/* * @(#)ContentModel.java	1.11 04/05/05 * * Copyright 2004 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */package javax.swing.text.html.parser;import java.util.Vector;import java.util.Enumeration;import java.io.*;/** * A representation of a content model. A content model is * basically a restricted BNF expression. It is restricted in * the sense that it must be deterministic. This means that you * don't have to represent it as a finite state automata.<p> * See Annex H on page 556 of the SGML handbook for more information. * * @author   Arthur van Hoff * @version  1.11,05/05/04 * */public final class ContentModel implements Serializable {    /**     * Type. Either '*', '?', '+', ',', '|', '&'.     */    public int type;    /**     * The content. Either an Element or a ContentModel.     */    public Object content;    /**     * The next content model (in a ',', '|' or '&' expression).     */    public ContentModel next;    public ContentModel() {    }    /**     * Create a content model for an element.     */    public ContentModel(Element content) {	this(0, content, null);    }    /**     * Create a content model of a particular type.     */    public ContentModel(int type, ContentModel content) {	this(type, content, null);    }    /**     * Create a content model of a particular type.     */    public ContentModel(int type, Object content, ContentModel next) {	this.type = type;	this.content = content;	this.next = next;    }    /**     * Return true if the content model could     * match an empty input stream.     */    public boolean empty() {	switch (type) {	  case '*':	  case '?':	    return true;	  case '+':	  case '|':	    for (ContentModel m = (ContentModel)content ; m != null ; m = m.next) {		if (m.empty()) {		    return true;		}	    }	    return false;	  case ',':	  case '&':	    for (ContentModel m = (ContentModel)content ; m != null ; m = m.next) {		if (!m.empty()) {		    return false;		}	    }	    return true;	  default:	    return false;	}    }    /**     * Update elemVec with the list of elements that are     * part of the this contentModel.     */     public void getElements(Vector<Element> elemVec) {	 switch (type) {	 case '*':	 case '?':	 case '+':	     ((ContentModel)content).getElements(elemVec);	     break;	 case ',':	 case '|':	 case '&':	     for (ContentModel m=(ContentModel)content; m != null; m=m.next){		 m.getElements(elemVec);	     }	     break;	 default:	     elemVec.addElement((Element)content);	 }     }     private boolean valSet[];     private boolean val[];     // A cache used by first().  This cache was found to speed parsing     // by about 10% (based on measurements of the 4-12 code base after     // buffering was fixed).    /**     * Return true if the token could potentially be the     * first token in the input stream.     */    public boolean first(Object token) {	switch (type) {	  case '*':	  case '?':	  case '+':	    return ((ContentModel)content).first(token);	  case ',':	    for (ContentModel m = (ContentModel)content ; m != null ; m = m.next) {		if (m.first(token)) {		    return true;		}		if (!m.empty()) {		    return false;		}	    }	    return false;	  case '|':	  case '&': {	    Element e = (Element) token;	    if (valSet == null) {		valSet = new boolean[Element.maxIndex + 1];		val = new boolean[Element.maxIndex + 1];		// All Element instances are created before this ever executes	    }	    if (valSet[e.index]) {		return val[e.index];	    }	    for (ContentModel m = (ContentModel)content ; m != null ; m = m.next) {		if (m.first(token)) {		    val[e.index] = true;		    break;		}	    }	    valSet[e.index] = true;	    return val[e.index];	  }	  default:	    return (content == token);            // PENDING: refer to comment in ContentModelState/*              if (content == token) {                  return true;              }              Element e = (Element)content;              if (e.omitStart() && e.content != null) {                  return e.content.first(token);              }              return false;*/	}    }    /**     * Return the element that must be next.     */    public Element first() {	switch (type) {	  case '&':	  case '|':	  case '*':	  case '?':	    return null;	  case '+':	  case ',':	    return ((ContentModel)content).first();	  default:	    return (Element)content;	}    }    /**     * Convert to a string.     */    public String toString() {	switch (type) {	  case '*':	    return content + "*";	  case '?':	    return content + "?";	  case '+':	    return content + "+";	  case ',':	  case '|':	  case '&':	    char data[] = {' ', (char)type, ' '};	    String str = "";	    for (ContentModel m = (ContentModel)content ; m != null ; m = m.next) {		str = str + m;		if (m.next != null) {		    str += new String(data);		}	    }	    return "(" + str + ")";	  default:	    return content.toString();	}    }}