1 /*
2 * Copyright (c) 1996, 2019, 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 1.1
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 * @throws 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 ({@code 0x00-0xffff}), or -1 if the
174 * end of the stream has been reached
175 * @throws 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} method of the underlying stream. This iterated
239 * {@code read} 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} method of the underlying stream returns
245 * {@code -1}, indicating end-of-file, or
246 *
247 * <li> The {@code ready} method of the underlying stream
248 * returns {@code false}, indicating that further input requests
249 * would block.
250 *
251 * </ul> If the first {@code read} on the underlying stream returns
252 * {@code -1} to indicate end-of-file then this method returns
253 * {@code -1}. 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}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 * @throws IOException If an I/O error occurs
275 * @throws IndexOutOfBoundsException {@inheritDoc}
276 */
277 public int read(char cbuf[], int off, int len) throws IOException {
278 synchronized (lock) {
279 ensureOpen();
280 if ((off < 0) || (off > cbuf.length) || (len < 0) ||
281 ((off + len) > cbuf.length) || ((off + len) < 0)) {
282 throw new IndexOutOfBoundsException();
283 } else if (len == 0) {
284 return 0;
285 }
286
287 int n = read1(cbuf, off, len);
288 if (n <= 0) return n;
289 while ((n < len) && in.ready()) {
290 int n1 = read1(cbuf, off + n, len - n);
291 if (n1 <= 0) break;
292 n += n1;
293 }
294 return n;
295 }
296 }
297
298 /**
299 * Reads a line of text. A line is considered to be terminated by any one
300 * of a line feed ('\n'), a carriage return ('\r'), a carriage return
301 * followed immediately by a line feed, or by reaching the end-of-file
302 * (EOF).
303 *
304 * @param ignoreLF If true, the next '\n' will be skipped
305 *
306 * @return A String containing the contents of the line, not including
307 * any line-termination characters, or null if the end of the
308 * stream has been reached without reading any characters
309 *
310 * @see java.io.LineNumberReader#readLine()
311 *
312 * @throws IOException If an I/O error occurs
313 */
314 String readLine(boolean ignoreLF) throws IOException {
315 StringBuilder s = null;
316 int startChar;
317
318 synchronized (lock) {
319 ensureOpen();
320 boolean omitLF = ignoreLF || skipLF;
321
322 bufferLoop:
323 for (;;) {
324
325 if (nextChar >= nChars)
326 fill();
327 if (nextChar >= nChars) { /* EOF */
328 if (s != null && s.length() > 0)
329 return s.toString();
330 else
331 return null;
332 }
333 boolean eol = false;
334 char c = 0;
335 int i;
336
337 /* Skip a leftover '\n', if necessary */
338 if (omitLF && (cb[nextChar] == '\n'))
339 nextChar++;
340 skipLF = false;
341 omitLF = false;
342
343 charLoop:
344 for (i = nextChar; i < nChars; i++) {
345 c = cb[i];
346 if ((c == '\n') || (c == '\r')) {
347 eol = true;
348 break charLoop;
349 }
350 }
351
352 startChar = nextChar;
353 nextChar = i;
354
355 if (eol) {
356 String str;
357 if (s == null) {
358 str = new String(cb, startChar, i - startChar);
359 } else {
360 s.append(cb, startChar, i - startChar);
361 str = s.toString();
362 }
363 nextChar++;
364 if (c == '\r') {
365 skipLF = true;
366 }
367 return str;
368 }
369
370 if (s == null)
371 s = new StringBuilder(defaultExpectedLineLength);
372 s.append(cb, startChar, i - startChar);
373 }
374 }
375 }
376
377 /**
378 * Reads a line of text. A line is considered to be terminated by any one
379 * of a line feed ('\n'), a carriage return ('\r'), a carriage return
380 * followed immediately by a line feed, or by reaching the end-of-file
381 * (EOF).
382 *
383 * @return A String containing the contents of the line, not including
384 * any line-termination characters, or null if the end of the
385 * stream has been reached without reading any characters
386 *
387 * @throws IOException If an I/O error occurs
388 *
389 * @see java.nio.file.Files#readAllLines
390 */
391 public String readLine() throws IOException {
392 return readLine(false);
393 }
394
395 /**
396 * Skips characters.
397 *
398 * @param n The number of characters to skip
399 *
400 * @return The number of characters actually skipped
401 *
402 * @throws IllegalArgumentException If {@code n} is negative.
403 * @throws IOException If an I/O error occurs
404 */
405 public long skip(long n) throws IOException {
406 if (n < 0L) {
407 throw new IllegalArgumentException("skip value is negative");
408 }
409 synchronized (lock) {
410 ensureOpen();
411 long r = n;
412 while (r > 0) {
413 if (nextChar >= nChars)
414 fill();
415 if (nextChar >= nChars) /* EOF */
416 break;
417 if (skipLF) {
418 skipLF = false;
419 if (cb[nextChar] == '\n') {
420 nextChar++;
421 }
422 }
423 long d = nChars - nextChar;
424 if (r <= d) {
425 nextChar += r;
426 r = 0;
427 break;
428 }
429 else {
430 r -= d;
431 nextChar = nChars;
432 }
433 }
434 return n - r;
435 }
436 }
437
438 /**
439 * Tells whether this stream is ready to be read. A buffered character
440 * stream is ready if the buffer is not empty, or if the underlying
441 * character stream is ready.
442 *
443 * @throws IOException If an I/O error occurs
444 */
445 public boolean ready() throws IOException {
446 synchronized (lock) {
447 ensureOpen();
448
449 /*
450 * If newline needs to be skipped and the next char to be read
451 * is a newline character, then just skip it right away.
452 */
453 if (skipLF) {
454 /* Note that in.ready() will return true if and only if the next
455 * read on the stream will not block.
456 */
457 if (nextChar >= nChars && in.ready()) {
458 fill();
459 }
460 if (nextChar < nChars) {
461 if (cb[nextChar] == '\n')
462 nextChar++;
463 skipLF = false;
464 }
465 }
466 return (nextChar < nChars) || in.ready();
467 }
468 }
469
470 /**
471 * Tells whether this stream supports the mark() operation, which it does.
472 */
473 public boolean markSupported() {
474 return true;
475 }
476
477 /**
478 * Marks the present position in the stream. Subsequent calls to reset()
479 * will attempt to reposition the stream to this point.
480 *
481 * @param readAheadLimit Limit on the number of characters that may be
482 * read while still preserving the mark. An attempt
483 * to reset the stream after reading characters
484 * up to this limit or beyond may fail.
485 * A limit value larger than the size of the input
486 * buffer will cause a new buffer to be allocated
487 * whose size is no smaller than limit.
488 * Therefore large values should be used with care.
489 *
490 * @throws IllegalArgumentException If {@code readAheadLimit < 0}
491 * @throws IOException If an I/O error occurs
492 */
493 public void mark(int readAheadLimit) throws IOException {
494 if (readAheadLimit < 0) {
495 throw new IllegalArgumentException("Read-ahead limit < 0");
496 }
497 synchronized (lock) {
498 ensureOpen();
499 this.readAheadLimit = readAheadLimit;
500 markedChar = nextChar;
501 markedSkipLF = skipLF;
502 }
503 }
504
505 /**
506 * Resets the stream to the most recent mark.
507 *
508 * @throws IOException If the stream has never been marked,
509 * or if the mark has been invalidated
510 */
511 public void reset() throws IOException {
512 synchronized (lock) {
513 ensureOpen();
514 if (markedChar < 0)
515 throw new IOException((markedChar == INVALIDATED)
516 ? "Mark invalid"
517 : "Stream not marked");
518 nextChar = markedChar;
519 skipLF = markedSkipLF;
520 }
521 }
522
523 public void close() throws IOException {
524 synchronized (lock) {
525 if (in == null)
526 return;
527 try {
528 in.close();
529 } finally {
530 in = null;
531 cb = null;
532 }
533 }
534 }
535
536 /**
537 * Returns a {@code Stream}, the elements of which are lines read from
538 * this {@code BufferedReader}. The {@link Stream} is lazily populated,
539 * i.e., read only occurs during the
540 * <a href="../util/stream/package-summary.html#StreamOps">terminal
541 * stream operation</a>.
542 *
543 * <p> The reader must not be operated on during the execution of the
544 * terminal stream operation. Otherwise, the result of the terminal stream
545 * operation is undefined.
546 *
547 * <p> After execution of the terminal stream operation there are no
548 * guarantees that the reader will be at a specific position from which to
549 * read the next character or line.
550 *
551 * <p> If an {@link IOException} is thrown when accessing the underlying
552 * {@code BufferedReader}, it is wrapped in an {@link
553 * UncheckedIOException} which will be thrown from the {@code Stream}
554 * method that caused the read to take place. This method will return a
555 * Stream if invoked on a BufferedReader that is closed. Any operation on
556 * that stream that requires reading from the BufferedReader after it is
557 * closed, will cause an UncheckedIOException to be thrown.
558 *
559 * @return a {@code Stream<String>} providing the lines of text
560 * described by this {@code BufferedReader}
561 *
562 * @since 1.8
563 */
564 public Stream<String> lines() {
565 Iterator<String> iter = new Iterator<>() {
566 String nextLine = null;
567
568 @Override
569 public boolean hasNext() {
570 if (nextLine != null) {
571 return true;
572 } else {
573 try {
574 nextLine = readLine();
575 return (nextLine != null);
576 } catch (IOException e) {
577 throw new UncheckedIOException(e);
578 }
579 }
580 }
581
582 @Override
583 public String next() {
584 if (nextLine != null || hasNext()) {
585 String line = nextLine;
586 nextLine = null;
587 return line;
588 } else {
589 throw new NoSuchElementException();
590 }
591 }
592 };
593 return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
594 iter, Spliterator.ORDERED | Spliterator.NONNULL), false);
595 }
596 }