1. /*

  2.  * $Id: ContentModelState.java,v 1.1.1.1 2000/11/23 01:53:33 edwingo Exp $

  3.  *

  4.  * The Apache Software License, Version 1.1

  5.  *

  6.  *

  7.  * Copyright (c) 2000 The Apache Software Foundation.  All rights 

  8.  * reserved.

  9.  *

  10.  * Redistribution and use in source and binary forms, with or without

  11.  * modification, are permitted provided that the following conditions

  12.  * are met:

  13.  *

  14.  * 1. Redistributions of source code must retain the above copyright

  15.  *    notice, this list of conditions and the following disclaimer. 

  16.  *

  17.  * 2. Redistributions in binary form must reproduce the above copyright

  18.  *    notice, this list of conditions and the following disclaimer in

  19.  *    the documentation and/or other materials provided with the

  20.  *    distribution.

  21.  *

  22.  * 3. The end-user documentation included with the redistribution,

  23.  *    if any, must include the following acknowledgment:  

  24.  *       "This product includes software developed by the

  25.  *        Apache Software Foundation (http://www.apache.org/)."

  26.  *    Alternately, this acknowledgment may appear in the software itself,

  27.  *    if and wherever such third-party acknowledgments normally appear.

  28.  *

  29.  * 4. The names "Crimson" and "Apache Software Foundation" must

  30.  *    not be used to endorse or promote products derived from this

  31.  *    software without prior written permission. For written 

  32.  *    permission, please contact apache@apache.org.

  33.  *

  34.  * 5. Products derived from this software may not be called "Apache",

  35.  *    nor may "Apache" appear in their name, without prior written

  36.  *    permission of the Apache Software Foundation.

  37.  *

  38.  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED

  39.  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

  40.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

  41.  * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR

  42.  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

  43.  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

  44.  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF

  45.  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

  46.  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,

  47.  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT

  48.  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

  49.  * SUCH DAMAGE.

  50.  * ====================================================================

  51.  *

  52.  * This software consists of voluntary contributions made by many

  53.  * individuals on behalf of the Apache Software Foundation and was

  54.  * originally based on software copyright (c) 1999, Sun Microsystems, Inc., 

  55.  * http://www.sun.com.  For more information on the Apache Software 

  56.  * Foundation, please see <http://www.apache.org/>.

  57.  */

  58. 

  59. package org.apache.crimson.parser;

  60. 

  61. 

  62. /**

  63.  * A content model state. This is basically an index into a content

  64.  * model node, emulating an automaton with primitives to consume tokens.

  65.  * It may create new content model states as a consequence of that

  66.  * consumption, or modify the current state.  "Next" is used to track

  67.  * states that are pending completion after the "current automaton"

  68.  * completes its task.

  69.  *

  70.  * @see ContentModel

  71.  * @see ValidatingParser

  72.  *

  73.  * @author David Brownell

  74.  * @author Arthur van Hoff

  75.  * @version 	$Revision: 1.1.1.1 $ 

  76.  */

  77. class ContentModelState

  78. {

  79.     private ContentModel	model;

  80.     private boolean		sawOne;

  81.     private ContentModelState	next;

  82. 

  83.     /**

  84.      * Create a content model state for a content model.  When

  85.      * the state advances to null, this automaton has finished.

  86.      */

  87.     ContentModelState (ContentModel model)

  88.     {

  89. 	this (model, null);

  90.     }

  91. 

  92.     /**

  93.      * Create a content model state for a content model, stacking

  94.      * a state for subsequent processing.

  95.      */

  96.     private ContentModelState (Object content, ContentModelState next)

  97.     {

  98. 	this.model = (ContentModel)content;

  99. 	this.next = next;

  100. 	this.sawOne = false;

  101.     }

  102. 

  103.     /**

  104.      * Check if the state can be terminated.  That is, there are no more

  105.      * tokens required in the input stream.

  106.      * @return true if the model can terminate without further input

  107.      */

  108.     boolean terminate ()

  109.     {

  110. 	switch (model.type) {

  111. 	  case '+':

  112. 	    if (!sawOne && !((ContentModel)model).empty ())

  113. 		return false;

  114. 	    // FALLTHROUGH

  115. 	  case '*':

  116. 	  case '?':

  117. 	    return (next == null) || next.terminate ();

  118. 

  119. 	  case '|':

  120. 	    return model.empty () && (next == null || next.terminate ());

  121. 

  122. 	  case ',':

  123. 	    ContentModel m;

  124. 	    for (m = model; (m != null) && m.empty () ; m = m.next)

  125. 		continue;

  126. 	    if (m != null)

  127. 		return false;

  128. 	    return (next == null) || next.terminate ();

  129. 

  130. 	  case 0:

  131. 	    return false;

  132. 	

  133. 	  default:

  134. 	    throw new InternalError ();

  135. 	}

  136.     }

  137. 

  138.     /**

  139.      * Advance this state to a new state, or throw an

  140.      * exception (use a more appropriate one?) if the

  141.      * token is illegal at this point in the content model.

  142.      * The current state is modified if possible, conserving

  143.      * memory that's already been allocated.

  144.      * @return next state after reducing a token

  145.      */

  146.     ContentModelState advance (String token)

  147.     throws EndOfInputException

  148.     {

  149. 	switch (model.type) {

  150. 	  case '+':

  151. 	  case '*':

  152. 	    if (model.first (token)) {

  153. 		sawOne = true;

  154. 		if (model.content instanceof String)

  155. 		    return this;

  156. 		return new ContentModelState (model.content, this)

  157. 			.advance (token);

  158. 	    }

  159. 	    if ((model.type == '*' || sawOne) && next != null)

  160. 		return next.advance (token);

  161. 	    break;

  162. 

  163. 	  case '?':

  164. 	    if (model.first (token)) {

  165. 		if (model.content instanceof String)

  166. 		    return next;

  167. 		return new ContentModelState (model.content, next)

  168. 			.advance (token);

  169. 	    }

  170. 	    if (next != null)

  171. 		return next.advance (token);

  172. 	    break;

  173. 

  174. 	  case '|':

  175. 	    for (ContentModel m = model; m != null; m = m.next) {

  176. 		if (m.content instanceof String) {

  177. 		    if (token == m.content)

  178. 			return next;

  179. 		    continue;

  180. 		}

  181. 		if (((ContentModel)m.content).first (token))

  182. 		    return new ContentModelState (m.content, next)

  183. 			.advance (token);

  184. 	    }

  185. 	    if (model.empty () && next != null)

  186. 		return next.advance (token);

  187. 	    break;

  188. 

  189. 	  case ',':

  190. 	    if (model.first (token)) {

  191. 		ContentModelState	nextState;

  192. 

  193. 		if (model.type == 0)

  194. 		    return next;

  195. 		if (model.next == null)

  196. 		    nextState = new ContentModelState (model.content, next);

  197. 		else {

  198. 		    nextState = new ContentModelState (model.content, this);

  199. 		    model = model.next;

  200. 		}

  201. 		return nextState.advance (token);

  202. 	    } else if (model.empty () && next != null) {

  203. 		return next.advance (token);

  204. 	    }

  205. 	    break;

  206. 

  207. 	  case 0:

  208. 	    if (model.content == token)

  209. 		return next;

  210. 	    // FALLTHROUGH

  211. 

  212. 	  default:

  213. 	    // FALLTHROUGH

  214. 	}

  215. 	throw new EndOfInputException ();

  216.     }

  217. }