001    /* Buffer.java -- 
002       Copyright (C) 2002, 2003, 2004  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    import gnu.gcj.RawData;
042    
043    /**
044     * @since 1.4
045     */
046    public abstract class Buffer
047    {
048      private final int cap;
049      int limit;
050      int pos;
051      int mark;
052      final RawData address;
053    
054      /**
055       * Creates a new Buffer.
056       *
057       * Should be package private.
058       */
059      Buffer (int capacity, int limit, int position, int mark,
060              RawData address)
061      {
062        if (capacity < 0)
063          throw new IllegalArgumentException ();
064        
065        this.address = address;
066        cap = capacity;
067        limit (limit);
068        position (position);
069        
070        if (mark >= 0)
071        {
072          if (mark > pos)
073            throw new IllegalArgumentException ();
074          
075          this.mark = mark;
076        }
077        else
078        {
079          this.mark = -1;
080        }
081      }
082      
083      /**
084       * Retrieves the capacity of the buffer.
085       *
086       * @return the capacity of the buffer
087       */
088      public final int capacity ()
089      {
090        return cap;
091      }
092    
093      /**
094       * Clears the buffer.
095       *
096       * @return this buffer
097       */
098      public final Buffer clear ()
099      {
100        limit = cap;
101        pos = 0;
102        mark = -1;
103        return this;
104      }
105        
106      /**
107       * Flips the buffer.
108       *
109       * @return this buffer
110       */
111      public final Buffer flip ()
112      {
113        limit = pos;
114        pos = 0;
115        mark = -1;
116        return this;
117      }
118        
119      /**
120       * Tells whether the buffer has remaining data to read or not.
121       *
122       * @return true if the buffer contains remaining data to read,
123       * false otherwise
124       */
125      public final boolean hasRemaining ()
126      {
127        return remaining() > 0;
128      }
129    
130      /**
131       * Tells whether this buffer is read only or not.
132       *
133       * @return true if the buffer is read only, false otherwise
134       */
135      public abstract boolean isReadOnly ();
136    
137      /**
138       * Retrieves the current limit of the buffer.
139       *
140       * @return the limit of the buffer
141       */
142      public final int limit ()
143      {
144        return limit;
145      }
146    
147      /**
148       * Sets this buffer's limit.
149       * 
150       * @param newLimit The new limit value; must be non-negative and no larger
151       * than this buffer's capacity.
152       *
153       * @return this buffer
154       *
155       * @exception IllegalArgumentException If the preconditions on newLimit
156       * do not hold.
157       */
158      public final Buffer limit (int newLimit)
159      {
160        if ((newLimit < 0) || (newLimit > cap))
161          throw new IllegalArgumentException ();
162    
163        if (newLimit < mark)
164            mark = -1;
165    
166        if (pos > newLimit)
167            pos = newLimit;
168    
169        limit = newLimit;
170        return this;
171      }
172    
173      /**
174       * Sets this buffer's mark at its position.
175       *
176       * @return this buffer
177       */
178      public final Buffer mark ()
179      {
180        mark = pos;
181        return this;
182      }
183    
184      /**
185       * Retrieves the current position of this buffer.
186       *
187       * @return the current position of this buffer
188       */
189      public final int position ()
190      {
191        return pos;
192      }
193        
194      /**
195       * Sets this buffer's position. If the mark is defined and larger than the
196       * new position then it is discarded.
197       * 
198       * @param newPosition The new position value; must be non-negative and no
199       * larger than the current limit.
200       *
201       * @return this buffer
202       *
203       * @exception IllegalArgumentException If the preconditions on newPosition
204       * do not hold
205       */
206      public final Buffer position (int newPosition)
207      {
208        if ((newPosition < 0) || (newPosition > limit))
209          throw new IllegalArgumentException ();
210    
211        if (newPosition <= mark)
212            mark = -1;
213    
214        pos = newPosition;
215        return this;
216      }
217    
218      /**
219       * Returns the number of elements between the current position and the limit.
220       *
221       * @return the number of remaining elements
222       */
223      public final int remaining()
224      {
225        return limit - pos;
226      }
227    
228      /**
229       * Resets this buffer's position to the previously-marked position.
230       *
231       * @return this buffer
232       *
233       * @exception InvalidMarkException If the mark has not been set.
234       */
235      public final Buffer reset()
236      {
237        if (mark == -1)
238          throw new InvalidMarkException ();
239    
240        pos = mark;
241        return this;
242      }
243    
244      /**
245       * Rewinds this buffer. The position is set to zero and the mark
246       * is discarded.
247       *
248       * @return this buffer
249       */
250      public final Buffer rewind()
251      {
252        pos = 0;
253        mark = -1;
254        return this;
255      }
256    
257      /**
258       * Checks for underflow. This method is used internally to check
259       * whether a buffer has enough elements left to satisfy a read 
260       * request.
261       *
262       * @exception BufferUnderflowException If there are no remaining
263       * elements in this buffer.
264       */
265      final void checkForUnderflow()
266      {
267        if (!hasRemaining())
268          throw new BufferUnderflowException();
269      }
270    
271      /**
272       * Checks for underflow. This method is used internally to check
273       * whether a buffer has enough elements left to satisfy a read 
274       * request for a given number of elements.
275       *
276       * @param length The length of a sequence of elements.
277       *
278       * @exception BufferUnderflowException If there are not enough 
279       * remaining elements in this buffer.
280       */
281      final void checkForUnderflow(int length)
282      {
283        if (remaining() < length)
284          throw new BufferUnderflowException();
285      }
286    
287      /**
288       * Checks for overflow. This method is used internally to check
289       * whether a buffer has enough space left to satisfy a write 
290       * request.
291       *
292       * @exception BufferOverflowException If there is no remaining
293       * space in this buffer.
294       */
295      final void checkForOverflow()
296      {
297        if (!hasRemaining())
298          throw new BufferOverflowException();
299      }
300    
301      /**
302       * Checks for overflow. This method is used internally to check
303       * whether a buffer has enough space left to satisfy a write 
304       * request for a given number of elements.
305       *
306       * @param length The length of a sequence of elements.
307       *
308       * @exception BufferUnderflowException If there is not enough 
309       * remaining space in this buffer.
310       */
311      final void checkForOverflow(int length)
312      {
313        if (remaining() < length)
314          throw new BufferOverflowException();
315      }
316    
317      /**
318       * Checks if index is negative or not smaller than the buffer's 
319       * limit. This method is used internally to check whether
320       * an indexed request can be fulfilled.
321       *
322       * @param index The requested position in the buffer.
323       *
324       * @exception IndexOutOfBoundsException If index is negative or not smaller
325       * than the buffer's limit.
326       */
327      final void checkIndex(int index)
328      {
329        if (index < 0
330            || index >= limit ())
331          throw new IndexOutOfBoundsException ();
332      }
333    
334      /**
335       * Checks if buffer is read-only. This method is used internally to
336       * check if elements can be put into a buffer.
337       *
338       * @exception ReadOnlyBufferException If this buffer is read-only.
339       */
340      final void checkIfReadOnly() 
341      {
342        if (isReadOnly())
343          throw new ReadOnlyBufferException ();
344      }
345    
346      /**
347       * Checks whether an array is large enough to hold the given number of
348       * elements at the given offset. This method is used internally to
349       * check if an array is big enough.
350       *
351       * @param arraylength The length of the array.
352       * @param offset The offset within the array of the first byte to be read;
353       * must be non-negative and no larger than arraylength.
354       * @param length The number of bytes to be read from the given array;
355       * must be non-negative and no larger than arraylength - offset.
356       *
357       * @exception IndexOutOfBoundsException If the preconditions on the offset
358       * and length parameters do not hold
359       */
360      static final void checkArraySize(int arraylength, int offset, int length)
361      {
362        if ((offset < 0) ||
363            (length < 0) ||
364            (arraylength < length + offset))
365          throw new IndexOutOfBoundsException ();
366      }
367    }