scriptruntime.java

這是一個javascript 的 interpreter是了解 web browser的好材料

                    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 (i == d) {
            return new Integer(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 (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) {
            // TODO: Change XMLObject to just use Scriptable interface
            // to avoid paying cost of instanceof check on *every property
            // lookup* !
            XMLObject xmlObject = (XMLObject)obj;
            return xmlObject.ecmaGet(cx, property);
        }

        Object result = ScriptableObject.getProperty(obj, property);
        if (result == Scriptable.NOT_FOUND) {
            if (cx.hasFeature(Context.FEATURE_STRICT_MODE)) {
                Context.reportWarning(ScriptRuntime.getMessage1(
                    "msg.ref.undefined.prop", property));
            }
            result = Undefined.instance;
        }

        return result;
    }
    
    public static Object getObjectPropNoWarn(Object obj, String property,
                                             Context cx)
    {
        Scriptable sobj = toObjectOrNull(cx, obj);
        if (sobj == null) {
            throw undefReadError(obj, property);
        }
        if (obj instanceof XMLObject) {
            // TODO: fix as mentioned in note in method above
            getObjectProp(sobj, property, cx);
        }
        Object result = ScriptableObject.getProperty(sobj, property);
        if (result == Scriptable.NOT_FOUND) {
          return 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 (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 (index == dblIndex) {
            return setObjectIndex(sobj, index, value, cx);