001/* ContentModel.java -- 002 Copyright (C) 2005 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package javax.swing.text.html.parser; 040 041import gnu.javax.swing.text.html.parser.models.transformer; 042 043import java.io.Serializable; 044 045import java.util.Vector; 046 047/** 048 * A representation of the element content. The instances of this class 049 * can be arranged into the linked list, representing a BNF expression. 050 * The content model is constructed as a branched tree structure in the 051 * following way: 052 * <pre> 053 * a = new ContentModel('+', A, null); // a reprensents A+ 054 * b = new ContentModel('&', B, a); // b represents B & A+ 055 * c = new ContentModel('*', b, null); // c represents ( B & A+) * 056 * d = new ContentModel('|', new ContentModel('*', A, null), 057 * new ContentModel('?', B, null)); // d represents ( A* | B? ) 058 * </pre> 059 * where the valid operations are: 060 * <ul> 061 * <li><code>E* </code> E occurs zero or more times</li> 062 * <li><code>E+ </code> E occurs one or more times</li> 063 * <li><code>E? </code> E occurs once or not atl all</li> 064 * <li><code>A,B</code> A occurs before B</li> 065 * <li><code>A|B</code> both A and B are permitted in any order. 066 * The '|' alone does not permit the repetetive occurence of A or B 067 * (use <code>(A|B)*</code>.</li> 068 * <li><code>A&B</code> both A and B must occur once (in any order)</li> 069 * </ul> 070 * @author Audrius Meskauskas, Lithuania (AudriusA@Bioinformatics.org) 071 */ 072public final class ContentModel 073 implements Serializable 074{ 075 /** Use serialVersionUID for interoperability. */ 076 private static final long serialVersionUID = -1130825523866321257L; 077 078 /** 079 * The next content model model ( = pointer to the next element of 080 * the linked list) for the binary expression (',','&' or '|'). Null 081 * for the last element in the list. 082 */ 083 public ContentModel next; 084 085 /** 086 * The document content, containing either Element or the enclosed 087 * content model (that would be in the parentheses in BNF expression). 088 */ 089 public Object content; 090 091 /** 092 * Specifies the BNF operation between this node and the node, 093 * stored in the field <code>next</code> (or for this node, if it is 094 * an unary operation. 095 */ 096 public int type; 097 098 /** 099 * Create a content model initializing all fields to default values. 100 */ 101 public ContentModel() 102 { 103 // Nothing to do here. 104 } 105 106 /** 107 * Create a content model, consisting of the single element. 108 * Examples: 109 *<code> 110 * a = new ContentModel('+', A, null); // a reprensents A+ 111 * b = new ContentModel('&', B, a); // b represents B & A+ 112 * c = new ContentModel('*', b, null); // c represents ( B & A+) * 113 * d = new ContentModel('|', A, 114 * new ContentModel('?',b, null); 115 * // d represents 116 * </code> 117 */ 118 public ContentModel(Element a_content) 119 { 120 content = a_content; 121 } 122 123 /** 124 * Create a content model, involving expression of the given type. 125 * @param a_type The expression operation type ('*','?' or '+' 126 * @param a_content The content for that the expression is applied. 127 */ 128 public ContentModel(int a_type, ContentModel a_content) 129 { 130 content = a_content; 131 type = a_type; 132 } 133 134 /** 135 * Create a content model, involving binary expression of the given type. 136 * @param a_type The expression operation type ( ',', '|' or '&'). 137 * @param a_content The content of the left part of the expression. 138 * @param a_next The content model, representing the right part of the 139 * expression. 140 */ 141 public ContentModel(int a_type, Object a_content, ContentModel a_next) 142 { 143 content = a_content; 144 type = a_type; 145 next = a_next; 146 } 147 148 /** 149 * Adds all list elements to the given vector, ignoring the 150 * operations between the elements. The old vector values are not 151 * discarded. 152 * @param elements - a vector to add the values to. 153 */ 154 public void getElements(Vector<Element> elements) 155 { 156 ContentModel c = this; 157 158 while (c != null) 159 { 160 // FIXME: correct? 161 if (c.content instanceof Element) 162 elements.add((Element) c.content); 163 c = c.next; 164 } 165 } 166 167 /** 168 * Checks if the content model matches an empty input stream. 169 * The empty content is created using SGML DTD keyword EMPTY. 170 * The empty model is a model with the content field equal to null. 171 * 172 * @return true if the content field is equal to null. 173 */ 174 public boolean empty() 175 { 176 return content == null; 177 } 178 179 /** 180 * Get the element, stored in the <code>next.content</code>. 181 * The method is programmed as the part of the standard API, but not 182 * used in this implementation. 183 * @return the value of the field <code>next</code>. 184 */ 185 public Element first() 186 { 187 return (Element) next.content; 188 } 189 190 /** 191 * Checks if this object can potentially be the first token in the 192 * ContenModel list. The method is programmed as the part of the 193 * standard API, but not used in this implementation. 194 */ 195 public boolean first(Object token) 196 { 197 ContentModel c = this; 198 while (c.next != null) 199 { 200 if (c.content != null && c.content.toString().equals(token.toString()) && 201 c.type != ',' 202 ) 203 204 // Agree if the operation with the preceeding element 205 // is not the comma operation. 206 return true; 207 c = c.next; 208 } 209 return false; 210 } 211 212 /** 213 * Returns a string representation (an expression) of this content model. 214 * The expression has BNF-like syntax, except the absence of the 215 * unary operator is additionally indicated by " ' ". It is 216 * advisable to check the created models for correctness using this 217 * method. 218 */ 219 public String toString() 220 { 221 return transformer.transform(this).toString(); 222 } 223}