chunkedoutputstream.java

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// ChunkedOutputStream - an OutputStream that implements HTTP/1.1 chunking
//
// Copyright (C)1996,1998 by Jef Poskanzer <[e-mail]>. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
//
// Visit the ACME Labs Java page for up-to-date versions of this and other
// fine Java utilities: http://www.acme.com/java/

package Acme.Serve.servlet.http;

import java.io.*;
import java.util.*;
import Acme.Serve.servlet.*;

/// An OutputStream that implements HTTP/1.1 chunking.
// <P>
// This class lets a Servlet send its response data as an HTTP/1.1 chunked
// stream.  Chunked streams are a way to send arbitrary-length data without
// having to know beforehand how much you're going to send.  They are
// introduced by a "Transfer-Encoding: chunked" header, so you have to
// set that header when you make one of these streams.
// <P>
// Sample usage:
// <BLOCKQUOTE><PRE><CODE>
// res.setHeader( "Transfer-Encoding", "chunked" );
// OutputStream out = res.getOutputStream();
// ChunkedOutputStream chunkOut = new ChunkedOutputStream( out );
// (write data to chunkOut instead of out)
// (optionally set footers)
// chunkOut.done();
// </CODE></PRE></BLOCKQUOTE>
// <P>
// Every time the stream gets flushed, a chunk is sent.  When done()
// is called, an empty chunk is sent, marking the end of the chunked
// stream as per the chunking spec.
// <P>
// <A HREF="/resources/classes/Acme/Serve/servlet/http/ChunkedOutputStream.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>

public class ChunkedOutputStream extends BufferedOutputStream
    {

    /// Make a ChunkedOutputStream with a default buffer size.
    // @param out the underlying output stream
    public ChunkedOutputStream( OutputStream out )
	{
	super( out );
	}

    /// Make a ChunkedOutputStream with a specified buffer size.
    // @param out the underlying output stream
    // @param size the buffer size
    public ChunkedOutputStream( OutputStream out, int size )
	{
	super( out, size );
	}


    /// Flush the stream.  This will write any buffered output
    // bytes as a chunk.
    // @exception IOException if an I/O error occurred
    public synchronized void flush() throws IOException
	{
	if ( count != 0 )
	    {
	    writeBuf( buf, 0, count );
	    count = 0;
	    }
	}
    

    private Vector footerNames = new Vector();
    private Vector footerValues = new Vector();

    /// Set a footer.  Footers are much like HTTP headers, except that
    // they come at the end of the data instead of at the beginning.
    public void setFooter( String name, String value )
	{
	footerNames.addElement( name );
	footerValues.addElement( value );
	}
    

    /// Indicate the end of the chunked data by sending a zero-length chunk,
    // possible including footers.
    // @exception IOException if an I/O error occurred
    public void done() throws IOException
	{
	flush();
	PrintStream pout = new PrintStream( out );
	pout.println( "0" );
	if ( footerNames.size() > 0 )
	    {
	    // Send footers.
	    for ( int i = 0; i < footerNames.size(); ++i )
		{
		String name = (String) footerNames.elementAt( i );
		String value = (String) footerValues.elementAt( i );
		pout.println( name + ": " + value );
		}
	    }
	footerNames = null;
	footerValues = null;
	pout.println( "" );
	pout.flush();
	}

    
    /// Make sure that calling close() terminates the chunked stream.
    public void close() throws IOException
	{
	if ( footerNames != null )
	    done();
	super.close();
	}


    /// Write a sub-array of bytes.
    // <P>
    // The only reason we have to override the BufferedOutputStream version
    // of this is that it writes the array directly to the output stream
    // if doesn't fit in the buffer.  So we make it use our own chunk-write
    // routine instead.  Otherwise this is identical to the parent-class
    // version.
    // @param b the data to be written
    // @param off the start offset in the data
    // @param len the number of bytes that are written
    // @exception IOException if an I/O error occurred
    public synchronized void write( byte b[], int off, int len ) throws IOException
	{
	int avail = buf.length - count;
	 
	if ( len <= avail )
	    {
	    System.arraycopy( b, off, buf, count, len );
	    count += len;
	    return;
	    }
	flush();
	writeBuf( b, off, len );
	}


    private static final byte[] crlf = { 13, 10 };

    /// The only routine that actually writes to the output stream.
    // This is where chunking semantics are implemented.
    // @exception IOException if an I/O error occurred
    private void writeBuf( byte b[], int off, int len ) throws IOException
	{
	// Write the chunk length as a hex number.
	String lenStr = Integer.toString( len, 16 );
	byte[] lenBytes = lenStr.getBytes();
	out.write( lenBytes );
	// Write a CRLF.
	out.write( crlf );
	// Write the data.
	if ( len != 0 )
	    out.write( b, off, len );
	// Write a CRLF.
	out.write( crlf );
	// And flush the real stream.
	out.flush();
	}

    }