/*

  * 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.myfaces.shared.util.io;

 import java.io.IOException;

 import java.io.InputStream;

 import java.io.PushbackInputStream;

 /**

  * NOTE: Copy of org.apache.abdera.i18n.text.io.DynamicPushbackInputStream

  * 

  * PushbackInputStream implementation that performs dynamic resizing of the unread buffer

  */

 public class DynamicPushbackInputStream extends PushbackInputStream

 {

     private final int origsize;

     public DynamicPushbackInputStream(InputStream in)

     {

         super(in);

         this.origsize = 1;

     }

     public DynamicPushbackInputStream(InputStream in, int initialSize)

     {

         super(in, initialSize);

         this.origsize = initialSize;

     }

     /**

      * Clear the buffer

      */

     public int clear()

     {

         int m = buf.length;

         buf = new byte[origsize];

         pos = origsize;

         return m;

     }

     /**

      * Shrink the buffer. This will reclaim currently unused space in the buffer, reducing memory but potentially

      * increasing the cost of resizing the buffer

      */

     public int shrink()

     {

         byte[] old = buf;

         if (pos == 0)

         {

             return 0; // nothing to do

         }

         int n = old.length - pos;

         int m;

         int p;

         int s;

         int l;

         if (n < origsize)

         {

             buf = new byte[origsize];

             p = pos;

             s = origsize - n;

             l = old.length - p;

             m = old.length - origsize;

             pos = s;

         }

         else

         {

             buf = new byte[n];

             p = pos;

             s = 0;

             l = n;

             m = old.length - l;

             pos = 0;

         }

         System.arraycopy(old, p, buf, s, l);

         return m;

     }

     private void resize(int len)

     {

         byte[] old = buf;

         buf = new byte[old.length + len];

         System.arraycopy(old, 0, buf, len, old.length);

     }

     public void unread(byte[] b, int off, int len) throws IOException

     {

         if (len > pos && pos + len > buf.length)

         {

             resize(len - pos);

             pos += len - pos;

         }

         super.unread(b, off, len);

     }

     public void unread(int b) throws IOException

     {

         if (pos == 0)

         {

             resize(1);

             pos++;

         }

         super.unread(b);

     }

     public int read() throws IOException

     {

         int m = super.read();

         if (pos >= buf.length && buf.length > origsize)

         {

             shrink();

         }

         return m;

     }

     public int read(byte[] b, int off, int len) throws IOException

     {

         this.available(); // workaround for a problem in PushbackInputStream, without this, the amount of bytes read

                           // from some streams will be incorrect

         int r = super.read(b, off, len);

         if (pos >= buf.length && buf.length > origsize)

         {

             shrink();

         }

         return r;

     }

     public long skip(long n) throws IOException

     {

         long r = super.skip(n);

         if (pos >= buf.length && buf.length > origsize)

         {

             shrink();

         }

         return r;

     }

 }