md5outputstream.java

文件验证

package utils.md5;

import java.io.*;

/** 
 * MD5OutputStream is a subclass of FilterOutputStream adding MD5
 * hashing of the output.
 * <p>
 * Originally written by Santeri Paavolainen, Helsinki Finland 1996 <br>
 * (c) Santeri Paavolainen, Helsinki Finland 1996 <br>
 * Some changes Copyright (c) 2002 Timothy W Macinta <br>
 * <p>
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * <p>
 * This library 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
 * Library General Public License for more details.
 * <p>
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * <p>
 * See http://www.twmacinta.com/myjava/fast_md5.php for more information
 * on this file.
 * <p>
 * Please note: I (Timothy Macinta) have put this code in the
 * com.twmacinta.util package only because it came without a package.  I
 * was not the the original author of the code, although I did
 * optimize it (substantially) and fix some bugs.
 *
 * @author	Santeri Paavolainen <[e-mail]>
 * @author	Timothy W Macinta ([e-mail]) (added main() method)
 **/

public class MD5OutputStream extends FilterOutputStream {
    /**
     * MD5 context
     */
    private MD5	md5;

    /**
     * Creates MD5OutputStream
     * @param out	The output stream
     */

    public MD5OutputStream (OutputStream out) {
	super(out);

	md5 = new MD5();
    }

    /**
     * Writes a byte. 
     *
     * @see java.io.FilterOutputStream
     */

    public void write (int b) throws IOException {
	out.write(b);
	md5.Update((byte) b);
    }

    /**
     * Writes a sub array of bytes.
     *
     * @see java.io.FilterOutputStream
     */

    public void write (byte b[], int off, int len) throws IOException {
	out.write(b, off, len);
	md5.Update(b, off, len);
    }

    /**
     * Returns array of bytes representing hash of the stream as finalized
     * for the current state.
     * @see MD5#Final
     */

    public byte[] hash () {
	return md5.Final();
    }

  public MD5 getMD5() {
    return md5;
  }

  /**
   * This method is here for testing purposes only - do not rely
   * on it being here.
   **/
  public static void main(String[] arg) {
    try {
      MD5OutputStream out = new MD5OutputStream(new NullOutputStream());
      InputStream in = new BufferedInputStream(new FileInputStream(arg[0]));
      byte[] buf = new byte[65536];
      int num_read;
      long total_read = 0;
      while ((num_read = in.read(buf)) != -1) {
	total_read += num_read;
	out.write(buf, 0, num_read);
      }
      System.out.println(MD5.asHex(out.hash())+"  "+arg[0]);
      in.close();
      out.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }


}