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