Java > Open Source Codes > java > nio > ByteBuffer


1 /*
2  * @(#)X-Buffer.java 1.56 04/07/16
3  *
4  * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5  * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6  */
7
8 // -- This file was mechanically generated: Do not edit! -- //
9
10 package java.nio;
11
12
13
14
15
16 /**
17  * A byte buffer.
18  *
19  * <p> This class defines six categories of operations upon
20  * byte buffers:
21  *
22  * <ul>
23  *
24  * <li><p> Absolute and relative {@link #get() </code><i>get</i><code>} and
25  * {@link #put(byte) </code><i>put</i><code>} methods that read and write
26  * single bytes; </p></li>
27  *
28  * <li><p> Relative {@link #get(byte[]) </code><i>bulk get</i><code>}
29  * methods that transfer contiguous sequences of bytes from this buffer
30  * into an array; </p></li>
31  *
32  * <li><p> Relative {@link #put(byte[]) </code><i>bulk put</i><code>}
33  * methods that transfer contiguous sequences of bytes from a
34  * byte array or some other byte
35  * buffer into this buffer; </p></li>
36  *
37
38  *
39  * <li><p> Absolute and relative {@link #getChar() </code><i>get</i><code>}
40  * and {@link #putChar(char) </code><i>put</i><code>} methods that read and
41  * write values of other primitive types, translating them to and from
42  * sequences of bytes in a particular byte order; </p></li>
43  *
44  * <li><p> Methods for creating <i><a HREF="#views">view buffers</a></i>,
45  * which allow a byte buffer to be viewed as a buffer containing values of
46  * some other primitive type; and </p></li>
47  *
48
49  *
50  * <li><p> Methods for {@link #compact </code>compacting<code>}, {@link
51  * #duplicate </code>duplicating<code>}, and {@link #slice
52  * </code>slicing<code>} a byte buffer. </p></li>
53  *
54  * </ul>
55  *
56  * <p> Byte buffers can be created either by {@link #allocate
57  * </code><i>allocation</i><code>}, which allocates space for the buffer's
58  *
59
60  *
61  * content, or by {@link #wrap(byte[]) </code><i>wrapping</i><code>} an
62  * existing byte array into a buffer.
63  *
64
65
66
67
68
69
70
71  *
72
73  *
74  * <a name="direct">
75  * <h4> Direct <i>vs.</i> non-direct buffers </h4>
76  *
77  * <p> A byte buffer is either <i>direct</i> or <i>non-direct</i>. Given a
78  * direct byte buffer, the Java virtual machine will make a best effort to
79  * perform native I/O operations directly upon it. That is, it will attempt to
80  * avoid copying the buffer's content to (or from) an intermediate buffer
81  * before (or after) each invocation of one of the underlying operating
82  * system's native I/O operations.
83  *
84  * <p> A direct byte buffer may be created by invoking the {@link
85  * #allocateDirect(int) allocateDirect} factory method of this class. The
86  * buffers returned by this method typically have somewhat higher allocation
87  * and deallocation costs than non-direct buffers. The contents of direct
88  * buffers may reside outside of the normal garbage-collected heap, and so
89  * their impact upon the memory footprint of an application might not be
90  * obvious. It is therefore recommended that direct buffers be allocated
91  * primarily for large, long-lived buffers that are subject to the underlying
92  * system's native I/O operations. In general it is best to allocate direct
93  * buffers only when they yield a measureable gain in program performance.
94  *
95  * <p> A direct byte buffer may also be created by {@link
96  * java.nio.channels.FileChannel#map </code>mapping<code>} a region of a file
97  * directly into memory. An implementation of the Java platform may optionally
98  * support the creation of direct byte buffers from native code via JNI. If an
99  * instance of one of these kinds of buffers refers to an inaccessible region
100  * of memory then an attempt to access that region will not change the buffer's
101  * content and will cause an unspecified exception to be thrown either at the
102  * time of the access or at some later time.
103  *
104  * <p> Whether a byte buffer is direct or non-direct may be determined by
105  * invoking its {@link #isDirect isDirect} method. This method is provided so
106  * that explicit buffer management can be done in performance-critical code.
107  *
108  *
109  * <a name="bin">
110  * <h4> Access to binary data </h4>
111  *
112  * <p> This class defines methods for reading and writing values of all other
113  * primitive types, except <tt>boolean</tt>. Primitive values are translated
114  * to (or from) sequences of bytes according to the buffer's current byte
115  * order, which may be retrieved and modified via the {@link #order order}
116  * methods. Specific byte orders are represented by instances of the {@link
117  * ByteOrder} class. The initial order of a byte buffer is always {@link
118  * ByteOrder#BIG_ENDIAN BIG_ENDIAN}.
119  *
120  * <p> For access to heterogeneous binary data, that is, sequences of values of
121  * different types, this class defines a family of absolute and relative
122  * <i>get</i> and <i>put</i> methods for each type. For 32-bit floating-point
123  * values, for example, this class defines:
124  *
125  * <blockquote><pre>
126  * float {@link #getFloat()}
127  * float {@link #getFloat(int) getFloat(int index)}
128  * void {@link #putFloat(float) putFloat(float f)}
129  * void {@link #putFloat(int,float) putFloat(int index, float f)}</pre></blockquote>
130  *
131  * <p> Corresponding methods are defined for the types <tt>char</tt>,
132  * <tt>short</tt>, <tt>int</tt>, <tt>long</tt>, and <tt>double</tt>. The index
133  * parameters of the absolute <i>get</i> and <i>put</i> methods are in terms of
134  * bytes rather than of the type being read or written.
135  *
136  * <a name="views">
137  *
138  * <p> For access to homogeneous binary data, that is, sequences of values of
139  * the same type, this class defines methods that can create <i>views</i> of a
140  * given byte buffer. A <i>view buffer</i> is simply another buffer whose
141  * content is backed by the byte buffer. Changes to the byte buffer's content
142  * will be visible in the view buffer, and vice versa; the two buffers'
143  * position, limit, and mark values are independent. The {@link
144  * #asFloatBuffer() asFloatBuffer} method, for example, creates an instance of
145  * the {@link FloatBuffer} class that is backed by the byte buffer upon which
146  * the method is invoked. Corresponding view-creation methods are defined for
147  * the types <tt>char</tt>, <tt>short</tt>, <tt>int</tt>, <tt>long</tt>, and
148  * <tt>double</tt>.
149  *
150  * <p> View buffers have three important advantages over the families of
151  * type-specific <i>get</i> and <i>put</i> methods described above:
152  *
153  * <ul>
154  *
155  * <li><p> A view buffer is indexed not in terms of bytes but rather in terms
156  * of the type-specific size of its values; </p></li>
157  *
158  * <li><p> A view buffer provides relative bulk <i>get</i> and <i>put</i>
159  * methods that can transfer contiguous sequences of values between a buffer
160  * and an array or some other buffer of the same type; and </p></li>
161  *
162  * <li><p> A view buffer is potentially much more efficient because it will
163  * be direct if, and only if, its backing byte buffer is direct. </p></li>
164  *
165  * </ul>
166  *
167  * <p> The byte order of a view buffer is fixed to be that of its byte buffer
168  * at the time that the view is created. </p>
169  *
170
171 *
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181
182
183 *
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191
192  *
193
194  * <h4> Invocation chaining </h4>
195
196  *
197  * <p> Methods in this class that do not otherwise have a value to return are
198  * specified to return the buffer upon which they are invoked. This allows
199  * method invocations to be chained.
200  *
201
202  *
203  * The sequence of statements
204  *
205  * <blockquote><pre>
206  * bb.putInt(0xCAFEBABE);
207  * bb.putShort(3);
208  * bb.putShort(45);</pre></blockquote>
209  *
210  * can, for example, be replaced by the single statement
211  *
212  * <blockquote><pre>
213  * bb.putInt(0xCAFEBABE).putShort(3).putShort(45);</pre></blockquote>
214  *
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231
232  *
233  *
234  * @author Mark Reinhold
235  * @author JSR-51 Expert Group
236  * @version 1.56, 04/07/16
237  * @since 1.4
238  */
239
240 public abstract class ByteBuffer
241     extends Buffer
242     implements Comparable <ByteBuffer >
243 {
244
245     // These fields are declared here rather than in Heap-X-Buffer in order to
246 // reduce the number of virtual method invocations needed to access these
247 // values, which is especially costly when coding small buffers.
248 //
249 final byte[] hb; // Non-null only for heap buffers
250 final int offset;
251     boolean isReadOnly; // Valid only for heap buffers
252
253     // Creates a new buffer with the given mark, position, limit, capacity,
254 // backing array, and array offset
255 //
256 ByteBuffer(int mark, int pos, int lim, int cap, // package-private
257 byte[] hb, int offset)
258     {
259     super(mark, pos, lim, cap);
260     this.hb = hb;
261     this.offset = offset;
262     }
263
264     // Creates a new buffer with the given mark, position, limit, and capacity
265 //
266 ByteBuffer(int mark, int pos, int lim, int cap) { // package-private
267 this(mark, pos, lim, cap, null, 0);
268     }
269
270
271
272     /**
273      * Allocates a new direct byte buffer.
274      *
275      * <p> The new buffer's position will be zero, its limit will be its
276      * capacity, and its mark will be undefined. Whether or not it has a
277      * {@link #hasArray </code>backing array<code>} is unspecified. </p>
278      *
279      * @param capacity
280      * The new buffer's capacity, in bytes
281      *
282      * @return The new byte buffer
283      *
284      * @throws IllegalArgumentException
285      * If the <tt>capacity</tt> is a negative integer
286      */
287     public static ByteBuffer allocateDirect(int capacity) {
288         return new DirectByteBuffer (capacity);
289     }
290
291
292
293     /**
294      * Allocates a new byte buffer.
295      *
296      * <p> The new buffer's position will be zero, its limit will be its
297      * capacity, and its mark will be undefined. It will have a {@link #array
298      * </code>backing array<code>}, and its {@link #arrayOffset </code>array
299      * offset<code>} will be zero.
300      *
301      * @param capacity
302      * The new buffer's capacity, in bytes
303      *
304      * @return The new byte buffer
305      *
306      * @throws IllegalArgumentException
307      * If the <tt>capacity</tt> is a negative integer
308      */
309     public static ByteBuffer allocate(int capacity) {
310     if (capacity < 0)
311         throw new IllegalArgumentException ();
312     return new HeapByteBuffer (capacity, capacity);
313     }
314
315     /**
316      * Wraps a byte array into a buffer.
317      *
318      * <p> The new buffer will be backed by the given byte array;
319      * that is, modifications to the buffer will cause the array to be modified
320      * and vice versa. The new buffer's capacity will be
321      * <tt>array.length</tt>, its position will be <tt>offset</tt>, its limit
322      * will be <tt>offset + length</tt>, and its mark will be undefined. Its
323      * {@link #array </code>backing array<code>} will be the given array, and
324      * its {@link #arrayOffset </code>array offset<code>} will be zero. </p>
325      *
326      * @param array
327      * The array that will back the new buffer
328      *
329      * @param offset
330      * The offset of the subarray to be used; must be non-negative and
331      * no larger than <tt>array.length</tt>. The new buffer's position
332      * will be set to this value.
333      *
334      * @param length
335      * The length of the subarray to be used;
336      * must be non-negative and no larger than
337      * <tt>array.length - offset</tt>.
338      * The new buffer's limit will be set to <tt>offset + length</tt>.
339      *
340      * @return The new byte buffer
341      *
342      * @throws IndexOutOfBoundsException
343      * If the preconditions on the <tt>offset</tt> and <tt>length</tt>
344      * parameters do not hold
345      */
346     public static ByteBuffer wrap(byte[] array,
347                     int offset, int length)
348     {
349     try {
350         return new HeapByteBuffer (array, offset, length);
351     } catch (IllegalArgumentException x) {
352         throw new IndexOutOfBoundsException ();
353     }
354     }
355
356     /**
357      * Wraps a byte array into a buffer.
358      *
359      * <p> The new buffer will be backed by the given byte array;
360      * that is, modifications to the buffer will cause the array to be modified
361      * and vice versa. The new buffer's capacity and limit will be
362      * <tt>array.length</tt>, its position will be zero, and its mark will be
363      * undefined. Its {@link #array </code>backing array<code>} will be the
364      * given array, and its {@link #arrayOffset </code>array offset<code>} will
365      * be zero. </p>
366      *
367      * @param array
368      * The array that will back this buffer
369      *
370      * @return The new byte buffer
371      */
372     public static ByteBuffer wrap(byte[] array) {
373     return wrap(array, 0, array.length);
374     }
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468     /**
469      * Creates a new byte buffer whose content is a shared subsequence of
470      * this buffer's content.
471      *
472      * <p> The content of the new buffer will start at this buffer's current
473      * position. Changes to this buffer's content will be visible in the new
474      * buffer, and vice versa; the two buffers' position, limit, and mark
475      * values will be independent.
476      *
477      * <p> The new buffer's position will be zero, its capacity and its limit
478      * will be the number of bytes remaining in this buffer, and its mark
479      * will be undefined. The new buffer will be direct if, and only if, this
480      * buffer is direct, and it will be read-only if, and only if, this buffer
481      * is read-only. </p>
482      *
483      * @return The new byte buffer
484      */
485     public abstract ByteBuffer slice();
486
487     /**
488      * Creates a new byte buffer that shares this buffer's content.
489      *
490      * <p> The content of the new buffer will be that of this buffer. Changes
491      * to this buffer's content will be visible in the new buffer, and vice
492      * versa; the two buffers' position, limit, and mark values will be
493      * independent.
494      *
495      * <p> The new buffer's capacity, limit, position, and mark values will be
496      * identical to those of this buffer. The new buffer will be direct if,
497      * and only if, this buffer is direct, and it will be read-only if, and
498      * only if, this buffer is read-only. </p>
499      *
500      * @return The new byte buffer
501      */
502     public abstract ByteBuffer duplicate();
503
504     /**
505      * Creates a new, read-only byte buffer that shares this buffer's
506      * content.
507      *
508      * <p> The content of the new buffer will be that of this buffer. Changes
509      * to this buffer's content will be visible in the new buffer; the new
510      * buffer itself, however, will be read-only and will not allow the shared
511      * content to be modified. The two buffers' position, limit, and mark
512      * values will be independent.
513      *
514      * <p> The new buffer's capacity, limit, position, and mark values will be
515      * identical to those of this buffer.
516      *
517      * <p> If this buffer is itself read-only then this method behaves in
518      * exactly the same way as the {@link #duplicate duplicate} method. </p>
519      *
520      * @return The new, read-only byte buffer
521      */
522     public abstract ByteBuffer asReadOnlyBuffer();
523
524 
525     // -- Singleton get/put methods --
526
527     /**
528      * Relative <i>get</i> method. Reads the byte at this buffer's
529      * current position, and then increments the position. </p>
530      *
531      * @return The byte at the buffer's current position
532      *
533      * @throws BufferUnderflowException
534      * If the buffer's current position is not smaller than its limit
535      */
536     public abstract byte get();
537
538     /**
539      * Relative <i>put</i> method&nbsp;&nbsp;<i>(optional operation)</i>.
540      *
541      * <p> Writes the given byte into this buffer at the current
542      * position, and then increments the position. </p>
543      *
544      * @param b
545      * The byte to be written
546      *
547      * @return This buffer
548      *
549      * @throws BufferOverflowException
550      * If this buffer's current position is not smaller than its limit
551      *
552      * @throws ReadOnlyBufferException
553      * If this buffer is read-only
554      */
555     public abstract ByteBuffer put(byte b);
556
557     /**
558      * Absolute <i>get</i> method. Reads the byte at the given
559      * index. </p>
560      *
561      * @param index
562      * The index from which the byte will be read
563      *
564      * @return The byte at the given index
565      *
566      * @throws IndexOutOfBoundsException
567      * If <tt>index</tt> is negative
568      * or not smaller than the buffer's limit
569      */
570     public abstract byte get(int index);
571
572     /**
573      * Absolute <i>put</i> method&nbsp;&nbsp;<i>(optional operation)</i>.
574      *
575      * <p> Writes the given byte into this buffer at the given
576      * index. </p>
577      *
578      * @param index
579      * The index at which the byte will be written
580      *
581      * @param b
582      * The byte value to be written
583      *
584      * @return This buffer
585      *
586      * @throws IndexOutOfBoundsException
587      * If <tt>index</tt> is negative
588      * or not smaller than the buffer's limit
589      *
590      * @throws ReadOnlyBufferException
591      * If this buffer is read-only
592      */
593     public abstract ByteBuffer put(int index, byte b);
594
595 
596     // -- Bulk get operations --
597
598     /**
599      * Relative bulk <i>get</i> method.
600      *
601      * <p> This method transfers bytes from this buffer into the given
602      * destination array. If there are fewer bytes remaining in the
603      * buffer than are required to satisfy the request, that is, if
604      * <tt>length</tt>&nbsp;<tt>&gt;</tt>&nbsp;<tt>remaining()</tt>, then no
605      * bytes are transferred and a {@link BufferUnderflowException} is
606      * thrown.
607      *
608      * <p> Otherwise, this method copies <tt>length</tt> bytes from this
609      * buffer into the given array, starting at the current position of this
610      * buffer and at the given offset in the array. The position of this
611      * buffer is then incremented by <tt>length</tt>.
612      *
613      * <p> In other words, an invocation of this method of the form
614      * <tt>src.get(dst,&nbsp;off,&nbsp;len)</tt> has exactly the same effect as
615      * the loop
616      *
617      * <pre>
618      * for (int i = off; i < off + len; i++)
619      * dst[i] = src.get(); </pre>
620      *
621      * except that it first checks that there are sufficient bytes in
622      * this buffer and it is potentially much more efficient. </p>
623      *
624      * @param dst
625      * The array into which bytes are to be written
626      *
627      * @param offset
628      * The offset within the array of the first byte to be
629      * written; must be non-negative and no larger than
630      * <tt>dst.length</tt>
631      *
632      * @param length
633      * The maximum number of bytes to be written to the given
634      * array; must be non-negative and no larger than
635      * <tt>dst.length - offset</tt>
636      *
637      * @return This buffer
638      *
639      * @throws BufferUnderflowException
640      * If there are fewer than <tt>length</tt> bytes
641      * remaining in this buffer
642      *
643      * @throws IndexOutOfBoundsException
644      * If the preconditions on the <tt>offset</tt> and <tt>length</tt>
645      * parameters do not hold
646      */
647     public ByteBuffer get(byte[] dst, int offset, int length) {
648     checkBounds(offset, length, dst.length);
649     if (length > remaining())
650         throw new BufferUnderflowException ();
651     int end = offset + length;
652     for (int i = offset; i < end; i++)
653         dst[i] = get();
654     return this;
655     }
656
657     /**
658      * Relative bulk <i>get</i> method.
659      *
660      * <p> This method transfers bytes from this buffer into the given
661      * destination array. An invocation of this method of the form
662      * <tt>src.get(a)</tt> behaves in exactly the same way as the invocation
663      *
664      * <pre>
665      * src.get(a, 0, a.length) </pre>
666      *
667      * @return This buffer
668      *
669      * @throws BufferUnderflowException
670      * If there are fewer than <tt>length</tt> bytes
671      * remaining in this buffer
672      */
673     public ByteBuffer get(byte[] dst) {
674     return get(dst, 0, dst.length);
675     }
676
677 
678     // -- Bulk put operations --
679
680     /**
681      * Relative bulk <i>put</i> method&nbsp;&nbsp;<i>(optional operation)</i>.
682      *
683      * <p> This method transfers the bytes remaining in the given source
684      * buffer into this buffer. If there are more bytes remaining in the
685      * source buffer than in this buffer, that is, if
686      * <tt>src.remaining()</tt>&nbsp;<tt>&gt;</tt>&nbsp;<tt>remaining()</tt>,
687      * then no bytes are transferred and a {@link
688      * BufferOverflowException} is thrown.
689      *
690      * <p> Otherwise, this method copies
691      * <i>n</i>&nbsp;=&nbsp;<tt>src.remaining()</tt> bytes from the given
692      * buffer into this buffer, starting at each buffer's current position.
693      * The positions of both buffers are then incremented by <i>n</i>.
694      *
695      * <p> In other words, an invocation of this method of the form
696      * <tt>dst.put(src)</tt> has exactly the same effect as the loop
697      *
698      * <pre>
699      * while (src.hasRemaining())
700      * dst.put(src.get()); </pre>
701      *
702      * except that it first checks that there is sufficient space in this
703      * buffer and it is potentially much more efficient. </p>
704      *
705      * @param src
706      * The source buffer from which bytes are to be read;
707      * must not be this buffer
708      *
709      * @return This buffer
710      *
711      * @throws BufferOverflowException
712      * If there is insufficient space in this buffer
713      * for the remaining bytes in the source buffer
714      *
715      * @throws IllegalArgumentException
716      * If the source buffer is this buffer
717      *
718      * @throws ReadOnlyBufferException
719      * If this buffer is read-only
720      */
721     public ByteBuffer put(ByteBuffer src) {
722     if (src == this)
723         throw new IllegalArgumentException ();
724     int n = src.remaining();
725     if (n > remaining())
726         throw new BufferOverflowException ();
727     for (int i = 0; i < n; i++)
728         put(src.get());
729     return this;
730     }
731
732     /**
733      * Relative bulk <i>put</i> method&nbsp;&nbsp;<i>(optional operation)</i>.
734      *
735      * <p> This method transfers bytes into this buffer from the given
736      * source array. If there are more bytes to be copied from the array
737      * than remain in this buffer, that is, if
738      * <tt>length</tt>&nbsp;<tt>&gt;</tt>&nbsp;<tt>remaining()</tt>, then no
739      * bytes are transferred and a {@link BufferOverflowException} is
740      * thrown.
741      *
742      * <p> Otherwise, this method copies <tt>length</tt> bytes from the
743      * given array into this buffer, starting at the given offset in the array
744      * and at the current position of this buffer. The position of this buffer
745      * is then incremented by <tt>length</tt>.
746      *
747      * <p> In other words, an invocation of this method of the form
748      * <tt>dst.put(src,&nbsp;off,&nbsp;len)</tt> has exactly the same effect as
749      * the loop
750      *
751      * <pre>
752      * for (int i = off; i < off + len; i++)
753      * dst.put(a[i]); </pre>
754      *
755      * except that it first checks that there is sufficient space in this
756      * buffer and it is potentially much more efficient. </p>
757      *
758      * @param src
759      * The array from which bytes are to be read
760      *
761      * @param offset
762      * The offset within the array of the first byte to be read;
763      * must be non-negative and no larger than <tt>array.length</tt>
764      *
765      * @param length
766      * The number of bytes to be read from the given array;
767      * must be non-negative and no larger than
768      * <tt>array.length - offset</tt>
769      *
770      * @return This buffer
771      *
772      * @throws BufferOverflowException
773      * If there is insufficient space in this buffer
774      *
775      * @throws IndexOutOfBoundsException
776      * If the preconditions on the <tt>offset</tt> and <tt>length</tt>
777      * parameters do not hold
778      *
779      * @throws ReadOnlyBufferException
780      * If this buffer is read-only
781      */
782     public ByteBuffer put(byte[] src, int offset, int length) {
783     checkBounds(offset, length, src.length);
784     if (length > remaining())
785         throw new BufferOverflowException ();
786     int end = offset + length;
787     for (int i = offset; i < end; i++)
788         this.put(src[i]);
789     return this;
790     }
791
792     /**
793      * Relative bulk <i>put</i> method&nbsp;&nbsp;<i>(optional operation)</i>.
794      *
795      * <p> This method transfers the entire content of the given source
796      * byte array into this buffer. An invocation of this method of the
797      * form <tt>dst.put(a)</tt> behaves in exactly the same way as the
798      * invocation
799      *
800      * <pre>
801      * dst.put(a, 0, a.length) </pre>
802      *
803      * @return This buffer
804      *
805      * @throws BufferOverflowException
806      * If there is insufficient space in this buffer
807      *
808      * @throws ReadOnlyBufferException
809      * If this buffer is read-only
810      */
811     public final ByteBuffer put(byte[] src) {
812     return put(src, 0, src.length);
813     }
814
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899
900 
901     // -- Other stuff --
902
903     /**
904      * Tells whether or not this buffer is backed by an accessible byte
905      * array.
906      *
907      * <p> If this method returns <tt>true</tt> then the {@link #array() array}
908      * and {@link #arrayOffset() arrayOffset} methods may safely be invoked.
909      * </p>
910      *
911      * @return <tt>true</tt> if, and only if, this buffer
912      * is backed by an array and is not read-only
913      */
914     public final boolean hasArray() {
915     return (hb != null) && !isReadOnly;
916     }
917
918     /**
919      * Returns the byte array that backs this
920      * buffer&nbsp;&nbsp;<i>(optional operation)</i>.
921      *
922      * <p> Modifications to this buffer's content will cause the returned
923      * array's content to be modified, and vice versa.
924      *
925      * <p> Invoke the {@link #hasArray hasArray} method before invoking this
926      * method in order to ensure that this buffer has an accessible backing
927      * array. </p>
928      *
929      * @return The array that backs this buffer
930      *
931      * @throws ReadOnlyBufferException
932      * If this buffer is backed by an array but is read-only
933      *
934      * @throws UnsupportedOperationException
935      * If this buffer is not backed by an accessible array
936      */
937     public final byte[] array() {
938     if (hb == null)
939         throw new UnsupportedOperationException ();
940     if (isReadOnly)
941         throw new ReadOnlyBufferException ();
942     return hb;
943     }
944
945     /**
946      * Returns the offset within this buffer's backing array of the first
947      * element of the buffer&nbsp;&nbsp;<i>(optional operation)</i>.
948      *
949      * <p> If this buffer is backed by an array then buffer position <i>p</i>
950      * corresponds to array index <i>p</i>&nbsp;+&nbsp;<tt>arrayOffset()</tt>.
951      *
952      * <p> Invoke the {@link #hasArray hasArray} method before invoking this
953      * method in order to ensure that this buffer has an accessible backing
954      * array. </p>
955      *
956      * @return The offset within this buffer's array
957      * of the first element of the buffer
958      *
959      * @throws ReadOnlyBufferException
960      * If this buffer is backed by an array but is read-only
961      *
962      * @throws UnsupportedOperationException
963      * If this buffer is not backed by an accessible array
964      */
965     public final int arrayOffset() {
966     if (hb == null)
967         throw new UnsupportedOperationException ();
968     if (isReadOnly)
969         throw new ReadOnlyBufferException ();
970     return offset;
971     }
972
973     /**
974      * Compacts this buffer&nbsp;&nbsp;<i>(optional operation)</i>.
975      *
976      * <p> The bytes between the buffer's current position and its limit,
977      * if any, are copied to the beginning of the buffer. That is, the
978      * byte at index <i>p</i>&nbsp;=&nbsp;<tt>position()</tt> is copied
979      * to index zero, the byte at index <i>p</i>&nbsp;+&nbsp;1 is copied
980      * to index one, and so forth until the byte at index
981      * <tt>limit()</tt>&nbsp;-&nbsp;1 is copied to index
982      * <i>n</i>&nbsp;=&nbsp;<tt>limit()</tt>&nbsp;-&nbsp;<tt>1</tt>&nbsp;-&nbsp;<i>p</i>.
983      * The buffer's position is then set to <i>n+1</i> and its limit is set to
984      * its capacity. The mark, if defined, is discarded.
985      *
986      * <p> The buffer's position is set to the number of bytes copied,
987      * rather than to zero, so that an invocation of this method can be
988      * followed immediately by an invocation of another relative <i>put</i>
989      * method. </p>
990      *
991
992      *
993      * <p> Invoke this method after writing data from a buffer in case the
994      * write was incomplete. The following loop, for example, copies bytes
995      * from one channel to another via the buffer <tt>buf</tt>:
996      *
997      * <blockquote><pre>
998      * buf.clear(); // Prepare buffer for use
999      * for (;;) {
1000     * if (in.read(buf) < 0 && !buf.hasRemaining())
1001     * break; // No more bytes to transfer
1002     * buf.flip();
1003     * out.write(buf);
1004     * buf.compact(); // In case of partial write
1005     * }</pre></blockquote>
1006     *
1007
1008     *
1009     * @return This buffer
1010     *
1011     * @throws ReadOnlyBufferException
1012     * If this buffer is read-only
1013     */
1014    public abstract ByteBuffer compact();
1015
1016    /**
1017     * Tells whether or not this byte buffer is direct. </p>
1018     *
1019     * @return <tt>true</tt> if, and only if, this buffer is direct
1020     */
1021    public abstract boolean isDirect();
1022
1023
1024
1025    /**
1026     * Returns a string summarizing the state of this buffer. </p>
1027     *
1028     * @return A summary string
1029     */
1030    public String toString() {
1031    StringBuffer sb = new StringBuffer ();
1032    sb.append(getClass().getName());
1033    sb.append("[pos=");
1034    sb.append(position());
1035    sb.append(" lim=");
1036    sb.append(limit());
1037    sb.append(" cap=");
1038    sb.append(capacity());
1039    sb.append("]");
1040    return sb.toString();
1041    }
1042
1043
1044
1045
1046    
1047
1048    /**
1049     * Returns the current hash code of this buffer.
1050     *
1051     * <p> The hash code of a byte buffer depends only upon its remaining
1052     * elements; that is, upon the elements from <tt>position()</tt> up to, and
1053     * including, the element at <tt>limit()</tt>&nbsp;-&nbsp;<tt>1</tt>.
1054     *
1055     * <p> Because buffer hash codes are content-dependent, it is inadvisable
1056     * to use buffers as keys in hash maps or similar data structures unless it
1057     * is known that their contents will not change. </p>
1058     *
1059     * @return The current hash code of this buffer
1060     */
1061    public int hashCode() {
1062    int h = 1;
1063    int p = position();
1064    for (int i = limit() - 1; i >= p; i--)
1065        h = 31 * h + (int)get(i);
1066    return h;
1067    }
1068
1069    /**
1070     * Tells whether or not this buffer is equal to another object.
1071     *
1072     * <p> Two byte buffers are equal if, and only if,
1073     *
1074     * <p><ol>
1075     *
1076     * <li><p> They have the same element type, </p></li>
1077     *
1078     * <li><p> They have the same number of remaining elements, and
1079     * </p></li>
1080     *
1081     * <li><p> The two sequences of remaining elements, considered
1082     * independently of their starting positions, are pointwise equal.
1083     * </p></li>
1084     *
1085     * </ol>
1086     *
1087     * <p> A byte buffer is not equal to any other type of object. </p>
1088     *
1089     * @param ob The object to which this buffer is to be compared
1090     *
1091     * @return <tt>true</tt> if, and only if, this buffer is equal to the
1092     * given object
1093     */
1094    public boolean equals(Object ob) {
1095    if (!(ob instanceof ByteBuffer ))
1096        return false;
1097    ByteBuffer that = (ByteBuffer )ob;
1098    if (this.remaining() != that.remaining())
1099        return false;
1100    int p = this.position();
1101    for (int i = this.limit() - 1, j = that.limit() - 1; i >= p; i--, j--) {
1102        byte v1 = this.get(i);
1103        byte v2 = that.get(j);
1104        if (v1 != v2) {
1105        if ((v1 != v1) && (v2 != v2)) // For float and double
1106 continue;
1107        return false;
1108        }
1109    }
1110    return true;
1111    }
1112
1113    /**
1114     * Compares this buffer to another.
1115     *
1116     * <p> Two byte buffers are compared by comparing their sequences of
1117     * remaining elements lexicographically, without regard to the starting
1118     * position of each sequence within its corresponding buffer.
1119     *
1120     * <p> A byte buffer is not comparable to any other type of object.
1121     *
1122     * @return A negative integer, zero, or a positive integer as this buffer
1123     * is less than, equal to, or greater than the given buffer
1124     */
1125    public int compareTo(ByteBuffer that) {
1126    int n = this.position() + Math.min(this.remaining(), that.remaining());
1127    for (int i = this.position(), j = that.position(); i < n; i++, j++) {
1128        byte v1 = this.get(i);
1129        byte v2 = that.get(j);
1130        if (v1 == v2)
1131        continue;
1132        if ((v1 != v1) && (v2 != v2)) // For float and double
1133 continue;
1134        if (v1 < v2)
1135        return -1;
1136        return +1;
1137    }
1138    return this.remaining() - that.remaining();
1139    }
1140
1141
1142
1143    // -- Other char stuff --
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