1 /*
2 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.io;
27
28
29 import java.util.Iterator;
30 import java.util.NoSuchElementException;
31 import java.util.Spliterator;
32 import java.util.Spliterators;
33 import java.util.stream.Stream;
34 import java.util.stream.StreamSupport;
35
36 /**
37 * Reads text from a character-input stream, buffering characters so as to
38 * provide for the efficient reading of characters, arrays, and lines.
39 *
40 * <p> The buffer size may be specified, or the default size may be used. The
41 * default is large enough for most purposes.
42 *
43 * <p> In general, each read request made of a Reader causes a corresponding
44 * read request to be made of the underlying character or byte stream. It is
45 * therefore advisable to wrap a BufferedReader around any Reader whose read()
46 * operations may be costly, such as FileReaders and InputStreamReaders. For
47 * example,
48 *
49 * <pre>
50 * BufferedReader in
51 * = new BufferedReader(new FileReader("foo.in"));
52 * </pre>
53 *
54 * will buffer the input from the specified file. Without buffering, each
55 * invocation of read() or readLine() could cause bytes to be read from the
56 * file, converted into characters, and then returned, which can be very
57 * inefficient.
58 *
59 * <p> Programs that use DataInputStreams for textual input can be localized by
60 * replacing each DataInputStream with an appropriate BufferedReader.
61 *
62 * @see FileReader
63 * @see InputStreamReader
64 * @see java.nio.file.Files#newBufferedReader
65 *
66 * @author Mark Reinhold
67 * @since JDK1.1
68 */
69
70 public class BufferedReader extends Reader {
71
72 private Reader in;
73
74 private char cb[];
75 private int nChars, nextChar;
76
77 private static final int INVALIDATED = -2;
78 private static final int UNMARKED = -1;
79 private int markedChar = UNMARKED;
80 private int readAheadLimit = 0; /* Valid only when markedChar > 0 */
81
82 /** If the next character is a line feed, skip it */
83 private boolean skipLF = false;
84
85 /** The skipLF flag when the mark was set */
86 private boolean markedSkipLF = false;
87
88 private static int defaultCharBufferSize = 8192;
89 private static int defaultExpectedLineLength = 80;
90
91 /**
92 * Creates a buffering character-input stream that uses an input buffer of
93 * the specified size.
94 *
95 * @param in A Reader
96 * @param sz Input-buffer size
97 *
98 * @exception IllegalArgumentException If {@code sz <= 0}
99 */
100 public BufferedReader(Reader in, int sz) {
101 super(in);
102 if (sz <= 0)
103 throw new IllegalArgumentException("Buffer size <= 0");
104 this.in = in;
105 cb = new char[sz];
106 nextChar = nChars = 0;
107 }
108
109 /**
110 * Creates a buffering character-input stream that uses a default-sized
111 * input buffer.
112 *
113 * @param in A Reader
114 */
115 public BufferedReader(Reader in) {
116 this(in, defaultCharBufferSize);
117 }
118
119 /** Checks to make sure that the stream has not been closed */
120 private void ensureOpen() throws IOException {
121 if (in == null)
122 throw new IOException("Stream closed");
123 }
124
125 /**
126 * Fills the input buffer, taking the mark into account if it is valid.
127 */
128 private void fill() throws IOException {
129 int dst;
130 if (markedChar <= UNMARKED) {
131 /* No mark */
132 dst = 0;
133 } else {
134 /* Marked */
135 int delta = nextChar - markedChar;
136 if (delta >= readAheadLimit) {
137 /* Gone past read-ahead limit: Invalidate mark */
138 markedChar = INVALIDATED;
139 readAheadLimit = 0;
140 dst = 0;
141 } else {
142 if (readAheadLimit <= cb.length) {
143 /* Shuffle in the current buffer */
144 System.arraycopy(cb, markedChar, cb, 0, delta);
145 markedChar = 0;
146 dst = delta;
147 } else {
148 /* Reallocate buffer to accommodate read-ahead limit */
149 char ncb[] = new char[readAheadLimit];
150 System.arraycopy(cb, markedChar, ncb, 0, delta);
151 cb = ncb;
152 markedChar = 0;
153 dst = delta;
154 }
155 nextChar = nChars = delta;
156 }
157 }
158
159 int n;
160 do {
161 n = in.read(cb, dst, cb.length - dst);
162 } while (n == 0);
163 if (n > 0) {
164 nChars = dst + n;
165 nextChar = dst;
166 }
167 }
168
169 /**
170 * Reads a single character.
171 *
172 * @return The character read, as an integer in the range
173 * 0 to 65535 (<tt>0x00-0xffff</tt>), or -1 if the
174 * end of the stream has been reached
175 * @exception IOException If an I/O error occurs
176 */
177 public int read() throws IOException {
178 synchronized (lock) {
179 ensureOpen();
180 for (;;) {
181 if (nextChar >= nChars) {
182 fill();
183 if (nextChar >= nChars)
184 return -1;
185 }
186 if (skipLF) {
187 skipLF = false;
188 if (cb[nextChar] == '\n') {
189 nextChar++;
190 continue;
191 }
192 }
193 return cb[nextChar++];
194 }
195 }
196 }
197
198 /**
199 * Reads characters into a portion of an array, reading from the underlying
200 * stream if necessary.
201 */
202 private int read1(char[] cbuf, int off, int len) throws IOException {
203 if (nextChar >= nChars) {
204 /* If the requested length is at least as large as the buffer, and
205 if there is no mark/reset activity, and if line feeds are not
206 being skipped, do not bother to copy the characters into the
207 local buffer. In this way buffered streams will cascade
208 harmlessly. */
209 if (len >= cb.length && markedChar <= UNMARKED && !skipLF) {
210 return in.read(cbuf, off, len);
211 }
212 fill();
213 }
214 if (nextChar >= nChars) return -1;
215 if (skipLF) {
216 skipLF = false;
217 if (cb[nextChar] == '\n') {
218 nextChar++;
219 if (nextChar >= nChars)
220 fill();
221 if (nextChar >= nChars)
222 return -1;
223 }
224 }
225 int n = Math.min(len, nChars - nextChar);
226 System.arraycopy(cb, nextChar, cbuf, off, n);
227 nextChar += n;
228 return n;
229 }
230
231 /**
232 * Reads characters into a portion of an array.
233 *
234 * <p> This method implements the general contract of the corresponding
235 * <code>{@link Reader#read(char[], int, int) read}</code> method of the
236 * <code>{@link Reader}</code> class. As an additional convenience, it
237 * attempts to read as many characters as possible by repeatedly invoking
238 * the <code>read</code> method of the underlying stream. This iterated
239 * <code>read</code> continues until one of the following conditions becomes
240 * true: <ul>
241 *
242 * <li> The specified number of characters have been read,
243 *
244 * <li> The <code>read</code> method of the underlying stream returns
245 * <code>-1</code>, indicating end-of-file, or
246 *
247 * <li> The <code>ready</code> method of the underlying stream
248 * returns <code>false</code>, indicating that further input requests
249 * would block.
250 *
251 * </ul> If the first <code>read</code> on the underlying stream returns
252 * <code>-1</code> to indicate end-of-file then this method returns
253 * <code>-1</code>. Otherwise this method returns the number of characters
254 * actually read.
255 *
256 * <p> Subclasses of this class are encouraged, but not required, to
257 * attempt to read as many characters as possible in the same fashion.
258 *
259 * <p> Ordinarily this method takes characters from this stream's character
260 * buffer, filling it from the underlying stream as necessary. If,
261 * however, the buffer is empty, the mark is not valid, and the requested
262 * length is at least as large as the buffer, then this method will read
263 * characters directly from the underlying stream into the given array.
264 * Thus redundant <code>BufferedReader</code>s will not copy data
265 * unnecessarily.
266 *
267 * @param cbuf Destination buffer
268 * @param off Offset at which to start storing characters
269 * @param len Maximum number of characters to read
270 *
271 * @return The number of characters read, or -1 if the end of the
272 * stream has been reached
273 *
274 * @exception IOException If an I/O error occurs
275 */
276 public int read(char cbuf[], int off, int len) throws IOException {
277 synchronized (lock) {
278 ensureOpen();
279 if ((off < 0) || (off > cbuf.length) || (len < 0) ||
280 ((off + len) > cbuf.length) || ((off + len) < 0)) {
281 throw new IndexOutOfBoundsException();
282 } else if (len == 0) {
283 return 0;
284 }
285
286 int n = read1(cbuf, off, len);
287 if (n <= 0) return n;
288 while ((n < len) && in.ready()) {
289 int n1 = read1(cbuf, off + n, len - n);
290 if (n1 <= 0) break;
291 n += n1;
292 }
293 return n;
294 }
295 }
296
297 /**
298 * Reads a line of text. A line is considered to be terminated by any one
299 * of a line feed ('\n'), a carriage return ('\r'), or a carriage return
300 * followed immediately by a linefeed.
301 *
302 * @param ignoreLF If true, the next '\n' will be skipped
303 *
304 * @return A String containing the contents of the line, not including
305 * any line-termination characters, or null if the end of the
306 * stream has been reached
307 *
308 * @see java.io.LineNumberReader#readLine()
309 *
310 * @exception IOException If an I/O error occurs
311 */
312 String readLine(boolean ignoreLF) throws IOException {
313 StringBuffer s = null;
314 int startChar;
315
316 synchronized (lock) {
317 ensureOpen();
318 boolean omitLF = ignoreLF || skipLF;
319
320 bufferLoop:
321 for (;;) {
322
323 if (nextChar >= nChars)
324 fill();
325 if (nextChar >= nChars) { /* EOF */
326 if (s != null && s.length() > 0)
327 return s.toString();
328 else
329 return null;
330 }
331 boolean eol = false;
332 char c = 0;
333 int i;
334
335 /* Skip a leftover '\n', if necessary */
336 if (omitLF && (cb[nextChar] == '\n'))
337 nextChar++;
338 skipLF = false;
339 omitLF = false;
340
341 charLoop:
342 for (i = nextChar; i < nChars; i++) {
343 c = cb[i];
344 if ((c == '\n') || (c == '\r')) {
345 eol = true;
346 break charLoop;
347 }
348 }
349
350 startChar = nextChar;
351 nextChar = i;
352
353 if (eol) {
354 String str;
355 if (s == null) {
356 str = new String(cb, startChar, i - startChar);
357 } else {
358 s.append(cb, startChar, i - startChar);
359 str = s.toString();
360 }
361 nextChar++;
362 if (c == '\r') {
363 skipLF = true;
364 }
365 return str;
366 }
367
368 if (s == null)
369 s = new StringBuffer(defaultExpectedLineLength);
370 s.append(cb, startChar, i - startChar);
371 }
372 }
373 }
374
375 /**
376 * Reads a line of text. A line is considered to be terminated by any one
377 * of a line feed ('\n'), a carriage return ('\r'), or a carriage return
378 * followed immediately by a linefeed.
379 *
380 * @return A String containing the contents of the line, not including
381 * any line-termination characters, or null if the end of the
382 * stream has been reached
383 *
384 * @exception IOException If an I/O error occurs
385 *
386 * @see java.nio.file.Files#readAllLines
387 */
388 public String readLine() throws IOException {
389 return readLine(false);
390 }
391
392 /**
393 * Skips characters.
394 *
395 * @param n The number of characters to skip
396 *
397 * @return The number of characters actually skipped
398 *
399 * @exception IllegalArgumentException If <code>n</code> is negative.
400 * @exception IOException If an I/O error occurs
401 */
402 public long skip(long n) throws IOException {
403 if (n < 0L) {
404 throw new IllegalArgumentException("skip value is negative");
405 }
406 synchronized (lock) {
407 ensureOpen();
408 long r = n;
409 while (r > 0) {
410 if (nextChar >= nChars)
411 fill();
412 if (nextChar >= nChars) /* EOF */
413 break;
414 if (skipLF) {
415 skipLF = false;
416 if (cb[nextChar] == '\n') {
417 nextChar++;
418 }
419 }
420 long d = nChars - nextChar;
421 if (r <= d) {
422 nextChar += r;
423 r = 0;
424 break;
425 }
426 else {
427 r -= d;
428 nextChar = nChars;
429 }
430 }
431 return n - r;
432 }
433 }
434
435 /**
436 * Tells whether this stream is ready to be read. A buffered character
437 * stream is ready if the buffer is not empty, or if the underlying
438 * character stream is ready.
439 *
440 * @exception IOException If an I/O error occurs
441 */
442 public boolean ready() throws IOException {
443 synchronized (lock) {
444 ensureOpen();
445
446 /*
447 * If newline needs to be skipped and the next char to be read
448 * is a newline character, then just skip it right away.
449 */
450 if (skipLF) {
451 /* Note that in.ready() will return true if and only if the next
452 * read on the stream will not block.
453 */
454 if (nextChar >= nChars && in.ready()) {
455 fill();
456 }
457 if (nextChar < nChars) {
458 if (cb[nextChar] == '\n')
459 nextChar++;
460 skipLF = false;
461 }
462 }
463 return (nextChar < nChars) || in.ready();
464 }
465 }
466
467 /**
468 * Tells whether this stream supports the mark() operation, which it does.
469 */
470 public boolean markSupported() {
471 return true;
472 }
473
474 /**
475 * Marks the present position in the stream. Subsequent calls to reset()
476 * will attempt to reposition the stream to this point.
477 *
478 * @param readAheadLimit Limit on the number of characters that may be
479 * read while still preserving the mark. An attempt
480 * to reset the stream after reading characters
481 * up to this limit or beyond may fail.
482 * A limit value larger than the size of the input
483 * buffer will cause a new buffer to be allocated
484 * whose size is no smaller than limit.
485 * Therefore large values should be used with care.
486 *
487 * @exception IllegalArgumentException If {@code readAheadLimit < 0}
488 * @exception IOException If an I/O error occurs
489 */
490 public void mark(int readAheadLimit) throws IOException {
491 if (readAheadLimit < 0) {
492 throw new IllegalArgumentException("Read-ahead limit < 0");
493 }
494 synchronized (lock) {
495 ensureOpen();
496 this.readAheadLimit = readAheadLimit;
497 markedChar = nextChar;
498 markedSkipLF = skipLF;
499 }
500 }
501
502 /**
503 * Resets the stream to the most recent mark.
504 *
505 * @exception IOException If the stream has never been marked,
506 * or if the mark has been invalidated
507 */
508 public void reset() throws IOException {
509 synchronized (lock) {
510 ensureOpen();
511 if (markedChar < 0)
512 throw new IOException((markedChar == INVALIDATED)
513 ? "Mark invalid"
514 : "Stream not marked");
515 nextChar = markedChar;
516 skipLF = markedSkipLF;
517 }
518 }
519
520 public void close() throws IOException {
521 synchronized (lock) {
522 if (in == null)
523 return;
524 try {
525 in.close();
526 } finally {
527 in = null;
528 cb = null;
529 }
530 }
531 }
532
533 /**
534 * Returns a {@code Stream}, the elements of which are lines read from
535 * this {@code BufferedReader}. The {@link Stream} is lazily populated,
536 * i.e., read only occurs during the
537 * <a href="../util/stream/package-summary.html#StreamOps">terminal
538 * stream operation</a>.
539 *
540 * <p> The reader must not be operated on during the execution of the
541 * terminal stream operation. Otherwise, the result of the terminal stream
542 * operation is undefined.
543 *
544 * <p> After execution of the terminal stream operation there are no
545 * guarantees that the reader will be at a specific position from which to
546 * read the next character or line.
547 *
548 * <p> If an {@link IOException} is thrown when accessing the underlying
549 * {@code BufferedReader}, it is wrapped in an {@link
550 * UncheckedIOException} which will be thrown from the {@code Stream}
551 * method that caused the read to take place. This method will return a
552 * Stream if invoked on a BufferedReader that is closed. Any operation on
553 * that stream that requires reading from the BufferedReader after it is
554 * closed, will cause an UncheckedIOException to be thrown.
555 *
556 * @return a {@code Stream<String>} providing the lines of text
557 * described by this {@code BufferedReader}
558 *
559 * @since 1.8
560 */
561 public Stream<String> lines() {
562 Iterator<String> iter = new Iterator<String>() {
563 String nextLine = null;
564
565 @Override
566 public boolean hasNext() {
567 if (nextLine != null) {
568 return true;
569 } else {
570 try {
571 nextLine = readLine();
572 return (nextLine != null);
573 } catch (IOException e) {
574 throw new UncheckedIOException(e);
575 }
576 }
577 }
578
579 @Override
580 public String next() {
581 if (nextLine != null || hasNext()) {
582 String line = nextLine;
583 nextLine = null;
584 return line;
585 } else {
586 throw new NoSuchElementException();
587 }
588 }
589 };
590 return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
591 iter, Spliterator.ORDERED | Spliterator.NONNULL), false);
592 }
593 }