/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You under the Apache License, Version 2.0

  * (the "License"); you may not use this file except in compliance with

  * the License.  You may obtain a copy of the License at

  *

  *      http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 package org.apache.commons.flatfile.util;

 import java.io.IOException;

 import java.io.InputStream;

 import java.util.Iterator;

 import org.apache.commons.collections.IteratorUtils;

 /**

  * Unified InputStream representation of multiple concatenated InputStreams.

  * @version $Revision: 758023 $ $Date: 2009-03-24 16:09:19 -0500 (Tue, 24 Mar 2009) $

  */

 public class ConcatenatedInputStream extends InputStream {

     /** EOF */

     public static final int EOF = -1;

     private static final String NO_NULL = "null arguments are unacceptable";

     private static final InputStream AT_EOF = new InputStream() {

         public int read() throws IOException {

             return EOF;

         }

     };

     private Iterator<InputStream> iter;

     private InputStream current;

     /**

      * Create a new ConcatenatedInputStream.

      * @param src InputStreams

      */

     public ConcatenatedInputStream(Iterable<InputStream> src) {

         if (src == null) {

             throw new IllegalArgumentException(NO_NULL);

         }

         iter = src.iterator();

         next();

     }

     /**

      * Convenience constructor.

      * @param is0 first InputStream

      * @param is1 next InputStream

      */

     @SuppressWarnings("unchecked")

     public ConcatenatedInputStream(InputStream is0, InputStream is1) {

         if (is0 == null || is1 == null) {

             throw new IllegalArgumentException(NO_NULL);

         }

         // shortcuts:

         current = is0;

         iter = IteratorUtils.singletonIterator(is1);

     }

     /**

      * {@inheritDoc}

      */

     public int read() throws IOException {

         int n = current.read();

         while (n == EOF && current != AT_EOF) {

             next();

             n = current.read();

         }

         return n;

     }

     /**

      * Position to the next InputStream

      */

     private void next() {

         current = iter.hasNext() ? iter.next() : AT_EOF;

     }

 }