Some work on streaming.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@3855 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/io/ArrayMask.as

@@ -1,6 +1,51 @@
 package com.threerings.io {
 
+import flash.util.ByteArray;
+
 public class ArrayMask
+    implements Streamable
 {
+    public function ArrayMask (length :int = 0)
+    {
+        var mlength :int = length / 8;
+        if (length % 8 != 0) {
+            mlength++;
+        }
+        _mask.length = mlength;
+    }
+
+    /**
+     * Set the specified index as containing a non-null element in the
+     * array we're representing.
+     */
+    public function setBit (index :int) :void
+    {
+        _mask[index/8] |= (1 << (index % 8));
+    }
+
+    /**
+     * Is the specified array element non-null?
+     */
+    public function isSet (index :int) :Boolean
+    {
+        return (_mask[index/8] & (1 << (index % 8))) != 0;
+    }
+
+    // documentation inherited from interface Streamable
+    public function writeObject (out :ObjectOutputStream) :void
+    {
+        out.writeShort(_mask.length);
+        out.writeBytes(_mask);
+    }
+
+    // documentation inherited from interface Streamable
+    public function readObject (ins :ObjectInputStream) :void
+    {
+        _mask.length = ins.readShort();
+        ins.readBytes(_mask, 0, _mask.length);
+    }
+
+    /** The array mask. */
+    protected var _mask :ByteArray = new ByteArray();
 }
 }