001    /* ByteBuffer.java -- 
002       Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    
039    package java.nio;
040    
041    // GCJ LOCAL: Change gnu.classpath.Pointer to RawData
042    import gnu.gcj.RawData;
043    import gnu.classpath.Pointer;
044    
045    /**
046     * @since 1.4
047     */
048    public abstract class ByteBuffer extends Buffer
049      implements Comparable<ByteBuffer>
050    {
051      ByteOrder endian = ByteOrder.BIG_ENDIAN;
052      final byte[] backing_buffer;
053      final int array_offset;
054    
055      ByteBuffer (int capacity, int limit, int position, int mark,
056                  RawData address, byte[] backing_buffer, int array_offset)
057      {
058        super (capacity, limit, position, mark, address);
059        this.backing_buffer = backing_buffer;
060        this.array_offset = array_offset;
061      }
062    
063      /**
064       * Allocates a new direct byte buffer.
065       */ 
066      public static ByteBuffer allocateDirect (int capacity)
067      {
068        return DirectByteBufferImpl.allocate (capacity);
069      }
070    
071      /**
072       * Allocates a new <code>ByteBuffer</code> object with a given capacity.
073       */
074      public static ByteBuffer allocate (int capacity)
075      {
076        return wrap(new byte[capacity], 0, capacity);
077      }
078    
079      /**
080       * Wraps a <code>byte</code> array into a <code>ByteBuffer</code>
081       * object.
082       *
083       * @exception IndexOutOfBoundsException If the preconditions on the offset
084       * and length parameters do not hold
085       */
086      public static final ByteBuffer wrap (byte[] array, int offset, int length)
087      {
088        // FIXME: In GCJ and other implementations where arrays may not
089        // move we might consider, at least when offset==0:
090        // return new DirectByteBufferImpl(array,
091        //                                 address_of_data(array) + offset,
092        //                                 length, length, 0, false);
093        // This may be more efficient, mainly because we can then use the
094        // same logic for all ByteBuffers.
095    
096        return new ByteBufferImpl (array, 0, array.length, offset + length, offset, -1, false);
097      }
098    
099      /**
100       * Wraps a <code>byte</code> array into a <code>ByteBuffer</code>
101       * object.
102       */
103      public static final ByteBuffer wrap (byte[] array)
104      {
105        return wrap (array, 0, array.length);
106      }
107      
108      /**
109       * This method transfers <code>byte</code>s from this buffer into the given
110       * destination array. Before the transfer, it checks if there are fewer than
111       * length <code>byte</code>s remaining in this buffer.
112       *
113       * @param dst The destination array
114       * @param offset The offset within the array of the first <code>byte</code>
115       * to be written; must be non-negative and no larger than dst.length.
116       * @param length The maximum number of bytes to be written to the given array;
117       * must be non-negative and no larger than dst.length - offset.
118       *
119       * @exception BufferUnderflowException If there are fewer than length
120       * <code>byte</code>s remaining in this buffer.
121       * @exception IndexOutOfBoundsException If the preconditions on the offset
122       * and length parameters do not hold.
123       */
124      public ByteBuffer get (byte[] dst, int offset, int length)
125      {
126        checkArraySize(dst.length, offset, length);
127        checkForUnderflow(length);
128    
129        for (int i = offset; i < offset + length; i++)
130          {
131            dst [i] = get ();
132          }
133    
134        return this;
135      }
136    
137      /**
138       * This method transfers <code>byte</code>s from this buffer into the given
139       * destination array.
140       *
141       * @param dst The byte array to write into.
142       *
143       * @exception BufferUnderflowException If there are fewer than dst.length
144       * <code>byte</code>s remaining in this buffer.
145       */
146      public ByteBuffer get (byte[] dst)
147      {
148        return get (dst, 0, dst.length);
149      }
150    
151      /**
152       * Writes the content of the the <code>ByteBUFFER</code> src
153       * into the buffer. Before the transfer, it checks if there is fewer than
154       * <code>src.remaining()</code> space remaining in this buffer.
155       *
156       * @param src The source data.
157       *
158       * @exception BufferOverflowException If there is insufficient space in this
159       * buffer for the remaining <code>byte</code>s in the source buffer.
160       * @exception IllegalArgumentException If the source buffer is this buffer.
161       * @exception ReadOnlyBufferException If this buffer is read-only.
162       */
163      public ByteBuffer put (ByteBuffer src)
164      {
165        if (src == this)
166          throw new IllegalArgumentException ();
167    
168        checkForOverflow(src.remaining());
169    
170        if (src.remaining () > 0)
171          {
172            byte[] toPut = new byte [src.remaining ()];
173            src.get (toPut);
174            put (toPut);
175          }
176    
177        return this;
178      }
179    
180      /**
181       * Writes the content of the the <code>byte array</code> src
182       * into the buffer. Before the transfer, it checks if there is fewer than
183       * length space remaining in this buffer.
184       *
185       * @param src The array to copy into the buffer.
186       * @param offset The offset within the array of the first byte to be read;
187       * must be non-negative and no larger than src.length.
188       * @param length The number of bytes to be read from the given array;
189       * must be non-negative and no larger than src.length - offset.
190       * 
191       * @exception BufferOverflowException If there is insufficient space in this
192       * buffer for the remaining <code>byte</code>s in the source array.
193       * @exception IndexOutOfBoundsException If the preconditions on the offset
194       * and length parameters do not hold
195       * @exception ReadOnlyBufferException If this buffer is read-only.
196       */
197      public ByteBuffer put (byte[] src, int offset, int length)
198      {
199        checkArraySize(src.length, offset, length);
200        checkForOverflow(length);
201    
202        for (int i = offset; i < offset + length; i++)
203          put (src [i]);
204    
205        return this;
206      }
207    
208      /**
209       * Writes the content of the the <code>byte array</code> src
210       * into the buffer.
211       *
212       * @param src The array to copy into the buffer.
213       * 
214       * @exception BufferOverflowException If there is insufficient space in this
215       * buffer for the remaining <code>byte</code>s in the source array.
216       * @exception ReadOnlyBufferException If this buffer is read-only.
217       */
218      public final ByteBuffer put (byte[] src)
219      {
220        return put (src, 0, src.length);
221      }
222    
223      /**
224       * Tells whether ot not this buffer is backed by an accessible
225       * <code>byte</code> array.
226       */
227      public final boolean hasArray ()
228      {
229        return (backing_buffer != null
230                && !isReadOnly ());
231      }
232    
233      /**
234       * Returns the <code>byte</code> array that backs this buffer.
235       *
236       * @exception ReadOnlyBufferException If this buffer is read-only.
237       * @exception UnsupportedOperationException If this buffer is not backed
238       * by an accessible array.
239       */
240      public final byte[] array ()
241      {
242        if (backing_buffer == null)
243          throw new UnsupportedOperationException ();
244    
245        checkIfReadOnly();
246        
247        return backing_buffer;
248      }
249    
250      /**
251       * Returns the offset within this buffer's backing array of the first element.
252       *
253       * @exception ReadOnlyBufferException If this buffer is read-only.
254       * @exception UnsupportedOperationException If this buffer is not backed
255       * by an accessible array.
256       */
257      public final int arrayOffset ()
258      {
259        if (backing_buffer == null)
260          throw new UnsupportedOperationException ();
261    
262        checkIfReadOnly();
263        
264        return array_offset;
265      }
266    
267      /**
268       * Calculates a hash code for this buffer.
269       *
270       * This is done with <code>int</code> arithmetic,
271       * where ** represents exponentiation, by this formula:<br>
272       * <code>s[position()] + 31 + (s[position()+1] + 30)*31**1 + ... +
273       * (s[limit()-1]+30)*31**(limit()-1)</code>.
274       * Where s is the buffer data. Note that the hashcode is dependent
275       * on buffer content, and therefore is not useful if the buffer
276       * content may change.
277       *
278       * @return the hash code
279       */
280      public int hashCode ()
281      {
282        int hashCode = get(position()) + 31;
283        int multiplier = 1;
284        for (int i = position() + 1; i < limit(); ++i)
285          {
286              multiplier *= 31;
287              hashCode += (get(i) + 30)*multiplier;
288          }
289        return hashCode;
290      }
291    
292      /**
293       * Checks if this buffer is equal to obj.
294       */
295      public boolean equals (Object obj)
296      {
297        if (obj instanceof ByteBuffer)
298          {
299            return compareTo ((ByteBuffer) obj) == 0;
300          }
301    
302        return false;
303      }
304    
305      /**
306       * Compares two <code>ByteBuffer</code> objects.
307       *
308       * @exception ClassCastException If obj is not an object derived from
309       * <code>ByteBuffer</code>.
310       */
311      public int compareTo (ByteBuffer other)
312      {
313        int num = Math.min(remaining(), other.remaining());
314        int pos_this = position();
315        int pos_other = other.position();
316        
317        for (int count = 0; count < num; count++)
318          {
319            byte a = get(pos_this++);
320            byte b = other.get(pos_other++);
321             
322            if (a == b)
323              continue;
324               
325            if (a < b)
326              return -1;
327               
328            return 1;
329          }
330          
331        return remaining() - other.remaining();
332      }
333    
334      /**
335       * Returns the byte order of this buffer.
336       */  
337      public final ByteOrder order ()
338      {
339        return endian;
340      }
341      
342      /**
343       * Modifies this buffer's byte order.
344       */
345      public final ByteBuffer order (ByteOrder endian)
346      {
347        this.endian = endian;
348        return this;
349      }
350      
351      /**
352       * Reads the <code>byte</code> at this buffer's current position,
353       * and then increments the position.
354       *
355       * @exception BufferUnderflowException If there are no remaining
356       * <code>byte</code>s in this buffer.
357       */
358      public abstract byte get ();
359    
360      /**
361       * Writes the <code>byte</code> at this buffer's current position,
362       * and then increments the position.
363       *
364       * @exception BufferOverflowException If there no remaining 
365       * <code>byte</code>s in this buffer.
366       * @exception ReadOnlyBufferException If this buffer is read-only.
367       */
368      public abstract ByteBuffer put (byte b);
369    
370      /**
371       * Absolute get method.
372       *
373       * @exception IndexOutOfBoundsException If index is negative or not smaller
374       * than the buffer's limit.
375       */
376      public abstract byte get (int index);
377      
378      /**
379       * Absolute put method.
380       *
381       * @exception IndexOutOfBoundsException If index is negative or not smaller
382       * than the buffer's limit.
383       * @exception ReadOnlyBufferException If this buffer is read-only.
384       */
385      public abstract ByteBuffer put (int index, byte b);
386    
387      /**
388       * Compacts this buffer.
389       * 
390       * @exception ReadOnlyBufferException If this buffer is read-only.
391       */
392      public abstract ByteBuffer compact ();
393    
394      void shiftDown (int dst_offset, int src_offset, int count)
395      {
396        for (int i = 0; i < count; i++)
397          put(dst_offset + i, get(src_offset + i));
398      }
399    
400      /**
401       * Tells whether or not this buffer is direct.
402       */
403      public abstract boolean isDirect ();
404    
405      /**
406       * Creates a new <code>ByteBuffer</code> whose content is a shared
407       * subsequence of this buffer's content.
408       */
409      public abstract ByteBuffer slice ();
410    
411      /**
412       * Creates a new <code>ByteBuffer</code> that shares this buffer's
413       * content.
414       */
415      public abstract ByteBuffer duplicate ();
416    
417      /**
418       * Creates a new read-only <code>ByteBuffer</code> that shares this
419       * buffer's content.
420       */
421      public abstract ByteBuffer asReadOnlyBuffer ();
422     
423      /**
424       * Creates a view of this byte buffer as a short buffer.
425       */
426      public abstract ShortBuffer asShortBuffer ();
427      
428      /**
429       * Creates a view of this byte buffer as a char buffer.
430       */
431      public abstract CharBuffer asCharBuffer ();
432      
433      /**
434       * Creates a view of this byte buffer as an integer buffer.
435       */
436      public abstract IntBuffer asIntBuffer ();
437      
438      /**
439       * Creates a view of this byte buffer as a long buffer.
440       */
441      public abstract LongBuffer asLongBuffer ();
442      
443      /**
444       * Creates a view of this byte buffer as a float buffer.
445       */
446      public abstract FloatBuffer asFloatBuffer ();
447      
448      /**
449       * Creates a view of this byte buffer as a double buffer.
450       */
451      public abstract DoubleBuffer asDoubleBuffer ();
452    
453      /**
454       * Relative get method for reading a character value.
455       *
456       * @exception BufferUnderflowException  If there are fewer than two bytes
457       * remaining in this buffer.
458       */
459      public abstract char getChar ();
460      
461      /**
462       * Relative put method for writing a character value.
463       *
464       * @exception BufferOverflowException If this buffer's current position is
465       * not smaller than its limit.
466       */
467      public abstract ByteBuffer putChar (char value);
468      
469      /**
470       * Absolute get method for reading a character value.
471       *
472       * @exception IndexOutOfBoundsException If there are fewer than two bytes
473       * remaining in this buffer
474       */
475      public abstract char getChar (int index);
476      
477      /**
478       * Absolute put method for writing a character value.
479       *
480       * @exception IndexOutOfBoundsException If index is negative or not smaller
481       * than the buffer's limit, minus one.
482       */
483      public abstract ByteBuffer putChar (int index, char value);
484      
485      /**
486       * Relative get method for reading a short value.
487       *
488       * @exception BufferUnderflowException If index is negative or not smaller
489       * than the buffer's limit, minus one.
490       */
491      public abstract short getShort ();
492      
493      /**
494       * Relative put method for writing a short value.
495       *
496       * @exception BufferOverflowException If this buffer's current position is
497       * not smaller than its limit.
498       */
499      public abstract ByteBuffer putShort (short value);
500      
501      /**
502       * Absolute get method for reading a short value.
503       *
504       * @exception IndexOutOfBoundsException If there are fewer than two bytes
505       * remaining in this buffer
506       */
507      public abstract short getShort (int index);
508     
509      /**
510       * Absolute put method for writing a short value.
511       *
512       * @exception IndexOutOfBoundsException If index is negative or not smaller
513       * than the buffer's limit, minus one.
514       */
515      public abstract ByteBuffer putShort (int index, short value);
516      
517      /**
518       * Relative get method for reading an integer value.
519       *
520       * @exception BufferUnderflowException If there are fewer than four bytes
521       * remaining in this buffer.
522       */
523      public abstract int getInt ();
524      
525      /**
526       * Relative put method for writing an integer value.
527       *
528       * @exception BufferOverflowException If this buffer's current position is
529       * not smaller than its limit.
530       */
531      public abstract ByteBuffer putInt (int value);
532      
533      /**
534       * Absolute get method for reading an integer value.
535       *
536       * @exception IndexOutOfBoundsException If index is negative or not smaller
537       * than the buffer's limit, minus three.
538       */
539      public abstract int getInt (int index);
540      
541      /**
542       * Absolute put method for writing an integer value.
543       *
544       * @exception IndexOutOfBoundsException If index is negative or not smaller
545       * than the buffer's limit, minus three.
546       */
547      public abstract ByteBuffer putInt (int index, int value);
548      
549      /**
550       * Relative get method for reading a long value.
551       *
552       * @exception BufferUnderflowException If there are fewer than eight bytes
553       * remaining in this buffer.
554       */
555      public abstract long getLong ();
556      
557      /**
558       * Relative put method for writing a long value.
559       *
560       * @exception BufferOverflowException If this buffer's current position is
561       * not smaller than its limit.
562       */
563      public abstract ByteBuffer putLong (long value);
564      
565      /**
566       * Absolute get method for reading a long value.
567       *
568       * @exception IndexOutOfBoundsException If index is negative or not smaller
569       * than the buffer's limit, minus seven.
570       */
571      public abstract long getLong (int index);
572      
573      /**
574       * Absolute put method for writing a float value.
575       *
576       * @exception IndexOutOfBoundsException If index is negative or not smaller
577       * than the buffer's limit, minus seven.
578       */
579      public abstract ByteBuffer putLong (int index, long value);
580      
581      /**
582       * Relative get method for reading a float value.
583       *
584       * @exception BufferUnderflowException If there are fewer than four bytes
585       * remaining in this buffer.
586       */
587      public abstract float getFloat ();
588      
589      /**
590       * Relative put method for writing a float value.
591       *
592       * @exception BufferOverflowException If there are fewer than four bytes
593       * remaining in this buffer.
594       */
595      public abstract ByteBuffer putFloat (float value);
596      
597      /**
598       * Absolute get method for reading a float value.
599       *
600       * @exception IndexOutOfBoundsException If index is negative or not smaller
601       * than the buffer's limit, minus three.
602       */
603      public abstract float getFloat (int index);
604      
605      /**
606       * Relative put method for writing a float value.
607       *
608       * @exception IndexOutOfBoundsException If index is negative or not smaller
609       * than the buffer's limit, minus three.
610       */
611      public abstract ByteBuffer putFloat (int index, float value);
612      
613      /**
614       * Relative get method for reading a double value.
615       *
616       * @exception BufferUnderflowException If there are fewer than eight bytes
617       * remaining in this buffer.
618       */
619      public abstract double getDouble ();
620      
621      /**
622       * Relative put method for writing a double value.
623       *
624       * @exception BufferOverflowException If this buffer's current position is
625       * not smaller than its limit.
626       */
627      public abstract ByteBuffer putDouble (double value);
628      
629      /**
630       * Absolute get method for reading a double value.
631       *
632       * @exception IndexOutOfBoundsException If index is negative or not smaller
633       * than the buffer's limit, minus seven.
634       */
635      public abstract double getDouble (int index);
636      
637      /**
638       * Absolute put method for writing a double value.
639       *
640       * @exception IndexOutOfBoundsException If index is negative or not smaller
641       * than the buffer's limit, minus seven.
642       */
643      public abstract ByteBuffer putDouble (int index, double value);
644    
645      /**
646       * Returns a string summarizing the state of this buffer.
647       */
648      public String toString ()
649      {
650        return getClass ().getName () +
651                "[pos=" + position () +
652                " lim=" + limit () +
653                " cap=" + capacity () + "]";
654      }
655    }