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package com.xagasoft.gats;
import java.io.OutputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
/**
* Facilitates writing GatsObjects to an OutputStream. This doesn't really
* inherit from OutputStream, so maybe it would make more sense to call it
* something else, but this is how it is right now. Use the writeObject
* function to write any given GatsObject to the OutputStream.
* <p>
* Each time you write an object with this class it actually writes a Gats
* Packet data structure which consists of a 5 byte header followed by the
* encoded GatsObject data. In the packet header is information about which
* version of Gats is in use, which options are enabled, etc. This ensures
* that Gats is backward compatible.
* <p>
* According to the GATS standard only fully formed Gats packets may be written
* to files or sockets to ensure integrity and context. Since each packet can
* only contain one GatsObject that means that each writeObject call should
* write one fully formed message or data structure to ensure maximum
* efficiency.
* <p>
* The OutputStream is written to frequently, and often in small increments, so
* it is highly advisable to pass in a BufferedOutputStream or similar structure
* to ensure maximum performance.
* <p>
* The Gats format stipulates that all zero bytes found in between packets are
* simply ignored, which allows you to pad streams of sequential Gats objects
* if necessary. This can be handy in some encoding/compression/encryption
* schemes.
*@see com.xagasoft.gats.GatsInputStream
*/
public class GatsOutputStream
{
private OutputStream os;
public GatsOutputStream( OutputStream os )
{
this.os = os;
}
/**
* Write an object to the provided output stream.
*@return The total number of bytes written.
*/
public int writeObject( GatsObject obj ) throws java.io.IOException
{
ByteArrayOutputStream bos1 = new ByteArrayOutputStream();
obj.write( bos1 );
ByteArrayOutputStream bos2 = new ByteArrayOutputStream(
5 + bos1.size()
);
DataOutputStream dos = new DataOutputStream( bos2 );
dos.writeByte( 1 );
dos.writeInt( bos1.size()+5 );
bos2.write( bos1.toByteArray() );
os.write( bos2.toByteArray() );
return bos1.size()+5;
}
};
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