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1: /* ContentModel.java -- 2: Copyright (C) 2005 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package javax.swing.text.html.parser; 40: 41: import gnu.javax.swing.text.html.parser.models.transformer; 42: 43: import java.io.Serializable; 44: 45: import java.util.Vector; 46: 47: /** 48: * A representation of the element content. The instances of this class 49: * can be arranged into the linked list, representing a BNF expression. 50: * The content model is constructed as a branched tree structure in the 51: * following way: 52: * <pre> 53: * a = new ContentModel('+', A, null); // a reprensents A+ 54: * b = new ContentModel('&', B, a); // b represents B & A+ 55: * c = new ContentModel('*', b, null); // c represents ( B & A+) * 56: * d = new ContentModel('|', new ContentModel('*', A, null), 57: * new ContentModel('?', B, null)); // d represents ( A* | B? ) 58: * </pre> 59: * where the valid operations are: 60: * <ul> 61: * <li><code>E* </code> E occurs zero or more times</li> 62: * <li><code>E+ </code> E occurs one or more times</li> 63: * <li><code>E? </code> E occurs once or not atl all</li> 64: * <li><code>A,B</code> A occurs before B</li> 65: * <li><code>A|B</code> both A and B are permitted in any order. 66: * The '|' alone does not permit the repetetive occurence of A or B 67: * (use <code>(A|B)*</code>.</li> 68: * <li><code>A&B</code> both A and B must occur once (in any order)</li> 69: * </ul> 70: * @author Audrius Meskauskas, Lithuania (AudriusA@Bioinformatics.org) 71: */ 72: public final class ContentModel 73: implements Serializable 74: { 75: /** Use serialVersionUID for interoperability. */ 76: private static final long serialVersionUID = -1130825523866321257L; 77: 78: /** 79: * The next content model model ( = pointer to the next element of 80: * the linked list) for the binary expression (',','&' or '|'). Null 81: * for the last element in the list. 82: */ 83: public ContentModel next; 84: 85: /** 86: * The document content, containing either Element or the enclosed 87: * content model (that would be in the parentheses in BNF expression). 88: */ 89: public Object content; 90: 91: /** 92: * Specifies the BNF operation between this node and the node, 93: * stored in the field <code>next</code> (or for this node, if it is 94: * an unary operation. 95: */ 96: public int type; 97: 98: /** 99: * 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: }