parser.java

一个用 java写的wap浏览器 对于浏览器感兴趣起的可以看看咯

/*
 * j2wap is distributed under the terms of the GNU Public License
 *
 *  j2wap was written by:
 *
 *	        Scott Campbell
 *			Michael Nordling
 *			Karl Maftoum
 * 			Julian Bright
 *
 *			This was a final project for Comp.Engineering at the University of Canberra, Australia
 *
 *			Now released as Open Source software. 28 November 2000
 *
 *			Email: [e-mail] for more info
 *
 *			Use entirely at your own risk.
 */
package wae;

import java.io.IOException;
import java.util.Stack;
import java.util.Vector;
import ui.*;

/**
 * Title:         Parser
 * Descrfiption:  An abstract class, which contains functionality required for
 *                the parsing of both cards and templates.
 * Company:       J2wap.com
 * @author:       Scott campbell
 * @version       1.1
 */
abstract class Parser extends WbxmlUtility
{
  /** Flags whether a event element is currently being parsed. */
  protected boolean         c_bolInEventElement   = false;
  /** Flags whether we have finished parsing the desired card or template. */
  protected boolean         c_bolFinishedParsing  = false;
  /**
   * Flags whether navigation to the card was via a <code>go</code> or
   *  <code>prev</code> event.
   */
  protected boolean         c_bolNavDirectionFlag = true;
  /** Flags whether a <code>anchor</code> element is currently being parsed. */
  protected boolean         c_bolInAnchorElement  = false;
  /** Flags whether a <code>onevent</code> element is currently being parsed. */
  protected boolean         c_bolInOnevent        = false;
  /** Flags whether a <code>ontimer</code> element has been found. */
  protected boolean         c_bolFoundOntimer     = false;
  /**
   * Flags whether the last <code>go</code> element parsed contained
   * <code>setvar</code> or <code>postfield</code> elements.
   */
  protected boolean         c_bolLastGoHasVars    = false;
  /** A count of open elements. */
  protected int             c_intOpenElements     = 0;
  /** Contains the end tags of currently open elements. */
  protected Stack           c_clsStackEndTags     = new Stack ();
  /** Reference to the <code>BrowserCore</code> object. */
  protected BrowserCore     c_clsBrowserCore;
  /** Reference to the <code>CurrentDeck</code> object containing the bytecode.*/
  protected CurrentDeck     c_clsDeck;
  /** Reference to the <code>EventManagement</code> object. */
  protected EventManagement c_clsEventManagement;
  /** Reference to the <code>BrowserContext</code> object. */
  protected BrowserContext  c_clsBrContext;
  /** Flags if we are currently parsing the deck's <code>template</code>. */
  protected boolean         c_bolParsingTemplate;
  /**
   * Attribute start and value delimeter as represented on the card vector
   * created by the parser.
   */
  protected static final String ATTR_DELIM  = (String) "=";
  /** Length of the start and value delimeter. */
  protected static final int ATTR_DELIM_LEN = ATTR_DELIM.length();
  /**  */
  public String c_strMethod = new String();

  /**
   * Set up links to other objects.
   * @param in_clsBrowserCore Reference to the </code>BrowserCore</code>.
   * @param in_clsDeck        Reference to the </code>CurrentDeck</code>.
   * @param in_clsEventManagement Reference to the </code>EventManagaement</code>.
   * @param in_clsBrContext   Reference to the </code>BrowserContext</code>.
   */
  public void init (BrowserCore     in_clsBrowserCore,
                    CurrentDeck     in_clsDeck,
                    EventManagement in_clsEventManagement,
                    BrowserContext  in_clsBrContext)
  {
    c_clsBrowserCore     = in_clsBrowserCore;
    c_clsDeck            = in_clsDeck;
    c_clsEventManagement = in_clsEventManagement;
    c_clsBrContext       = in_clsBrContext;
  } // init

  /**
   * Resolve the value of the variable that the extension token refers to.
   * @param   bytId Token in byte form.
   * @return  String representing the extension.
   */
  public String handleExtensions (int bytId)
    throws IOException, NullPointerException, J2WapException
  {
    String clsVariableValue;
    switch (bytId)
    {
      case Wbxml.EXT_I_0: case Wbxml.EXT_I_1: case Wbxml.EXT_I_2:
        // Variable substitution - escaped. Name of the variable is inline and
        // follows as termstr.
        return (c_clsBrowserCore.getVariable (readInlineString()));
      case Wbxml.EXT_T_0: case Wbxml.EXT_T_1: case Wbxml.EXT_T_2:
        // Variable substitution - escaped. Variable name is encoded as a
        // reference into the string table.
        return (c_clsBrowserCore.getVariable (readStringFromStringTable()));
      case Wbxml.EXT_0: case Wbxml.EXT_1: case Wbxml.EXT_2:
        // Reserved for future use.
        break;
      case Wbxml.OPAQUE:
        int len = readMultiByteInteger ();
        byte [] buf = new byte[len];
        for (int i = 0; i < len; i++)
          buf [len] = nextByte ();

        // Represent byte array as a String and put it in the vector.
        return (new String(buf));
    } // switch

    return "";
  } // handleExtensions


  /**
   * Get the string that the extension token is referring to.
   * @param:  byte Extension Token.
   * @return: String  The String that the extension token is referring to.
   */
  public String resolveExtension (int bytId)
    throws IOException, NullPointerException, J2WapException
  {
    String clsVariableValue;
    switch (bytId)
    {
      case Wbxml.EXT_I_0: case Wbxml.EXT_I_1: case Wbxml.EXT_I_2:
        // Variable substitution - Name of the variable is inline and
        // follows as termstr.
        return ("$" + readInlineString() + "$");
      case Wbxml.EXT_T_0: case Wbxml.EXT_T_1: case Wbxml.EXT_T_2:
        // Variable substitution - Name of the variable is encoded as a
        // reference into the string table.
        return ("$" + readStringFromStringTable() + "$");
      case Wbxml.EXT_0: case Wbxml.EXT_1: case Wbxml.EXT_2:
        // Reserved for future use.
        break;
      case Wbxml.OPAQUE:
        int len = readMultiByteInteger ();
        byte [] buf = new byte[len];
        for (int i = 0; i < len; i++)
          buf [len] = nextByte ();

        // Represent byte array as a String and put it in the vector.
        return (new String(buf));
    } // switch

    return "";
  } // resolveExtension

  /**
   * Parses a card or template's attributes. If an intrinsic event is found,
   * check if it should be acted upon.
   * @param   in_bolCardOrTemplate  Indicates whether a card or template is
   *                                being parsed.
   * @return  Event ID of any intrinsic event that is invoked. If non,
   *          WmlTags.NO_EVENT is returned.
   */
  public int readCardOrTemplateAttrs (boolean in_bolCardOrTemplate)
      throws IOException, NullPointerException, J2WapException
  {
    int intAttrDelim;
    String clsStrAttr = null;
    String clsStrAttrValue = null;

    byte bytId = nextByte ();
    while (bytId != Wbxml.END)
    {
      clsStrAttr      = new String (readAttribute (bytId));
      intAttrDelim    = clsStrAttr.indexOf ("=");
      clsStrAttrValue = clsStrAttr.substring(intAttrDelim+2,
                                             clsStrAttr.length()-1);

      if (bytId == WmlTags.BYTE_NEWCONT_TRUE && parsingDesiredCard())
        c_clsBrContext.resetBrowserContext ();
      else if (isAnIntrinsicEvent (bytId))
      {
        /* We have an intrinsic event. Check if the the direction of navigation
         * to the card fires the event. A <template> only has intrinsic events
         * as attributes, hence the elseif.
         */
        if (parsingDesiredCardOrTemplate ())
        {
          if (bytId == WmlTags.BYTE_ONTIMER)
            c_clsBrowserCore.setOntimerId (c_clsEventManagement.registerGo (
              clsStrAttrValue, false, null, null));
          else if (fireIntrinsicEvent (bytId))
            return c_clsEventManagement.registerGo (
              clsStrAttrValue, false, null, null);
        } // if
      } // if
      else if (parsingDesiredCard ()) // Templates only have intrinsic event attrs.
        conditionalAddToVector (clsStrAttr);  // Add attribute to vector.

      bytId = nextByte ();
    } // while

    // Have all the attributes. Add the end of attributes flag to vector.
    conditionalAddToVector(WmlTags.ENDATTRIBS);

    return WmlTags.NO_EVENT;
  } // readCardOrTemplateAttrs

  /**
   * Determines if a byte represents an intrinsic event.
   * @param   in_bytId  Tag as a byte.
   * @return  True if byte repesents an intrinsic event, false otherwise.
   */
  private boolean isAnIntrinsicEvent (byte in_bytId)
  {
    return ((in_bytId == WmlTags.TYPE_ONENTERFWRDS)  ||
            (in_bytId == WmlTags.TYPE_ONENTERBKWRDS) ||
            (in_bytId == WmlTags.BYTE_ONTIMER));
  } // isAnIntrinsicEvent

  /**
   * Determines if an intrinsic event should be invoked.
   * @param   in_bytId  Tag as a byte.
   * @return  True if intrinsic event should be invoked, false otherwise.
   */
  private boolean fireIntrinsicEvent (byte in_bytId)
  {
    return (((in_bytId == WmlTags.BYTE_ONENTERFORWARDS    ||
              in_bytId == WmlTags.AVAL_ONENTERFWRDS       ||
              in_bytId == WmlTags.TYPE_ONENTERFWRDS)      &&
              c_bolNavDirectionFlag == WmlTags.ONENTER_FORWARDS) ||
            ((in_bytId == WmlTags.BYTE_ONENTERBACKWARDS   ||
              in_bytId == WmlTags.AVAL_ONENTERBKWRDS      ||
              in_bytId == WmlTags.TYPE_ONENTERBKWRDS)     &&
              c_bolNavDirectionFlag == WmlTags.ONENTER_BACKWARDS));
  } // fireIntrinsicEvent

  /**
   * Parses a card's attributes. If an intrinsic event is found, check
   * if it should be acted upon, otherwise just add the attribute to
   * the vector.
   * @return  Event ID of event that is invoked. WmlTags.NO_EVENT if no event
   *          was invoked.
   */
  public int readOnevent ()
    throws IOException, NullPointerException, J2WapException
  {
    int intEventId = 0;

    // Get "type" attribute.
    byte bytId = nextByte ();
    byte bytEventType = (byte) intrinsicEventType (bytId);

    if (bytEventType == Wbxml.INVALID_BYTE)
    {
        J2WapException clsExc = new J2WapException ("The \"type\" attribute " +
          "of an <onevent> is not a valid intrinsic event");
        throw (clsExc);
    } // if

    // Check if the intrinisic enevent identified by the "type" attribute
    // is to be executed.
    if ((bytEventType == WmlTags.BYTE_ONENTERFORWARDS       &&
         c_bolNavDirectionFlag == true) ||
        (bytEventType == WmlTags.BYTE_ONENTERBACKWARDS      &&
         c_bolNavDirectionFlag == WmlTags.ONENTER_BACKWARDS))
    {
      // Get the content, (Either <go>, <prev>, <refresh> or <noop>) then
      // read past the end attributes byte.
      byte bytTemp = nextByte (); // Get past the end of attribute token.
      bytTemp = nextByte ();
      bytId = (byte) (Wbxml.ELEMENT_TAG_ID & bytTemp);
      if (bytId == WmlTags.GO)
        return readGoEvent(true, hasContent(bytId));
      else if (bytId == WmlTags.PREV || bytId == WmlTags.REFRESH)
        return readPrevOrResfreshEvent(bytId, true);
    }
    else if (bytEventType == WmlTags.BYTE_ONPICK ||
             bytEventType == WmlTags.BYTE_ONTIMER)
    {
      // Check if the attribute is legal.
      if (!c_bolFoundOntimer)
        c_bolFoundOntimer = true;
      else
      {
        // Raise exception.
        J2WapException clsExcep = new J2WapException(
          "Too many <timer> elements. A <timer> element " +
          "has already been found in the card.");
        throw (clsExcep);
      } // if-else

      // Get the content, (Either <go>, <prev>, <refresh> or <noop>) then
      // read past the end attributes byte.
      byte bytTemp = nextByte (); // Get past the end of attribute token.
      bytTemp = nextByte ();
      bytId = (byte) (bytTemp & Wbxml.ELEMENT_TAG_ID);

      if (bytId == WmlTags.GO)
        intEventId = readGoEvent(false, hasContent(bytId));
      else if (bytId == WmlTags.PREV || bytId == WmlTags.REFRESH)
        intEventId = readPrevOrResfreshEvent(bytId, false);

      // If the type is "ontimer" than set the ontimer event id.
      if (parsingDesiredCardOrTemplate () &&
          bytEventType == WmlTags.BYTE_ONTIMER)
        c_clsBrowserCore.setOntimerId (intEventId);
    }
    else
    {
      // Error. Raise an exception.
      J2WapException clsExcep = new J2WapException(
        "The type attribute (" + bytId + ") of an <onevent> was illegal");
      throw (clsExcep);
    } // if-else

    // Get the onevent end tag.
    if (nextByte () != Wbxml.END)
    {
      // Error raise an exception.
      J2WapException clsExcep = new J2WapException(
        "Too many elements. An <onevent> can only have one element.");
      throw (clsExcep);
    }

    return WmlTags.NO_EVENT;
  } // readOnevent

  /**
   * Check what type of intrinsic event the type attribute really represents
   * @param   in_bytId First byte of the <code>onevent</code> "type" attribute.
   * @return  Type of intrinsic event.
   */
  private byte intrinsicEventType (byte in_bytId)
    throws IOException, NullPointerException
  {
    switch (in_bytId)
    {
      case WmlTags.TYPE_ONENTERBKWRDS:
        return WmlTags.BYTE_ONENTERBACKWARDS;
      case WmlTags.TYPE_ONENTERFWRDS:
        return WmlTags.BYTE_ONENTERFORWARDS;
      case WmlTags.TYPE_ONTIMER:
        return WmlTags.BYTE_ONTIMER;
      case WmlTags.BYTE_TYPE:
        byte bytAttrVal = nextByte ();
        if (bytAttrVal == WmlTags.AVAL_ONENTERBKWRDS)
          return WmlTags.BYTE_ONENTERBACKWARDS;
        if (bytAttrVal == WmlTags.AVAL_ONENTERFWRDS)
          return WmlTags.BYTE_ONENTERFORWARDS;
        if (bytAttrVal == WmlTags.AVAL_ONTIMER)
          return WmlTags.BYTE_ONTIMER;
    } // switch

    // This return is only in here so that the method will compile.
    return Wbxml.INVALID_BYTE;
  } // intrinsicEventType

  /**
   * Read the next attribute of an element. This method is called in a loop by
   * another method to read all attributes of an element.
   * @param in_bytId  Attribute start token as a byte.
   * @return  Attribute start = attribute value as a string.
   */
  public String readAttribute (byte in_bytId)
    throws IOException, NullPointerException, J2WapException
  {
    StringBuffer clsSBufAttrib = new StringBuffer ();

    // Get the attribute start token
    clsSBufAttrib.append (c_clsDeck.resolveAttrStartToken (in_bytId));

    // Find the position of '=' in name.
    int intDelim = clsSBufAttrib.toString().indexOf ('=');

    /* If attribute start token does not contain part of attribute
       value, '=' or '"', then append or insert '="' or '"' as needed. */
    if (intDelim == -1)
      clsSBufAttrib.append("=\"");
    else
      clsSBufAttrib.insert(intDelim+1, "\"");

    // Append a " (double quote) to the attribute then return it.
    readRestOfAttr (clsSBufAttrib, true);
    return (clsSBufAttrib.append ("\"").toString ());
  } // readAttribute

  /**
   * Reads whats left of the attribute.
   * @param in_clsSBufAttr  The rest of the attribute is appended to this.
   * @param in_bolGetValue  If True the value of the variable will be
   *            obtained. Otherwise "$" followed by the variable name will