType.UNDEFINED || xType == JSType.NULL) {
 759             return true;
 760         }
 761 
 762         if (xType == JSType.NUMBER) {
 763             final double xVal = ((Number)x).doubleValue();
 764             final double yVal = ((Number)y).doubleValue();
 765 
 766             if (Double.isNaN(xVal) || Double.isNaN(yVal)) {
 767                 return false;
 768             }
 769 
 770             return xVal == yVal;
 771         }
 772 
 773         if (xType == JSType.STRING) {
 774             // String may be represented by ConsString
 775             return x.toString().equals(y.toString());
 776         }
 777 
 778         if (xType == JSType.BOOLEAN) {
 779             return x.equals(y);
 780         }
 781 
 782         // finally, the object identity comparison
 783         return x == y;
 784     }
 785 
 786     /**
 787      * ECMA 11.8.6 - The in operator - generic implementation
 788      *
 789      * @param property property to check for
 790      * @param obj object in which to check for property
 791      *
 792      * @return true if objects are equal
 793      */
 794     public static boolean IN(final Object property, final Object obj) {
 795         final JSType rvalType = JSType.of(obj);
 796 
 797         if (rvalType == JSType.OBJECT || rvalType == JSType.FUNCTION) {
 798             if (obj instanceof ScriptObject) {
 799                 return ((ScriptObject)obj).has(property);
 800             }
 801 
 802             return false;
 803         }
 804 
 805         throw typeError("in.with.non.object", rvalType.toString().toLowerCase(Locale.ENGLISH));
 806     }
 807 
 808     /**
 809      * ECMA 11.8.6 - The strict instanceof operator - generic implementation
 810      *
 811      * @param obj first object to compare
 812      * @param clazz type to check against
 813      *
 814      * @return true if {@code obj} is an instanceof {@code clazz}
 815      */
 816     public static boolean INSTANCEOF(final Object obj, final Object clazz) {
 817         if (clazz instanceof ScriptFunction) {
 818             if (obj instanceof ScriptObject) {
 819                 return ((ScriptObject)clazz).isInstance((ScriptObject)obj);
 820             }
 821             return false;
 822         }
 823 
 824         if (clazz instanceof StaticClass) {
 825             return ((StaticClass)clazz).getRepresentedClass().isInstance(obj);
 826         }
 827 
 828         if (clazz instanceof ScriptObjectMirror) {
 829             if (obj instanceof ScriptObjectMirror) {
 830                 return ((ScriptObjectMirror)clazz).isInstance((ScriptObjectMirror)obj);
 831             }
 832             return false;
 833         }
 834 
 835         throw typeError("instanceof.on.non.object");
 836     }
 837 
 838     /**
 839      * ECMA 11.8.1 - The less than operator ({@literal <}) - generic implementation
 840      *
 841      * @param x first object to compare
 842      * @param y second object to compare
 843      *
 844      * @return true if x is less than y
 845      */
 846     public static boolean LT(final Object x, final Object y) {
 847         final Object value = lessThan(x, y, true);
 848         return (value == UNDEFINED) ? false : (Boolean)value;
 849     }
 850 
 851     /**
 852      * ECMA 11.8.2 - The greater than operator ({@literal >}) - generic implementation
 853      *
 854      * @param x first object to compare
 855      * @param y second object to compare
 856      *
 857      * @return true if x is greater than y
 858      */
 859     public static boolean GT(final Object x, final Object y) {
 860         final Object value = lessThan(y, x, false);
 861         return (value == UNDEFINED) ? false : (Boolean)value;
 862     }
 863 
 864     /**
 865      * ECMA 11.8.3 - The less than or equal operator ({@literal <=}) - generic implementation
 866      *
 867      * @param x first object to compare
 868      * @param y second object to compare
 869      *
 870      * @return true if x is less than or equal to y
 871      */
 872     public static boolean LE(final Object x, final Object y) {
 873         final Object value = lessThan(y, x, false);
 874         return (!(Boolean.TRUE.equals(value) || value == UNDEFINED));
 875     }
 876 
 877     /**
 878      * ECMA 11.8.4 - The greater than or equal operator ({@literal >=}) - generic implementation
 879      *
 880      * @param x first object to compare
 881      * @param y second object to compare
 882      *
 883      * @return true if x is greater than or equal to y
 884      */
 885     public static boolean GE(final Object x, final Object y) {
 886         final Object value = lessThan(x, y, true);
 887         return (!(Boolean.TRUE.equals(value) || value == UNDEFINED));
 888     }
 889 
 890     /** ECMA 11.8.5 The Abstract Relational Comparison Algorithm */
 891     private static Object lessThan(final Object x, final Object y, final boolean leftFirst) {
 892         Object px, py;
 893 
 894         //support e.g. x < y should throw exception correctly if x or y are not numeric
 895         if (leftFirst) {
 896             px = JSType.toPrimitive(x, Number.class);
 897             py = JSType.toPrimitive(y, Number.class);
 898         } else {
 899             py = JSType.toPrimitive(y, Number.class);
 900             px = JSType.toPrimitive(x, Number.class);
 901         }
 902 
 903         if (JSType.of(px) == JSType.STRING && JSType.of(py) == JSType.STRING) {
 904             // May be String or ConsString
 905             return (px.toString()).compareTo(py.toString()) < 0;
 906         }
 907 
 908         final double nx = JSType.toNumber(px);
 909         final double ny = JSType.toNumber(py);
 910 
 911         if (Double.isNaN(nx) || Double.isNaN(ny)) {
 912             return UNDEFINED;
 913         }
 914 
 915         if (nx == ny) {
 916             return false;
 917         }
 918 
 919         if (nx > 0 && ny > 0 && Double.isInfinite(nx) && Double.isInfinite(ny)) {
 920             return false;
 921         }
 922 
 923         if (nx < 0 && ny < 0 && Double.isInfinite(nx) && Double.isInfinite(ny)) {
 924             return false;
 925         }
 926 
 927         return nx < ny;
 928     }
 929 
 930 }
--- EOF ---