New object streaming code is born!

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@1605 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/io/ObjectInputStream.java

@@ -0,0 +1,169 @@
+//
+// $Id: ObjectInputStream.java,v 1.1 2002/07/23 05:42:34 mdb Exp $
+
+package com.threerings.io;
+
+import java.io.InputStream;
+import java.io.DataInputStream;
+import java.io.IOException;
+
+import com.samskivert.util.HashIntMap;
+
+import com.threerings.presents.Log;
+
+/**
+ * Used to read {@link Streamable} objects from an {@link InputStream}.
+ * Other common object types are supported as well (@see {@link
+ * ObjectOutputStream}).
+ *
+ * @see Streamable
+ */
+public class ObjectInputStream extends DataInputStream
+{
+    /**
+     * Constructs an object input stream which will read its data from the
+     * supplied source stream.
+     */
+    public ObjectInputStream (InputStream source)
+    {
+        super(source);
+    }
+
+    /**
+     * Reads a {@link Streamable} instance or one of the supported object
+     * types from the input stream.
+     */
+    public Object readObject ()
+        throws IOException, ClassNotFoundException
+    {
+        ClassMapping cmap;
+
+        // create our classmap if necessary
+        if (_classmap == null) {
+            _classmap = new HashIntMap();
+        }
+
+        try {
+            // read in the class code for this instance
+            short code = readShort();
+
+            // a zero code indicates a null value
+            if (code == 0) {
+                return null;
+
+            // if the code is negative, that means that we've never
+            // seen it before and class metadata follows
+            } else if (code < 0) {
+                // first swap the code into positive-land
+                code *= -1;
+
+                // read in the class metadata, create a class mapping record
+                // for the class, and cache it
+                String cname = readUTF();
+                Class sclass = Class.forName(cname);
+                Streamer streamer = Streamer.getStreamer(sclass);
+
+                // sanity check
+                if (streamer == null) {
+                    String errmsg = "Aiya! Unable to create streamer for " +
+                        "newly seen class [code=" + code +
+                        ", class=" + cname + "]";
+                    throw new RuntimeException(errmsg);
+                }
+
+                cmap = new ClassMapping(code, sclass, streamer);
+                _classmap.put(code, cmap);
+
+            } else {
+                cmap = (ClassMapping)_classmap.get(code);
+
+                // sanity check
+                if (cmap == null) {
+                    String errmsg = "Aiya! Read object code for which we " +
+                        "have no registered class metadata [code=" + code + "]";
+                    throw new RuntimeException(errmsg);
+                }
+            }
+
+            // create an instance of the appropriate object
+            _streamer = cmap.streamer;
+            Object target = _streamer.createObject(this);
+            _current = target;
+
+            // now read the instance data
+            _streamer.readObject(target, this, true);
+
+            // and return the newly read object
+            return target;
+
+        } finally {
+            // clear out our current object references
+            _current = null;
+            _streamer = null;
+        }
+    }
+
+    /**
+     * Reads an object from the input stream that was previously written
+     * with {@link ObjectOutputStream#writeBareObject}.
+     *
+     * @param object the object to be populated from data on the stream.
+     * It cannot be <code>null</code>.
+     */
+    public void readBareObject (Object object)
+        throws IOException, ClassNotFoundException
+    {
+        try {
+            // obtain the streamer for objects of this class
+            _streamer = Streamer.getStreamer(object.getClass());
+            _current = object;
+
+            // now read the instance data
+            _streamer.readObject(object, this, true);
+
+        } finally {
+            // clear out our current object references
+            _current = null;
+            _streamer = null;
+        }
+    }
+
+    /**
+     * Reads the fields of the specified {@link Streamable} instance from
+     * the input stream using the default object streaming mechanisms (a
+     * call is not made to <code>readObject()</code>, even if such a
+     * method exists).
+     */
+    public void defaultReadObject ()
+        throws IOException, ClassNotFoundException
+    {
+        // sanity check
+        if (_current == null) {
+            throw new RuntimeException(
+                "defaultReadObject() called illegally.");
+        }
+
+        // read the instance data
+        _streamer.readObject(_current, this, false);
+    }
+
+    /**
+     * Used by a {@link Streamer} that is reading an array of {@link
+     * Streamable} instances.
+     */
+    protected void setCurrent (Streamer streamer, Object current)
+    {
+        _streamer = streamer;
+        _current = current;
+    }
+
+    /** Used to map classes to numeric codes and the {@link Streamer}
+     * instance used to write them. */
+    protected HashIntMap _classmap;
+
+    /** The object currently being read from the stream. */
+    protected Object _current;
+
+    /** The streamer being used currently. */
+    protected Streamer _streamer;
+}