# MultiStream.java

    /*
    ** Module   : MultiStream.java
    ** Abstract : Implements a simple switchable input stream.
    **            switchTo method is provided to switch the input to any
    **            existing stream.
    **
    ** Copyright (c) 2004-2017, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- -T- --JPRM-- ----------------Description-----------------
    ** 001 NVS 20041112 ADD   @18753 Created.  Needed a class that would multiplex
    **                               input streams into a single input stream.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program 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 Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
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    */

    package com.goldencode.p2j.io;

    import java.io.*;

    /**
     * Implements a simple switchable input stream based on any number of
     * underlying input streams. Input streams can be
     * switched to at any time. There is no history kept inside the class.
     * That means, there is no switch back capability.
     * <p>
     * When instantiated, the MultiStream object has no connection to any
     * input stream. If <code>read()</code> method is called while in this
     * state, <code>-1</code> is returned signalling EOF condition.
     * <p>
     * Once the <code>switchTo</code> method is called, <code>read()</code>
     * delegates the work to the <code>read()</code> method of the current
     * underlying input stream.
     * <p>
     * This class may be useful in many situations. For instance,
     * PushbackInputStream can provide pushback functionality for multiple
     * underlying streams at once in an efficient way.
     * <p>
     * @author NVS
     * @version 1.0.1
     */
    public class MultiStream extends FilterInputStream
    {
       /**
        * Constructor.
        * Creates a MultiStream with no associated stream.
        */
       public MultiStream()
       {
          super(null);
       }

       /**
        * Switches input to the specified stream.
        *
        * @param   in
        *          an input stream of any kind to be switched to.
        */
       public void switchTo(InputStream in)
       {
          super.in = in;
       }

       /**
        * Reads the next byte from the current stream. If no stream was
        * switched to, returns -1 as the indication of EOF condition.
        *
        * @return    byte read from the underlying stream or -1 if no
        *            stream was switched to.
        * @throws    IOException
        */
       public int read()
       throws IOException
       {
          if (super.in == null)
             return -1;
          else
             return super.read();
       }
    }