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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 }