// ChunkedInputStream - an InputStream that implements HTTP/1.1 chunking
//
// Copyright (C) 1996,1998 by Jef Poskanzer <jef@mail.acme.com>. 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 InputStream that implements HTTP/1.1 chunking.
// <P>
// This class lets a Servlet read its request 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 if such a header
// appears in an HTTP request you should use this class to read any data.
// <P>
// Sample usage:
// <BLOCKQUOTE><PRE><CODE>
// InputStream in = req.getInputStream();
// if ( "chunked".equals( req.getHeader( "Transfer-Encoding" ) ) )
//     in = new ChunkedInputStream( in );
// </CODE></PRE></BLOCKQUOTE>
// <P>
// Because it would be impolite to make the authors of every Servlet include
// the above code, this is general done at the server level so that it
// happens automatically.  Servlet authors will generally not create
// ChunkedInputStreams.  This is in contrast with ChunkedOutputStream,
// which Servlets have to call themselves if they want to use it.
// <P>
// <A HREF="/resources/classes/Acme/Serve/servlet/http/ChunkedInputStream.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>

public class ChunkedInputStream extends FilterInputStream
    {

    private DataInputStream din;
    private int contentLength;

    /// Make a ChunkedInputStream.
    public ChunkedInputStream( InputStream in )
	{
	super( new DataInputStream( in ) );
	din = (DataInputStream) this.in;
	contentLength = 0;
	}


    private byte[] b1 = new byte[1];

    /// The FilterInputStream implementation of the single-byte read()
    // method just reads directly from the underlying stream.  We want
    // to go through our own read-block method, so we have to override.
    // Seems like FilterInputStream really ought to do this itself.
    public int read() throws IOException
	{
	if ( read( b1, 0, 1 ) == -1 )
	    return -1;
	return b1[0];
	}


    private int chunkCount = 0;

    /// Reads into an array of bytes.
    // @param b the buffer into which the data is read
    // @param off the start offset of the data
    // @param len the maximum number of bytes read
    // @return the actual number of bytes read, or -1 on EOF
    // @exception IOException if an I/O error has occurred
    public int read( byte b[], int off, int len ) throws IOException
	{
	if ( chunkCount == 0 )
	    {
	    startChunk();
	    if ( chunkCount == 0 )
		return -1;
	    }
	int toRead = Math.min( chunkCount, len );
	int r = din.read( b, off, toRead );
	if ( r != -1 )
	    chunkCount -= r;
	return r;
	}


    /// Reads the start of a chunk.
    private void startChunk() throws IOException
	{
	String line = din.readLine();
	try
	    {
	    chunkCount = Integer.parseInt( line, 16 );
	    }
	catch ( NumberFormatException e )
	    {
	    throw new IOException( "malformed chunk" );
	    }
	contentLength += chunkCount;
	if ( chunkCount == 0 )
	    readFooters();
	}


    private Vector footerNames = null;
    private Vector footerValues = null;

    /// Reads any footers.
    private void readFooters() throws IOException
	{
	footerNames = new Vector();
	footerValues = new Vector();
	String line;
	while ( true )
	    {
	    line = din.readLine();
	    if ( line.length() == 0 )
		break;
	    int colon = line.indexOf( ':' );
	    if ( colon != -1 )
		{
		String name = line.substring( 0, colon ).toLowerCase();
		String value = line.substring( colon + 1 ).trim();
		footerNames.addElement( name.toLowerCase() );
		footerValues.addElement( value );
		}
	    }
	}


    /// Returns the value of a footer field, or null if not known.
    // Footers come at the end of a chunked stream, so trying to
    // retrieve them before the stream has given an EOF will return
    // only nulls.
    // @param name the footer field name
    public String getFooter( String name )
	{
	if ( ! isDone() )
	    return null;
	int i = footerNames.indexOf( name.toLowerCase() );
	if ( i == -1 )
	    return null;
	return (String) footerValues.elementAt( i );
	}


    /// Returns an Enumeration of the footer names.
    public Enumeration getFooters()
	{
	if ( ! isDone() )
	    return null;
	return footerNames.elements();
	}


    /// Returns the size of the request entity data, or -1 if not known.
    public int getContentLength()
	{
	if ( ! isDone() )
	    return -1;
	return contentLength;
	}


    /// Tells whether the stream has gotten to its end yet.  Remembering
    // whether you've gotten an EOF works fine too, but this is a convenient
    // predicate.  java.io.InputStream should probably have its own isEof()
    // predicate.
    public boolean isDone()
	{
	return footerNames != null;
	}

    }