1 files changed, 198 insertions, 0 deletions
diff --git a/src/jdk/nashorn/internal/runtime/arrays/LengthNotWritableFilter.java b/src/jdk/nashorn/internal/runtime/arrays/LengthNotWritableFilter.java
new file mode 100644
index 00000000..945d80d2
--- /dev/null
+++ b/src/jdk/nashorn/internal/runtime/arrays/LengthNotWritableFilter.java
@@ -0,0 +1,198 @@
+package jdk.nashorn.internal.runtime.arrays;
+
+import java.util.Iterator;
+import java.util.List;
+import java.util.SortedMap;
+import java.util.TreeMap;
+import jdk.nashorn.internal.runtime.JSType;
+import jdk.nashorn.internal.runtime.ScriptRuntime;
+
+/**
+ * Filter to use for ArrayData where the length is not writable.
+ * The default behavior is just to ignore {@link ArrayData#setLength}
+ */
+final class LengthNotWritableFilter extends ArrayFilter {
+    private final SortedMap<Long, Object> extraElements; //elements with index >= length
+
+    /**
+     * Constructor
+     * @param underlying array
+     */
+    LengthNotWritableFilter(final ArrayData underlying) {
+        this(underlying, new TreeMap<Long, Object>());
+    }
+
+    private LengthNotWritableFilter(final ArrayData underlying, final SortedMap<Long, Object> extraElements) {
+        super(underlying);
+        this.extraElements = extraElements;
+    }
+
+    @Override
+    public ArrayData copy() {
+        return new LengthNotWritableFilter(underlying.copy(), new TreeMap<>(extraElements));
+    }
+
+    @Override
+    public boolean has(final int index) {
+        return super.has(index) || extraElements.containsKey((long)index);
+    }
+
+    /**
+     * Set the length of the data array
+     *
+     * @param length the new length for the data array
+     */
+    @Override
+    public void setLength(final long length) {
+        //empty - setting length for a LengthNotWritableFilter is always a nop
+    }
+
+    @Override
+    public ArrayData ensure(final long index) {
+        return this;
+    }
+
+    @Override
+    public ArrayData slice(final long from, final long to) {
+        //return array[from...to), or array[from...length] if undefined, in this case not as we are an ArrayData
+        return new LengthNotWritableFilter(underlying.slice(from, to), extraElements.subMap(from, to));
+    }
+
+    private boolean checkAdd(final long index, final Object value) {
+        if (index >= length()) {
+            extraElements.put(index, value);
+            return true;
+        }
+        return false;
+    }
+
+    private Object get(final long index) {
+        final Object obj = extraElements.get(index);
+        if (obj == null) {
+            return ScriptRuntime.UNDEFINED;
+        }
+        return obj;
+    }
+
+    @Override
+    public int getInt(final int index) {
+        if (index >= length()) {
+            return JSType.toInt32(get(index));
+        }
+        return underlying.getInt(index);
+    }
+
+    @Override
+    public int getIntOptimistic(final int index, final int programPoint) {
+        if (index >= length()) {
+            return JSType.toInt32Optimistic(get(index), programPoint);
+        }
+        return underlying.getIntOptimistic(index, programPoint);
+    }
+
+    @Override
+    public long getLong(final int index) {
+        if (index >= length()) {
+            return JSType.toLong(get(index));
+        }
+        return underlying.getLong(index);
+    }
+
+    @Override
+    public long getLongOptimistic(final int index, final int programPoint) {
+        if (index >= length()) {
+            return JSType.toLongOptimistic(get(index), programPoint);
+        }
+        return underlying.getLongOptimistic(index, programPoint);
+    }
+
+    @Override
+    public double getDouble(final int index) {
+        if (index >= length()) {
+            return JSType.toNumber(get(index));
+        }
+        return underlying.getDouble(index);
+    }
+
+    @Override
+    public double getDoubleOptimistic(final int index, final int programPoint) {
+        if (index >= length()) {
+            return JSType.toNumberOptimistic(get(index), programPoint);
+        }
+        return underlying.getDoubleOptimistic(index, programPoint);
+    }
+
+    @Override
+    public Object getObject(final int index) {
+        if (index >= length()) {
+            return get(index);
+        }
+        return underlying.getObject(index);
+    }
+
+    @Override
+    public ArrayData set(final int index, final Object value, final boolean strict) {
+        if (checkAdd(index, value)) {
+            return this;
+        }
+        underlying = underlying.set(index, value, strict);
+        return this;
+    }
+
+    @Override
+    public ArrayData set(final int index, final int value, final boolean strict) {
+        if (checkAdd(index, value)) {
+            return this;
+        }
+        underlying = underlying.set(index, value, strict);
+        return this;
+    }
+
+    @Override
+    public ArrayData set(final int index, final long value, final boolean strict) {
+        if (checkAdd(index, value)) {
+            return this;
+        }
+        underlying = underlying.set(index, value, strict);
+        return this;
+    }
+
+    @Override
+    public ArrayData set(final int index, final double value, final boolean strict) {
+        if (checkAdd(index, value)) {
+            return this;
+        }
+        underlying = underlying.set(index, value, strict);
+        return this;
+    }
+
+    @Override
+    public ArrayData delete(final int index) {
+        extraElements.remove(index);
+        underlying = underlying.delete(index);
+        return this;
+    }
+
+    @Override
+    public ArrayData delete(final long fromIndex, final long toIndex) {
+        for (final Iterator<Long> iter = extraElements.keySet().iterator(); iter.hasNext();) {
+            final long next = iter.next();
+            if (next >= fromIndex && next <= toIndex) {
+                iter.remove();
+            }
+            if (next > toIndex) { //ordering guaranteed because TreeSet
+                break;
+            }
+        }
+        underlying = underlying.delete(fromIndex, toIndex);
+        return this;
+    }
+
+    @Override
+    public Iterator<Long> indexIterator() {
+        final List<Long> keys = computeIteratorKeys();
+        keys.addAll(extraElements.keySet()); //even if they are outside length this is fine
+        return keys.iterator();
+    }
+
+}