deroutputstream.java

这是linux下ssl vpn的实现程序

/*
 *  SSL-Explorer
 *
 *  Copyright (C) 2003-2006 3SP LTD. All Rights Reserved
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version 2 of
 *  the License, or (at your option) any later version.
 *  This program 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 for more details.
 *
 *  You should have received a copy of the GNU General Public
 *  License along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
			
package com.maverick.crypto.asn1;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class DEROutputStream
    extends FilterOutputStream implements DERTags
{
    public DEROutputStream(
        OutputStream    os)
    {
        super(os);
    }

    private void writeLength(
        int length)
        throws IOException
    {
        if (length > 127)
        {
            int size = 1;
            int val = length;

            while ((val >>>= 8) != 0)
            {
                size++;
            }

            write((byte)(size | 0x80));

            for (int i = (size - 1) * 8; i >= 0; i -= 8)
            {
                write((byte)(length >> i));
            }
        }
        else
        {
            write((byte)length);
        }
    }

    void writeEncoded(
        int     tag,
        byte[]  bytes)
        throws IOException
    {
        write(tag);
        writeLength(bytes.length);
        write(bytes);
    }

    protected void writeNull()
        throws IOException
    {
        write(NULL);
        write(0x00);
    }

    public void writeObject(
        Object    obj)
        throws IOException
    {
        if (obj == null)
        {
            writeNull();
        }
        else if (obj instanceof DERObject)
        {
            ((DERObject)obj).encode(this);
        }
        else if (obj instanceof DEREncodable)
        {
            ((DEREncodable)obj).getDERObject().encode(this);
        }
        else
        {
            throw new IOException("object not DEREncodable");
        }
    }
}