/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * The contents of this file are subject to the Netscape Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/NPL/
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1997-2000 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Contributor(s):
 * Patrick Beard
 * Norris Boyd
 * Igor Bukanov
 * Ethan Hugg
 * Roger Lawrence
 * Terry Lucas
 * Frank Mitchell
 * Milen Nankov
 * Andrew Wason
 *
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU Public License (the "GPL"), in which case the
 * provisions of the GPL are applicable instead of those above.
 * If you wish to allow use of your version of this file only
 * under the terms of the GPL and not to allow others to use your
 * version of this file under the NPL, indicate your decision by
 * deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL.  If you do not delete
 * the provisions above, a recipient may use your version of this
 * file under either the NPL or the GPL.
 */

package org.mozilla.javascript;

import java.lang.reflect.*;
import java.text.MessageFormat;
import java.util.Locale;
import java.util.ResourceBundle;

import org.mozilla.javascript.xml.XMLObject;
import org.mozilla.javascript.xml.XMLLib;
import org.mozilla.javascript.continuations.Continuation;

/**
 * This is the class that implements the runtime.
 *
 * @author Norris Boyd
 */

public class ScriptRuntime {

    /**
     * No instances should be created.
     */
    protected ScriptRuntime() {
    }

    /*
     * There's such a huge space (and some time) waste for the Foo.class
     * syntax: the compiler sticks in a test of a static field in the
     * enclosing class for null and the code for creating the class value.
     * It has to do this since the reference has to get pushed off til
     * executiontime (i.e. can't force an early load), but for the
     * 'standard' classes - especially those in java.lang, we can trust
     * that they won't cause problems by being loaded early.
     */

    public final static Class
        BooleanClass      = Kit.classOrNull("java.lang.Boolean"),
        ByteClass         = Kit.classOrNull("java.lang.Byte"),
        CharacterClass    = Kit.classOrNull("java.lang.Character"),
        ClassClass        = Kit.classOrNull("java.lang.Class"),
        DoubleClass       = Kit.classOrNull("java.lang.Double"),
        FloatClass        = Kit.classOrNull("java.lang.Float"),
        IntegerClass      = Kit.classOrNull("java.lang.Integer"),
        LongClass         = Kit.classOrNull("java.lang.Long"),
        NumberClass       = Kit.classOrNull("java.lang.Number"),
        ObjectClass       = Kit.classOrNull("java.lang.Object"),
        ShortClass        = Kit.classOrNull("java.lang.Short"),
        StringClass       = Kit.classOrNull("java.lang.String"),
        DateClass         = Kit.classOrNull("java.util.Date");

    public final static Class
        ContextClass
            = Kit.classOrNull("org.mozilla.javascript.Context"),
        ContextFactoryClass
            = Kit.classOrNull("org.mozilla.javascript.ContextFactory"),
        FunctionClass
            = Kit.classOrNull("org.mozilla.javascript.Function"),
        ScriptableClass
            = Kit.classOrNull("org.mozilla.javascript.Scriptable"),
        ScriptableObjectClass
            = Kit.classOrNull("org.mozilla.javascript.ScriptableObject");

    private static final String
        XML_INIT_CLASS = "org.mozilla.javascript.xmlimpl.XMLLibImpl";

    private static final String[] lazilyNames = {
        "RegExp",        "org.mozilla.javascript.regexp.NativeRegExp",
        "Packages",      "org.mozilla.javascript.NativeJavaTopPackage",
        "java",          "org.mozilla.javascript.NativeJavaTopPackage",
        "getClass",      "org.mozilla.javascript.NativeJavaTopPackage",
        "JavaAdapter",   "org.mozilla.javascript.JavaAdapter",
        "JavaImporter",  "org.mozilla.javascript.ImporterTopLevel",
        "XML",           XML_INIT_CLASS,
        "XMLList",       XML_INIT_CLASS,
        "Namespace",     XML_INIT_CLASS,
        "QName",         XML_INIT_CLASS,
    };

    private static final Object LIBRARY_SCOPE_KEY = new Object();

    public static boolean isRhinoRuntimeType(Class cl)
    {
        if (cl.isPrimitive()) {
            return (cl != Character.TYPE);
        } else {
            return (cl == StringClass || cl == BooleanClass
                    || NumberClass.isAssignableFrom(cl)
                    || ScriptableClass.isAssignableFrom(cl));
        }
    }

    public static ScriptableObject initStandardObjects(Context cx,
                                                       ScriptableObject scope,
                                                       boolean sealed)
    {
        if (scope == null) {
            scope = new NativeObject();
        }
        scope.associateValue(LIBRARY_SCOPE_KEY, scope);
        (new ClassCache()).associate(scope);

        BaseFunction.init(scope, sealed);
        NativeObject.init(scope, sealed);

        Scriptable objectProto = ScriptableObject.getObjectPrototype(scope);

        // Function.prototype.__proto__ should be Object.prototype
        Scriptable functionProto = ScriptableObject.getFunctionPrototype(scope);
        functionProto.setPrototype(objectProto);

        // Set the prototype of the object passed in if need be
        if (scope.getPrototype() == null)
            scope.setPrototype(objectProto);

        // must precede NativeGlobal since it's needed therein
        NativeError.init(scope, sealed);
        NativeGlobal.init(cx, scope, sealed);

        NativeArray.init(scope, sealed);
        NativeString.init(scope, sealed);
        NativeBoolean.init(scope, sealed);
        NativeNumber.init(scope, sealed);
        NativeDate.init(scope, sealed);
        NativeMath.init(scope, sealed);

        NativeWith.init(scope, sealed);
        NativeCall.init(scope, sealed);
        NativeScript.init(scope, sealed);

        boolean withXml = cx.hasFeature(Context.FEATURE_E4X);

        for (int i = 0; i != lazilyNames.length; i += 2) {
            String topProperty = lazilyNames[i];
            String className = lazilyNames[i + 1];
            if (!withXml && className == XML_INIT_CLASS) {
                continue;
            }
            new LazilyLoadedCtor(scope, topProperty, className, sealed);
        }

        Continuation.init(scope, sealed);

        return scope;
    }

    public static ScriptableObject getLibraryScopeOrNull(Scriptable scope)
    {
        ScriptableObject libScope;
        libScope = (ScriptableObject)ScriptableObject.
                       getTopScopeValue(scope, LIBRARY_SCOPE_KEY);
        return libScope;
    }

    // It is public so NativeRegExp can access it .
    public static boolean isJSLineTerminator(int c)
    {
        // Optimization for faster check for eol character:
        // they do not have 0xDFD0 bits set
        if ((c & 0xDFD0) != 0) {
            return false;
        }
        return c == '\n' || c == '\r' || c == 0x2028 || c == 0x2029;
    }

    public static Boolean wrapBoolean(boolean b)
    {
        return b ? Boolean.TRUE : Boolean.FALSE;
    }

    public static Integer wrapInt(int i)
    {
        return new Integer(i);
    }

    public static Number wrapNumber(double x)
    {
        if (x != x) {
            return ScriptRuntime.NaNobj;
        }
        return new Double(x);
    }

    /**
     * Convert the value to a boolean.
     *
     * See ECMA 9.2.
     */
    public static boolean toBoolean(Object val)
    {
        for (;;) {
            if (val instanceof Boolean)
                return ((Boolean) val).booleanValue();
            if (val == null || val == Undefined.instance)
                return false;
            if (val instanceof String)
                return ((String) val).length() != 0;
            if (val instanceof Number) {
                double d = ((Number) val).doubleValue();
                return (d == d && d != 0.0);
            }
            if (val instanceof Scriptable) {
                if (Context.getContext().isVersionECMA1()) {
                    // pure ECMA
                    return true;
                }
                // ECMA extension
                val = ((Scriptable) val).getDefaultValue(BooleanClass);
                if (val instanceof Scriptable)
                    throw errorWithClassName("msg.primitive.expected", val);
                continue;
            }
            warnAboutNonJSObject(val);
            return true;
        }
    }

    public static boolean toBoolean(Object[] args, int index) {
        return (index < args.length) ? toBoolean(args[index]) : false;
    }

    /**
     * Convert the value to a number.
     *
     * See ECMA 9.3.
     */
    public static double toNumber(Object val)
    {
        for (;;) {
            if (val instanceof Number)
                return ((Number) val).doubleValue();
            if (val == null)
                return +0.0;
            if (val == Undefined.instance)
                return NaN;
            if (val instanceof String)
                return toNumber((String) val);
            if (val instanceof Boolean)
                return ((Boolean) val).booleanValue() ? 1 : +0.0;
            if (val instanceof Scriptable) {
                val = ((Scriptable) val).getDefaultValue(NumberClass);
                if (val instanceof Scriptable)
                    throw errorWithClassName("msg.primitive.expected", val);
                continue;
            }
            warnAboutNonJSObject(val);
            return NaN;
        }
    }

    public static double toNumber(Object[] args, int index) {
        return (index < args.length) ? toNumber(args[index]) : NaN;
    }

    // Can not use Double.NaN defined as 0.0d / 0.0 as under the Microsoft VM,
    // versions 2.01 and 3.0P1, that causes some uses (returns at least) of
    // Double.NaN to be converted to 1.0.
    // So we use ScriptRuntime.NaN instead of Double.NaN.
    public static final double
        NaN = Double.longBitsToDouble(0x7ff8000000000000L);

    // A similar problem exists for negative zero.
    public static final double
        negativeZero = Double.longBitsToDouble(0x8000000000000000L);

    public static final Double NaNobj = new Double(NaN);

    /*
     * Helper function for toNumber, parseInt, and TokenStream.getToken.
     */
    static double stringToNumber(String s, int start, int radix) {
        char digitMax = '9';
        char lowerCaseBound = 'a';
        char upperCaseBound = 'A';
        int len = s.length();
        if (radix < 10) {
            digitMax = (char) ('0' + radix - 1);
        }
        if (radix > 10) {
            lowerCaseBound = (char) ('a' + radix - 10);
            upperCaseBound = (char) ('A' + radix - 10);
        }
        int end;
        double sum = 0.0;
        for (end=start; end < len; end++) {
            char c = s.charAt(end);
            int newDigit;
            if ('0' <= c && c <= digitMax)
                newDigit = c - '0';
            else if ('a' <= c && c < lowerCaseBound)
                newDigit = c - 'a' + 10;
            else if ('A' <= c && c < upperCaseBound)
                newDigit = c - 'A' + 10;
            else
                break;
            sum = sum*radix + newDigit;
        }
        if (start == end) {
            return NaN;
        }
        if (sum >= 9007199254740992.0) {
            if (radix == 10) {
                /* If we're accumulating a decimal number and the number
                 * is >= 2^53, then the result from the repeated multiply-add
                 * above may be inaccurate.  Call Java to get the correct
                 * answer.
                 */
                try {
                    return Double.valueOf(s.substring(start, end)).doubleValue();
                } catch (NumberFormatException nfe) {
                    return NaN;
                }
            } else if (radix == 2 || radix == 4 || radix == 8 ||
                       radix == 16 || radix == 32)
            {
                /* The number may also be inaccurate for one of these bases.
                 * This happens if the addition in value*radix + digit causes
                 * a round-down to an even least significant mantissa bit
                 * when the first dropped bit is a one.  If any of the
                 * following digits in the number (which haven't been added
                 * in yet) are nonzero then the correct action would have
                 * been to round up instead of down.  An example of this
                 * occurs when reading the number 0x1000000000000081, which
                 * rounds to 0x1000000000000000 instead of 0x1000000000000100.
                 */
                int bitShiftInChar = 1;
                int digit = 0;

                final int SKIP_LEADING_ZEROS = 0;
                final int FIRST_EXACT_53_BITS = 1;
                final int AFTER_BIT_53         = 2;
                final int ZEROS_AFTER_54 = 3;
                final int MIXED_AFTER_54 = 4;

                int state = SKIP_LEADING_ZEROS;
                int exactBitsLimit = 53;
                double factor = 0.0;
                boolean bit53 = false;
                // bit54 is the 54th bit (the first dropped from the mantissa)
                boolean bit54 = false;

                for (;;) {
                    if (bitShiftInChar == 1) {
                        if (start == end)
                            break;
                        digit = s.charAt(start++);
                        if ('0' <= digit && digit <= '9')
                            digit -= '0';
                        else if ('a' <= digit && digit <= 'z')
                            digit -= 'a' - 10;
                        else
                            digit -= 'A' - 10;
                        bitShiftInChar = radix;
                    }
                    bitShiftInChar >>= 1;
                    boolean bit = (digit & bitShiftInChar) != 0;

                    switch (state) {
                      case SKIP_LEADING_ZEROS:
                          if (bit) {
                            --exactBitsLimit;
                            sum = 1.0;
                            state = FIRST_EXACT_53_BITS;
                        }
                        break;
                      case FIRST_EXACT_53_BITS:
                           sum *= 2.0;
                        if (bit)
                            sum += 1.0;
                        --exactBitsLimit;
                        if (exactBitsLimit == 0) {
                            bit53 = bit;
                            state = AFTER_BIT_53;
                        }
                        break;
                      case AFTER_BIT_53:
                        bit54 = bit;
                        factor = 2.0;
                        state = ZEROS_AFTER_54;
                        break;
                      case ZEROS_AFTER_54:
                        if (bit) {
                            state = MIXED_AFTER_54;
                        }
                        // fallthrough
                      case MIXED_AFTER_54:
                        factor *= 2;
                        break;
                    }
                }
                switch (state) {
                  case SKIP_LEADING_ZEROS:
                    sum = 0.0;
                    break;
                  case FIRST_EXACT_53_BITS:
                  case AFTER_BIT_53:
                    // do nothing
                    break;
                  case ZEROS_AFTER_54:
                    // x1.1 -> x1 + 1 (round up)
                    // x0.1 -> x0 (round down)
                    if (bit54 & bit53)
                        sum += 1.0;
                    sum *= factor;
                    break;
                  case MIXED_AFTER_54:
                    // x.100...1.. -> x + 1 (round up)
                    // x.0anything -> x (round down)
                    if (bit54)
                        sum += 1.0;
                    sum *= factor;
                    break;
                }
            }
            /* We don't worry about inaccurate numbers for any other base. */
        }
        return sum;
    }


    /**
     * ToNumber applied to the String type
     *
     * See ECMA 9.3.1
     */
    public static double toNumber(String s) {
        int len = s.length();
        int start = 0;
        char startChar;
        for (;;) {
            if (start == len) {
                // Empty or contains only whitespace
                return +0.0;
            }
            startChar = s.charAt(start);
            if (!Character.isWhitespace(startChar))
                break;
            start++;
        }

        if (startChar == '0') {
            if (start + 2 < len) {
                int c1 = s.charAt(start + 1);
                if (c1 == 'x' || c1 == 'X') {
                    // A hexadecimal number
                    return stringToNumber(s, start + 2, 16);
                }
            }
        } else if (startChar == '+' || startChar == '-') {
            if (start + 3 < len && s.charAt(start + 1) == '0') {
                int c2 = s.charAt(start + 2);
                if (c2 == 'x' || c2 == 'X') {
                    // A hexadecimal number with sign
                    double val = stringToNumber(s, start + 3, 16);
                    return startChar == '-' ? -val : val;
                }
            }
        }

        int end = len - 1;
        char endChar;
        while (Character.isWhitespace(endChar = s.charAt(end)))
            end--;
        if (endChar == 'y') {
            // check for "Infinity"
            if (startChar == '+' || startChar == '-')
                start++;
            if (start + 7 == end && s.regionMatches(start, "Infinity", 0, 8))
                return startChar == '-'
                    ? Double.NEGATIVE_INFINITY
                    : Double.POSITIVE_INFINITY;
            return NaN;
        }
        // A non-hexadecimal, non-infinity number:
        // just try a normal floating point conversion
        String sub = s.substring(start, end+1);
        if (MSJVM_BUG_WORKAROUNDS) {
            // The MS JVM will accept non-conformant strings
            // rather than throwing a NumberFormatException
            // as it should.
            for (int i=sub.length()-1; i >= 0; i--) {
                char c = sub.charAt(i);
                if (('0' <= c && c <= '9') || c == '.' ||
                    c == 'e' || c == 'E'  ||
                    c == '+' || c == '-')
                    continue;
                return NaN;
            }
        }
        try {
            return Double.valueOf(sub).doubleValue();
        } catch (NumberFormatException ex) {
            return NaN;
        }
    }

    /**
     * Helper function for builtin objects that use the varargs form.
     * ECMA function formal arguments are undefined if not supplied;
     * this function pads the argument array out to the expected
     * length, if necessary.
     */
    public static Object[] padArguments(Object[] args, int count) {
        if (count < args.length)
            return args;

        int i;
        Object[] result = new Object[count];
        for (i = 0; i < args.length; i++) {
            result[i] = args[i];
        }

        for (; i < count; i++) {
            result[i] = Undefined.instance;
        }

        return result;
    }

    /* Work around Microsoft Java VM bugs. */
    private final static boolean MSJVM_BUG_WORKAROUNDS = true;

    public static String escapeString(String s)
    {
        return escapeString(s, '"');
    }

    /**
     * For escaping strings printed by object and array literals; not quite
     * the same as 'escape.'
     */
    public static String escapeString(String s, char escapeQuote)
    {
        if (!(escapeQuote == '"' || escapeQuote == '\'')) Kit.codeBug();
        StringBuffer sb = null;

        for(int i = 0, L = s.length(); i != L; ++i) {
            int c = s.charAt(i);

            if (' ' <= c && c <= '~' && c != escapeQuote && c != '\\') {
                // an ordinary print character (like C isprint()) and not "
                // or \ .
                if (sb != null) {
                    sb.append((char)c);
                }
                continue;
            }
            if (sb == null) {
                sb = new StringBuffer(L + 3);
                sb.append(s);
                sb.setLength(i);
            }

            int escape = -1;
            switch (c) {
                case '\b':  escape = 'b';  break;
                case '\f':  escape = 'f';  break;
                case '\n':  escape = 'n';  break;
                case '\r':  escape = 'r';  break;
                case '\t':  escape = 't';  break;
                case 0xb:   escape = 'v';  break; // Java lacks \v.
                case ' ':   escape = ' ';  break;
                case '\\':  escape = '\\'; break;
            }
            if (escape >= 0) {
                // an \escaped sort of character
                sb.append('\\');
                sb.append((char)escape);
            } else if (c == escapeQuote) {
                sb.append('\\');
                sb.append(escapeQuote);
            } else {
                int hexSize;
                if (c < 256) {
                    // 2-digit hex
                    sb.append("\\x");
                    hexSize = 2;
                } else {
                    // Unicode.
                    sb.append("\\u");
                    hexSize = 4;
                }
                // append hexadecimal form of c left-padded with 0
                for (int shift = (hexSize - 1) * 4; shift >= 0; shift -= 4) {
                    int digit = 0xf & (c >> shift);
                    int hc = (digit < 10) ? '0' + digit : 'a' - 10 + digit;
                    sb.append((char)hc);
                }
            }
        }
        return (sb == null) ? s : sb.toString();
    }

    static boolean isValidIdentifierName(String s)
    {
        int L = s.length();
        if (L == 0)
            return false;
        if (!Character.isJavaIdentifierStart(s.charAt(0)))
            return false;
        for (int i = 1; i != L; ++i) {
            if (!Character.isJavaIdentifierPart(s.charAt(i)))
                return false;
        }
        return !TokenStream.isKeyword(s);
    }

    /**
     * Convert the value to a string.
     *
     * See ECMA 9.8.
     */
    public static String toString(Object val) {
        for (;;) {
            if (val == null) {
                return "null";
            }
            if (val == Undefined.instance) {
                return "undefined";
            }
            if (val instanceof String) {
                return (String)val;
            }
            if (val instanceof Number) {
                // XXX should we just teach NativeNumber.stringValue()
                // about Numbers?
                return numberToString(((Number)val).doubleValue(), 10);
            }
            if (val instanceof Scriptable) {
                val = ((Scriptable) val).getDefaultValue(StringClass);
                if (val instanceof Scriptable) {
                    throw errorWithClassName("msg.primitive.expected", val);
                }
                continue;
            }
            return val.toString();
        }
    }

    static String defaultObjectToString(Scriptable obj)
    {
        return "[object " + obj.getClassName() + ']';
    }

    public static String toString(Object[] args, int index)
    {
        return (index < args.length) ? toString(args[index]) : "undefined";
    }

    /**
     * Optimized version of toString(Object) for numbers.
     */
    public static String toString(double val) {
        return numberToString(val, 10);
    }

    public static String numberToString(double d, int base) {
        if (d != d)
            return "NaN";
        if (d == Double.POSITIVE_INFINITY)
            return "Infinity";
        if (d == Double.NEGATIVE_INFINITY)
            return "-Infinity";
        if (d == 0.0)
            return "0";

        if ((base < 2) || (base > 36)) {
            throw Context.reportRuntimeError1(
                "msg.bad.radix", Integer.toString(base));
        }

        if (base != 10) {
            return DToA.JS_dtobasestr(base, d);
        } else {
            StringBuffer result = new StringBuffer();
            DToA.JS_dtostr(result, DToA.DTOSTR_STANDARD, 0, d);
            return result.toString();
        }

    }

    static String uneval(Context cx, Scriptable scope, Object value)
    {
        if (value == null) {
            return "null";
        }
        if (value == Undefined.instance) {
            return "undefined";
        }
        if (value instanceof String) {
            String escaped = escapeString((String)value);
            StringBuffer sb = new StringBuffer(escaped.length() + 2);
            sb.append('\"');
            sb.append(escaped);
            sb.append('\"');
            return sb.toString();
        }
        if (value instanceof Number) {
            double d = ((Number)value).doubleValue();
            if (d == 0 && 1 / d < 0) {
                return "-0";
            }
            return toString(d);
        }
        if (value instanceof Boolean) {
            return toString(value);
        }
        if (value instanceof Scriptable) {
            Scriptable obj = (Scriptable)value;
            Object v = ScriptableObject.getProperty(obj, "toSource");
            if (v instanceof Function) {
                Function f = (Function)v;
                return toString(f.call(cx, scope, obj, emptyArgs));
            }
            return toString(value);
        }
        warnAboutNonJSObject(value);
        return value.toString();
    }

    static String defaultObjectToSource(Context cx, Scriptable scope,
                                        Scriptable thisObj, Object[] args)
    {
        boolean toplevel, iterating;
        if (cx.iterating == null) {
            toplevel = true;
            iterating = false;
            cx.iterating = new ObjToIntMap(31);
        } else {
            toplevel = false;
            iterating = cx.iterating.has(thisObj);
        }

        StringBuffer result = new StringBuffer(128);
        if (toplevel) {
            result.append("(");
        }
        result.append('{');

        // Make sure cx.iterating is set to null when done
        // so we don't leak memory
        try {
            if (!iterating) {
                cx.iterating.intern(thisObj); // stop recursion.
                Object[] ids = thisObj.getIds();
                for(int i=0; i < ids.length; i++) {
                    if (i > 0)
                        result.append(", ");
                    Object id = ids[i];
                    Object value;
                    if (id instanceof Integer) {
                        int intId = ((Integer)id).intValue();
                        value = thisObj.get(intId, thisObj);
                        result.append(intId);
                    } else {
                        String strId = (String)id;
                        value = thisObj.get(strId, thisObj);
                        if (ScriptRuntime.isValidIdentifierName(strId)) {
                            result.append(strId);
                        } else {
                            result.append('\'');
                            result.append(
                                ScriptRuntime.escapeString(strId, '\''));
                            result.append('\'');
                        }
                    }
                    result.append(':');
                    result.append(ScriptRuntime.uneval(cx, scope, value));
                }
            }
        } finally {
            if (toplevel) {
                cx.iterating = null;
            }
        }

        result.append('}');
        if (toplevel) {
            result.append(')');
        }
        return result.toString();
    }

    public static Scriptable toObject(Scriptable scope, Object val)
    {
        if (val instanceof Scriptable) {
            return (Scriptable)val;
        }
        return toObject(Context.getContext(), scope, val);
    }

    public static Scriptable toObjectOrNull(Context cx, Object obj)
    {
        if (obj instanceof Scriptable) {
            return (Scriptable)obj;
        } else if (obj != null && obj != Undefined.instance) {
            return toObject(cx, getTopCallScope(cx), obj);
        }
        return null;
    }

    /**
     * @deprecated Use {@link #toObject(Scriptable, Object)} instead.
     */
    public static Scriptable toObject(Scriptable scope, Object val,
                                      Class staticClass)
    {
        if (val instanceof Scriptable) {
            return (Scriptable)val;
        }
        return toObject(Context.getContext(), scope, val);
    }

    /**
     * Convert the value to an object.
     *
     * See ECMA 9.9.
     */
    public static Scriptable toObject(Context cx, Scriptable scope, Object val)
    {
        if (val instanceof Scriptable) {
            return (Scriptable) val;
        }
        if (val == null) {
            throw typeError0("msg.null.to.object");
        }
        if (val == Undefined.instance) {
            throw typeError0("msg.undef.to.object");
        }
        String className = val instanceof String ? "String" :
                           val instanceof Number ? "Number" :
                           val instanceof Boolean ? "Boolean" :
                           null;
        if (className != null) {
            Object[] args = { val };
            scope = ScriptableObject.getTopLevelScope(scope);
            return newObject(cx, scope, className, args);
        }

        // Extension: Wrap as a LiveConnect object.
        Object wrapped = cx.getWrapFactory().wrap(cx, scope, val, null);
        if (wrapped instanceof Scriptable)
            return (Scriptable) wrapped;
        throw errorWithClassName("msg.invalid.type", val);
    }

    /**
     * @deprecated Use {@link #toObject(Context, Scriptable, Object)} instead.
     */
    public static Scriptable toObject(Context cx, Scriptable scope, Object val,
                                      Class staticClass)
    {
        return toObject(cx, scope, val);
    }

    /**
     * @deprecated The method is only present for compatibility.
     */
    public static Object call(Context cx, Object fun, Object thisArg,
                              Object[] args, Scriptable scope)
    {
        if (!(fun instanceof Function)) {
            throw notFunctionError(toString(fun));
        }
        Function function = (Function)fun;
        Scriptable thisObj = toObjectOrNull(cx, thisArg);
        if (thisObj == null) {
            throw undefCallError(thisObj, "function");
        }
        return function.call(cx, scope, thisObj, args);
    }

    public static Scriptable newObject(Context cx, Scriptable scope,
                                       String constructorName, Object[] args)
    {
        scope = ScriptableObject.getTopLevelScope(scope);
        Function ctor = getExistingCtor(cx, scope, constructorName);
        if (args == null) { args = ScriptRuntime.emptyArgs; }
        return ctor.construct(cx, scope, args);
    }

    /**
     *
     * See ECMA 9.4.
     */
    public static double toInteger(Object val) {
        return toInteger(toNumber(val));
    }

    // convenience method
    public static double toInteger(double d) {
        // if it's NaN
        if (d != d)
            return +0.0;

        if (d == 0.0 ||
            d == Double.POSITIVE_INFINITY ||
            d == Double.NEGATIVE_INFINITY)
            return d;

        if (d > 0.0)
            return Math.floor(d);
        else
            return Math.ceil(d);
    }

    public static double toInteger(Object[] args, int index) {
        return (index < args.length) ? toInteger(args[index]) : +0.0;
    }

    /**
     *
     * See ECMA 9.5.
     */
    public static int toInt32(Object val)
    {
        // short circuit for common integer values
        if (val instanceof Integer)
            return ((Integer)val).intValue();

        return toInt32(toNumber(val));
    }

    public static int toInt32(Object[] args, int index) {
        return (index < args.length) ? toInt32(args[index]) : 0;
    }

    public static int toInt32(double d) {
        int id = (int)d;
        if (id == d) {
            // This covers -0.0 as well
            return id;
        }

        if (d != d
            || d == Double.POSITIVE_INFINITY
            || d == Double.NEGATIVE_INFINITY)
        {
            return 0;
        }

        d = (d >= 0) ? Math.floor(d) : Math.ceil(d);

        double two32 = 4294967296.0;
        d = Math.IEEEremainder(d, two32);
        // (double)(long)d == d should hold here

        long l = (long)d;
        // returning (int)d does not work as d can be outside int range
        // but the result must always be 32 lower bits of l
        return (int)l;
    }

    /**
     * See ECMA 9.6.
     * @return long value representing 32 bits unsigned integer
     */
    public static long toUint32(double d) {
        long l = (long)d;
        if (l == d) {
            // This covers -0.0 as well
            return l & 0xffffffffL;
        }

        if (d != d
            || d == Double.POSITIVE_INFINITY
            || d == Double.NEGATIVE_INFINITY)
        {
            return 0;
        }

        d = (d >= 0) ? Math.floor(d) : Math.ceil(d);

        // 0x100000000 gives me a numeric overflow...
        double two32 = 4294967296.0;
        l = (long)Math.IEEEremainder(d, two32);

        return l & 0xffffffffL;
    }

    public static long toUint32(Object val) {
        return toUint32(toNumber(val));
    }

    /**
     *
     * See ECMA 9.7.
     */
    public static char toUint16(Object val) {
        double d = toNumber(val);

        int i = (int)d;
        if (i == d) {
            return (char)i;
        }

        if (d != d
            || d == Double.POSITIVE_INFINITY
            || d == Double.NEGATIVE_INFINITY)
        {
            return 0;
        }

        d = (d >= 0) ? Math.floor(d) : Math.ceil(d);

        int int16 = 0x10000;
        i = (int)Math.IEEEremainder(d, int16);

        return (char)i;
    }

    // XXX: this is until setDefaultNamespace will learn how to store NS
    // properly and separates namespace form Scriptable.get etc.
    private static final String DEFAULT_NS_TAG = "__default_namespace__";

    public static Object setDefaultNamespace(Object namespace, Context cx)
    {
        Scriptable scope = cx.currentActivationCall;
        if (scope == null) {
            scope = getTopCallScope(cx);
        }

        XMLLib xmlLib = currentXMLLib(cx);
        Object ns = xmlLib.toDefaultXmlNamespace(cx, namespace);

        // XXX : this should be in separated namesapce from Scriptable.get/put
        if (!scope.has(DEFAULT_NS_TAG, scope)) {
            // XXX: this is racy of cause
            ScriptableObject.defineProperty(scope, DEFAULT_NS_TAG, ns,
                                            ScriptableObject.PERMANENT
                                            | ScriptableObject.DONTENUM);
        } else {
            scope.put(DEFAULT_NS_TAG, scope, ns);
        }

        return Undefined.instance;
    }

    public static Object searchDefaultNamespace(Context cx)
    {
        Scriptable scope = cx.currentActivationCall;
        if (scope == null) {
            scope = getTopCallScope(cx);
        }
        Object nsObject;
        for (;;) {
            Scriptable parent = scope.getParentScope();
            if (parent == null) {
                nsObject = ScriptableObject.getProperty(scope, DEFAULT_NS_TAG);
                if (nsObject == Scriptable.NOT_FOUND) {
                    return null;
                }
                break;
            }
            nsObject = scope.get(DEFAULT_NS_TAG, scope);
            if (nsObject != Scriptable.NOT_FOUND) {
                break;
            }
            scope = parent;
        }
        return nsObject;
    }

    public static Object getTopLevelProp(Scriptable scope, String id) {
        scope = ScriptableObject.getTopLevelScope(scope);
        return ScriptableObject.getProperty(scope, id);
    }

    static Function getExistingCtor(Context cx, Scriptable scope,
                                    String constructorName)
    {
        Object ctorVal = ScriptableObject.getProperty(scope, constructorName);
        if (ctorVal instanceof Function) {
            return (Function)ctorVal;
        }
        if (ctorVal == Scriptable.NOT_FOUND) {
            throw Context.reportRuntimeError1(
                "msg.ctor.not.found", constructorName);
        } else {
            throw Context.reportRuntimeError1(
                "msg.not.ctor", constructorName);
        }
    }

    /**
     * Return -1L if str is not an index or the index value as lower 32
     * bits of the result.
     */
    private static long indexFromString(String str)
    {
        // The length of the decimal string representation of
        //  Integer.MAX_VALUE, 2147483647
        final int MAX_VALUE_LENGTH = 10;

        int len = str.length();
        if (len > 0) {
            int i = 0;
            boolean negate = false;
            int c = str.charAt(0);
            if (c == '-') {
                if (len > 1) {
                    c = str.charAt(1);
                    i = 1;
                    negate = true;
                }
            }
            c -= '0';
            if (0 <= c && c <= 9
                && len <= (negate ? MAX_VALUE_LENGTH + 1 : MAX_VALUE_LENGTH))
            {
                // Use negative numbers to accumulate index to handle
                // Integer.MIN_VALUE that is greater by 1 in absolute value
                // then Integer.MAX_VALUE
                int index = -c;
                int oldIndex = 0;
                i++;
                if (index != 0) {
                    // Note that 00, 01, 000 etc. are not indexes
                    while (i != len && 0 <= (c = str.charAt(i) - '0') && c <= 9)
                    {
                        oldIndex = index;
                        index = 10 * index - c;
                        i++;
                    }
                }
                // Make sure all characters were consumed and that it couldn't
                // have overflowed.
                if (i == len &&
                    (oldIndex > (Integer.MIN_VALUE / 10) ||
                     (oldIndex == (Integer.MIN_VALUE / 10) &&
                      c <= (negate ? -(Integer.MIN_VALUE % 10)
                                   : (Integer.MAX_VALUE % 10)))))
                {
                    return 0xFFFFFFFFL & (negate ? index : -index);
                }
            }
        }
        return -1L;
    }

    /**
     * If str is a decimal presentation of Uint32 value, return it as long.
     * Othewise return -1L;
     */
    public static long testUint32String(String str)
    {
        // The length of the decimal string representation of
        //  UINT32_MAX_VALUE, 4294967296
        final int MAX_VALUE_LENGTH = 10;

        int len = str.length();
        if (1 <= len && len <= MAX_VALUE_LENGTH) {
            int c = str.charAt(0);
            c -= '0';
            if (c == 0) {
                // Note that 00,01 etc. are not valid Uint32 presentations
                return (len == 1) ? 0L : -1L;
            }
            if (1 <= c && c <= 9) {
                long v = c;
                for (int i = 1; i != len; ++i) {
                    c = str.charAt(i) - '0';
                    if (!(0 <= c && c <= 9)) {
                        return -1;
                    }
                    v = 10 * v + c;
                }
                // Check for overflow
                if ((v >>> 32) == 0) {
                    return v;
                }
            }
        }
        return -1;
    }

    /**
     * If s represents index, then return index value wrapped as Integer
     * and othewise return s.
     */
    static Object getIndexObject(String s)
    {
        long indexTest = indexFromString(s);
        if (indexTest >= 0) {
            return new Integer((int)indexTest);
        }
        return s;
    }

    /**
     * If d is exact int value, return its value wrapped as Integer
     * and othewise return d converted to String.
     */
    static Object getIndexObject(double d)
    {
        int i = (int)d;
        if ((double)i == d) {
            return new Integer((int)i);
        }
        return toString(d);
    }

    /**
     * If toString(id) is a decimal presentation of int32 value, then id
     * is index. In this case return null and make the index available
     * as ScriptRuntime.lastIndexResult(cx). Otherwise return toString(id).
     */
    static String toStringIdOrIndex(Context cx, Object id)
    {
        if (id instanceof Number) {
            double d = ((Number)id).doubleValue();
            int index = (int)d;
            if (((double)index) == d) {
                storeIndexResult(cx, index);
                return null;
            }
            return toString(id);
        } else {
            String s;
            if (id instanceof String) {
                s = (String)id;
            } else {
                s = toString(id);
            }
            long indexTest = indexFromString(s);
            if (indexTest >= 0) {
                storeIndexResult(cx, (int)indexTest);
                return null;
            }
            return s;
        }
    }

    /**
     * Call obj.[[Get]](id)
     */
    public static Object getObjectElem(Object obj, Object elem, Context cx)
    {
        Scriptable sobj = toObjectOrNull(cx, obj);
        if (sobj == null) {
            throw undefReadError(obj, elem);
        }
        return getObjectElem(sobj, elem, cx);
    }

    public static Object getObjectElem(Scriptable obj, Object elem,
                                       Context cx)
    {
        if (obj instanceof XMLObject) {
            XMLObject xmlObject = (XMLObject)obj;
            return xmlObject.ecmaGet(cx, elem);
        }

        Object result;

        String s = toStringIdOrIndex(cx, elem);
        if (s == null) {
            int index = lastIndexResult(cx);
            result = ScriptableObject.getProperty(obj, index);
        } else {
            result = ScriptableObject.getProperty(obj, s);
        }

        if (result == Scriptable.NOT_FOUND) {
            result = Undefined.instance;
        }

        return result;
    }

    /**
     * Version of getObjectElem when elem is a valid JS identifier name.
     */
    public static Object getObjectProp(Object obj, String property,
                                       Context cx)
    {
        Scriptable sobj = toObjectOrNull(cx, obj);
        if (sobj == null) {
            throw undefReadError(obj, property);
        }
        return getObjectProp(sobj, property, cx);
    }

    public static Object getObjectProp(Scriptable obj, String property,
                                       Context cx)
    {
        if (obj instanceof XMLObject) {
            XMLObject xmlObject = (XMLObject)obj;
            return xmlObject.ecmaGet(cx, property);
        }

        Object result = ScriptableObject.getProperty(obj, property);
        if (result == Scriptable.NOT_FOUND) {
            result = Undefined.instance;
        }

        return result;
    }

    /*
     * A cheaper and less general version of the above for well-known argument
     * types.
     */
    public static Object getObjectIndex(Object obj, double dblIndex,
                                        Context cx)
    {
        Scriptable sobj = toObjectOrNull(cx, obj);
        if (sobj == null) {
            throw undefReadError(obj, toString(dblIndex));
        }

        int index = (int)dblIndex;
        if ((double)index == dblIndex) {
            return getObjectIndex(sobj, index, cx);
        } else {
            String s = toString(dblIndex);
            return getObjectProp(sobj, s, cx);
        }
    }

    public static Object getObjectIndex(Scriptable obj, int index,
                                        Context cx)
    {
        if (obj instanceof XMLObject) {
            XMLObject xmlObject = (XMLObject)obj;
            return xmlObject.ecmaGet(cx, new Integer(index));
        }

        Object result = ScriptableObject.getProperty(obj, index);
        if (result == Scriptable.NOT_FOUND) {
            result = Undefined.instance;
        }

        return result;
    }

    /*
     * Call obj.[[Put]](id, value)
     */
    public static Object setObjectElem(Object obj, Object elem, Object value,
                                       Context cx)
    {
        Scriptable sobj = toObjectOrNull(cx, obj);
        if (sobj == null) {
            throw undefWriteError(obj, elem, value);
        }
        return setObjectElem(sobj, elem, value, cx);
    }

    public static Object setObjectElem(Scriptable obj, Object elem,
                                       Object value, Context cx)
    {
        if (obj instanceof XMLObject) {
            XMLObject xmlObject = (XMLObject)obj;
            xmlObject.ecmaPut(cx, elem, value);
            return value;
        }

        String s = toStringIdOrIndex(cx, elem);
        if (s == null) {
            int index = lastIndexResult(cx);
            ScriptableObject.putProperty(obj, index, value);
        } else {
            ScriptableObject.putProperty(obj, s, value);
        }

        return value;
    }

    /**
     * Version of setObjectElem when elem is a valid JS identifier name.
     */
    public static Object setObjectProp(Object obj, String property,
                                       Object value, Context cx)
    {
        Scriptable sobj = toObjectOrNull(cx, obj);
        if (sobj == null) {
            throw undefWriteError(obj, property, value);
        }
        return setObjectProp(sobj, property, value, cx);
    }

    public static Object setObjectProp(Scriptable obj, String property,
                                       Object value, Context cx)
    {
        if (obj instanceof XMLObject) {
            XMLObject xmlObject = (XMLObject)obj;
            xmlObject.ecmaPut(cx, property, value);
        } else {
            ScriptableObject.putProperty(obj, property, value);
        }
        return value;
    }

    /*
     * A cheaper and less general version of the above for well-known argument
     * types.
     */
    public static Object setObjectIndex(Object obj, double dblIndex,
                                        Object value, Context cx)
    {
        Scriptable sobj = toObjectOrNull(cx, obj);
        if (sobj == null) {
            throw undefWriteError(obj, String.valueOf(dblIndex), value);
        }

        int index = (int)dblIndex;
        if ((double)index == dblIndex) {
            return setObjectIndex(sobj, index, value, cx);
        } else {
            String s = toString(dblIndex);
            return setObjectProp(sobj, s, value, cx);
        }
    }

    public static Object setObjectIndex(Scriptable obj, int index, Object value,
                                        Context cx)
    {
        if (obj instanceof XMLObject) {
            XMLObject xmlObject = (XMLObject)obj;
            xmlObject.ecmaPut(cx, new Integer(index), value);
        } else {
            ScriptableObject.putProperty(obj, index, value);
        }
        return value;
    }

    public static boolean deleteObjectElem(Scriptable target, Object elem,
                                           Context cx)
    {
        boolean result;
        if (target instanceof XMLObject) {
            XMLObject xmlObject = (XMLObject)target;
            result = xmlObject.ecmaDelete(cx, elem);
        } else {
            String s = toStringIdOrIndex(cx, elem);
            if (s == null) {
                int index = lastIndexResult(cx);
                result = ScriptableObject.deleteProperty(target, index);
            } else {
                result = ScriptableObject.deleteProperty(target, s);
            }
        }
        return result;
    }

    public static boolean hasObjectElem(Scriptable target, Object elem,
                                        Context cx)
    {
        boolean result;

        if (target instanceof XMLObject) {
            XMLObject xmlObject = (XMLObject)target;
            result = xmlObject.ecmaHas(cx, elem);
        } else {
            String s = toStringIdOrIndex(cx, elem);
            if (s == null) {
                int index = lastIndexResult(cx);
                result = ScriptableObject.hasProperty(target, index);
            } else {
                result = ScriptableObject.hasProperty(target, s);
            }
        }

        return result;
    }

    public static Object refGet(Ref ref, Context cx)
    {
        return ref.get(cx);
    }

    public static Object refSet(Ref ref, Object value, Context cx)
    {
        return ref.set(cx, value);
    }

    public static Object refDel(Ref ref, Context cx)
    {
        return wrapBoolean(ref.delete(cx));
    }

    static boolean isSpecialProperty(String s)
    {
        return s.equals("__proto__") || s.equals("__parent__");
    }

    public static Ref specialRef(Object obj, String specialProperty,
                                 Context cx)
    {
        return SpecialRef.createSpecial(cx, obj, specialProperty);
    }

    /**
     * The delete operator
     *
     * See ECMA 11.4.1
     *
     * In ECMA 0.19, the description of the delete operator (11.4.1)
     * assumes that the [[Delete]] method returns a value. However,
     * the definition of the [[Delete]] operator (8.6.2.5) does not
     * define a return value. Here we assume that the [[Delete]]
     * method doesn't return a value.
     */
    public static Object delete(Object obj, Object id, Context cx)
    {
        Scriptable sobj = toObjectOrNull(cx, obj);
        if (sobj == null) {
            String idStr = (id == null) ? "null" : id.toString();
            throw typeError2("msg.undef.prop.delete", toString(obj), idStr);
        }
        boolean result = deleteObjectElem(sobj, id, cx);
        return wrapBoolean(result);
    }

    /**
     * Looks up a name in the scope chain and returns its value.
     */
    public static Object name(Context cx, Scriptable scope, String name)
    {
        Scriptable parent = scope.getParentScope();
        if (parent == null) {
            Object result = topScopeName(cx, scope, name);
            if (result == Scriptable.NOT_FOUND) {
                throw notFoundError(scope, name);
            }
            return result;
        }

        return nameOrFunction(cx, scope, parent, name, false);
    }

    private static Object nameOrFunction(Context cx, Scriptable scope,
                                         Scriptable parentScope, String name,
                                         boolean asFunctionCall)
    {
        Object result;
        Scriptable thisObj = scope; // It is used only if asFunctionCall==true.

        XMLObject firstXMLObject = null;
        for (;;) {
            if (scope instanceof NativeWith) {
                Scriptable withObj = scope.getPrototype();
                if (withObj instanceof XMLObject) {
                    XMLObject xmlObj = (XMLObject)withObj;
                    if (xmlObj.ecmaHas(cx, name)) {
                        // function this should be the target object of with
                        thisObj = xmlObj;
                        result = xmlObj.ecmaGet(cx, name);
                        break;
                    }
                    if (firstXMLObject == null) {
                        firstXMLObject = xmlObj;
                    }
                } else {
                    result = ScriptableObject.getProperty(withObj, name);
                    if (result != Scriptable.NOT_FOUND) {
                        // function this should be the target object of with
                        thisObj = withObj;
                        break;
                    }
                }
            } else if (scope instanceof NativeCall) {
                // NativeCall does not prototype chain and Scriptable.get
                // can be called directly.
                result = scope.get(name, scope);
                if (result != Scriptable.NOT_FOUND) {
                    if (asFunctionCall) {
                        // ECMA 262 requires that this for nested funtions
                        // should be top scope
                        thisObj = ScriptableObject.
                                      getTopLevelScope(parentScope);
                    }
                    break;
                }
            } else {
                // Can happen if Rhino embedding decided that nested
                // scopes are useful for what ever reasons.
                result = ScriptableObject.getProperty(scope, name);
                if (result != Scriptable.NOT_FOUND) {
                    thisObj = scope;
                    break;
                }
            }
            scope = parentScope;
            parentScope = parentScope.getParentScope();
            if (parentScope == null) {
                result = topScopeName(cx, scope, name);
                if (result == Scriptable.NOT_FOUND) {
                    if (firstXMLObject == null || asFunctionCall) {
                        throw notFoundError(scope, name);
                    }
                    // The name was not found, but we did find an XML
                    // object in the scope chain and we are looking for name,
                    // not function. The result should be an empty XMLList
                    // in name context.
                    result = firstXMLObject.ecmaGet(cx, name);
                }
                // For top scope thisObj for functions is always scope itself.
                thisObj = scope;
                break;
            }
        }

        if (asFunctionCall) {
            if (!(result instanceof Callable)) {
                throw notFunctionError(result, name);
            }
            storeScriptable(cx, thisObj);
        }

        return result;
    }

    private static Object topScopeName(Context cx, Scriptable scope,
                                       String name)
    {
        if (cx.useDynamicScope) {
            scope = checkDynamicScope(cx.topCallScope, scope);
        }
        return ScriptableObject.getProperty(scope, name);
    }


    /**
     * Returns the object in the scope chain that has a given property.
     *
     * The order of evaluation of an assignment expression involves
     * evaluating the lhs to a reference, evaluating the rhs, and then
     * modifying the reference with the rhs value. This method is used
     * to 'bind' the given name to an object containing that property
     * so that the side effects of evaluating the rhs do not affect
     * which property is modified.
     * Typically used in conjunction with setName.
     *
     * See ECMA 10.1.4
     */
    public static Scriptable bind(Context cx, Scriptable scope, String id)
    {
        Scriptable firstXMLObject = null;
        Scriptable parent = scope.getParentScope();
        childScopesChecks: if (parent != null) {
            // Check for possibly nested "with" scopes first
            while (scope instanceof NativeWith) {
                Scriptable withObj = scope.getPrototype();
                if (withObj instanceof XMLObject) {
                    XMLObject xmlObject = (XMLObject)withObj;
                    if (xmlObject.ecmaHas(cx, id)) {
                        return xmlObject;
                    }
                    if (firstXMLObject == null) {
                        firstXMLObject = xmlObject;
                    }
                } else {
                    if (ScriptableObject.hasProperty(withObj, id)) {
                        return withObj;
                    }
                }
                scope = parent;
                parent = parent.getParentScope();
                if (parent == null) {
                    break childScopesChecks;
                }
            }
            for (;;) {
                if (ScriptableObject.hasProperty(scope, id)) {
                    return scope;
                }
                scope = parent;
                parent = parent.getParentScope();
                if (parent == null) {
                    break childScopesChecks;
                }
            }
        }
        // scope here is top scope
        if (cx.useDynamicScope) {
            scope = checkDynamicScope(cx.topCallScope, scope);
        }
        if (ScriptableObject.hasProperty(scope, id)) {
            return scope;
        }
        // Nothing was found, but since XML objects always bind
        // return one if found
        return firstXMLObject;
    }

    public static Object setName(Scriptable bound, Object value,
                                 Context cx, Scriptable scope, String id)
    {
        if (bound != null) {
            if (bound instanceof XMLObject) {
                XMLObject xmlObject = (XMLObject)bound;
                xmlObject.ecmaPut(cx, id, value);
            } else {
                ScriptableObject.putProperty(bound, id, value);
            }
        } else {
            // "newname = 7;", where 'newname' has not yet
            // been defined, creates a new property in the
            // top scope unless strict mode is specified.
            if (cx.hasFeature(Context.FEATURE_STRICT_VARS)) {
                throw Context.reportRuntimeError1("msg.assn.create.strict", id);
            }
            // Find the top scope by walking up the scope chain.
            bound = ScriptableObject.getTopLevelScope(scope);
            if (cx.useDynamicScope) {
                bound = checkDynamicScope(cx.topCallScope, bound);
            }
            bound.put(id, bound, value);
        }
        return value;
    }

    /**
     * This is the enumeration needed by the for..in statement.
     *
     * See ECMA 12.6.3.
     *
     * IdEnumeration maintains a ObjToIntMap to make sure a given
     * id is enumerated only once across multiple objects in a
     * prototype chain.
     *
     * XXX - ECMA delete doesn't hide properties in the prototype,
     * but js/ref does. This means that the js/ref for..in can
     * avoid maintaining a hash table and instead perform lookups
     * to see if a given property has already been enumerated.
     *
     */
    private static class IdEnumeration
    {
        Scriptable obj;
        Object[] ids;
        int index;
        ObjToIntMap used;
        String currentId;
        boolean enumValues;
    }

    public static Object enumInit(Object value, Context cx, boolean enumValues)
    {
        IdEnumeration x = new IdEnumeration();
        x.obj = toObjectOrNull(cx, value);
        if (x.obj != null) {
            // null or undefined do not cause errors but rather lead to empty
            // "for in" loop
            x.enumValues = enumValues;
            // enumInit should read all initial ids before returning
            // or "for (a.i in a)" would wrongly enumerate i in a as well
            enumChangeObject(x);
        }
        return x;
    }

    public static Boolean enumNext(Object enumObj)
    {
        // OPT this could be more efficient
        boolean result;
        IdEnumeration x = (IdEnumeration)enumObj;
        for (;;) {
            if (x.obj == null) {
                result = false;
                break;
            }
            if (x.index == x.ids.length) {
                x.obj = x.obj.getPrototype();
                enumChangeObject(x);
                continue;
            }
            Object id = x.ids[x.index++];
            if (x.used != null && x.used.has(id)) {
                continue;
            }
            if (id instanceof String) {
                String strId = (String)id;
                if (!x.obj.has(strId, x.obj))
                    continue;   // must have been deleted
                x.currentId = strId;
            } else {
                int intId = ((Number)id).intValue();
                if (!x.obj.has(intId, x.obj))
                    continue;   // must have been deleted
                x.currentId = String.valueOf(intId);
            }
            result = true;
            break;
        }
        return wrapBoolean(result);
    }

    public static Object enumId(Object enumObj, Context cx)
    {
        IdEnumeration x = (IdEnumeration)enumObj;
        if (!x.enumValues) return x.currentId;

        Object result;

        String s = toStringIdOrIndex(cx, x.currentId);
        if (s == null) {
            int index = lastIndexResult(cx);
            result = x.obj.get(index, x.obj);
        } else {
            result = x.obj.get(s, x.obj);
        }

        return result;
    }

    private static void enumChangeObject(IdEnumeration x)
    {
        Object[] ids = null;
        while (x.obj != null) {
            ids = x.obj.getIds();
            if (ids.length != 0) {
                break;
            }
            x.obj = x.obj.getPrototype();
        }
        if (x.obj != null && x.ids != null) {
            Object[] previous = x.ids;
            int L = previous.length;
            if (x.used == null) {
                x.used = new ObjToIntMap(L);
            }
            for (int i = 0; i != L; ++i) {
                x.used.intern(previous[i]);
            }
        }
        x.ids = ids;
        x.index = 0;
    }

    /**
     * Prepare for calling name(...): return function corresponding to
     * name and make current top scope available
     * as ScriptRuntime.lastStoredScriptable() for consumption as thisObj.
     * The caller must call ScriptRuntime.lastStoredScriptable() immediately
     * after calling this method.
     */
    public static Callable getNameFunctionAndThis(String name,
                                                  Context cx,
                                                  Scriptable scope)
    {
        Scriptable parent = scope.getParentScope();
        if (parent == null) {
            Object result = topScopeName(cx, scope, name);
            if (!(result instanceof Callable)) {
                if (result == Scriptable.NOT_FOUND) {
                    throw notFoundError(scope, name);
                } else {
                    throw notFunctionError(result, name);
                }
            }
            // Top scope is not NativeWith or NativeCall => thisObj == scope
            Scriptable thisObj = scope;
            storeScriptable(cx, thisObj);
            return (Callable)result;
        }

        // name will call storeScriptable(cx, thisObj);
        return (Callable)nameOrFunction(cx, scope, parent, name, true);
    }

    /**
     * Prepare for calling obj[id](...): return function corresponding to
     * obj[id] and make obj properly converted to Scriptable available
     * as ScriptRuntime.lastStoredScriptable() for consumption as thisObj.
     * The caller must call ScriptRuntime.lastStoredScriptable() immediately
     * after calling this method.
     */
    public static Callable getElemFunctionAndThis(Object obj,
                                                  Object elem,
                                                  Context cx)
    {
        String s = toStringIdOrIndex(cx, elem);
        if (s != null) {
            return getPropFunctionAndThis(obj, s, cx);
        }
        int index = lastIndexResult(cx);

        Scriptable thisObj = toObjectOrNull(cx, obj);
        if (thisObj == null) {
            throw undefCallError(obj, String.valueOf(index));
        }

        Object value;
        for (;;) {
            // Ignore XML lookup as requred by ECMA 357, 11.2.2.1
            value = ScriptableObject.getProperty(thisObj, index);
            if (value != Scriptable.NOT_FOUND) {
                break;
            }
            if (!(thisObj instanceof XMLObject)) {
                break;
            }
            XMLObject xmlObject = (XMLObject)thisObj;
            Scriptable extra = xmlObject.getExtraMethodSource(cx);
            if (extra == null) {
                break;
            }
            thisObj = extra;
        }
        if (!(value instanceof Callable)) {
            throw notFunctionError(value, elem);
        }

        storeScriptable(cx, thisObj);
        return (Callable)value;
    }

    /**
     * Prepare for calling obj.property(...): return function corresponding to
     * obj.property and make obj properly converted to Scriptable available
     * as ScriptRuntime.lastStoredScriptable() for consumption as thisObj.
     * The caller must call ScriptRuntime.lastStoredScriptable() immediately
     * after calling this method.
     */
    public static Callable getPropFunctionAndThis(Object obj,
                                                  String property,
                                                  Context cx)
    {
        Scriptable thisObj = toObjectOrNull(cx, obj);
        if (thisObj == null) {
            throw undefCallError(obj, property);
        }

        Object value;
        for (;;) {
            // Ignore XML lookup as requred by ECMA 357, 11.2.2.1
            value = ScriptableObject.getProperty(thisObj, property);
            if (value != Scriptable.NOT_FOUND) {
                break;
            }
            if (!(thisObj instanceof XMLObject)) {
                break;
            }
            XMLObject xmlObject = (XMLObject)thisObj;
            Scriptable extra = xmlObject.getExtraMethodSource(cx);
            if (extra == null) {
                break;
            }
            thisObj = extra;
        }

        if (!(value instanceof Callable)) {
            throw notFunctionError(value, property);
        }

        storeScriptable(cx, thisObj);
        return (Callable)value;
    }

    /**
     * Prepare for calling <expression>(...): return function corresponding to
     * <expression> and make parent scope of the function available
     * as ScriptRuntime.lastStoredScriptable() for consumption as thisObj.
     * The caller must call ScriptRuntime.lastStoredScriptable() immediately
     * after calling this method.
     */
    public static Callable getValueFunctionAndThis(Object value, Context cx)
    {
        if (!(value instanceof Callable)) {
            throw notFunctionError(value);
        }

        Callable f = (Callable)value;
        Scriptable thisObj;
        if (f instanceof Scriptable) {
            thisObj = ((Scriptable)f).getParentScope();
        } else {
            if (cx.topCallScope == null) throw new IllegalStateException();
            thisObj = cx.topCallScope;
        }
        if (thisObj.getParentScope() != null) {
            if (thisObj instanceof NativeWith) {
                // functions defined inside with should have with target
                // as their thisObj
            } else if (thisObj instanceof NativeCall) {
                // nested functions should have top scope as their thisObj
                thisObj = ScriptableObject.getTopLevelScope(thisObj);
            }
        }
        storeScriptable(cx, thisObj);
        return f;
    }

    /**
     * Perform function call in reference context. Should always
     * return value that can be passed to
     * {@link #refGet(Object)} or @link #refSet(Object, Object)}
     * arbitrary number of times.
     * The args array reference should not be stored in any object that is
     * can be GC-reachable after this method returns. If this is necessary,
     * store args.clone(), not args array itself.
     */
    public static Ref callRef(Callable function, Scriptable thisObj,
                              Object[] args, Context cx)
    {
        if (function instanceof RefCallable) {
            RefCallable rfunction = (RefCallable)function;
            Ref ref = rfunction.refCall(cx, thisObj, args);
            if (ref == null) {
                throw new IllegalStateException(rfunction.getClass().getName()+".refCall() returned null");
            }
            return ref;
        }
        // No runtime support for now
        String msg = getMessage1("msg.no.ref.from.function",
                                 toString(function));
        throw constructError("ReferenceError", msg);
    }

    /**
     * Operator new.
     *
     * See ECMA 11.2.2
     */
    public static Scriptable newObject(Object fun, Context cx,
                                       Scriptable scope, Object[] args)
    {
        if (!(fun instanceof Function)) {
            throw notFunctionError(fun);
        }
        Function function = (Function)fun;
        return function.construct(cx, scope, args);
    }

    public static Object callSpecial(Context cx, Callable fun,
                                     Scriptable thisObj,
                                     Object[] args, Scriptable scope,
                                     Scriptable callerThis, int callType,
                                     String filename, int lineNumber)
    {
        if (callType == Node.SPECIALCALL_EVAL) {
            if (NativeGlobal.isEvalFunction(fun)) {
                return evalSpecial(cx, scope, callerThis, args,
                                   filename, lineNumber);
            }
        } else if (callType == Node.SPECIALCALL_WITH) {
            if (NativeWith.isWithFunction(fun)) {
                throw Context.reportRuntimeError1("msg.only.from.new",
                                                  "With");
            }
        } else {
            throw Kit.codeBug();
        }

        return fun.call(cx, scope, thisObj, args);
    }

    public static Object newSpecial(Context cx, Object fun,
                                    Object[] args, Scriptable scope,
                                    int callType)
    {
        if (callType == Node.SPECIALCALL_EVAL) {
            if (NativeGlobal.isEvalFunction(fun)) {
                throw typeError1("msg.not.ctor", "eval");
            }
        } else if (callType == Node.SPECIALCALL_WITH) {
            if (NativeWith.isWithFunction(fun)) {
                return NativeWith.newWithSpecial(cx, scope, args);
            }
        } else {
            throw Kit.codeBug();
        }

        return newObject(fun, cx, scope, args);
    }

    /**
     * Function.prototype.apply and Function.prototype.call
     *
     * See Ecma 15.3.4.[34]
     */
    public static Object applyOrCall(boolean isApply,
                                     Context cx, Scriptable scope,
                                     Scriptable thisObj, Object[] args)
    {
        int L = args.length;
        Callable function;
        if (thisObj instanceof Callable) {
            function = (Callable)thisObj;
        } else {
            Object value = thisObj.getDefaultValue(ScriptRuntime.FunctionClass);
            if (!(value instanceof Callable)) {
                throw ScriptRuntime.notFunctionError(value, thisObj);
            }
            function = (Callable)value;
        }

        Scriptable callThis = null;
        if (L != 0) {
            callThis = toObjectOrNull(cx, args[0]);
        }
        if (callThis == null) {
            // This covers the case of args[0] == (null|undefined) as well.
            callThis = getTopCallScope(cx);
        }

        Object[] callArgs;
        if (isApply) {
            // Follow Ecma 15.3.4.3
            if (L <= 1) {
                callArgs = ScriptRuntime.emptyArgs;
            } else {
                Object arg1 = args[1];
                if (arg1 == null || arg1 == Undefined.instance) {
                    callArgs = ScriptRuntime.emptyArgs;
                } else if (arg1 instanceof NativeArray
                           || arg1 instanceof Arguments)
                {
                    callArgs = cx.getElements((Scriptable) arg1);
                } else {
                    throw ScriptRuntime.typeError0("msg.arg.isnt.array");
                }
            }
        } else {
            // Follow Ecma 15.3.4.4
            if (L <= 1) {
                callArgs = ScriptRuntime.emptyArgs;
            } else {
                callArgs = new Object[L - 1];
                System.arraycopy(args, 1, callArgs, 0, L - 1);
            }
        }

        return function.call(cx, scope, callThis, callArgs);
    }

    /**
     * The eval function property of the global object.
     *
     * See ECMA 15.1.2.1
     */
    public static Object evalSpecial(Context cx, Scriptable scope,
                                     Object thisArg, Object[] args,
                                     String filename, int lineNumber)
    {
        if (args.length < 1)
            return Undefined.instance;
        Object x = args[0];
        if (!(x instanceof String)) {
            if (cx.hasFeature(Context.FEATURE_STRICT_EVAL)) {
                throw Context.reportRuntimeError0("msg.eval.nonstring.strict");
            }
            String message = ScriptRuntime.getMessage0("msg.eval.nonstring");
            Context.reportWarning(message);
            return x;
        }
        if (filename == null) {
            int[] linep = new int[1];
            filename = Context.getSourcePositionFromStack(linep);
            if (filename != null) {
                lineNumber = linep[0];
            } else {
                filename = "";
            }
        }
        String sourceName = ScriptRuntime.
            makeUrlForGeneratedScript(true, filename, lineNumber);

        ErrorReporter reporter;
        reporter = DefaultErrorReporter.forEval(cx.getErrorReporter());

        // Compile with explicit interpreter instance to force interpreter
        // mode.
        Script script = cx.compileString((String)x, new Interpreter(),
                                         reporter, sourceName, 1, null);
        ((InterpretedFunction)script).idata.evalScriptFlag = true;
        Callable c = (Callable)script;
        return c.call(cx, scope, (Scriptable)thisArg, ScriptRuntime.emptyArgs);
    }

    /**
     * The typeof operator
     */
    public static String typeof(Object value)
    {
        if (value == null)
            return "object";
        if (value == Undefined.instance)
            return "undefined";
        if (value instanceof Scriptable)
        {
            if (value instanceof XMLObject)
                return "xml";

            return (value instanceof Callable) ? "function" : "object";
        }
        if (value instanceof String)
            return "string";
        if (value instanceof Number)
            return "number";
        if (value instanceof Boolean)
            return "boolean";
        throw errorWithClassName("msg.invalid.type", value);
    }

    /**
     * The typeof operator that correctly handles the undefined case
     */
    public static String typeofName(Scriptable scope, String id)
    {
        Context cx = Context.getContext();
        Scriptable val = bind(cx, scope, id);
        if (val == null)
            return "undefined";
        return typeof(getObjectProp(val, id, cx));
    }

    // neg:
    // implement the '-' operator inline in the caller
    // as "-toNumber(val)"

    // not:
    // implement the '!' operator inline in the caller
    // as "!toBoolean(val)"

    // bitnot:
    // implement the '~' operator inline in the caller
    // as "~toInt32(val)"

    public static Object add(Object val1, Object val2, Context cx)
    {
        if(val1 instanceof Number && val2 instanceof Number) {
            return wrapNumber(((Number)val1).doubleValue() +
                              ((Number)val2).doubleValue());
        }
        if (val1 instanceof XMLObject) {
            Object test = ((XMLObject)val1).addValues(cx, true, val2);
            if (test != Scriptable.NOT_FOUND) {
                return test;
            }
        }
        if (val2 instanceof XMLObject) {
            Object test = ((XMLObject)val2).addValues(cx, false, val1);
            if (test != Scriptable.NOT_FOUND) {
                return test;
            }
        }
        if (val1 instanceof Scriptable)
            val1 = ((Scriptable) val1).getDefaultValue(null);
        if (val2 instanceof Scriptable)
            val2 = ((Scriptable) val2).getDefaultValue(null);
        if (!(val1 instanceof String) && !(val2 instanceof String))
            if ((val1 instanceof Number) && (val2 instanceof Number))
                return wrapNumber(((Number)val1).doubleValue() +
                                  ((Number)val2).doubleValue());
            else
                return wrapNumber(toNumber(val1) + toNumber(val2));
        return toString(val1).concat(toString(val2));
    }

    public static Object nameIncrDecr(Scriptable scopeChain, String id,
                                      int incrDecrMask)
    {
        Scriptable target;
        Object value;
      search: {
            do {
                target = scopeChain;
                do {
                    value = target.get(id, scopeChain);
                    if (value != Scriptable.NOT_FOUND) {
                        break search;
                    }
                    target = target.getPrototype();
                } while (target != null);
                scopeChain = scopeChain.getParentScope();
            } while (scopeChain != null);
            throw notFoundError(scopeChain, id);
        }
        return doScriptableIncrDecr(target, id, scopeChain, value,
                                    incrDecrMask);
    }

    public static Object propIncrDecr(Object obj, String id,
                                      Context cx, int incrDecrMask)
    {
        Scriptable start = toObjectOrNull(cx, obj);
        if (start == null) {
            throw undefReadError(obj, id);
        }

        Scriptable target = start;
        Object value;
      search: {
            do {
                value = target.get(id, start);
                if (value != Scriptable.NOT_FOUND) {
                    break search;
                }
                target = target.getPrototype();
            } while (target != null);
            start.put(id, start, NaNobj);
            return NaNobj;
        }
        return doScriptableIncrDecr(target, id, start, value,
                                    incrDecrMask);
    }

    private static Object doScriptableIncrDecr(Scriptable target,
                                               String id,
                                               Scriptable protoChainStart,
                                               Object value,
                                               int incrDecrMask)
    {
        boolean post = ((incrDecrMask & Node.POST_FLAG) != 0);
        double number;
        if (value instanceof Number) {
            number = ((Number)value).doubleValue();
        } else {
            number = toNumber(value);
            if (post) {
                // convert result to number
                value = wrapNumber(number);
            }
        }
        if ((incrDecrMask & Node.DECR_FLAG) == 0) {
            ++number;
        } else {
            --number;
        }
        Number result = wrapNumber(number);
        target.put(id, protoChainStart, result);
        if (post) {
            return value;
        } else {
            return result;
        }
    }

    public static Object elemIncrDecr(Object obj, Object index,
                                      Context cx, int incrDecrMask)
    {
        Object value = getObjectElem(obj, index, cx);
        boolean post = ((incrDecrMask & Node.POST_FLAG) != 0);
        double number;
        if (value instanceof Number) {
            number = ((Number)value).doubleValue();
        } else {
            number = toNumber(value);
            if (post) {
                // convert result to number
                value = wrapNumber(number);
            }
        }
        if ((incrDecrMask & Node.DECR_FLAG) == 0) {
            ++number;
        } else {
            --number;
        }
        Number result = wrapNumber(number);
        setObjectElem(obj, index, result, cx);
        if (post) {
            return value;
        } else {
            return result;
        }
    }

    public static Object refIncrDecr(Ref ref, Context cx, int incrDecrMask)
    {
        Object value = ref.get(cx);
        boolean post = ((incrDecrMask & Node.POST_FLAG) != 0);
        double number;
        if (value instanceof Number) {
            number = ((Number)value).doubleValue();
        } else {
            number = toNumber(value);
            if (post) {
                // convert result to number
                value = wrapNumber(number);
            }
        }
        if ((incrDecrMask & Node.DECR_FLAG) == 0) {
            ++number;
        } else {
            --number;
        }
        Number result = wrapNumber(number);
        ref.set(cx, result);
        if (post) {
            return value;
        } else {
            return result;
        }
    }

    private static Object toPrimitive(Object val)
    {
        if (!(val instanceof Scriptable)) {
            return val;
        }
        Scriptable s = (Scriptable)val;
        Object result = s.getDefaultValue(null);
        if (result instanceof Scriptable)
            throw typeError0("msg.bad.default.value");
        return result;
    }

    /**
     * Equality
     *
     * See ECMA 11.9
     */
    public static boolean eq(Object x, Object y)
    {
        if (x == null || x == Undefined.instance) {
            if (y == null || y == Undefined.instance) {
                return true;
            }
            if (y instanceof ScriptableObject) {
                Object test = ((ScriptableObject)y).equivalentValues(x);
                if (test != Scriptable.NOT_FOUND) {
                    return ((Boolean)test).booleanValue();
                }
            }
            return false;
        } else if (x instanceof Number) {
            return eqNumber(((Number)x).doubleValue(), y);
        } else if (x instanceof String) {
            return eqString((String)x, y);
        } else if (x instanceof Boolean) {
            boolean b = ((Boolean)x).booleanValue();
            if (y instanceof Boolean) {
                return b == ((Boolean)y).booleanValue();
            }
            if (y instanceof ScriptableObject) {
                Object test = ((ScriptableObject)y).equivalentValues(x);
                if (test != Scriptable.NOT_FOUND) {
                    return ((Boolean)test).booleanValue();
                }
            }
            return eqNumber(b ? 1.0 : 0.0, y);
        } else if (x instanceof Scriptable) {
            if (y instanceof Scriptable) {
                if (x == y) {
                    return true;
                }
                if (x instanceof ScriptableObject) {
                    Object test = ((ScriptableObject)x).equivalentValues(y);
                    if (test != Scriptable.NOT_FOUND) {
                        return ((Boolean)test).booleanValue();
                    }
                }
                if (y instanceof ScriptableObject) {
                    Object test = ((ScriptableObject)y).equivalentValues(x);
                    if (test != Scriptable.NOT_FOUND) {
                        return ((Boolean)test).booleanValue();
                    }
                }
                if (x instanceof Wrapper && y instanceof Wrapper) {
                    return ((Wrapper)x).unwrap() == ((Wrapper)y).unwrap();
                }
                return false;
            } else if (y instanceof Boolean) {
                if (x instanceof ScriptableObject) {
                    Object test = ((ScriptableObject)x).equivalentValues(y);
                    if (test != Scriptable.NOT_FOUND) {
                        return ((Boolean)test).booleanValue();
                    }
                }
                double d = ((Boolean)y).booleanValue() ? 1.0 : 0.0;
                return eqNumber(d, x);
            } else if (y instanceof Number) {
                return eqNumber(((Number)y).doubleValue(), x);
            } else if (y instanceof String) {
                return eqString((String)y, x);
            }
            // covers the case when y == Undefined.instance as well
            return false;
        } else {
            warnAboutNonJSObject(x);
            return x == y;
        }
    }

    static boolean eqNumber(double x, Object y)
    {
        for (;;) {
            if (y == null || y == Undefined.instance) {
                return false;
            } else if (y instanceof Number) {
                return x == ((Number)y).doubleValue();
            } else if (y instanceof String) {
                return x == toNumber(y);
            } else if (y instanceof Boolean) {
                return x == (((Boolean)y).booleanValue() ? 1.0 : +0.0);
            } else if (y instanceof Scriptable) {
                if (y instanceof ScriptableObject) {
                    Object xval = wrapNumber(x);
                    Object test = ((ScriptableObject)y).equivalentValues(xval);
                    if (test != Scriptable.NOT_FOUND) {
                        return ((Boolean)test).booleanValue();
                    }
                }
                y = toPrimitive(y);
            } else {
                warnAboutNonJSObject(y);
                return false;
            }
        }
    }

    private static boolean eqString(String x, Object y)
    {
        for (;;) {
            if (y == null || y == Undefined.instance) {
                return false;
            } else if (y instanceof String) {
                return x.equals(y);
            } else if (y instanceof Number) {
                return toNumber(x) == ((Number)y).doubleValue();
            } else if (y instanceof Boolean) {
                return toNumber(x) == (((Boolean)y).booleanValue() ? 1.0 : 0.0);
            } else if (y instanceof Scriptable) {
                if (y instanceof ScriptableObject) {
                    Object test = ((ScriptableObject)y).equivalentValues(x);
                    if (test != Scriptable.NOT_FOUND) {
                        return ((Boolean)test).booleanValue();
                    }
                }
                y = toPrimitive(y);
                continue;
            } else {
                warnAboutNonJSObject(y);
                return false;
            }
        }
    }
    public static boolean shallowEq(Object x, Object y)
    {
        if (x == y) {
            if (!(x instanceof Number)) {
                return true;
            }
            // NaN check
            double d = ((Number)x).doubleValue();
            return d == d;
        }
        if (x == null || x == Undefined.instance) {
            return false;
        } else if (x instanceof Number) {
            if (y instanceof Number) {
                return ((Number)x).doubleValue() == ((Number)y).doubleValue();
            }
        } else if (x instanceof String) {
            if (y instanceof String) {
                return x.equals(y);
            }
        } else if (x instanceof Boolean) {
            if (y instanceof Boolean) {
                return x.equals(y);
            }
        } else if (x instanceof Scriptable) {
            if (x instanceof Wrapper && y instanceof Wrapper) {
                return ((Wrapper)x).unwrap() == ((Wrapper)y).unwrap();
            }
        } else {
            warnAboutNonJSObject(x);
            return x == y;
        }
        return false;
    }

    /**
     * The instanceof operator.
     *
     * @return a instanceof b
     */
    public static boolean instanceOf(Object a, Object b, Context cx)
    {
        // Check RHS is an object
        if (! (b instanceof Scriptable)) {
            throw typeError0("msg.instanceof.not.object");
        }

        // for primitive values on LHS, return false
        // XXX we may want to change this so that
        // 5 instanceof Number == true
        if (! (a instanceof Scriptable))
            return false;

        return ((Scriptable)b).hasInstance((Scriptable)a);
    }

    /**
     * Delegates to
     *
     * @return true iff rhs appears in lhs' proto chain
     */
    protected static boolean jsDelegatesTo(Scriptable lhs, Scriptable rhs) {
        Scriptable proto = lhs.getPrototype();

        while (proto != null) {
            if (proto.equals(rhs)) return true;
            proto = proto.getPrototype();
        }

        return false;
    }

    /**
     * The in operator.
     *
     * This is a new JS 1.3 language feature.  The in operator mirrors
     * the operation of the for .. in construct, and tests whether the
     * rhs has the property given by the lhs.  It is different from the
     * for .. in construct in that:
     * <BR> - it doesn't perform ToObject on the right hand side
     * <BR> - it returns true for DontEnum properties.
     * @param a the left hand operand
     * @param b the right hand operand
     *
     * @return true if property name or element number a is a property of b
     */
    public static boolean in(Object a, Object b, Context cx)
    {
        if (!(b instanceof Scriptable)) {
            throw typeError0("msg.instanceof.not.object");
        }

        return hasObjectElem((Scriptable)b, a, cx);
    }

    public static boolean cmp_LT(Object val1, Object val2)
    {
        double d1, d2;
        if (val1 instanceof Number && val2 instanceof Number) {
            d1 = ((Number)val1).doubleValue();
            d2 = ((Number)val2).doubleValue();
        } else {
            if (val1 instanceof Scriptable)
                val1 = ((Scriptable) val1).getDefaultValue(NumberClass);
            if (val2 instanceof Scriptable)
                val2 = ((Scriptable) val2).getDefaultValue(NumberClass);
            if (val1 instanceof String && val2 instanceof String) {
                return ((String)val1).compareTo((String)val2) < 0;
            }
            d1 = toNumber(val1);
            d2 = toNumber(val2);
        }
        return d1 < d2;
    }

    public static boolean cmp_LE(Object val1, Object val2)
    {
        double d1, d2;
        if (val1 instanceof Number && val2 instanceof Number) {
            d1 = ((Number)val1).doubleValue();
            d2 = ((Number)val2).doubleValue();
        } else {
            if (val1 instanceof Scriptable)
                val1 = ((Scriptable) val1).getDefaultValue(NumberClass);
            if (val2 instanceof Scriptable)
                val2 = ((Scriptable) val2).getDefaultValue(NumberClass);
            if (val1 instanceof String && val2 instanceof String) {
                return ((String)val1).compareTo((String)val2) <= 0;
            }
            d1 = toNumber(val1);
            d2 = toNumber(val2);
        }
        return d1 <= d2;
    }

    // ------------------
    // Statements
    // ------------------

    public static ScriptableObject getGlobal(Context cx) {
        final String GLOBAL_CLASS = "org.mozilla.javascript.tools.shell.Global";
        Class globalClass = Kit.classOrNull(GLOBAL_CLASS);
        if (globalClass != null) {
            try {
                Class[] parm = { ScriptRuntime.ContextClass };
                Constructor globalClassCtor = globalClass.getConstructor(parm);
                Object[] arg = { cx };
                return (ScriptableObject) globalClassCtor.newInstance(arg);
            } catch (Exception e) {
                // fall through...
            }
        }
        return new ImporterTopLevel(cx);
    }

    public static boolean hasTopCall(Context cx)
    {
        return (cx.topCallScope != null);
    }

    public static Scriptable getTopCallScope(Context cx)
    {
        Scriptable scope = cx.topCallScope;
        if (scope == null) {
            throw new IllegalStateException();
        }
        return scope;
    }

    public static Object doTopCall(Callable callable,
                                   Context cx, Scriptable scope,
                                   Scriptable thisObj, Object[] args)
    {
        if (scope == null) throw new IllegalArgumentException();
        if (cx.topCallScope != null) throw new IllegalStateException();

        Object result;
        cx.topCallScope = ScriptableObject.getTopLevelScope(scope);
        cx.useDynamicScope = cx.hasFeature(Context.FEATURE_DYNAMIC_SCOPE);
        ContextFactory f = cx.getFactory();
        try {
            result = f.doTopCall(callable, cx, scope, thisObj, args);
        } finally {
            cx.topCallScope = null;
            // Cleanup cached references
            cx.cachedXMLLib = null;

            if (cx.currentActivationCall != null) {
                // Function should always call exitActivationFunction
                // if it creates activation record
                throw new IllegalStateException();
            }
        }
        return result;
    }

    /**
     * Return <tt>possibleDynamicScope</tt> if <tt>staticTopScope</tt>
     * is present on its prototype chain and return <tt>staticTopScope</tt>
     * otherwise.
     * Should only be called when <tt>staticTopScope</tt> is top scope.
     */
    static Scriptable checkDynamicScope(Scriptable possibleDynamicScope,
                                        Scriptable staticTopScope)
    {
        // Return cx.topCallScope if scope
        if (possibleDynamicScope == staticTopScope) {
            return possibleDynamicScope;
        }
        Scriptable proto = possibleDynamicScope;
        for (;;) {
            proto = proto.getPrototype();
            if (proto == staticTopScope) {
                return possibleDynamicScope;
            }
            if (proto == null) {
                return staticTopScope;
            }
        }
    }

    public static void initScript(NativeFunction funObj, Scriptable thisObj,
                                  Context cx, Scriptable scope,
                                  boolean evalScript)
    {
        if (cx.topCallScope == null)
            throw new IllegalStateException();

        int varCount = funObj.getParamAndVarCount();
        if (varCount != 0) {

            Scriptable varScope = scope;
            // Never define any variables from var statements inside with
            // object. See bug 38590.
            while (varScope instanceof NativeWith) {
                varScope = varScope.getParentScope();
            }

            for (int i = varCount; i-- != 0;) {
                String name = funObj.getParamOrVarName(i);
                // Don't overwrite existing def if already defined in object
                // or prototypes of object.
                if (!ScriptableObject.hasProperty(scope, name)) {
                    if (!evalScript) {
                        // Global var definitions are supposed to be DONTDELETE
                        ScriptableObject.defineProperty(
                            varScope, name, Undefined.instance,
                            ScriptableObject.PERMANENT);
                    } else {
                        varScope.put(name, varScope, Undefined.instance);
                    }
                }
            }
        }
    }

    public static Scriptable createFunctionActivation(NativeFunction funObj,
                                                      Scriptable scope,
                                                      Object[] args)
    {
        return new NativeCall(funObj, scope, args);
    }


    public static void enterActivationFunction(Context cx,
                                               Scriptable activation)
    {
        if (cx.topCallScope == null)
            throw new IllegalStateException();

        NativeCall call = (NativeCall)activation;
        call.parentActivationCall = cx.currentActivationCall;
        cx.currentActivationCall = call;
    }

    public static void exitActivationFunction(Context cx)
    {
        NativeCall call = cx.currentActivationCall;
        cx.currentActivationCall = call.parentActivationCall;
        call.parentActivationCall = null;
    }

    static NativeCall findFunctionActivation(Context cx, Function f)
    {
        NativeCall call = cx.currentActivationCall;
        while (call != null) {
            if (call.function == f)
                return call;
            call = call.parentActivationCall;
        }
        return null;
    }

    public static Scriptable newCatchScope(Throwable t,
                                           Scriptable lastCatchScope,
                                           String exceptionName,
                                           Context cx, Scriptable scope)
    {
        Object obj;
        boolean cacheObj;

      getObj:
        if (t instanceof JavaScriptException) {
            cacheObj = false;
            obj = ((JavaScriptException)t).getValue();
        } else {
            cacheObj = true;

            // Create wrapper object unless it was associated with
            // the previous scope object

            if (lastCatchScope != null) {
                NativeObject last = (NativeObject)lastCatchScope;
                obj = last.getAssociatedValue(t);
                if (obj == null) Kit.codeBug();
                break getObj;
            }

            RhinoException re;
            String errorName;
            String errorMsg;
            Throwable javaException = null;

            if (t instanceof EcmaError) {
                EcmaError ee = (EcmaError)t;
                re = ee;
                errorName = ee.getName();
                errorMsg = ee.getErrorMessage();
            } else if (t instanceof WrappedException) {
                WrappedException we = (WrappedException)t;
                re = we;
                javaException = we.getWrappedException();
                errorName = "JavaException";
                errorMsg = javaException.getClass().getName()
                           +": "+javaException.getMessage();
            } else if (t instanceof EvaluatorException) {
                // Pure evaluator exception, nor WrappedException instance
                EvaluatorException ee = (EvaluatorException)t;
                re = ee;
                errorName = "InternalError";
                errorMsg = ee.getMessage();
            } else {
                // Script can catch only instances of JavaScriptException,
                // EcmaError and EvaluatorException
                throw Kit.codeBug();
            }

            String sourceUri = re.sourceName();
            if (sourceUri == null) {
                sourceUri = "";
            }
            int line = re.lineNumber();
            Object args[];
            if (line > 0) {
                args = new Object[] { errorMsg, sourceUri, new Integer(line) };
            } else {
                args = new Object[] { errorMsg, sourceUri };
            }

            Scriptable errorObject = cx.newObject(scope, errorName, args);
            ScriptableObject.putProperty(errorObject, "name", errorName);

            if (javaException != null) {
                Object wrap = cx.getWrapFactory().wrap(cx, scope, javaException,
                                                       null);
                ScriptableObject.defineProperty(
                    errorObject, "javaException", wrap,
                    ScriptableObject.PERMANENT | ScriptableObject.READONLY);
            }
            if (re != null) {
                Object wrap = cx.getWrapFactory().wrap(cx, scope, re, null);
                ScriptableObject.defineProperty(
                    errorObject, "rhinoException", wrap,
                    ScriptableObject.PERMANENT | ScriptableObject.READONLY);
            }

            obj = errorObject;
        }


        NativeObject catchScopeObject = new NativeObject();
        // See ECMA 12.4
        catchScopeObject.defineProperty(
            exceptionName, obj, ScriptableObject.PERMANENT);
        if (cacheObj) {
            catchScopeObject.associateValue(t, obj);
        }
        return catchScopeObject;
    }

    public static Scriptable enterWith(Object obj, Context cx,
                                       Scriptable scope)
    {
        Scriptable sobj = toObjectOrNull(cx, obj);
        if (sobj == null) {
            throw typeError1("msg.undef.with", toString(obj));
        }
        if (sobj instanceof XMLObject) {
            XMLObject xmlObject = (XMLObject)sobj;
            return xmlObject.enterWith(scope);
        }
        return new NativeWith(scope, sobj);
    }

    public static Scriptable leaveWith(Scriptable scope)
    {
        NativeWith nw = (NativeWith)scope;
        return nw.getParentScope();
    }

    public static Scriptable enterDotQuery(Object value, Scriptable scope)
    {
        if (!(value instanceof XMLObject)) {
            throw notXmlError(value);
        }
        XMLObject object = (XMLObject)value;
        return object.enterDotQuery(scope);
    }

    public static Object updateDotQuery(boolean value, Scriptable scope)
    {
        // Return null to continue looping
        NativeWith nw = (NativeWith)scope;
        return nw.updateDotQuery(value);
    }

    public static Scriptable leaveDotQuery(Scriptable scope)
    {
        NativeWith nw = (NativeWith)scope;
        return nw.getParentScope();
    }

    public static void setFunctionProtoAndParent(BaseFunction fn,
                                                 Scriptable scope)
    {
        fn.setParentScope(scope);
        fn.setPrototype(ScriptableObject.getFunctionPrototype(scope));
    }

    public static void setObjectProtoAndParent(ScriptableObject object,
                                               Scriptable scope)
    {
        // Compared with function it always sets the scope to top scope
        scope = ScriptableObject.getTopLevelScope(scope);
        object.setParentScope(scope);
        Scriptable proto
            = ScriptableObject.getClassPrototype(scope, object.getClassName());
        object.setPrototype(proto);
    }

    public static void initFunction(Context cx, Scriptable scope,
                                    NativeFunction function, int type,
                                    boolean fromEvalCode)
    {
        if (type == FunctionNode.FUNCTION_STATEMENT) {
            String name = function.getFunctionName();
            if (name != null && name.length() != 0) {
                if (!fromEvalCode) {
                    // ECMA specifies that functions defined in global and
                    // function scope outside eval should have DONTDELETE set.
                    ScriptableObject.defineProperty
                        (scope, name, function, ScriptableObject.PERMANENT);
                } else {
                    scope.put(name, scope, function);
                }
            }
        } else if (type == FunctionNode.FUNCTION_EXPRESSION_STATEMENT) {
            String name = function.getFunctionName();
            if (name != null && name.length() != 0) {
                // Always put function expression statements into initial
                // activation object ignoring the with statement to follow
                // SpiderMonkey
                while (scope instanceof NativeWith) {
                    scope = scope.getParentScope();
                }
                scope.put(name, scope, function);
            }
        } else {
            throw Kit.codeBug();
        }
    }

    public static Scriptable newArrayLiteral(Object[] objects,
                                             int[] skipIndexces,
                                             Context cx, Scriptable scope)
    {
        int count = objects.length;
        int skipCount = 0;
        if (skipIndexces != null) {
            skipCount = skipIndexces.length;
        }
        int length = count + skipCount;
        Integer lengthObj = new Integer(length);
        Scriptable arrayObj;
        /*
         * If the version is 120, then new Array(4) means create a new
         * array with 4 as the first element.  In this case, we have to
         * set length property manually.
         */
        if (cx.getLanguageVersion() == Context.VERSION_1_2) {
            arrayObj = cx.newObject(scope, "Array", ScriptRuntime.emptyArgs);
            ScriptableObject.putProperty(arrayObj, "length", lengthObj);
        } else {
            arrayObj = cx.newObject(scope, "Array", new Object[] { lengthObj });
        }
        int skip = 0;
        for (int i = 0, j = 0; i != length; ++i) {
            if (skip != skipCount && skipIndexces[skip] == i) {
                ++skip;
                continue;
            }
            ScriptableObject.putProperty(arrayObj, i, objects[j]);
            ++j;
        }
        return arrayObj;
    }

    public static Scriptable newObjectLiteral(Object[] propertyIds,
                                              Object[] propertyValues,
                                              Context cx, Scriptable scope)
    {
        Scriptable object = cx.newObject(scope);
        for (int i = 0, end = propertyIds.length; i != end; ++i) {
            Object id = propertyIds[i];
            Object value = propertyValues[i];
            if (id instanceof String) {
                ScriptableObject.putProperty(object, (String)id, value);
            } else {
                int index = ((Integer)id).intValue();
                ScriptableObject.putProperty(object, index, value);
            }
        }
        return object;
    }

    public static boolean isArrayObject(Object obj)
    {
        return obj instanceof NativeArray || obj instanceof Arguments;
    }

    public static Object[] getArrayElements(Scriptable object)
    {
        Context cx = Context.getContext();
        long longLen = NativeArray.getLengthProperty(cx, object);
        if (longLen > Integer.MAX_VALUE) {
            // arrays beyond  MAX_INT is not in Java in any case
            throw new IllegalArgumentException();
        }
        int len = (int) longLen;
        if (len == 0) {
            return ScriptRuntime.emptyArgs;
        } else {
            Object[] result = new Object[len];
            for (int i=0; i < len; i++) {
                Object elem = ScriptableObject.getProperty(object, i);
                result[i] = (elem == Scriptable.NOT_FOUND) ? Undefined.instance
                                                           : elem;
            }
            return result;
        }
    }

    static void checkDeprecated(Context cx, String name) {
        int version = cx.getLanguageVersion();
        if (version >= Context.VERSION_1_4 || version == Context.VERSION_DEFAULT) {
            String msg = getMessage1("msg.deprec.ctor", name);
            if (version == Context.VERSION_DEFAULT)
                Context.reportWarning(msg);
            else
                throw Context.reportRuntimeError(msg);
        }
    }

    public static String getMessage0(String messageId)
    {
        return getMessage(messageId, null);
    }

    public static String getMessage1(String messageId, Object arg1)
    {
        Object[] arguments = {arg1};
        return getMessage(messageId, arguments);
    }

    public static String getMessage2(
        String messageId, Object arg1, Object arg2)
    {
        Object[] arguments = {arg1, arg2};
        return getMessage(messageId, arguments);
    }

    public static String getMessage3(
        String messageId, Object arg1, Object arg2, Object arg3)
    {
        Object[] arguments = {arg1, arg2, arg3};
        return getMessage(messageId, arguments);
    }

    public static String getMessage4(
        String messageId, Object arg1, Object arg2, Object arg3, Object arg4)
    {
        Object[] arguments = {arg1, arg2, arg3, arg4};
        return getMessage(messageId, arguments);
    }

    /* OPT there's a noticable delay for the first error!  Maybe it'd
     * make sense to use a ListResourceBundle instead of a properties
     * file to avoid (synchronized) text parsing.
     */
    public static String getMessage(String messageId, Object[] arguments)
    {
        final String defaultResource
            = "org.mozilla.javascript.resources.Messages";

        Context cx = Context.getCurrentContext();
        Locale locale = cx != null ? cx.getLocale() : Locale.getDefault();

        // ResourceBundle does cacheing.
        ResourceBundle rb = ResourceBundle.getBundle(defaultResource, locale);

        String formatString;
        try {
            formatString = rb.getString(messageId);
        } catch (java.util.MissingResourceException mre) {
            throw new RuntimeException
                ("no message resource found for message property "+ messageId);
        }

        /*
         * It's OK to format the string, even if 'arguments' is null;
         * we need to format it anyway, to make double ''s collapse to
         * single 's.
         */
        // TODO: MessageFormat is not available on pJava
        MessageFormat formatter = new MessageFormat(formatString);
        return formatter.format(arguments);
    }

    public static EcmaError constructError(String error, String message)
    {
        int[] linep = new int[1];
        String filename = Context.getSourcePositionFromStack(linep);
        return constructError(error, message, filename, linep[0], null, 0);
    }

    public static EcmaError constructError(String error,
                                           String message,
                                           String sourceName,
                                           int lineNumber,
                                           String lineSource,
                                           int columnNumber)
    {
        return new EcmaError(error, message, sourceName,
                             lineNumber, lineSource, columnNumber);
    }

    public static EcmaError typeError(String message)
    {
        return constructError("TypeError", message);
    }

    public static EcmaError typeError0(String messageId)
    {
        String msg = getMessage0(messageId);
        return typeError(msg);
    }

    public static EcmaError typeError1(String messageId, String arg1)
    {
        String msg = getMessage1(messageId, arg1);
        return typeError(msg);
    }

    public static EcmaError typeError2(String messageId, String arg1,
                                       String arg2)
    {
        String msg = getMessage2(messageId, arg1, arg2);
        return typeError(msg);
    }

    public static EcmaError typeError3(String messageId, String arg1,
                                       String arg2, String arg3)
    {
        String msg = getMessage3(messageId, arg1, arg2, arg3);
        return typeError(msg);
    }

    public static RuntimeException undefReadError(Object object, Object id)
    {
        String idStr = (id == null) ? "null" : id.toString();
        return typeError2("msg.undef.prop.read", toString(object), idStr);
    }

    public static RuntimeException undefCallError(Object object, Object id)
    {
        String idStr = (id == null) ? "null" : id.toString();
        return typeError2("msg.undef.method.call", toString(object), idStr);
    }

    public static RuntimeException undefWriteError(Object object,
                                                   Object id,
                                                   Object value)
    {
        String idStr = (id == null) ? "null" : id.toString();
        String valueStr = (value instanceof Scriptable)
                          ? value.toString() : toString(value);
        return typeError3("msg.undef.prop.write", toString(object), idStr,
                          valueStr);
    }

    public static RuntimeException notFoundError(Scriptable object,
                                                 String property)
    {
        // XXX: use object to improve the error message
        String msg = getMessage1("msg.is.not.defined", property);
        throw constructError("ReferenceError", msg);
    }

    public static RuntimeException notFunctionError(Object value)
    {
        return notFunctionError(value, value);
    }

    public static RuntimeException notFunctionError(Object value,
                                                    Object messageHelper)
    {
        // XXX Use value for better error reporting
        String msg = (messageHelper == null)
                     ? "null" : messageHelper.toString();
        if (value == Scriptable.NOT_FOUND) {
            return typeError1("msg.function.not.found", msg);
        }
        return typeError2("msg.isnt.function", msg,
                value == null ? "null" : value.getClass().getName());
    }

    private static RuntimeException notXmlError(Object value)
    {
        throw typeError1("msg.isnt.xml.object", ScriptRuntime.toString(value));
    }

    private static void warnAboutNonJSObject(Object nonJSObject)
    {
        String message =
"RHINO USAGE WARNING: Missed Context.javaToJS() conversion:\n"
+"Rhino runtime detected object "+nonJSObject+" of class "+nonJSObject.getClass().getName()+" where it expected String, Number, Boolean or Scriptable instance. Please check your code for missig Context.javaToJS() call.";
        Context.reportWarning(message);
        // Just to be sure that it would be noticed
        System.err.println(message);
    }

    public static RegExpProxy getRegExpProxy(Context cx)
    {
        return cx.getRegExpProxy();
    }

    public static void setRegExpProxy(Context cx, RegExpProxy proxy)
    {
        if (proxy == null) throw new IllegalArgumentException();
        cx.regExpProxy = proxy;
    }

    public static RegExpProxy checkRegExpProxy(Context cx)
    {
        RegExpProxy result = getRegExpProxy(cx);
        if (result == null) {
            throw Context.reportRuntimeError0("msg.no.regexp");
        }
        return result;
    }

    private static XMLLib currentXMLLib(Context cx)
    {
        // Scripts should be running to access this
        if (cx.topCallScope == null)
            throw new IllegalStateException();

        XMLLib xmlLib = cx.cachedXMLLib;
        if (xmlLib == null) {
            xmlLib = XMLLib.extractFromScope(cx.topCallScope);
            if (xmlLib == null)
                throw new IllegalStateException();
            cx.cachedXMLLib = xmlLib;
        }

        return xmlLib;
    }

    /**
     * Escapes the reserved characters in a value of an attribute
     *
     * @param value Unescaped text
     * @return The escaped text
     */
    public static String escapeAttributeValue(Object value, Context cx)
    {
        XMLLib xmlLib = currentXMLLib(cx);
        return xmlLib.escapeAttributeValue(value);
    }

    /**
     * Escapes the reserved characters in a value of a text node
     *
     * @param value Unescaped text
     * @return The escaped text
     */
    public static String escapeTextValue(Object value, Context cx)
    {
        XMLLib xmlLib = currentXMLLib(cx);
        return xmlLib.escapeTextValue(value);
    }

    public static Ref memberRef(Object obj, Object elem,
                                Context cx, int memberTypeFlags)
    {
        if (!(obj instanceof XMLObject)) {
            throw notXmlError(obj);
        }
        XMLObject xmlObject = (XMLObject)obj;
        return xmlObject.memberRef(cx, elem, memberTypeFlags);
    }

    public static Ref memberRef(Object obj, Object namespace, Object elem,
                                Context cx, int memberTypeFlags)
    {
        if (!(obj instanceof XMLObject)) {
            throw notXmlError(obj);
        }
        XMLObject xmlObject = (XMLObject)obj;
        return xmlObject.memberRef(cx, namespace, elem, memberTypeFlags);
    }

    public static Ref nameRef(Object name, Context cx,
                              Scriptable scope, int memberTypeFlags)
    {
        XMLLib xmlLib = currentXMLLib(cx);
        return xmlLib.nameRef(cx, name, scope, memberTypeFlags);
    }

    public static Ref nameRef(Object namespace, Object name, Context cx,
                              Scriptable scope, int memberTypeFlags)
    {
        XMLLib xmlLib = currentXMLLib(cx);
        return xmlLib.nameRef(cx, namespace, name, scope, memberTypeFlags);
    }

    private static void storeIndexResult(Context cx, int index)
    {
        cx.scratchIndex = index;
    }

    static int lastIndexResult(Context cx)
    {
        return cx.scratchIndex;
    }

    public static void storeUint32Result(Context cx, long value)
    {
        if ((value >>> 32) != 0)
            throw new IllegalArgumentException();
        cx.scratchUint32 = value;
    }

    public static long lastUint32Result(Context cx)
    {
        long value = cx.scratchUint32;
        if ((value >>> 32) != 0)
            throw new IllegalStateException();
        return value;
    }

    private static void storeScriptable(Context cx, Scriptable value)
    {
        // The previosly stored scratchScriptable should be consumed
        if (cx.scratchScriptable != null)
            throw new IllegalStateException();
        cx.scratchScriptable = value;
    }

    public static Scriptable lastStoredScriptable(Context cx)
    {
        Scriptable result = cx.scratchScriptable;
        cx.scratchScriptable = null;
        return result;
    }

    static String makeUrlForGeneratedScript
        (boolean isEval, String masterScriptUrl, int masterScriptLine)
    {
        if (isEval) {
            return masterScriptUrl+'#'+masterScriptLine+"(eval)";
        } else {
            return masterScriptUrl+'#'+masterScriptLine+"(Function)";
        }
    }

    static boolean isGeneratedScript(String sourceUrl) {
        // ALERT: this may clash with a valid URL containing (eval) or
        // (Function)
        return sourceUrl.indexOf("(eval)") >= 0
               || sourceUrl.indexOf("(Function)") >= 0;
    }

    private static RuntimeException errorWithClassName(String msg, Object val)
    {
        return Context.reportRuntimeError1(msg, val.getClass().getName());
    }

    public static final Object[] emptyArgs = new Object[0];
    public static final String[] emptyStrings = new String[0];

}

