nativearray.java

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

                if (Long.toString(index).equals(id)) {
                    return index;
                }
            }
        }
        return -1;
    }

    public void put(String id, Scriptable start, Object value)
    {
        super.put(id, start, value);
        if (start == this) {
            // If the object is sealed, super will throw exception
            long index = toArrayIndex(id);
            if (index >= length) {
                length = index + 1;
                denseOnly = false;
            }
        }
    }

    private boolean ensureCapacity(int capacity)
    {
        if (capacity > dense.length) {
            if (capacity > MAX_PRE_GROW_SIZE) {
                denseOnly = false;
                return false;
            }
            capacity = Math.max(capacity, (int)(dense.length * GROW_FACTOR));
            Object[] newDense = new Object[capacity];
            System.arraycopy(dense, 0, newDense, 0, dense.length);
            Arrays.fill(newDense, dense.length, newDense.length,
                        Scriptable.NOT_FOUND);
            dense = newDense;
        }
        return true;
    }

    public void put(int index, Scriptable start, Object value)
    {
        if (start == this && !isSealed() && dense != null && 0 <= index &&
            (denseOnly || !isGetterOrSetter(null, index, true)))
        {
            if (index < dense.length) {
                dense[index] = value;
                if (this.length <= index)
                    this.length = (long)index + 1;
                return;
            } else if (denseOnly && index < dense.length * GROW_FACTOR &&
                       ensureCapacity(index+1))
            {
                dense[index] = value;
                this.length = (long)index + 1;
                return;
            } else {
                denseOnly = false;
            }
        }
        super.put(index, start, value);
        if (start == this) {
            // only set the array length if given an array index (ECMA 15.4.0)
            if (this.length <= index) {
                // avoid overflowing index!
                this.length = (long)index + 1;
            }
        }
    }

    public void delete(int index)
    {
        if (dense != null && 0 <= index && index < dense.length &&
            !isSealed() && (denseOnly || !isGetterOrSetter(null, index, true)))
        {
            dense[index] = NOT_FOUND;
        } else {
            super.delete(index);
        }
    }

    public Object[] getIds()
    {
        Object[] superIds = super.getIds();
        if (dense == null) { return superIds; }
        int N = dense.length;
        long currentLength = length;
        if (N > currentLength) {
            N = (int)currentLength;
        }
        if (N == 0) { return superIds; }
        int superLength = superIds.length;
        Object[] ids = new Object[N + superLength];

        int presentCount = 0;
        for (int i = 0; i != N; ++i) {
            // Replace existing elements by their indexes
            if (dense[i] != NOT_FOUND) {
                ids[presentCount] = new Integer(i);
                ++presentCount;
            }
        }
        if (presentCount != N) {
            // dense contains deleted elems, need to shrink the result
            Object[] tmp = new Object[presentCount + superLength];
            System.arraycopy(ids, 0, tmp, 0, presentCount);
            ids = tmp;
        }
        System.arraycopy(superIds, 0, ids, presentCount, superLength);
        return ids;
    }

    public Object getDefaultValue(Class hint)
    {
        if (hint == ScriptRuntime.NumberClass) {
            Context cx = Context.getContext();
            if (cx.getLanguageVersion() == Context.VERSION_1_2)
                return new Long(length);
        }
        return super.getDefaultValue(hint);
    }

    /**
     * See ECMA 15.4.1,2
     */
    private static Object jsConstructor(Context cx, Scriptable scope,
                                        Object[] args)
    {
        if (args.length == 0)
            return new NativeArray(0);

        // Only use 1 arg as first element for version 1.2; for
        // any other version (including 1.3) follow ECMA and use it as
        // a length.
        if (cx.getLanguageVersion() == Context.VERSION_1_2) {
            return new NativeArray(args);
        } else {
            Object arg0 = args[0];
            if (args.length > 1 || !(arg0 instanceof Number)) {
                return new NativeArray(args);
            } else {
                long len = ScriptRuntime.toUint32(arg0);
                if (len != ((Number)arg0).doubleValue())
                    throw Context.reportRuntimeError0("msg.arraylength.bad");
                return new NativeArray(len);
            }
        }
    }

    public long getLength() {
        return length;
    }

    /** @deprecated Use {@link #getLength()} instead. */
    public long jsGet_length() {
        return getLength();
    }
    
    /**
     * Change the value of the internal flag that determines whether all
     * storage is handed by a dense backing array rather than an associative
     * store.
     * @param denseOnly new value for denseOnly flag
     * @throws IllegalArgumentException if an attempt is made to enable
     *   denseOnly after it was disabled; NativeArray code is not written
     *   to handle switching back to a dense representation
     */
    void setDenseOnly(boolean denseOnly) {
        if (denseOnly && !this.denseOnly)
            throw new IllegalArgumentException();
        this.denseOnly = denseOnly;
    }

    private void setLength(Object val) {
        /* XXX do we satisfy this?
         * 15.4.5.1 [[Put]](P, V):
         * 1. Call the [[CanPut]] method of A with name P.
         * 2. If Result(1) is false, return.
         * ?
         */

        double d = ScriptRuntime.toNumber(val);
        long longVal = ScriptRuntime.toUint32(d);
        if (longVal != d)
            throw Context.reportRuntimeError0("msg.arraylength.bad");

        if (denseOnly) {
            if (longVal < length) {
                // downcast okay because denseOnly
                Arrays.fill(dense, (int) longVal, dense.length, NOT_FOUND);
                length = longVal;
                return;
            } else if (longVal < MAX_PRE_GROW_SIZE &&
                       longVal < (length * GROW_FACTOR) &&
                       ensureCapacity((int)longVal))
            {
                length = longVal;
                return;
            } else {
                denseOnly = false;
            }
        }
        if (longVal < length) {
            // remove all properties between longVal and length
            if (length - longVal > 0x1000) {
                // assume that the representation is sparse
                Object[] e = getIds(); // will only find in object itself
                for (int i=0; i < e.length; i++) {
                    Object id = e[i];
                    if (id instanceof String) {
                        // > MAXINT will appear as string
                        String strId = (String)id;
                        long index = toArrayIndex(strId);
                        if (index >= longVal)
                            delete(strId);
                    } else {
                        int index = ((Integer)id).intValue();
                        if (index >= longVal)
                            delete(index);
                    }
                }
            } else {
                // assume a dense representation
                for (long i = longVal; i < length; i++) {
                    deleteElem(this, i);
                }
            }
        }
        length = longVal;
    }

    /* Support for generic Array-ish objects.  Most of the Array
     * functions try to be generic; anything that has a length
     * property is assumed to be an array.
     * getLengthProperty returns 0 if obj does not have the length property
     * or its value is not convertible to a number.
     */
    static long getLengthProperty(Context cx, Scriptable obj) {
        // These will both give numeric lengths within Uint32 range.
        if (obj instanceof NativeString) {
            return ((NativeString)obj).getLength();
        } else if (obj instanceof NativeArray) {
            return ((NativeArray)obj).getLength();
        }
        return ScriptRuntime.toUint32(
            ScriptRuntime.getObjectProp(obj, "length", cx));
    }

    private static Object setLengthProperty(Context cx, Scriptable target,
                                            long length)
    {
        return ScriptRuntime.setObjectProp(
                   target, "length", ScriptRuntime.wrapNumber(length), cx);
    }

    /* Utility functions to encapsulate index > Integer.MAX_VALUE
     * handling.  Also avoids unnecessary object creation that would
     * be necessary to use the general ScriptRuntime.get/setElem
     * functions... though this is probably premature optimization.
     */
    private static void deleteElem(Scriptable target, long index) {
        int i = (int)index;
        if (i == index) { target.delete(i); }
        else { target.delete(Long.toString(index)); }
    }

    private static Object getElem(Context cx, Scriptable target, long index)
    {
        if (index > Integer.MAX_VALUE) {
            String id = Long.toString(index);
            return ScriptRuntime.getObjectProp(target, id, cx);
        } else {
            return ScriptRuntime.getObjectIndex(target, (int)index, cx);
        }
    }

    private static void setElem(Context cx, Scriptable target, long index,
                                Object value)
    {
        if (index > Integer.MAX_VALUE) {
            String id = Long.toString(index);
            ScriptRuntime.setObjectProp(target, id, value, cx);
        } else {
            ScriptRuntime.setObjectIndex(target, (int)index, value, cx);
        }
    }

    private static String toStringHelper(Context cx, Scriptable scope,
                                         Scriptable thisObj,
                                         boolean toSource, boolean toLocale)
    {
        /* It's probably redundant to handle long lengths in this
         * function; StringBuffers are limited to 2^31 in java.
         */

        long length = getLengthProperty(cx, thisObj);

        StringBuffer result = new StringBuffer(256);

        // whether to return '4,unquoted,5' or '[4, "quoted", 5]'
        String separator;

        if (toSource) {
            result.append('[');
            separator = ", ";
        } else {
            separator = ",";
        }

        boolean haslast = false;
        long i = 0;

        boolean toplevel, iterating;
        if (cx.iterating == null) {
            toplevel = true;
            iterating = false;
            cx.iterating = new ObjToIntMap(31);
        } else {
            toplevel = false;
            iterating = cx.iterating.has(thisObj);
        }

        // Make sure cx.iterating is set to null when done
        // so we don't leak memory
        try {
            if (!iterating) {
                cx.iterating.put(thisObj, 0); // stop recursion.
                for (i = 0; i < length; i++) {
                    if (i > 0) result.append(separator);
                    Object elem = getElem(cx, thisObj, i);
                    if (elem == null || elem == Undefined.instance) {
                        haslast = false;
                        continue;
                    }
                    haslast = true;

                    if (toSource) {
                        result.append(ScriptRuntime.uneval(cx, scope, elem));

                    } else if (elem instanceof String) {
                        String s = (String)elem;
                        if (toSource) {
                            result.append('\"');
                            result.append(ScriptRuntime.escapeString(s));
                            result.append('\"');
                        } else {
                            result.append(s);
                        }