Source for javax.swing.text.GapContent

   1: /* GapContent.java --
   2:    Copyright (C) 2002, 2004, 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;
  40: 
  41: import java.io.Serializable;
  42: 
  43: import javax.swing.undo.UndoableEdit;
  44: 
  45: /**
  46:  * This implementation of {@link AbstractDocument.Content} uses a gapped
  47:  * buffer. This takes advantage of the fact that text area content is
  48:  * mostly inserted sequentially. The buffer is a char array that maintains
  49:  * a gap at the current insertion point. If characters a inserted at
  50:  * gap boundaries, the cost is minimal (simple array access). The array only
  51:  * has to be shifted around when the insertion point moves (then the gap also
  52:  * moves and one array copy is necessary) or when the gap is filled up and
  53:  * the buffer has to be enlarged.
  54:  *
  55:  * TODO: Implement UndoableEdit support stuff
  56:  */
  57: public class GapContent
  58:   implements AbstractDocument.Content, Serializable
  59: {
  60:   private static final long serialVersionUID = 8374645204155842629L;
  61: 
  62:   /**
  63:    * This is the default buffer size and the amount of bytes that
  64:    * a buffer is extended if it is full.
  65:    */
  66:   static final int DEFAULT_BUFSIZE = 64;
  67: 
  68:   /**
  69:    * The text buffer.
  70:    */
  71:   char[] buffer;
  72: 
  73:   /**
  74:    * The index of the first character of the gap.
  75:    */
  76:   int gapStart;
  77: 
  78:   /**
  79:    * The index of the character after the last character of the gap.
  80:    */
  81:   int gapEnd;
  82: 
  83:   /**
  84:    * Creates a new GapContent object.
  85:    */
  86:   public GapContent()
  87:   {
  88:     this(DEFAULT_BUFSIZE);
  89:   }
  90: 
  91:   /**
  92:    * Creates a new GapContent object with a specified initial size.
  93:    *
  94:    * @param size the initial size of the buffer
  95:    */
  96:   public GapContent(int size)
  97:   {
  98:     buffer = (char[]) allocateArray(size);
  99:     gapStart = 0;
 100:     gapEnd = size - 1;
 101:     buffer[size - 1] = '\n';
 102:   }
 103: 
 104:   /**
 105:    * Allocates an array of the specified length that can then be used as
 106:    * buffer.
 107:    *
 108:    * @param size the size of the array to be allocated
 109:    *
 110:    * @return the allocated array
 111:    */
 112:   protected Object allocateArray(int size)
 113:   {
 114:     return new char[size];
 115:   }
 116: 
 117:   /**
 118:    * Returns the length of the allocated buffer array.
 119:    *
 120:    * @return the length of the allocated buffer array
 121:    */
 122:   protected int getArrayLength()
 123:   {
 124:     return buffer.length;
 125:   }
 126: 
 127:   /**
 128:    * Returns the length of the content.
 129:    *
 130:    * @return the length of the content
 131:    */
 132:   public int length()
 133:   {
 134:     return buffer.length - (gapEnd - gapStart);
 135:   }
 136: 
 137:   /**
 138:    * Inserts a string at the specified position.
 139:    *
 140:    * @param where the position where the string is inserted
 141:    * @param str the string that is to be inserted
 142:    *
 143:    * @return an UndoableEdit object (currently not supported, so
 144:    *         <code>null</code> is returned)
 145:    *
 146:    * @throws BadLocationException if <code>where</code> is not a valid location
 147:    *         in the buffer
 148:    */
 149:   public UndoableEdit insertString(int where, String str)
 150:     throws BadLocationException
 151:   {
 152:     // check arguments
 153:     int length = length();
 154:     int strLen = str.length();
 155: 
 156:     if (where >= length)
 157:       throw new BadLocationException("the where argument cannot be greater"
 158:                                      + " than the content length", where);
 159: 
 160:     // check if the gap is big enough to hold the string
 161:     if ((gapEnd - gapStart) < strLen)
 162:       // make room for this string and some more
 163:       shiftEnd(strLen + DEFAULT_BUFSIZE);
 164: 
 165:     // are we at the gap boundary?
 166:     if (where != gapStart)
 167:       shiftGap(where);
 168: 
 169:     // now we can simple copy the string into the gap and adjust the
 170:     // gap boundaries
 171:     System.arraycopy(str.toCharArray(), 0, buffer, gapStart, strLen);
 172:     gapStart += strLen;
 173:     return null;
 174:   }
 175: 
 176:   /**
 177:    * Removes a piece of content at th specified position.
 178:    *
 179:    * @param where the position where the content is to be removed
 180:    * @param nitems number of characters to be removed
 181:    *
 182:    * @return an UndoableEdit object (currently not supported, so
 183:    *         <code>null</code> is returned)
 184:    *
 185:    * @throws BadLocationException if <code>where</code> is not a valid location
 186:    *         in the buffer
 187:    */
 188:   public UndoableEdit remove(int where, int nitems)
 189:     throws BadLocationException
 190:   {
 191:     // check arguments
 192:     int length = length();
 193: 
 194:     if (where >= length)
 195:       throw new BadLocationException("the where argument cannot be greater"
 196:                                      + " than the content length", where);
 197:     if ((where + nitems) > length)
 198:       throw new BadLocationException("where + nitems cannot be greater"
 199:                                      + " than the content length",
 200:                                      where + nitems);
 201: 
 202:     // check if we are at the gap boundary
 203:     if (where != gapStart)
 204:       shiftGap(where);
 205: 
 206:     // now we simply have to enlarge the gap
 207:     gapEnd += nitems;
 208:     return null;
 209:   }
 210: 
 211:   /**
 212:    * Returns a piece of content as String.
 213:    *
 214:    * @param where the start location of the fragment
 215:    * @param len the length of the fragment
 216:    *
 217:    * @throws BadLocationException if <code>where</code> or
 218:    *         <code>where + len</code> are no valid locations in the buffer
 219:    */
 220:   public String getString(int where, int len) throws BadLocationException
 221:   {
 222:     Segment seg = new Segment();
 223:     getChars(where, len, seg);
 224:     return new String(seg.array, seg.offset, seg.count);
 225:   }
 226: 
 227:   /**
 228:    * Fetches a piece of content and stores it in a {@link Segment} object.
 229:    *
 230:    * If the requested piece of text spans the gap, the content is copied
 231:    * into a new array. If it doesn't then it is contiguous and the
 232:    * actual content store is returned.
 233:    *
 234:    * @param where the start location of the fragment
 235:    * @param len the length of the fragment
 236:    * @param txt the Segment object to store the fragment in
 237:    *
 238:    * @throws BadLocationException if <code>where</code> or
 239:    *         <code>where + len</code> are no valid locations in the buffer
 240:    */
 241:   public void getChars(int where, int len, Segment txt)
 242:     throws BadLocationException
 243:   {
 244:     // check arguments
 245:     int length = length();
 246:     if (where >= length)
 247:       throw new BadLocationException("the where argument cannot be greater"
 248:                                      + " than the content length", where);
 249:     if ((where + len) > length)
 250:       throw new BadLocationException("len plus where cannot be greater"
 251:                                      + " than the content length",
 252:                                      len + where);
 253: 
 254:     // check if requested segment is contiguous
 255:     if ((where < gapStart) && ((gapStart - where) < len))
 256:       {
 257:         // requested segment is not contiguous -> copy the pieces together
 258:         char[] copy = new char[len];
 259:         int lenFirst = gapStart - where; // the length of the first segment
 260:         System.arraycopy(buffer, where, copy, 0, lenFirst);
 261:         System.arraycopy(buffer, gapEnd, copy, lenFirst, len - lenFirst);
 262:         txt.array = copy;
 263:         txt.offset = 0;
 264:         txt.count = len;
 265:       }
 266:     else
 267:       {
 268:         // requested segment is contiguous -> we can simply return the
 269:         // actual content
 270:         txt.array = buffer;
 271:         if (where < gapStart)
 272:           txt.offset = where;
 273:         else
 274:           txt.offset = where + (gapEnd - gapStart);
 275:         txt.count = len;
 276:       }
 277:   }
 278: 
 279:   /**
 280:    * Creates and returns a mark at the specified position.
 281:    *
 282:    * @param offset the position at which to create the mark
 283:    *
 284:    * @return the create Position object for the mark
 285:    *
 286:    * @throws BadLocationException if the offset is not a valid position in
 287:    *         the buffer
 288:    */
 289:   public Position createPosition(final int offset) throws BadLocationException
 290:   {
 291:     return new Position()
 292:       {
 293:     int off = offset;
 294: 
 295:     public int getOffset()
 296:     {
 297:       return off;
 298:     }
 299:       };
 300:   }
 301: 
 302:   /**
 303:    * Enlarges the gap. This allocates a new bigger buffer array, copy the
 304:    * segment before the gap as it is and the segment after the gap at
 305:    * the end of the new buffer array. This does change the gapEnd mark
 306:    * but not the gapStart mark.
 307:    *
 308:    * @param newSize the new size of the gap
 309:    */
 310:   protected void shiftEnd(int newSize)
 311:   {
 312:     char[] newBuf = (char[]) allocateArray(length() + newSize);
 313:     System.arraycopy(buffer, 0, newBuf, 0, gapStart);
 314:     System.arraycopy(buffer, gapEnd, newBuf, gapStart + newSize,
 315:                      buffer.length - gapEnd);
 316:     gapEnd = gapStart + newSize;
 317:     buffer = newBuf;
 318:   }
 319: 
 320:   /**
 321:    * Shifts the gap to the specified position.
 322:    *
 323:    * @param newGapStart the new start position of the gap
 324:    */
 325:   protected void shiftGap(int newGapStart)
 326:   {
 327:     int newGapEnd = newGapStart + (gapEnd - gapStart);
 328: 
 329:     if (newGapStart == gapStart)
 330:       return;
 331:     else if (newGapStart < gapStart)
 332:       {
 333:         System.arraycopy(buffer, newGapStart, buffer, newGapEnd,
 334:                          gapStart - newGapStart);
 335:         gapStart = newGapStart;
 336:         gapEnd = newGapEnd;
 337:       }
 338:     else
 339:       {
 340:         System.arraycopy(buffer, gapEnd, buffer, gapStart,
 341:                          newGapStart - gapStart);
 342:         gapStart = newGapStart;
 343:         gapEnd = newGapEnd;
 344:       }
 345:   }
 346: 
 347:   /**
 348:    * Returns the allocated buffer array.
 349:    *
 350:    * @return the allocated buffer array
 351:    */
 352:   protected Object getArray()
 353:   {
 354:     return buffer;
 355:   }
 356: }