/*
    *  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
    *  
   *    https://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.directory.api.util;
  
  
  import org.apache.directory.api.i18n.I18n;
  
  
  /**
   * A dynamically growing byte[]. 
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class ExpansibleByteBuffer
  {
      /** the default initial buffer size */
      private static final int DEFAULT_INITIAL_SIZE = 10;
  
      /** the initial size of the buffer in number of bytes: also increment for allocations */
      private final int initialSize;
  
      /** the position into the buffer */
      private int pos = 0;
  
      /** the bytes of the buffer */
      private byte[] buf;
  
  
      /**
       * Create a default ExpansibleByteBuffer capable of holding 10 bytes
       */
      public ExpansibleByteBuffer()
      {
          this( DEFAULT_INITIAL_SIZE );
      }
  
  
      /**
       * Creates a ExpansibleByteBuffer which has an initialze size
       *  
       * @param initialSize The initial buffer size
       */
      public ExpansibleByteBuffer( int initialSize )
      {
          if ( initialSize <= 0 )
          {
              throw new IllegalArgumentException( I18n.err( I18n.ERR_17042_INITIAL_SIZE_ABOVE_ZERO ) );
          }
  
          this.initialSize = initialSize;
          this.buf = new byte[initialSize];
      }
  
  
      /**
       * Reset the Buffer position to 0. Every new added byte will be put on position 0.
       * Note that whatever this buffer contained before a call to the clear() method
       * will not be removed.
       */
      public final void clear()
      {
          pos = 0;
      }
  
  
      /**
       * @return The position of the last byte in the buffer
       */
      public final int position()
      {
          return pos;
      }
  
  
      /**
       * Set the position to a specific value
       * 
       * @param pos the new position
       */
      public final void position( int pos )
      {
          this.pos = pos;
     }
 
 
     /**
      * @return The number of bytes that can be added into this buffer
      */
     public final int capacity()
     {
         return buf.length;
     }
 
 
     /**
      * Returns the byte at a given position. Note that no control is done
      * on the position validity.
      * 
      * @param i The position
      * @return The byte at the given position in the buffer
      */
     public final byte get( int i )
     {
         return buf[i];
     }
 
 
     /**
      * Get's the bytes, the backing store for this buffer.  Note
      * that you need to use the position index to determine where
      * to stop reading from this buffer.
      * 
      * @return The interned Byte[]
      */
     public final byte[] buffer()
     {
         return buf;
     }
 
 
     /**
      * Get's a copy of the bytes used.
      * 
      * @return A copy of the interned Byte[]
      */
     public final byte[] copyOfUsedBytes()
     {
         byte[] copy = new byte[pos];
         System.arraycopy( buf, 0, copy, 0, pos );
         return copy;
     }
 
 
     /**
      * Appends the bytes to this buffer.
      * 
      * @param bytes The byte[] to append to the buffer
      */
     public final void append( byte[] bytes )
     {
         if ( pos + bytes.length > buf.length )
         {
             growBuffer( bytes.length );
         }
 
         System.arraycopy( bytes, 0, buf, pos, bytes.length );
         pos += bytes.length;
     }
 
 
     /**
      * Appends a byte to this buffer.
      * 
      * @param b The byte to append to the buffer
      */
     public final void append( byte b )
     {
         if ( pos >= buf.length )
         {
             growBuffer();
         }
 
         buf[pos] = b;
         pos++;
     }
 
 
     /**
      * Appends an int to this buffer.  WARNING: the int is truncated to 
      * a byte value.
      * 
      * @param val The integer to append to the buffer
      */
     public final void append( int val )
     {
         if ( pos >= buf.length )
         {
             growBuffer();
         }
 
         buf[pos] = ( byte ) val;
         pos++;
     }
 
 
     private void growBuffer( int size )
     {
         if ( size > initialSize )
         {
             byte[] copy = new byte[buf.length + size];
             System.arraycopy( buf, 0, copy, 0, pos );
             this.buf = copy;
         }
         else
         {
             byte[] copy = new byte[buf.length + initialSize];
             System.arraycopy( buf, 0, copy, 0, pos );
             this.buf = copy;
         }
     }
 
 
     private void growBuffer()
     {
         byte[] copy = new byte[buf.length + initialSize];
         System.arraycopy( buf, 0, copy, 0, pos );
         this.buf = copy;
     }
 }