/*
 * JBoss, the OpenSource J2EE webOS
 *
 * Distributable under LGPL license.
 * See terms of license at gnu.org.
 */
package org.jboss.ejb.plugins.cmp.jdbc;

import java.io.InputStream;
import java.io.ByteArrayInputStream;
import java.io.OutputStream;
import java.sql.SQLException;
import java.sql.Blob;

/**
 * The representation (mapping) in the Java<sup><font size=-2>TM</font></sup>
 * programming language of an SQL <code>BLOB</code> value to an array of bytes.
 * A ByteArrayBlob contains an internal buffer that contains bytes that may be
 * read from the stream. The <code>Blob</code> interface provides methods for
 * getting the length of an SQL <code>BLOB</code> (Binary Large Object) value, 
 * for materializing a <code>BLOB</code> value on the client, and for 
 * determining the position of a pattern of bytes within a <code>BLOB</code> 
 * value. The ByteArrayBlob has static factory methods for construting an 
 * <code>BLOB</code> using either an existing serializable object, or an array 
 * of bytes. This is a nice way to store serialized objects in a relational 
 * field of type SQL <code>BLOB</code>.
 * 
 * @author <a href="mailto:amccullo@sourceforge.new">Andrew McCulloch</a>
 * @version $Revision: 1.3.4.1 $
 */
public final class ByteArrayBlob implements Blob
{
   /**
    * The internal buffer for the bytes of the Blob.
    */
   private final byte[] mBytes;

   public ByteArrayBlob(byte[] bytes)
   {
      if (bytes == null)
      {
         bytes = new byte[0];
      }

      mBytes = bytes;
   }

   public InputStream getBinaryStream() throws SQLException
   {
      return new ByteArrayInputStream(mBytes);
   }

   public byte[] getBytes(long pos, int length) throws SQLException
   {
      // Defensive code, parameter checks.
      if (length < 0 || length > mBytes.length || pos > mBytes.length)
      {
         return new byte[0];
      }

      if (pos <= 0)
      {
         pos = 1; // One since the copy starts at pos.
      }

      byte[] buffer = new byte[length];

      System.arraycopy(mBytes, (int)pos - 1, buffer, 0, length);
      return buffer;
   }

   public long length() throws SQLException
   {
      return mBytes.length;
   }

   public long position(Blob pattern , long start) throws SQLException
   {
      return position(pattern.getBytes(0, (int)pattern.length()), start);
   }

   public long position(byte pattern[], long start) throws SQLException
   {
      // Small optimization, no need to look beyond this.
      int max = mBytes.length - pattern.length; 

      if (start < 0)
      {
         start = 0; // Cannot start negative, so put it at the beginning.
      } else if (start >= mBytes.length)
      {
         return -1; // Out of bounds, start was past the end of the buffer.
      }

      if (pattern.length == 0)
      {
         return -1; // Indicate that the pattern was not found.
      }

      byte first  = pattern[0];
      int i = (int)start;

      while (true)
      {
         // Look for the first character.
         while (i <= max && mBytes[i] != first)
         {
            i++;
         }

         if (i > max)
         {
            return -1; // Went to far, reject the pattern.
         }

         // Found the first character, now look for remainder of v2.
         int j = i + 1;
         int end = j + pattern.length - 1;
         int k = 1;
         boolean cont = true;

         // While the bytes remain equal and the end of v1 is not reached
         // continue the either rejecting this match, or accepting it.
         while (cont && j < end)
         {
            if (mBytes[j++] != pattern[k++])
            {
               i++;
               cont = false;
            }
         } // If cont == false then the pattern was found.

         if (cont)
         {
            return i;
         }
      }
   }

   public OutputStream setBinaryStream(long pos)
      throws SQLException
   {
      throw new UnsupportedOperationException("ByteArrayBlob is immutable");
   }
   public int setBytes(long pos, byte[] bytes)
      throws SQLException
   {
      throw new UnsupportedOperationException("ByteArrayBlob is immutable");
   }
   public int setBytes(long pos, byte[] bytes, int offset, int length)
      throws SQLException
   {
      throw new UnsupportedOperationException("ByteArrayBlob is immutable");
   }
   public void truncate(long length)
      throws SQLException
   {
      throw new UnsupportedOperationException("ByteArrayBlob is immutable");
   }
}

