J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1998-2002 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package javax.swing.text; |
| 27 | |
| 28 | import java.util.Stack; |
| 29 | import java.util.Enumeration; |
| 30 | |
| 31 | /** |
| 32 | * <p> |
| 33 | * ElementIterator, as the name suggests, iteratates over the Element |
| 34 | * tree. The constructor can be invoked with either Document or an Element |
| 35 | * as an argument. If the constructor is invoked with a Document as an |
| 36 | * argument then the root of the iteration is the return value of |
| 37 | * document.getDefaultRootElement(). |
| 38 | * |
| 39 | * The iteration happens in a depth-first manner. In terms of how |
| 40 | * boundary conditions are handled: |
| 41 | * a) if next() is called before first() or current(), the |
| 42 | * root will be returned. |
| 43 | * b) next() returns null to indicate the end of the list. |
| 44 | * c) previous() returns null when the current element is the root |
| 45 | * or next() has returned null. |
| 46 | * |
| 47 | * The ElementIterator does no locking of the Element tree. This means |
| 48 | * that it does not track any changes. It is the responsibility of the |
| 49 | * user of this class, to ensure that no changes happen during element |
| 50 | * iteration. |
| 51 | * |
| 52 | * Simple usage example: |
| 53 | * |
| 54 | * public void iterate() { |
| 55 | * ElementIterator it = new ElementIterator(root); |
| 56 | * Element elem; |
| 57 | * while (true) { |
| 58 | * if ((elem = next()) != null) { |
| 59 | * // process element |
| 60 | * System.out.println("elem: " + elem.getName()); |
| 61 | * } else { |
| 62 | * break; |
| 63 | * } |
| 64 | * } |
| 65 | * } |
| 66 | * |
| 67 | * @author Sunita Mani |
| 68 | * |
| 69 | */ |
| 70 | |
| 71 | public class ElementIterator implements Cloneable { |
| 72 | |
| 73 | |
| 74 | private Element root; |
| 75 | private Stack elementStack = null; |
| 76 | |
| 77 | /** |
| 78 | * The StackItem class stores the element |
| 79 | * as well as a child index. If the |
| 80 | * index is -1, then the element represented |
| 81 | * on the stack is the element itself. |
| 82 | * Otherwise, the index functions as as index |
| 83 | * into the vector of children of the element. |
| 84 | * In this case, the item on the stack |
| 85 | * represents the "index"th child of the element |
| 86 | * |
| 87 | */ |
| 88 | private class StackItem implements Cloneable { |
| 89 | Element item; |
| 90 | int childIndex; |
| 91 | |
| 92 | private StackItem(Element elem) { |
| 93 | /** |
| 94 | * -1 index implies a self reference, |
| 95 | * as opposed to an index into its |
| 96 | * list of children. |
| 97 | */ |
| 98 | this.item = elem; |
| 99 | this.childIndex = -1; |
| 100 | } |
| 101 | |
| 102 | private void incrementIndex() { |
| 103 | childIndex++; |
| 104 | } |
| 105 | |
| 106 | private Element getElement() { |
| 107 | return item; |
| 108 | } |
| 109 | |
| 110 | private int getIndex() { |
| 111 | return childIndex; |
| 112 | } |
| 113 | |
| 114 | protected Object clone() throws java.lang.CloneNotSupportedException { |
| 115 | return super.clone(); |
| 116 | } |
| 117 | } |
| 118 | |
| 119 | /** |
| 120 | * Creates a new ElementIterator. The |
| 121 | * root element is taken to get the |
| 122 | * default root element of the document. |
| 123 | * |
| 124 | * @param document a Document. |
| 125 | */ |
| 126 | public ElementIterator(Document document) { |
| 127 | root = document.getDefaultRootElement(); |
| 128 | } |
| 129 | |
| 130 | |
| 131 | /** |
| 132 | * Creates a new ElementIterator. |
| 133 | * |
| 134 | * @param root the root Element. |
| 135 | */ |
| 136 | public ElementIterator(Element root) { |
| 137 | this.root = root; |
| 138 | } |
| 139 | |
| 140 | |
| 141 | /** |
| 142 | * Clones the ElementIterator. |
| 143 | * |
| 144 | * @return a cloned ElementIterator Object. |
| 145 | */ |
| 146 | public synchronized Object clone() { |
| 147 | |
| 148 | try { |
| 149 | ElementIterator it = new ElementIterator(root); |
| 150 | if (elementStack != null) { |
| 151 | it.elementStack = new Stack(); |
| 152 | for (int i = 0; i < elementStack.size(); i++) { |
| 153 | StackItem item = (StackItem)elementStack.elementAt(i); |
| 154 | StackItem clonee = (StackItem)item.clone(); |
| 155 | it.elementStack.push(clonee); |
| 156 | } |
| 157 | } |
| 158 | return it; |
| 159 | } catch (CloneNotSupportedException e) { |
| 160 | throw new InternalError(); |
| 161 | } |
| 162 | } |
| 163 | |
| 164 | |
| 165 | /** |
| 166 | * Fetches the first element. |
| 167 | * |
| 168 | * @return an Element. |
| 169 | */ |
| 170 | public Element first() { |
| 171 | // just in case... |
| 172 | if (root == null) { |
| 173 | return null; |
| 174 | } |
| 175 | |
| 176 | elementStack = new Stack(); |
| 177 | if (root.getElementCount() != 0) { |
| 178 | elementStack.push(new StackItem(root)); |
| 179 | } |
| 180 | return root; |
| 181 | } |
| 182 | |
| 183 | /** |
| 184 | * Fetches the current depth of element tree. |
| 185 | * |
| 186 | * @return the depth. |
| 187 | */ |
| 188 | public int depth() { |
| 189 | if (elementStack == null) { |
| 190 | return 0; |
| 191 | } |
| 192 | return elementStack.size(); |
| 193 | } |
| 194 | |
| 195 | |
| 196 | /** |
| 197 | * Fetches the current Element. |
| 198 | * |
| 199 | * @return element on top of the stack or |
| 200 | * <code>null</code> if the root element is <code>null</code> |
| 201 | */ |
| 202 | public Element current() { |
| 203 | |
| 204 | if (elementStack == null) { |
| 205 | return first(); |
| 206 | } |
| 207 | |
| 208 | /* |
| 209 | get a handle to the element on top of the stack. |
| 210 | */ |
| 211 | if (! elementStack.empty()) { |
| 212 | StackItem item = (StackItem)elementStack.peek(); |
| 213 | Element elem = item.getElement(); |
| 214 | int index = item.getIndex(); |
| 215 | // self reference |
| 216 | if (index == -1) { |
| 217 | return elem; |
| 218 | } |
| 219 | // return the child at location "index". |
| 220 | return elem.getElement(index); |
| 221 | } |
| 222 | return null; |
| 223 | } |
| 224 | |
| 225 | |
| 226 | /** |
| 227 | * Fetches the next Element. The strategy |
| 228 | * used to locate the next element is |
| 229 | * a depth-first search. |
| 230 | * |
| 231 | * @return the next element or <code>null</code> |
| 232 | * at the end of the list. |
| 233 | */ |
| 234 | public Element next() { |
| 235 | |
| 236 | /* if current() has not been invoked |
| 237 | and next is invoked, the very first |
| 238 | element will be returned. */ |
| 239 | if (elementStack == null) { |
| 240 | return first(); |
| 241 | } |
| 242 | |
| 243 | // no more elements |
| 244 | if (elementStack.isEmpty()) { |
| 245 | return null; |
| 246 | } |
| 247 | |
| 248 | // get a handle to the element on top of the stack |
| 249 | |
| 250 | StackItem item = (StackItem)elementStack.peek(); |
| 251 | Element elem = item.getElement(); |
| 252 | int index = item.getIndex(); |
| 253 | |
| 254 | if (index+1 < elem.getElementCount()) { |
| 255 | Element child = elem.getElement(index+1); |
| 256 | if (child.isLeaf()) { |
| 257 | /* In this case we merely want to increment |
| 258 | the child index of the item on top of the |
| 259 | stack.*/ |
| 260 | item.incrementIndex(); |
| 261 | } else { |
| 262 | /* In this case we need to push the child(branch) |
| 263 | on the stack so that we can iterate over its |
| 264 | children. */ |
| 265 | elementStack.push(new StackItem(child)); |
| 266 | } |
| 267 | return child; |
| 268 | } else { |
| 269 | /* No more children for the item on top of the |
| 270 | stack therefore pop the stack. */ |
| 271 | elementStack.pop(); |
| 272 | if (!elementStack.isEmpty()) { |
| 273 | /* Increment the child index for the item that |
| 274 | is now on top of the stack. */ |
| 275 | StackItem top = (StackItem)elementStack.peek(); |
| 276 | top.incrementIndex(); |
| 277 | /* We now want to return its next child, therefore |
| 278 | call next() recursively. */ |
| 279 | return next(); |
| 280 | } |
| 281 | } |
| 282 | return null; |
| 283 | } |
| 284 | |
| 285 | |
| 286 | /** |
| 287 | * Fetches the previous Element. If howver the current |
| 288 | * element is the last element, or the current element |
| 289 | * is null, then null is returned. |
| 290 | * |
| 291 | * @return previous <code>Element</code> if available |
| 292 | * |
| 293 | */ |
| 294 | public Element previous() { |
| 295 | |
| 296 | int stackSize; |
| 297 | if (elementStack == null || (stackSize = elementStack.size()) == 0) { |
| 298 | return null; |
| 299 | } |
| 300 | |
| 301 | // get a handle to the element on top of the stack |
| 302 | // |
| 303 | StackItem item = (StackItem)elementStack.peek(); |
| 304 | Element elem = item.getElement(); |
| 305 | int index = item.getIndex(); |
| 306 | |
| 307 | if (index > 0) { |
| 308 | /* return child at previous index. */ |
| 309 | return getDeepestLeaf(elem.getElement(--index)); |
| 310 | } else if (index == 0) { |
| 311 | /* this implies that current is the element's |
| 312 | first child, therefore previous is the |
| 313 | element itself. */ |
| 314 | return elem; |
| 315 | } else if (index == -1) { |
| 316 | if (stackSize == 1) { |
| 317 | // current is the root, nothing before it. |
| 318 | return null; |
| 319 | } |
| 320 | /* We need to return either the item |
| 321 | below the top item or one of the |
| 322 | former's children. */ |
| 323 | Object top = elementStack.pop(); |
| 324 | item = (StackItem)elementStack.peek(); |
| 325 | |
| 326 | // restore the top item. |
| 327 | elementStack.push(top); |
| 328 | elem = item.getElement(); |
| 329 | index = item.getIndex(); |
| 330 | return ((index == -1) ? elem : getDeepestLeaf(elem.getElement |
| 331 | (index))); |
| 332 | } |
| 333 | // should never get here. |
| 334 | return null; |
| 335 | } |
| 336 | |
| 337 | /** |
| 338 | * Returns the last child of <code>parent</code> that is a leaf. If the |
| 339 | * last child is a not a leaf, this method is called with the last child. |
| 340 | */ |
| 341 | private Element getDeepestLeaf(Element parent) { |
| 342 | if (parent.isLeaf()) { |
| 343 | return parent; |
| 344 | } |
| 345 | int childCount = parent.getElementCount(); |
| 346 | if (childCount == 0) { |
| 347 | return parent; |
| 348 | } |
| 349 | return getDeepestLeaf(parent.getElement(childCount - 1)); |
| 350 | } |
| 351 | |
| 352 | /* |
| 353 | Iterates through the element tree and prints |
| 354 | out each element and its attributes. |
| 355 | */ |
| 356 | private void dumpTree() { |
| 357 | |
| 358 | Element elem; |
| 359 | while (true) { |
| 360 | if ((elem = next()) != null) { |
| 361 | System.out.println("elem: " + elem.getName()); |
| 362 | AttributeSet attr = elem.getAttributes(); |
| 363 | String s = ""; |
| 364 | Enumeration names = attr.getAttributeNames(); |
| 365 | while (names.hasMoreElements()) { |
| 366 | Object key = names.nextElement(); |
| 367 | Object value = attr.getAttribute(key); |
| 368 | if (value instanceof AttributeSet) { |
| 369 | // don't go recursive |
| 370 | s = s + key + "=**AttributeSet** "; |
| 371 | } else { |
| 372 | s = s + key + "=" + value + " "; |
| 373 | } |
| 374 | } |
| 375 | System.out.println("attributes: " + s); |
| 376 | } else { |
| 377 | break; |
| 378 | } |
| 379 | } |
| 380 | } |
| 381 | } |