/[classpath]/classpath/java/io/DataInputStream.java
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Revision 1.23 - (show annotations) (download)
Tue May 20 11:25:01 2003 UTC (20 years, 11 months ago) by mkoch
Branch: MAIN
CVS Tags: classpath-0_07-release, classpath-0_08-release, classpath-0_06-release
Changes since 1.22: +159 -128 lines
2003-05-20  Michael Koch  <konqueror@gmx.de>

	* java/io/DataInputStream.java:
	New version from libgcj.
	* java/io/PrintStream.java
	(error_occured): Inititialize with false.

1 /* DataInputStream.java -- FilteredInputStream that implements DataInput
2 Copyright (C) 1998, 1999, 2000, 2001, 2003 Free Software Foundation
3
4 This file is part of GNU Classpath.
5
6 GNU Classpath is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
9 any later version.
10
11 GNU Classpath is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GNU Classpath; see the file COPYING. If not, write to the
18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
19 02111-1307 USA.
20
21 Linking this library statically or dynamically with other modules is
22 making a combined work based on this library. Thus, the terms and
23 conditions of the GNU General Public License cover the whole
24 combination.
25
26 As a special exception, the copyright holders of this library give you
27 permission to link this library with independent modules to produce an
28 executable, regardless of the license terms of these independent
29 modules, and to copy and distribute the resulting executable under
30 terms of your choice, provided that you also meet, for each linked
31 independent module, the terms and conditions of the license of that
32 module. An independent module is a module which is not derived from
33 or based on this library. If you modify this library, you may extend
34 this exception to your version of the library, but you are not
35 obligated to do so. If you do not wish to do so, delete this
36 exception statement from your version. */
37
38 package java.io;
39
40 /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
41 * "The Java Language Specification", ISBN 0-201-63451-1
42 * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
43 * Status: Believed complete and correct.
44 */
45
46 /**
47 * This subclass of <code>FilteredInputStream</code> implements the
48 * <code>DataInput</code> interface that provides method for reading primitive
49 * Java data types from a stream.
50 *
51 * @see DataInput
52 *
53 * @author Warren Levy <warrenl@cygnus.com>
54 * @author Aaron M. Renn <arenn@urbanophile.com>
55 * @date October 20, 1998.
56 */
57 public class DataInputStream extends FilterInputStream implements DataInput
58 {
59 // readLine() hack to ensure that an '\r' not followed by an '\n' is
60 // handled correctly. If set, readLine() will ignore the first char it sees
61 // if that char is a '\n'
62 boolean ignoreInitialNewline = false;
63
64 // Byte buffer, used to make primitive read calls more efficient.
65 byte[] buf = new byte [8];
66
67 /**
68 * This constructor initializes a new <code>DataInputStream</code>
69 * to read from the specified subordinate stream.
70 *
71 * @param in The subordinate <code>InputStream</code> to read from
72 */
73 public DataInputStream (InputStream in)
74 {
75 super (in);
76 }
77
78 /**
79 * This method reads bytes from the underlying stream into the specified
80 * byte array buffer. It will attempt to fill the buffer completely, but
81 * may return a short count if there is insufficient data remaining to be
82 * read to fill the buffer.
83 *
84 * @param b The buffer into which bytes will be read.
85 *
86 * @return The actual number of bytes read, or -1 if end of stream reached
87 * before reading any bytes.
88 *
89 * @exception IOException If an error occurs.
90 */
91 public final int read (byte[] b) throws IOException
92 {
93 return in.read (b, 0, b.length);
94 }
95
96 /**
97 * This method reads bytes from the underlying stream into the specified
98 * byte array buffer. It will attempt to read <code>len</code> bytes and
99 * will start storing them at position <code>off</code> into the buffer.
100 * This method can return a short count if there is insufficient data
101 * remaining to be read to complete the desired read length.
102 *
103 * @param b The buffer into which bytes will be read.
104 * @param off The offset into the buffer to start storing bytes.
105 * @param len The requested number of bytes to read.
106 *
107 * @return The actual number of bytes read, or -1 if end of stream reached
108 * before reading any bytes.
109 *
110 * @exception IOException If an error occurs.
111 */
112 public final int read (byte[] b, int off, int len) throws IOException
113 {
114 return in.read (b, off, len);
115 }
116
117 /**
118 * This method reads a Java boolean value from an input stream. It does
119 * so by reading a single byte of data. If that byte is zero, then the
120 * value returned is <code>false</code>. If the byte is non-zero, then
121 * the value returned is <code>true</code>.
122 * <p>
123 * This method can read a <code>boolean</code> written by an object
124 * implementing the <code>writeBoolean()</code> method in the
125 * <code>DataOutput</code> interface.
126 *
127 * @return The <code>boolean</code> value read
128 *
129 * @exception EOFException If end of file is reached before reading
130 * the boolean
131 * @exception IOException If any other error occurs
132 *
133 * @see DataOutput#writeBoolean
134 */
135 public final boolean readBoolean () throws IOException
136 {
137 return convertToBoolean (in.read ());
138 }
139
140 /**
141 * This method reads a Java byte value from an input stream. The value
142 * is in the range of -128 to 127.
143 * <p>
144 * This method can read a <code>byte</code> written by an object
145 * implementing the <code>writeByte()</code> method in the
146 * <code>DataOutput</code> interface.
147 *
148 * @return The <code>byte</code> value read
149 *
150 * @exception EOFException If end of file is reached before reading the byte
151 * @exception IOException If any other error occurs
152 *
153 * @see DataOutput#writeByte
154 */
155 public final byte readByte () throws IOException
156 {
157 return convertToByte (in.read ());
158 }
159
160 /**
161 * This method reads a Java <code>char</code> value from an input stream.
162 * It operates by reading two bytes from the stream and converting them to
163 * a single 16-bit Java <code>char</code>. The two bytes are stored most
164 * significant byte first (i.e., "big endian") regardless of the native
165 * host byte ordering.
166 * <p>
167 * As an example, if <code>byte1</code> and <code>byte2</code>
168 * represent the first and second byte read from the stream
169 * respectively, they will be transformed to a <code>char</code> in
170 * the following manner:
171 * <p>
172 * <code>(char)(((byte1 &amp; 0xFF) &lt;&lt; 8) | (byte2 &amp; 0xFF)</code>
173 * <p>
174 * This method can read a <code>char</code> written by an object
175 * implementing the <code>writeChar()</code> method in the
176 * <code>DataOutput</code> interface.
177 *
178 * @return The <code>char</code> value read
179 *
180 * @exception EOFException If end of file is reached before reading the char
181 * @exception IOException If any other error occurs
182 *
183 * @see DataOutput#writeChar
184 */
185 public final char readChar () throws IOException
186 {
187 readFully (buf, 0, 2);
188 return convertToChar (buf);
189 }
190
191 /**
192 * This method reads a Java double value from an input stream. It operates
193 * by first reading a <code>long</code> value from the stream by calling the
194 * <code>readLong()</code> method in this interface, then converts
195 * that <code>long</code> to a <code>double</code> using the
196 * <code>longBitsToDouble</code> method in the class
197 * <code>java.lang.Double</code>
198 * <p>
199 * This method can read a <code>double</code> written by an object
200 * implementing the <code>writeDouble()</code> method in the
201 * <code>DataOutput</code> interface.
202 *
203 * @return The <code>double</code> value read
204 *
205 * @exception EOFException If end of file is reached before reading
206 * the double
207 * @exception IOException If any other error occurs
208 *
209 * @see DataOutput#writeDouble
210 * @see java.lang.Double#longBitsToDouble
211 */
212 public final double readDouble () throws IOException
213 {
214 return Double.longBitsToDouble (readLong ());
215 }
216
217 /**
218 * This method reads a Java float value from an input stream. It
219 * operates by first reading an <code>int</code> value from the
220 * stream by calling the <code>readInt()</code> method in this
221 * interface, then converts that <code>int</code> to a
222 * <code>float</code> using the <code>intBitsToFloat</code> method
223 * in the class <code>java.lang.Float</code>
224 * <p>
225 * This method can read a <code>float</code> written by an object
226 * implementing the <code>writeFloat()</code> method in the
227 * <code>DataOutput</code> interface.
228 *
229 * @return The <code>float</code> value read
230 *
231 * @exception EOFException If end of file is reached before reading the float
232 * @exception IOException If any other error occurs
233 *
234 * @see DataOutput#writeFloat
235 * @see java.lang.Float#intBitsToFloat
236 */
237 public final float readFloat () throws IOException
238 {
239 return Float.intBitsToFloat (readInt ());
240 }
241
242 /**
243 * This method reads raw bytes into the passed array until the array is
244 * full. Note that this method blocks until the data is available and
245 * throws an exception if there is not enough data left in the stream to
246 * fill the buffer. Note also that zero length buffers are permitted.
247 * In this case, the method will return immediately without reading any
248 * bytes from the stream.
249 *
250 * @param b The buffer into which to read the data
251 *
252 * @exception EOFException If end of file is reached before filling the
253 * buffer
254 * @exception IOException If any other error occurs
255 */
256 public final void readFully (byte[] b) throws IOException
257 {
258 readFully (b, 0, b.length);
259 }
260
261 /**
262 * This method reads raw bytes into the passed array <code>buf</code>
263 * starting
264 * <code>offset</code> bytes into the buffer. The number of bytes read
265 * will be
266 * exactly <code>len</code>. Note that this method blocks until the data is
267 * available and throws an exception if there is not enough data left in
268 * the stream to read <code>len</code> bytes. Note also that zero length
269 * buffers are permitted. In this case, the method will return immediately
270 * without reading any bytes from the stream.
271 *
272 * @param buf The buffer into which to read the data
273 * @param offset The offset into the buffer to start storing data
274 * @param len The number of bytes to read into the buffer
275 *
276 * @exception EOFException If end of file is reached before filling the
277 * buffer
278 * @exception IOException If any other error occurs
279 */
280 public final void readFully (byte[] b, int off, int len) throws IOException
281 {
282 while (len > 0)
283 {
284 // in.read will block until some data is available.
285 int numread = in.read (b, off, len);
286 if (numread < 0)
287 throw new EOFException ();
288 len -= numread;
289 off += numread;
290 }
291 }
292
293 /**
294 * This method reads a Java <code>int</code> value from an input stream
295 * It operates by reading four bytes from the stream and converting them to
296 * a single Java <code>int</code>. The bytes are stored most
297 * significant byte first (i.e., "big endian") regardless of the native
298 * host byte ordering.
299 * <p>
300 * As an example, if <code>byte1</code> through <code>byte4</code> represent
301 * the first four bytes read from the stream, they will be
302 * transformed to an <code>int</code> in the following manner:
303 * <p>
304 * <code>(int)(((byte1 &amp; 0xFF) &lt;&lt; 24) + ((byte2 &amp; 0xFF) &lt;&lt; 16) +
305 * ((byte3 &amp; 0xFF)&lt;&lt; 8) + (byte4 &amp; 0xFF)))</code>
306 * <p>
307 * The value returned is in the range of -2147483648 to 2147483647.
308 * <p>
309 * This method can read an <code>int</code> written by an object
310 * implementing the <code>writeInt()</code> method in the
311 * <code>DataOutput</code> interface.
312 *
313 * @return The <code>int</code> value read
314 *
315 * @exception EOFException If end of file is reached before reading the int
316 * @exception IOException If any other error occurs
317 *
318 * @see DataOutput#writeInt
319 */
320 public final int readInt () throws IOException
321 {
322 readFully (buf, 0, 4);
323 return convertToInt (buf);
324 }
325
326 /**
327 * This method reads the next line of text data from an input
328 * stream. It operates by reading bytes and converting those bytes
329 * to <code>char</code> values by treating the byte read as the low
330 * eight bits of the <code>char</code> and using 0 as the high eight
331 * bits. Because of this, it does not support the full 16-bit
332 * Unicode character set.
333 * <p>
334 * The reading of bytes ends when either the end of file or a line
335 * terminator is encountered. The bytes read are then returned as a
336 * <code>String</code> A line terminator is a byte sequence
337 * consisting of either <code>\r</code>, <code>\n</code> or
338 * <code>\r\n</code>. These termination charaters are discarded and
339 * are not returned as part of the string.
340 * <p>
341 * This method can read data that was written by an object implementing the
342 * <code>writeLine()</code> method in <code>DataOutput</code>.
343 *
344 * @return The line read as a <code>String</code>
345 *
346 * @exception IOException If an error occurs
347 *
348 * @see DataOutput
349 *
350 * @deprecated
351 */
352 public final String readLine () throws IOException
353 {
354 StringBuffer strb = new StringBuffer ();
355
356 readloop: while (true)
357 {
358 int c = 0;
359 char ch = ' ';
360 boolean getnext = true;
361 while (getnext)
362 {
363 getnext = false;
364 c = in.read();
365 if (c < 0) // got an EOF
366 return strb.length () > 0 ? strb.toString () : null;
367 ch = (char) c;
368 if ((ch &= 0xFF) == '\n')
369 // hack to correctly handle '\r\n' sequences
370 if (ignoreInitialNewline)
371 {
372 ignoreInitialNewline = false;
373 getnext = true;
374 }
375 else
376 break readloop;
377 }
378
379 if (ch == '\r')
380 {
381 // FIXME: The following code tries to adjust the stream back one
382 // character if the next char read is '\n'. As a last resort,
383 // it tries to mark the position before reading but the bottom
384 // line is that it is possible that this method will not properly
385 // deal with a '\r' '\n' combination thus not fulfilling the
386 // DataInput contract for readLine. It's not a particularly
387 // safe approach threadwise since it is unsynchronized and
388 // since it might mark an input stream behind the users back.
389 // Along the same vein it could try the same thing for
390 // ByteArrayInputStream and PushbackInputStream, but that is
391 // probably overkill since this is deprecated & BufferedInputStream
392 // is the most likely type of input stream.
393 //
394 // The alternative is to somehow push back the next byte if it
395 // isn't a '\n' or to have the reading methods of this class
396 // keep track of whether the last byte read was '\r' by readLine
397 // and then skip the very next byte if it is '\n'. Either way,
398 // this would increase the complexity of the non-deprecated methods
399 // and since it is undesirable to make non-deprecated methods
400 // less efficient, the following seems like the most reasonable
401 // approach.
402 int next_c = 0;
403 char next_ch = ' ';
404 if (in instanceof BufferedInputStream)
405 {
406 next_c = in.read();
407 next_ch = (char) (next_c & 0xFF);
408 if ((next_ch != '\n') && (next_c >= 0))
409 {
410 BufferedInputStream bin = (BufferedInputStream) in;
411 if (bin.pos > 0)
412 bin.pos--;
413 }
414 }
415 else if (markSupported())
416 {
417 next_c = in.read();
418 next_ch = (char) (next_c & 0xFF);
419 if ((next_ch != '\n') && (next_c >= 0))
420 {
421 mark(1);
422 if ((in.read() & 0xFF) != '\n')
423 reset();
424 }
425 }
426 // In order to catch cases where 'in' isn't a BufferedInputStream
427 // and doesn't support mark() (such as reading from a Socket), set
428 // a flag that instructs readLine() to ignore the first character
429 // it sees _if_ that character is a '\n'.
430 else ignoreInitialNewline = true;
431 break;
432 }
433 strb.append(ch);
434 }
435
436 return strb.length() > 0 ? strb.toString() : "";
437 }
438
439 /**
440 * This method reads a Java <code>long</code> value from an input stream
441 * It operates by reading eight bytes from the stream and converting them to
442 * a single Java <code>long</code>. The bytes are stored most
443 * significant byte first (i.e., "big endian") regardless of the native
444 * host byte ordering.
445 * <p>
446 * As an example, if <code>byte1</code> through <code>byte8</code> represent
447 * the first eight bytes read from the stream, they will be
448 * transformed to an <code>long</code> in the following manner:
449 * <p>
450 * <code>(long)(((byte1 &amp; 0xFF) &lt;&lt; 56) + ((byte2 &amp; 0xFF) &lt;&lt; 48) +
451 * ((byte3 &amp; 0xFF) &lt;&lt; 40) + ((byte4 &amp; 0xFF) &lt;&lt; 32) +
452 * ((byte5 &amp; 0xFF) &lt;&lt; 24) + ((byte6 &amp; 0xFF) &lt;&lt; 16) +
453 * ((byte7 &amp; 0xFF) &lt;&lt; 8) + (byte8 &amp; 0xFF)))
454 * </code>
455 * <p>
456 * The value returned is in the range of -9223372036854775808 to
457 * 9223372036854775807.
458 * <p>
459 * This method can read an <code>long</code> written by an object
460 * implementing the <code>writeLong()</code> method in the
461 * <code>DataOutput</code> interface.
462 *
463 * @return The <code>long</code> value read
464 *
465 * @exception EOFException If end of file is reached before reading the long
466 * @exception IOException If any other error occurs
467 *
468 * @see DataOutput#writeLong
469 */
470 public final long readLong () throws IOException
471 {
472 readFully (buf, 0, 8);
473 return convertToLong (buf);
474 }
475
476 /**
477 * This method reads a signed 16-bit value into a Java in from the
478 * stream. It operates by reading two bytes from the stream and
479 * converting them to a single 16-bit Java <code>short</code>. The
480 * two bytes are stored most significant byte first (i.e., "big
481 * endian") regardless of the native host byte ordering.
482 * <p>
483 * As an example, if <code>byte1</code> and <code>byte2</code>
484 * represent the first and second byte read from the stream
485 * respectively, they will be transformed to a <code>short</code>. in
486 * the following manner:
487 * <p>
488 * <code>(short)(((byte1 &amp; 0xFF) &lt;&lt; 8) | (byte2 &amp; 0xFF))</code>
489 * <p>
490 * The value returned is in the range of -32768 to 32767.
491 * <p>
492 * This method can read a <code>short</code> written by an object
493 * implementing the <code>writeShort()</code> method in the
494 * <code>DataOutput</code> interface.
495 *
496 * @return The <code>short</code> value read
497 *
498 * @exception EOFException If end of file is reached before reading the value
499 * @exception IOException If any other error occurs
500 *
501 * @see DataOutput#writeShort
502 */
503 public final short readShort () throws IOException
504 {
505 readFully (buf, 0, 2);
506 return convertToShort (buf);
507 }
508
509 /**
510 * This method reads 8 unsigned bits into a Java <code>int</code>
511 * value from the stream. The value returned is in the range of 0 to
512 * 255.
513 * <p>
514 * This method can read an unsigned byte written by an object
515 * implementing the <code>writeUnsignedByte()</code> method in the
516 * <code>DataOutput</code> interface.
517 *
518 * @return The unsigned bytes value read as a Java <code>int</code>.
519 *
520 * @exception EOFException If end of file is reached before reading the value
521 * @exception IOException If any other error occurs
522 *
523 * @see DataOutput#writeByte
524 */
525 public final int readUnsignedByte () throws IOException
526 {
527 return convertToUnsignedByte (in.read ());
528 }
529
530 /**
531 * This method reads 16 unsigned bits into a Java int value from the stream.
532 * It operates by reading two bytes from the stream and converting them to
533 * a single Java <code>int</code> The two bytes are stored most
534 * significant byte first (i.e., "big endian") regardless of the native
535 * host byte ordering.
536 * <p>
537 * As an example, if <code>byte1</code> and <code>byte2</code>
538 * represent the first and second byte read from the stream
539 * respectively, they will be transformed to an <code>int</code> in
540 * the following manner:
541 * <p>
542 * <code>(int)(((byte1 &amp; 0xFF) &lt;&lt; 8) + (byte2 &amp; 0xFF))</code>
543 * <p>
544 * The value returned is in the range of 0 to 65535.
545 * <p>
546 * This method can read an unsigned short written by an object
547 * implementing the <code>writeUnsignedShort()</code> method in the
548 * <code>DataOutput</code> interface.
549 *
550 * @return The unsigned short value read as a Java <code>int</code>
551 *
552 * @exception EOFException If end of file is reached before reading the value
553 * @exception IOException If any other error occurs
554 *
555 * @see DataOutput#writeShort
556 */
557 public final int readUnsignedShort () throws IOException
558 {
559 readFully (buf, 0, 2);
560 return convertToUnsignedShort (buf);
561 }
562
563 /**
564 * This method reads a <code>String</code> from an input stream that
565 * is encoded in a modified UTF-8 format. This format has a leading
566 * two byte sequence that contains the remaining number of bytes to
567 * read. This two byte sequence is read using the
568 * <code>readUnsignedShort()</code> method of this interface.
569 * <p>
570 * After the number of remaining bytes have been determined, these
571 * bytes are read an transformed into <code>char</code> values.
572 * These <code>char</code> values are encoded in the stream using
573 * either a one, two, or three byte format. The particular format
574 * in use can be determined by examining the first byte read.
575 * <p>
576 * If the first byte has a high order bit of 0, then that character
577 * consists on only one byte. This character value consists of
578 * seven bits that are at positions 0 through 6 of the byte. As an
579 * example, if <code>byte1</code> is the byte read from the stream,
580 * it would be converted to a <code>char</code> like so:
581 * <p>
582 * <code>(char)byte1</code>
583 * <p>
584 * If the first byte has 110 as its high order bits, then the
585 * character consists of two bytes. The bits that make up the character
586 * value are in positions 0 through 4 of the first byte and bit positions
587 * 0 through 5 of the second byte. (The second byte should have
588 * 10 as its high order bits). These values are in most significant
589 * byte first (i.e., "big endian") order.
590 * <p>
591 * As an example, if <code>byte1</code> and <code>byte2</code> are
592 * the first two bytes read respectively, and the high order bits of
593 * them match the patterns which indicate a two byte character
594 * encoding, then they would be converted to a Java
595 * <code>char</code> like so:
596 * <p>
597 * <code>(char)(((byte1 & 0x1F) << 6) | (byte2 & 0x3F))</code>
598 * <p>
599 * If the first byte has a 1110 as its high order bits, then the
600 * character consists of three bytes. The bits that make up the character
601 * value are in positions 0 through 3 of the first byte and bit positions
602 * 0 through 5 of the other two bytes. (The second and third bytes should
603 * have 10 as their high order bits). These values are in most
604 * significant byte first (i.e., "big endian") order.
605 * <p>
606 * As an example, if <code>byte1</code> <code>byte2</code> and
607 * <code>byte3</code> are the three bytes read, and the high order
608 * bits of them match the patterns which indicate a three byte
609 * character encoding, then they would be converted to a Java
610 * <code>char</code> like so:
611 * <p>
612 * <code>(char)(((byte1 & 0x0F) << 12) | ((byte2 & 0x3F) << 6) |
613 * (byte3 & 0x3F))</code>
614 * <p>
615 * Note that all characters are encoded in the method that requires
616 * the fewest number of bytes with the exception of the character
617 * with the value of <code>&#92;u0000</code> which is encoded as two
618 * bytes. This is a modification of the UTF standard used to
619 * prevent C language style <code>NUL</code> values from appearing
620 * in the byte stream.
621 * <p>
622 * This method can read data that was written by an object implementing the
623 * <code>writeUTF()</code> method in <code>DataOutput</code>
624 *
625 * @return The <code>String</code> read
626 *
627 * @exception EOFException If end of file is reached before reading
628 * the String
629 * @exception UTFDataFormatException If the data is not in UTF-8 format
630 * @exception IOException If any other error occurs
631 *
632 * @see DataOutput#writeUTF
633 */
634 public final String readUTF () throws IOException
635 {
636 return readUTF (this);
637 }
638
639 /**
640 * This method reads a String encoded in UTF-8 format from the
641 * specified <code>DataInput</code> source.
642 *
643 * @param in The <code>DataInput</code> source to read from
644 *
645 * @return The String read from the source
646 *
647 * @exception IOException If an error occurs
648 *
649 * @see DataInput#readUTF
650 */
651 public final static String readUTF (DataInput in) throws IOException
652 {
653 final int UTFlen = in.readUnsignedShort ();
654 byte[] buf = new byte [UTFlen];
655
656 // This blocks until the entire string is available rather than
657 // doing partial processing on the bytes that are available and then
658 // blocking. An advantage of the latter is that Exceptions
659 // could be thrown earlier. The former is a bit cleaner.
660 in.readFully (buf, 0, UTFlen);
661
662 return convertFromUTF (buf);
663 }
664
665 /**
666 * This method attempts to skip and discard the specified number of bytes
667 * in the input stream. It may actually skip fewer bytes than requested.
668 * This method will not skip any bytes if passed a negative number of bytes
669 * to skip.
670 *
671 * @param n The requested number of bytes to skip.
672 *
673 * @return The requested number of bytes to skip.
674 *
675 * @exception IOException If an error occurs.
676 * @specnote The JDK docs claim that this returns the number of bytes
677 * actually skipped. The JCL claims that this method can throw an
678 * EOFException. Neither of these appear to be true in the JDK 1.3's
679 * implementation. This tries to implement the actual JDK behaviour.
680 */
681 public final int skipBytes (int n) throws IOException
682 {
683 if (n <= 0)
684 return 0;
685 try
686 {
687 return (int) in.skip (n);
688 }
689 catch (EOFException x)
690 {
691 // do nothing.
692 }
693 return n;
694 }
695
696 static boolean convertToBoolean (int b) throws EOFException
697 {
698 if (b < 0)
699 throw new EOFException ();
700
701 return (b != 0);
702 }
703
704 static byte convertToByte (int i) throws EOFException
705 {
706 if (i < 0)
707 throw new EOFException ();
708
709 return (byte) i;
710 }
711
712 static int convertToUnsignedByte (int i) throws EOFException
713 {
714 if (i < 0)
715 throw new EOFException ();
716
717 return (i & 0xFF);
718 }
719
720 static char convertToChar (byte[] buf)
721 {
722 return (char) ((buf [0] << 8)
723 | (buf [1] & 0xff));
724 }
725
726 static short convertToShort (byte[] buf)
727 {
728 return (short) ((buf [0] << 8)
729 | (buf [1] & 0xff));
730 }
731
732 static int convertToUnsignedShort (byte[] buf)
733 {
734 return (((buf [0] & 0xff) << 8)
735 | (buf [1] & 0xff));
736 }
737
738 static int convertToInt (byte[] buf)
739 {
740 return (((buf [0] & 0xff) << 24)
741 | ((buf [1] & 0xff) << 16)
742 | ((buf [2] & 0xff) << 8)
743 | (buf [3] & 0xff));
744 }
745
746 static long convertToLong (byte[] buf)
747 {
748 return (((long)(buf [0] & 0xff) << 56) |
749 ((long)(buf [1] & 0xff) << 48) |
750 ((long)(buf [2] & 0xff) << 40) |
751 ((long)(buf [3] & 0xff) << 32) |
752 ((long)(buf [4] & 0xff) << 24) |
753 ((long)(buf [5] & 0xff) << 16) |
754 ((long)(buf [6] & 0xff) << 8) |
755 ((long)(buf [7] & 0xff)));
756 }
757
758 // FIXME: This method should be re-thought. I suspect we have multiple
759 // UTF-8 decoders floating around. We should use the standard charset
760 // converters, maybe and adding a direct call into one of the new
761 // NIO converters for a super-fast UTF8 decode.
762 static String convertFromUTF (byte[] buf)
763 throws EOFException, UTFDataFormatException
764 {
765 // Give StringBuffer an initial estimated size to avoid
766 // enlarge buffer frequently
767 StringBuffer strbuf = new StringBuffer (buf.length / 2 + 2);
768
769 for (int i = 0; i < buf.length; )
770 {
771 if ((buf [i] & 0x80) == 0) // bit pattern 0xxxxxxx
772 strbuf.append ((char) (buf [i++] & 0xFF));
773 else if ((buf [i] & 0xE0) == 0xC0) // bit pattern 110xxxxx
774 {
775 if (i + 1 >= buf.length
776 || (buf [i + 1] & 0xC0) != 0x80)
777 throw new UTFDataFormatException ();
778
779 strbuf.append((char) (((buf [i++] & 0x1F) << 6)
780 | (buf [i++] & 0x3F)));
781 }
782 else if ((buf [i] & 0xF0) == 0xE0) // bit pattern 1110xxxx
783 {
784 if (i + 2 >= buf.length
785 || (buf [i + 1] & 0xC0) != 0x80
786 || (buf [i + 2] & 0xC0) != 0x80)
787 throw new UTFDataFormatException ();
788
789 strbuf.append ((char) (((buf [i++] & 0x0F) << 12)
790 | ((buf [i++] & 0x3F) << 6)
791 | (buf [i++] & 0x3F)));
792 }
793 else // must be ((buf [i] & 0xF0) == 0xF0 || (buf [i] & 0xC0) == 0x80)
794 throw new UTFDataFormatException (); // bit patterns 1111xxxx or
795 // 10xxxxxx
796 }
797
798 return strbuf.toString ();
799 }
800 }

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