java/engine/org/apache/derby/impl/jdbc/BinaryToRawStream.java

/*

   Derby - Class org.apache.derby.impl.jdbc.BinaryToRawStream

   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.derby.impl.jdbc;

import org.apache.derby.shared.common.sanity.SanityManager;

import java.io.InputStream;
import java.io.IOException;
import java.io.EOFException;

/**
	Converts a stream containing the Derby stored binary form
	to one that just contains the application's data.
	Simply read and save the length information.
*/
class BinaryToRawStream
extends java.io.FilterInputStream
{
    /**
     * Length of the value represented by this stream.
     * Set to -1 if the length is unknown.
     */
    private int length;

    // used by caller to insure that parent can not be GC'd until this
    // stream is no longer being used.
    private Object          parent;

	BinaryToRawStream(InputStream in, Object parent) 
        throws IOException
	{
		super(in);

		this.parent     = parent;

		int bl = in.read();
		if (bl == -1)
			throw new java.io.EOFException();

		if ((bl & 0x80) != 0)
		{
			if (bl == 0xC0)
			{
				int v1 = in.read();
				int v2 = in.read();
				int v3 = in.read();
				int v4 = in.read();

				if (v1 == -1 || v2 == -1 || v3 == -1 || v4 == -1)
					throw new java.io.EOFException();
                length = (((v1 & 0xff) << 24) |
                          ((v2 & 0xff) << 16) |
                          ((v3 & 0xff) << 8)  |
                           (v4 & 0xff));

			}
			else if (bl == 0xA0)
			{
				// read an unsigned short
				int v1 = in.read();
				int v2 = in.read();
				if (v1 == -1 || v2 == -1)
					throw new java.io.EOFException();
                length = (((v1 & 0xff) << 8) + (v2 & 0xff));

			}
			else
			{
				length = bl & 0x1F;
			}
		}
		else
		{
			// old length in bits
			int v2 = in.read();
			int v3 = in.read();
			int v4 = in.read();
			if (v2 == -1 || v3 == -1 || v4 == -1)
				throw new java.io.EOFException();
            int lenInBits = (((bl & 0xff) << 24) | ((v2 & 0xff) << 16) | ((v3 & 0xff) << 8) | (v4 & 0xff));

			length = lenInBits / 8;
			if ((lenInBits % 8) != 0)
			    length++;
            
            // Signifies unknown length
            if (length == 0)
                length = -1;
		}
	}
    
    /**
     * Return the length of the value in thie stream in bytes.
     * If the value is unknown then -1 is returned.
     */
    int getLength()
    {
        return length;
    }
}