libjava/java/nio/ByteBuffer.java

   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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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 }