/* ContentModel.java -- Copyright (C) 2005 Free Software Foundation, Inc. This file is part of GNU Classpath. GNU Classpath 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, or (at your option) any later version. GNU Classpath 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 GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version. */ package javax.swing.text.html.parser; import gnu.javax.swing.text.html.parser.models.transformer; import java.io.Serializable; import java.util.Vector; /** * A representation of the element content. The instances of this class * can be arranged into the linked list, representing a BNF expression. * The content model is constructed as a branched tree structure in the * following way: *
 * a = new ContentModel('+', A, null); // a reprensents A+
 * b = new ContentModel('&', B, a); // b represents B & A+
 * c = new ContentModel('*', b, null); // c represents ( B & A+) *
 * d = new ContentModel('|', new ContentModel('*', A, null),
 *          new ContentModel('?', B, null)); // d represents ( A* | B? )
 * 
* where the valid operations are: * * @author Audrius Meskauskas, Lithuania (AudriusA@Bioinformatics.org) */ public final class ContentModel implements Serializable { /** Use serialVersionUID for interoperability. */ private final static long serialVersionUID = -1130825523866321257L; /** * The next content model model ( = pointer to the next element of * the linked list) for the binary expression (',','&' or '|'). Null * for the last element in the list. */ public ContentModel next; /** * The document content, containing either Element or the enclosed * content model (that would be in the parentheses in BNF expression). */ public Object content; /** * Specifies the BNF operation between this node and the node, * stored in the field next (or for this node, if it is * an unary operation. */ public int type; /** Create a content model initializing all fields to default values. */ public ContentModel() { } /** * Create a content model, consisting of the single element. * Examples: * * a = new ContentModel('+', A, null); // a reprensents A+ * b = new ContentModel('&', B, a); // b represents B & A+ * c = new ContentModel('*', b, null); // c represents ( B & A+) * * d = new ContentModel('|', A, * new ContentModel('?',b, null); * // d represents * */ public ContentModel(Element a_content) { content = a_content; } /** * Create a content model, involving expression of the given type. * @param a_type The expression operation type ('*','?' or '+' * @param a_content The content for that the expression is applied. */ public ContentModel(int a_type, ContentModel a_content) { content = a_content; type = a_type; } /** * Create a content model, involving binary expression of the given type. * @param a_type The expression operation type ( ',', '|' or '&'). * @param a_content The content of the left part of the expression. * @param a_next The content model, representing the right part of the * expression. */ public ContentModel(int a_type, Object a_content, ContentModel a_next) { content = a_content; type = a_type; next = a_next; } /** * Adds all list elements to the given vector, ignoring the * operations between the elements. The old vector values are not * discarded. * @param elements - a vector to add the values to. */ public void getElements(Vector elements) { ContentModel c = this; while (c != null) { elements.add(c.content); c = c.next; } } /** * Checks if the content model matches an empty input stream. * The empty content is created using SGML DTD keyword EMPTY. * The empty model is a model with the content field equal to null. * * @return true if the content field is equal to null. */ public boolean empty() { return content == null; } /** * Get the element, stored in the next.content. * The method is programmed as the part of the standard API, but not * used in this implementation. * @return the value of the field next. */ public Element first() { return (Element) next.content; } /** * Checks if this object can potentially be the first token in the * ContenModel list. The method is programmed as the part of the * standard API, but not used in this implementation. */ public boolean first(Object token) { ContentModel c = this; while (c.next != null) { if (c.content != null && c.content.toString().equals(token.toString()) && c.type != ',' ) // Agree if the operation with the preceeding element // is not the comma operation. return true; c = c.next; } return false; } /** * Returns a string representation (an expression) of this content model. * The expression has BNF-like syntax, except the absence of the * unary operator is additionally indicated by " ' ". It is * advisable to check the created models for correctness using this * method. */ public String toString() { return transformer.transform(this).toString(); } }