Source for java.nio.ByteBuffer

   1: /* ByteBuffer.java -- 
   2:    Copyright (C) 2002, 2003, 2004 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 java.nio;
  40: 
  41: /**
  42:  * @since 1.4
  43:  */
  44: public abstract class ByteBuffer extends Buffer
  45:   implements Comparable
  46: {
  47:   ByteOrder endian = ByteOrder.BIG_ENDIAN;
  48: 
  49:   int array_offset;
  50:   byte[] backing_buffer;
  51: 
  52:   ByteBuffer (int capacity, int limit, int position, int mark)
  53:   {
  54:     super (capacity, limit, position, mark);
  55:   }
  56: 
  57:   /**
  58:    * Allocates a new direct byte buffer.
  59:    */ 
  60:   public static ByteBuffer allocateDirect (int capacity)
  61:   {
  62:     return DirectByteBufferImpl.allocate (capacity);
  63:   }
  64: 
  65:   /**
  66:    * Allocates a new <code>ByteBuffer</code> object with a given capacity.
  67:    */
  68:   public static ByteBuffer allocate (int capacity)
  69:   {
  70:     return wrap(new byte[capacity], 0, capacity);
  71:   }
  72: 
  73:   /**
  74:    * Wraps a <code>byte</code> array into a <code>ByteBuffer</code>
  75:    * object.
  76:    *
  77:    * @exception IndexOutOfBoundsException If the preconditions on the offset
  78:    * and length parameters do not hold
  79:    */
  80:   public static final ByteBuffer wrap (byte[] array, int offset, int length)
  81:   {
  82:     // FIXME: In GCJ and other implementations where arrays may not
  83:     // move we might consider, at least when offset==0:
  84:     // return new DirectByteBufferImpl(array,
  85:     //                                 address_of_data(array) + offset,
  86:     //                                 length, length, 0, false);
  87:     // This may be more efficient, mainly because we can then use the
  88:     // same logic for all ByteBuffers.
  89: 
  90:     return new ByteBufferImpl (array, 0, array.length, offset + length, offset, -1, false);
  91:   }
  92: 
  93:   /**
  94:    * Wraps a <code>byte</code> array into a <code>ByteBuffer</code>
  95:    * object.
  96:    */
  97:   public static final ByteBuffer wrap (byte[] array)
  98:   {
  99:     return wrap (array, 0, array.length);
 100:   }
 101:   
 102:   /**
 103:    * This method transfers <code>byte</code>s from this buffer into the given
 104:    * destination array. Before the transfer, it checks if there are fewer than
 105:    * length <code>byte</code>s remaining in this buffer.
 106:    *
 107:    * @param dst The destination array
 108:    * @param offset The offset within the array of the first <code>byte</code>
 109:    * to be written; must be non-negative and no larger than dst.length.
 110:    * @param length The maximum number of bytes to be written to the given array;
 111:    * must be non-negative and no larger than dst.length - offset.
 112:    *
 113:    * @exception BufferUnderflowException If there are fewer than length
 114:    * <code>byte</code>s remaining in this buffer.
 115:    * @exception IndexOutOfBoundsException If the preconditions on the offset
 116:    * and length parameters do not hold.
 117:    */
 118:   public ByteBuffer get (byte[] dst, int offset, int length)
 119:   {
 120:     checkArraySize(dst.length, offset, length);
 121:     checkForUnderflow(length);
 122: 
 123:     for (int i = offset; i < offset + length; i++)
 124:       {
 125:         dst [i] = get ();
 126:       }
 127: 
 128:     return this;
 129:   }
 130: 
 131:   /**
 132:    * This method transfers <code>byte</code>s from this buffer into the given
 133:    * destination array.
 134:    *
 135:    * @param dst The byte array to write into.
 136:    *
 137:    * @exception BufferUnderflowException If there are fewer than dst.length
 138:    * <code>byte</code>s remaining in this buffer.
 139:    */
 140:   public ByteBuffer get (byte[] dst)
 141:   {
 142:     return get (dst, 0, dst.length);
 143:   }
 144: 
 145:   /**
 146:    * Writes the content of the the <code>ByteBUFFER</code> src
 147:    * into the buffer. Before the transfer, it checks if there is fewer than
 148:    * <code>src.remaining()</code> space remaining in this buffer.
 149:    *
 150:    * @param src The source data.
 151:    *
 152:    * @exception BufferOverflowException If there is insufficient space in this
 153:    * buffer for the remaining <code>byte</code>s in the source buffer.
 154:    * @exception IllegalArgumentException If the source buffer is this buffer.
 155:    * @exception ReadOnlyBufferException If this buffer is read-only.
 156:    */
 157:   public ByteBuffer put (ByteBuffer src)
 158:   {
 159:     if (src == this)
 160:       throw new IllegalArgumentException ();
 161: 
 162:     checkForOverflow(src.remaining());
 163: 
 164:     if (src.remaining () > 0)
 165:       {
 166:         byte[] toPut = new byte [src.remaining ()];
 167:         src.get (toPut);
 168:         put (toPut);
 169:       }
 170: 
 171:     return this;
 172:   }
 173: 
 174:   /**
 175:    * Writes the content of the the <code>byte array</code> src
 176:    * into the buffer. Before the transfer, it checks if there is fewer than
 177:    * length space remaining in this buffer.
 178:    *
 179:    * @param src The array to copy into the buffer.
 180:    * @param offset The offset within the array of the first byte to be read;
 181:    * must be non-negative and no larger than src.length.
 182:    * @param length The number of bytes to be read from the given array;
 183:    * must be non-negative and no larger than src.length - offset.
 184:    * 
 185:    * @exception BufferOverflowException If there is insufficient space in this
 186:    * buffer for the remaining <code>byte</code>s in the source array.
 187:    * @exception IndexOutOfBoundsException If the preconditions on the offset
 188:    * and length parameters do not hold
 189:    * @exception ReadOnlyBufferException If this buffer is read-only.
 190:    */
 191:   public ByteBuffer put (byte[] src, int offset, int length)
 192:   {
 193:     checkArraySize(src.length, offset, length);
 194:     checkForOverflow(length);
 195: 
 196:     for (int i = offset; i < offset + length; i++)
 197:       put (src [i]);
 198: 
 199:     return this;
 200:   }
 201: 
 202:   /**
 203:    * Writes the content of the the <code>byte array</code> src
 204:    * into the buffer.
 205:    *
 206:    * @param src The array to copy into the buffer.
 207:    * 
 208:    * @exception BufferOverflowException If there is insufficient space in this
 209:    * buffer for the remaining <code>byte</code>s in the source array.
 210:    * @exception ReadOnlyBufferException If this buffer is read-only.
 211:    */
 212:   public final ByteBuffer put (byte[] src)
 213:   {
 214:     return put (src, 0, src.length);
 215:   }
 216: 
 217:   /**
 218:    * Tells whether ot not this buffer is backed by an accessible
 219:    * <code>byte</code> array.
 220:    */
 221:   public final boolean hasArray ()
 222:   {
 223:     return (backing_buffer != null
 224:             && !isReadOnly ());
 225:   }
 226: 
 227:   /**
 228:    * Returns the <code>byte</code> array that backs this buffer.
 229:    *
 230:    * @exception ReadOnlyBufferException If this buffer is read-only.
 231:    * @exception UnsupportedOperationException If this buffer is not backed
 232:    * by an accessible array.
 233:    */
 234:   public final byte[] array ()
 235:   {
 236:     if (backing_buffer == null)
 237:       throw new UnsupportedOperationException ();
 238: 
 239:     checkIfReadOnly();
 240:     
 241:     return backing_buffer;
 242:   }
 243: 
 244:   /**
 245:    * Returns the offset within this buffer's backing array of the first element.
 246:    *
 247:    * @exception ReadOnlyBufferException If this buffer is read-only.
 248:    * @exception UnsupportedOperationException If this buffer is not backed
 249:    * by an accessible array.
 250:    */
 251:   public final int arrayOffset ()
 252:   {
 253:     if (backing_buffer == null)
 254:       throw new UnsupportedOperationException ();
 255: 
 256:     checkIfReadOnly();
 257:     
 258:     return array_offset;
 259:   }
 260: 
 261:   /**
 262:    * Calculates a hash code for this buffer.
 263:    *
 264:    * This is done with <code>int</code> arithmetic,
 265:    * where ** represents exponentiation, by this formula:<br>
 266:    * <code>s[position()] + 31 + (s[position()+1] + 30)*31**1 + ... +
 267:    * (s[limit()-1]+30)*31**(limit()-1)</code>.
 268:    * Where s is the buffer data. Note that the hashcode is dependent
 269:    * on buffer content, and therefore is not useful if the buffer
 270:    * content may change.
 271:    *
 272:    * @return the hash code
 273:    */
 274:   public int hashCode ()
 275:   {
 276:     int hashCode = get(position()) + 31;
 277:     int multiplier = 1;
 278:     for (int i = position() + 1; i < limit(); ++i)
 279:       {
 280:       multiplier *= 31;
 281:       hashCode += (get(i) + 30)*multiplier;
 282:       }
 283:     return hashCode;
 284:   }
 285: 
 286:   /**
 287:    * Checks if this buffer is equal to obj.
 288:    */
 289:   public boolean equals (Object obj)
 290:   {
 291:     if (obj instanceof ByteBuffer)
 292:       {
 293:         return compareTo (obj) == 0;
 294:       }
 295: 
 296:     return false;
 297:   }
 298: 
 299:   /**
 300:    * Compares two <code>ByteBuffer</code> objects.
 301:    *
 302:    * @exception ClassCastException If obj is not an object derived from
 303:    * <code>ByteBuffer</code>.
 304:    */
 305:   public int compareTo (Object obj)
 306:   {
 307:     ByteBuffer other = (ByteBuffer) obj;
 308: 
 309:     int num = Math.min(remaining(), other.remaining());
 310:     int pos_this = position();
 311:     int pos_other = other.position();
 312:     
 313:     for (int count = 0; count < num; count++)
 314:       {
 315:         byte a = get(pos_this++);
 316:     byte b = other.get(pos_other++);
 317:            
 318:     if (a == b)
 319:       continue;
 320:              
 321:     if (a < b)
 322:       return -1;
 323:              
 324:     return 1;
 325:       }
 326:       
 327:     return remaining() - other.remaining();
 328:   }
 329: 
 330:   /**
 331:    * Returns the byte order of this buffer.
 332:    */  
 333:   public final ByteOrder order ()
 334:   {
 335:     return endian;
 336:   }
 337:   
 338:   /**
 339:    * Modifies this buffer's byte order.
 340:    */
 341:   public final ByteBuffer order (ByteOrder endian)
 342:   {
 343:     this.endian = endian;
 344:     return this;
 345:   }
 346:   
 347:   /**
 348:    * Reads the <code>byte</code> at this buffer's current position,
 349:    * and then increments the position.
 350:    *
 351:    * @exception BufferUnderflowException If there are no remaining
 352:    * <code>byte</code>s in this buffer.
 353:    */
 354:   public abstract byte get ();
 355: 
 356:   /**
 357:    * Writes the <code>byte</code> at this buffer's current position,
 358:    * and then increments the position.
 359:    *
 360:    * @exception BufferOverflowException If there no remaining 
 361:    * <code>byte</code>s in this buffer.
 362:    * @exception ReadOnlyBufferException If this buffer is read-only.
 363:    */
 364:   public abstract ByteBuffer put (byte b);
 365: 
 366:   /**
 367:    * Absolute get method.
 368:    *
 369:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 370:    * than the buffer's limit.
 371:    */
 372:   public abstract byte get (int index);
 373:   
 374:   /**
 375:    * Absolute put method.
 376:    *
 377:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 378:    * than the buffer's limit.
 379:    * @exception ReadOnlyBufferException If this buffer is read-only.
 380:    */
 381:   public abstract ByteBuffer put (int index, byte b);
 382: 
 383:   /**
 384:    * Compacts this buffer.
 385:    * 
 386:    * @exception ReadOnlyBufferException If this buffer is read-only.
 387:    */
 388:   public abstract ByteBuffer compact ();
 389: 
 390:   void shiftDown (int dst_offset, int src_offset, int count)
 391:   {
 392:     for (int i = 0; i < count; i++)
 393:       put(dst_offset + i, get(src_offset + i));
 394:   }
 395: 
 396:   /**
 397:    * Tells whether or not this buffer is direct.
 398:    */
 399:   public abstract boolean isDirect ();
 400: 
 401:   /**
 402:    * Creates a new <code>ByteBuffer</code> whose content is a shared
 403:    * subsequence of this buffer's content.
 404:    */
 405:   public abstract ByteBuffer slice ();
 406: 
 407:   /**
 408:    * Creates a new <code>ByteBuffer</code> that shares this buffer's
 409:    * content.
 410:    */
 411:   public abstract ByteBuffer duplicate ();
 412: 
 413:   /**
 414:    * Creates a new read-only <code>ByteBuffer</code> that shares this
 415:    * buffer's content.
 416:    */
 417:   public abstract ByteBuffer asReadOnlyBuffer ();
 418:  
 419:   /**
 420:    * Creates a view of this byte buffer as a short buffer.
 421:    */
 422:   public abstract ShortBuffer asShortBuffer ();
 423:   
 424:   /**
 425:    * Creates a view of this byte buffer as a char buffer.
 426:    */
 427:   public abstract CharBuffer asCharBuffer ();
 428:   
 429:   /**
 430:    * Creates a view of this byte buffer as an integer buffer.
 431:    */
 432:   public abstract IntBuffer asIntBuffer ();
 433:   
 434:   /**
 435:    * Creates a view of this byte buffer as a long buffer.
 436:    */
 437:   public abstract LongBuffer asLongBuffer ();
 438:   
 439:   /**
 440:    * Creates a view of this byte buffer as a float buffer.
 441:    */
 442:   public abstract FloatBuffer asFloatBuffer ();
 443:   
 444:   /**
 445:    * Creates a view of this byte buffer as a double buffer.
 446:    */
 447:   public abstract DoubleBuffer asDoubleBuffer ();
 448: 
 449:   /**
 450:    * Relative get method for reading a character value.
 451:    *
 452:    * @exception BufferUnderflowException  If there are fewer than two bytes
 453:    * remaining in this buffer.
 454:    */
 455:   public abstract char getChar ();
 456:   
 457:   /**
 458:    * Relative put method for writing a character value.
 459:    *
 460:    * @exception BufferOverflowException If this buffer's current position is
 461:    * not smaller than its limit.
 462:    */
 463:   public abstract ByteBuffer putChar (char value);
 464:   
 465:   /**
 466:    * Absolute get method for reading a character value.
 467:    *
 468:    * @exception IndexOutOfBoundsException If there are fewer than two bytes
 469:    * remaining in this buffer
 470:    */
 471:   public abstract char getChar (int index);
 472:   
 473:   /**
 474:    * Absolute put method for writing a character value.
 475:    *
 476:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 477:    * than the buffer's limit, minus one.
 478:    */
 479:   public abstract ByteBuffer putChar (int index, char value);
 480:   
 481:   /**
 482:    * Relative get method for reading a short value.
 483:    *
 484:    * @exception BufferUnderflowException If index is negative or not smaller
 485:    * than the buffer's limit, minus one.
 486:    */
 487:   public abstract short getShort ();
 488:   
 489:   /**
 490:    * Relative put method for writing a short value.
 491:    *
 492:    * @exception BufferOverflowException If this buffer's current position is
 493:    * not smaller than its limit.
 494:    */
 495:   public abstract ByteBuffer putShort (short value);
 496:   
 497:   /**
 498:    * Absolute get method for reading a short value.
 499:    *
 500:    * @exception IndexOutOfBoundsException If there are fewer than two bytes
 501:    * remaining in this buffer
 502:    */
 503:   public abstract short getShort (int index);
 504:  
 505:   /**
 506:    * Absolute put method for writing a short value.
 507:    *
 508:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 509:    * than the buffer's limit, minus one.
 510:    */
 511:   public abstract ByteBuffer putShort (int index, short value);
 512:   
 513:   /**
 514:    * Relative get method for reading an integer value.
 515:    *
 516:    * @exception BufferUnderflowException If there are fewer than four bytes
 517:    * remaining in this buffer.
 518:    */
 519:   public abstract int getInt ();
 520:   
 521:   /**
 522:    * Relative put method for writing an integer value.
 523:    *
 524:    * @exception BufferOverflowException If this buffer's current position is
 525:    * not smaller than its limit.
 526:    */
 527:   public abstract ByteBuffer putInt (int value);
 528:   
 529:   /**
 530:    * Absolute get method for reading an integer value.
 531:    *
 532:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 533:    * than the buffer's limit, minus three.
 534:    */
 535:   public abstract int getInt (int index);
 536:   
 537:   /**
 538:    * Absolute put method for writing an integer value.
 539:    *
 540:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 541:    * than the buffer's limit, minus three.
 542:    */
 543:   public abstract ByteBuffer putInt (int index, int value);
 544:   
 545:   /**
 546:    * Relative get method for reading a long value.
 547:    *
 548:    * @exception BufferUnderflowException If there are fewer than eight bytes
 549:    * remaining in this buffer.
 550:    */
 551:   public abstract long getLong ();
 552:   
 553:   /**
 554:    * Relative put method for writing a long value.
 555:    *
 556:    * @exception BufferOverflowException If this buffer's current position is
 557:    * not smaller than its limit.
 558:    */
 559:   public abstract ByteBuffer putLong (long value);
 560:   
 561:   /**
 562:    * Absolute get method for reading a long value.
 563:    *
 564:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 565:    * than the buffer's limit, minus seven.
 566:    */
 567:   public abstract long getLong (int index);
 568:   
 569:   /**
 570:    * Absolute put method for writing a float value.
 571:    *
 572:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 573:    * than the buffer's limit, minus seven.
 574:    */
 575:   public abstract ByteBuffer putLong (int index, long value);
 576:   
 577:   /**
 578:    * Relative get method for reading a float value.
 579:    *
 580:    * @exception BufferUnderflowException If there are fewer than four bytes
 581:    * remaining in this buffer.
 582:    */
 583:   public abstract float getFloat ();
 584:   
 585:   /**
 586:    * Relative put method for writing a float value.
 587:    *
 588:    * @exception BufferOverflowException If there are fewer than four bytes
 589:    * remaining in this buffer.
 590:    */
 591:   public abstract ByteBuffer putFloat (float value);
 592:   
 593:   /**
 594:    * Absolute get method for reading a float value.
 595:    *
 596:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 597:    * than the buffer's limit, minus three.
 598:    */
 599:   public abstract float getFloat (int index);
 600:   
 601:   /**
 602:    * Relative put method for writing a float value.
 603:    *
 604:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 605:    * than the buffer's limit, minus three.
 606:    */
 607:   public abstract ByteBuffer putFloat (int index, float value);
 608:   
 609:   /**
 610:    * Relative get method for reading a double value.
 611:    *
 612:    * @exception BufferUnderflowException If there are fewer than eight bytes
 613:    * remaining in this buffer.
 614:    */
 615:   public abstract double getDouble ();
 616:   
 617:   /**
 618:    * Relative put method for writing a double value.
 619:    *
 620:    * @exception BufferOverflowException If this buffer's current position is
 621:    * not smaller than its limit.
 622:    */
 623:   public abstract ByteBuffer putDouble (double value);
 624:   
 625:   /**
 626:    * Absolute get method for reading a double value.
 627:    *
 628:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 629:    * than the buffer's limit, minus seven.
 630:    */
 631:   public abstract double getDouble (int index);
 632:   
 633:   /**
 634:    * Absolute put method for writing a double value.
 635:    *
 636:    * @exception IndexOutOfBoundsException If index is negative or not smaller
 637:    * than the buffer's limit, minus seven.
 638:    */
 639:   public abstract ByteBuffer putDouble (int index, double value);
 640: 
 641:   /**
 642:    * Returns a string summarizing the state of this buffer.
 643:    */
 644:   public String toString ()
 645:   {
 646:     return getClass ().getName () +
 647:         "[pos=" + position () +
 648:         " lim=" + limit () +
 649:         " cap=" + capacity () + "]";
 650:   }
 651: }