com.threerings.io.ObjectOutputStream Maven / Gradle / Ivy
//
// $Id$
//
// Narya library - tools for developing networked games
// Copyright (C) 2002-2012 Three Rings Design, Inc., All Rights Reserved
// http://code.google.com/p/narya/
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation; either version 2.1 of the License, or
// (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package com.threerings.io;
import java.util.Map;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import com.google.common.collect.Maps;
import static com.threerings.NaryaLog.log;
/**
* Used to write {@link Streamable} objects to an {@link OutputStream}. Other common object types
* are supported as well: Boolean, Byte, Character, Short, Integer, Long, Float, Double,
* boolean[], byte[], char[], short[], int[], long[], float[], double[], Object[].
*
* @see Streamable
*/
public class ObjectOutputStream extends DataOutputStream
{
/**
* Constructs an object output stream which will write its data to the supplied target stream.
*/
public ObjectOutputStream (OutputStream target)
{
super(target);
}
/**
* Configures this object output stream with a mapping from a classname to a streamed name.
*/
public void addTranslation (String className, String streamedName)
{
if (_translations == null) {
_translations = Maps.newHashMap();
}
_translations.put(className, streamedName);
}
/**
* Writes a {@link Streamable} instance or one of the support object types to the output
* stream.
*/
public void writeObject (Object object)
throws IOException
{
// if the object to be written is null, simply write a zero
if (object == null) {
writeShort(0);
return;
}
// otherwise, write the class mapping, then the bare object
Class sclass = Streamer.getStreamerClass(object);
ClassMapping cmap = writeClassMapping(sclass);
writeBareObject(object, cmap.streamer, true);
}
/**
* Writes a pooled string value to the output stream.
*/
public void writeIntern (String value)
throws IOException
{
// if the value to be written is null, simply write a zero
if (value == null) {
writeShort(0);
return;
}
// create our intern map if necessary
if (_internmap == null) {
_internmap = Maps.newHashMap();
}
// look up the intern mapping record
Short code = _internmap.get(value);
// create a mapping for the value if we've not got one
if (code == null) {
if (ObjectInputStream.STREAM_DEBUG) {
log.info(hashCode() + ": Creating intern mapping", "code", _nextInternCode,
"value", value);
}
code = createInternMapping(_nextInternCode++);
_internmap.put(value.intern(), code);
// make sure we didn't blow past our maximum intern count
if (_nextInternCode <= 0) {
throw new RuntimeException("Too many unique interns written to ObjectOutputStream");
}
writeNewInternMapping(code, value);
} else {
writeExistingInternMapping(code, value);
}
}
/**
* Creates and returns a new intern mapping.
*/
protected Short createInternMapping (short code)
{
return code;
}
/**
* Writes a new intern mapping to the stream.
*/
protected void writeNewInternMapping (short code, String value)
throws IOException
{
// writing a negative code indicates that the value will follow
writeInternMapping(-code, value);
}
/**
* Writes an existing intern mapping to the stream.
*/
protected void writeExistingInternMapping (short code, String value)
throws IOException
{
writeShort(code);
}
/**
* Writes out the mapping for an intern.
*/
protected void writeInternMapping (int code, String value)
throws IOException
{
writeShort(code);
writeUTF(value);
}
/**
* Retrieves or creates the class mapping for the supplied class, writes it out to the stream,
* and returns a reference to it.
*/
protected ClassMapping writeClassMapping (Class sclass)
throws IOException
{
// create our classmap if necessary
if (_classmap == null) {
_classmap = Maps.newHashMap();
}
// look up the class mapping record
ClassMapping cmap = _classmap.get(sclass);
// create a class mapping for this class if we've not got one
if (cmap == null) {
// see if we just want to use an existing class mapping
Class collClass = Streamer.getCollectionClass(sclass);
if (collClass != null && !collClass.equals(sclass)) {
cmap = writeClassMapping(collClass);
_classmap.put(sclass, cmap);
return cmap;
}
// create a streamer instance and assign a code to this class
Streamer streamer = Streamer.getStreamer(sclass);
// we specifically do not inline the getStreamer() call into the ClassMapping
// constructor because we want to be sure not to call _nextClassCode++ if getStreamer()
// throws an exception
if (ObjectInputStream.STREAM_DEBUG) {
log.info(hashCode() + ": Creating class mapping", "code", _nextClassCode,
"class", sclass.getName());
}
cmap = createClassMapping(_nextClassCode++, sclass, streamer);
_classmap.put(sclass, cmap);
// make sure we didn't blow past our maximum class count
if (_nextClassCode <= 0) {
throw new RuntimeException("Too many unique classes written to ObjectOutputStream");
}
writeNewClassMapping(cmap);
} else {
writeExistingClassMapping(cmap);
}
return cmap;
}
/**
* Creates and returns a new class mapping.
*/
protected ClassMapping createClassMapping (short code, Class sclass, Streamer streamer)
{
return new ClassMapping(code, sclass, streamer);
}
/**
* Writes a new class mapping to the stream.
*/
protected void writeNewClassMapping (ClassMapping cmap)
throws IOException
{
// writing a negative class code indicates that the class name will follow
writeClassMapping(-cmap.code, cmap.sclass);
}
/**
* Writes an existing class mapping to the stream.
*/
protected void writeExistingClassMapping (ClassMapping cmap)
throws IOException
{
writeShort(cmap.code);
}
/**
* Writes out the mapping for a class.
*/
protected void writeClassMapping (int code, Class sclass)
throws IOException
{
writeShort(code);
String cname = sclass.getName();
if (_translations != null) {
String tname = _translations.get(cname);
if (tname != null) {
cname = tname;
}
}
writeUTF(cname);
}
/**
* Writes a {@link Streamable} instance or one of the support object types without
* associated class metadata to the output stream. The caller is responsible for knowing
* the exact class of the written object, creating an instance of such and calling {@link
* ObjectInputStream#readBareObject(Object)} to read its data from the stream.
*
* @param object the object to be written. It cannot be null.
*/
public void writeBareObject (Object object)
throws IOException
{
writeBareObject(object, Streamer.getStreamer(Streamer.getStreamerClass(object)), true);
}
/**
* Write a {@link Streamable} instance without associated class metadata.
*/
protected void writeBareObject (Object obj, Streamer streamer, boolean useWriter)
throws IOException
{
_current = obj;
_streamer = streamer;
try {
_streamer.writeObject(obj, this, useWriter);
} finally {
_current = null;
_streamer = null;
}
}
/**
* Uses the default streamable mechanism to write the contents of the object currently being
* streamed. This can only be called from within a writeObject implementation in a
* {@link Streamable} object.
*/
public void defaultWriteObject ()
throws IOException
{
// sanity check
if (_current == null) {
throw new RuntimeException("defaultWriteObject() called illegally.");
}
// log.info("Writing default", "cmap", _streamer, "current", _current);
// write the instance data
_streamer.writeObject(_current, this, false);
}
/**
* Write a string encoded as real UTF-8 (rather than the modified format handled by
* {link #writeUTF}).
*/
public void writeUnmodifiedUTF (String str)
throws IOException
{
// prepare a buffer to accept the encoded UTF-8
ByteArrayOutputStream baos = new ByteArrayOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(baos, "UTF-8");
// do the deed
osw.write(str);
osw.flush();
// now that we know how many bytes we'll need, write that number to the stream
writeShort(baos.size());
// then finally the bytes themselves
write(baos.toByteArray());
}
/** Used to map classes to numeric codes and the {@link Streamer} instance used to write
* them. */
protected Map, ClassMapping> _classmap;
/** Used to map pooled strings to numeric codes. */
protected Map _internmap;
/** A counter used to assign codes to streamed classes. */
protected short _nextClassCode = 1;
/** A counter used to assign codes to pooled strings. */
protected short _nextInternCode = 1;
/** The object currently being written to the stream. */
protected Object _current;
/** The streamer being used currently. */
protected Streamer _streamer;
/** An optional set of class name translations to use when serializing objects. */
protected Map _translations;
}
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