/*

 * Copyright (c) 2000, 2005, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 *

 *  (C) Copyright IBM Corp. 1999 All Rights Reserved.

 *  Copyright 1997 The Open Group Research Institute.  All rights reserved.

 */

package sun.security.krb5.internal.util;

import java.io.BufferedInputStream;

import java.io.InputStream;

import java.io.IOException;

/**

 * This class implements a buffered input stream. It provides methods to read a chunck

 * of data from underlying data stream.

 *

 * @author Yanni Zhang

 *

 */

public class KrbDataInputStream extends BufferedInputStream{

    private boolean bigEndian = true;

    public void setNativeByteOrder() {

        if (java.nio.ByteOrder.nativeOrder().

                equals(java.nio.ByteOrder.BIG_ENDIAN)) {

            bigEndian = true;

        } else {

            bigEndian = false;

        }

    }

    public KrbDataInputStream(InputStream is){

        super(is);

    }

    /**

     * Reads a length value which is represented in 4 bytes from

     * this input stream. The value must be positive.

     * @return the length value represented by this byte array.

     * @throws IOException if there are not enough bytes or it represents

     * a negative value

     */

    final public int readLength4() throws IOException {

        int len = read(4);

        if (len < 0) {

            throw new IOException("Invalid encoding");

        }

        return len;

    }

    /**

     * Reads up to the specific number of bytes from this input stream.

     * @param num the number of bytes to be read.

     * @return the int value of this byte array.

     * @throws IOException if there are not enough bytes

     */

    public int read(int num) throws IOException {

        byte[] bytes = new byte[num];

        if (read(bytes, 0, num) != num) {

            throw new IOException("Premature end of stream reached");

        }

        int result = 0;

        for (int i = 0; i < num; i++) {

            if (bigEndian) {

                result |= (bytes[i] & 0xff) << (num - i - 1) * 8;

            } else {

                result |= (bytes[i] & 0xff) << i * 8;

            }

        }

        return result;

    }

    public int readVersion() throws IOException {

        // always read in big-endian mode

        int result = (read() & 0xff) << 8;

        return result | (read() & 0xff);

    }

}