hexviewer.java

一个用java写的mail.里面的代码值得我们去研究！学习。

/*
** $Id: HexViewer.java,v 1.3 2001/05/07 12:37:22 kunugi Exp $
**
** Copyright (c) 2000-2001 Jeff Gay
** on behalf of ICEMail.org <http://www.icemail.org>
** Copyright (c) 1998-2000 by Timothy Gerard Endres
** 
** This program is free software.
** 
** You may redistribute it and/or modify it under the terms of the GNU
** General Public License as published by the Free Software Foundation.
** Version 2 of the license should be included with this distribution in
** the file LICENSE, as well as License.html. If the license is not
** included with this distribution, you may find a copy at the FSF web
** site at 'www.gnu.org' or 'www.fsf.org', or you may write to the
** Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139 USA.
**
** THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY OF ANY KIND,
** NOT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY. THE AUTHOR
** OF THIS SOFTWARE, ASSUMES _NO_ RESPONSIBILITY FOR ANY
** CONSEQUENCE RESULTING FROM THE USE, MODIFICATION, OR
** REDISTRIBUTION OF THIS SOFTWARE. 
** 
*/

package org.icemail.mail;

import java.awt.Color;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;

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

import java.util.Vector;

import java.text.FieldPosition;

import javax.activation.CommandObject;
import javax.activation.DataHandler;

import javax.swing.JComponent;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollBar;
import javax.swing.JTextField;

import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

import javax.swing.border.EmptyBorder;

import org.icemail.util.AWTUtilities;
import org.icemail.text.HexNumberFormat;


/**
 * Class ImageViewer implements a CommandObject for the Java Activation Framework.
 * HexViewer displays the bytes of a data stream in a readable form.
 * <p>
 * The only verb supported is "view", converting the contents into a series of hex
 * words laid out onto a JPanel for display.
 */
public class HexViewer
  extends JComponent
  implements CommandObject
{
  private static final int   BLOCKSIZE = 256;
  private static final int   HEXBYTES = 16;
  private static final int   HEXLINES = 16;
  private static final int   PAGEINCR = 8;

  private boolean           hitEOF = false;
  private int               dataLength;
  private InputStream       dataStream = null;

  private int               currentBlkIdx;
  private Vector            blockCache = new Vector();
  private HexNumberFormat   hexFmt;

  private HexCanvas         hexCanvas;
  private JScrollBar        scrollBar;
  private JTextField        blkHexField;
  private JTextField        blkDecField;
  private JTextField        offHexField;
  private JTextField        offDecField;
  private Cursor            saveCursor = null;


  /**
   * Construct an empty viewer, which can be loaded later.
   */
  public
  HexViewer() {
    super();
    setDoubleBuffered( true );

    establishContents();
  }

  public void
  finalize() {
    checkClose();
  }

  /**
   * Initialize the command object from the data handler as described by the verb.
   * <p>
   * Implements CommandObject.setCommandContext().
   * <p>
   * @param verb the command from the activation framework
   * @param dh the datahandler containing the data contents and type
   * @see javax.activation.CommandObject
   */
  public void
  setCommandContext( String verb, DataHandler dh ) throws IOException {
    if ( verb == null || dh == null )
      throw new IOException( "Invalid parameters to HexViewer.setCommandContext()" );
    if ( ! verb.equalsIgnoreCase( "view" ) )
      throw new IOException( "Only 'view' accepted to HexViewer.setCommandContext()" );

    InputStream content = dh.getInputStream();
    
    this.dataStream = content;
    this.dataLength = -1;

    adjustScroller();

    if ( content != null ) {
      setCurrentBlock( 0 );
    }

    invalidate();
    validate();

    content.close();
  }

  private void
  checkClose() {
    if ( this.dataStream != null ) {
      try {
        this.dataStream.close();
      } catch ( IOException ex ) {
      }
      this.dataStream = null;
    }
  }

  private void
  adjustScroller() {
    if ( this.dataLength < 0 ) {
      this.scrollBar.setMaximum( HexViewer.PAGEINCR );
    } else {
      this.scrollBar.setMaximum( (this.dataLength + (HexViewer.BLOCKSIZE - 1))
                                  / HexViewer.BLOCKSIZE );
    }
  }

  private void
  setCurrentBlock( int offset ) {
    setWaitCursor();

    int blkNum = offset / HexViewer.BLOCKSIZE;
    
    if ( blkNum >= this.blockCache.size() ) {
      try {
        if ( readBlock( blkNum ) == -1 ) {
          checkClose();
          this.hitEOF = true;
          blkNum = this.blockCache.size() - 1;
          this.scrollBar.setValue( blkNum );
          this.scrollBar.setMaximum( blkNum + 1 );
        }
      } catch ( IOException ex ) {
        ex.printStackTrace( System.err );
        blkNum = this.blockCache.size() - 1;
      }
    }

    this.currentBlkIdx = blkNum;

    if ( this.currentBlkIdx < this.blockCache.size() ) {
      byte[] dispData = (byte[])this.blockCache.elementAt( blkNum );

      if ( this.hitEOF && this.dataLength >= 0 &&
           this.currentBlkIdx == (this.blockCache.size() - 1) ) {
        int rem = this.dataLength - (this.currentBlkIdx * HexViewer.BLOCKSIZE);

        if ( rem != HexViewer.BLOCKSIZE ) {
          byte[] remData = new byte[ rem ];
          System.arraycopy( dispData, 0, remData, 0, rem );
          dispData = remData;
        }
      }

      this.hexCanvas.displayData( dispData );
    } else {
      this.hexCanvas.displayEOF();
    }

    if ( this.dataLength < 0 ) {
      if ( this.currentBlkIdx > ( this.scrollBar.getMaximum() - HexViewer.PAGEINCR ) ) {
        this.scrollBar.setMaximum( this.currentBlkIdx + HexViewer.PAGEINCR );
      }
    }

    int hexVal = this.currentBlkIdx;
    String fldStr = this.hexFmt.format(hexVal);
    this.blkHexField.setText( fldStr );
    fldStr = "" + hexVal;
    this.blkDecField.setText( fldStr );

    hexVal = (this.currentBlkIdx * HexViewer.BLOCKSIZE);
    fldStr = this.hexFmt.format(hexVal);
    this.offHexField.setText( fldStr );
    fldStr = "" + hexVal;
    this.offDecField.setText( fldStr );

    this.scrollBar.setValue( this.currentBlkIdx );

    setWaitCursor();
   }

  private int
  readBlock( int blkNum ) throws IOException {
    int result = 0;
    int curBlk = this.blockCache.size();

    for ( ; curBlk <= blkNum ; ++curBlk ) {
      byte[] buf = new byte[ HexViewer.BLOCKSIZE ];

      int off = 0;
      int need = buf.length;
      for ( ; need > 0 ; ) {
        int numRead = this.dataStream.read( buf, off, need );
        if ( numRead < 0 ) {
          result = -1;
          if ( this.dataLength < 0 ) {
            this.dataLength = (curBlk * HexViewer.BLOCKSIZE) + off;
          }
          break;
        }

        off += numRead;
        need -= numRead;
      }

      if ( off > 0 )
        this.blockCache.addElement( buf );
    }

    return result;
  }
    
  private void
  establishContents() {
    int row = 0;
    setLayout( new GridBagLayout() );

    this.hexFmt = new HexNumberFormat( "XXXXXXXX" );

    JPanel ctlPanel = new JPanel();
    ctlPanel.setLayout( new GridBagLayout() );
    ctlPanel.setBorder( new EmptyBorder( 2, 2, 2, 2 ) );
    AWTUtilities.constrain( this, ctlPanel, GridBagConstraints.HORIZONTAL,
                            GridBagConstraints.CENTER, 0, row++, 1, 1, 1.0, 0.0 );

    int ctlRow = 0;
    int ctlCol = 0;

    JLabel label = new JLabel( "Block:" );
    label.setHorizontalAlignment( JLabel.RIGHT );