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 }