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 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 * @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 * @exception 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'), or a carriage return 301 * followed immediately by a linefeed. 302 * 303 * @param ignoreLF If true, the next '\n' will be skipped 304 * 305 * @return A String containing the contents of the line, not including 306 * any line-termination characters, or null if the end of the 307 * stream has been reached 308 * 309 * @see java.io.LineNumberReader#readLine() 310 * 311 * @exception IOException If an I/O error occurs 312 */ 313 String readLine(boolean ignoreLF) throws IOException { 314 StringBuffer s = null; 315 int startChar; 316 317 synchronized (lock) { 318 ensureOpen(); 319 boolean omitLF = ignoreLF || skipLF; 320 321 bufferLoop: 322 for (;;) { 323 324 if (nextChar >= nChars) 325 fill(); 326 if (nextChar >= nChars) { /* EOF */ 327 if (s != null && s.length() > 0) 328 return s.toString(); 329 else 330 return null; 331 } 332 boolean eol = false; 333 char c = 0; 334 int i; 335 336 /* Skip a leftover '\n', if necessary */ 337 if (omitLF && (cb[nextChar] == '\n')) 338 nextChar++; 339 skipLF = false; 340 omitLF = false; 341 342 charLoop: 343 for (i = nextChar; i < nChars; i++) { 344 c = cb[i]; 345 if ((c == '\n') || (c == '\r')) { 346 eol = true; 347 break charLoop; 348 } 349 } 350 351 startChar = nextChar; 352 nextChar = i; 353 354 if (eol) { 355 String str; 356 if (s == null) { 357 str = new String(cb, startChar, i - startChar); 358 } else { 359 s.append(cb, startChar, i - startChar); 360 str = s.toString(); 361 } 362 nextChar++; 363 if (c == '\r') { 364 skipLF = true; 365 } 366 return str; 367 } 368 369 if (s == null) 370 s = new StringBuffer(defaultExpectedLineLength); 371 s.append(cb, startChar, i - startChar); 372 } 373 } 374 } 375 376 /** 377 * Reads a line of text. A line is considered to be terminated by any one 378 * of a line feed ('\n'), a carriage return ('\r'), or a carriage return 379 * followed immediately by a linefeed. 380 * 381 * @return A String containing the contents of the line, not including 382 * any line-termination characters, or null if the end of the 383 * stream has been reached 384 * 385 * @exception IOException If an I/O error occurs 386 * 387 * @see java.nio.file.Files#readAllLines 388 */ 389 public String readLine() throws IOException { 390 return readLine(false); 391 } 392 393 /** 394 * Skips characters. 395 * 396 * @param n The number of characters to skip 397 * 398 * @return The number of characters actually skipped 399 * 400 * @exception IllegalArgumentException If <code>n</code> is negative. 401 * @exception IOException If an I/O error occurs 402 */ 403 public long skip(long n) throws IOException { 404 if (n < 0L) { 405 throw new IllegalArgumentException("skip value is negative"); 406 } 407 synchronized (lock) { 408 ensureOpen(); 409 long r = n; 410 while (r > 0) { 411 if (nextChar >= nChars) 412 fill(); 413 if (nextChar >= nChars) /* EOF */ 414 break; 415 if (skipLF) { 416 skipLF = false; 417 if (cb[nextChar] == '\n') { 418 nextChar++; 419 } 420 } 421 long d = nChars - nextChar; 422 if (r <= d) { 423 nextChar += r; 424 r = 0; 425 break; 426 } 427 else { 428 r -= d; 429 nextChar = nChars; 430 } 431 } 432 return n - r; 433 } 434 } 435 436 /** 437 * Tells whether this stream is ready to be read. A buffered character 438 * stream is ready if the buffer is not empty, or if the underlying 439 * character stream is ready. 440 * 441 * @exception IOException If an I/O error occurs 442 */ 443 public boolean ready() throws IOException { 444 synchronized (lock) { 445 ensureOpen(); 446 447 /* 448 * If newline needs to be skipped and the next char to be read 449 * is a newline character, then just skip it right away. 450 */ 451 if (skipLF) { 452 /* Note that in.ready() will return true if and only if the next 453 * read on the stream will not block. 454 */ 455 if (nextChar >= nChars && in.ready()) { 456 fill(); 457 } 458 if (nextChar < nChars) { 459 if (cb[nextChar] == '\n') 460 nextChar++; 461 skipLF = false; 462 } 463 } 464 return (nextChar < nChars) || in.ready(); 465 } 466 } 467 468 /** 469 * Tells whether this stream supports the mark() operation, which it does. 470 */ 471 public boolean markSupported() { 472 return true; 473 } 474 475 /** 476 * Marks the present position in the stream. Subsequent calls to reset() 477 * will attempt to reposition the stream to this point. 478 * 479 * @param readAheadLimit Limit on the number of characters that may be 480 * read while still preserving the mark. An attempt 481 * to reset the stream after reading characters 482 * up to this limit or beyond may fail. 483 * A limit value larger than the size of the input 484 * buffer will cause a new buffer to be allocated 485 * whose size is no smaller than limit. 486 * Therefore large values should be used with care. 487 * 488 * @exception IllegalArgumentException If {@code readAheadLimit < 0} 489 * @exception IOException If an I/O error occurs 490 */ 491 public void mark(int readAheadLimit) throws IOException { 492 if (readAheadLimit < 0) { 493 throw new IllegalArgumentException("Read-ahead limit < 0"); 494 } 495 synchronized (lock) { 496 ensureOpen(); 497 this.readAheadLimit = readAheadLimit; 498 markedChar = nextChar; 499 markedSkipLF = skipLF; 500 } 501 } 502 503 /** 504 * Resets the stream to the most recent mark. 505 * 506 * @exception IOException If the stream has never been marked, 507 * or if the mark has been invalidated 508 */ 509 public void reset() throws IOException { 510 synchronized (lock) { 511 ensureOpen(); 512 if (markedChar < 0) 513 throw new IOException((markedChar == INVALIDATED) 514 ? "Mark invalid" 515 : "Stream not marked"); 516 nextChar = markedChar; 517 skipLF = markedSkipLF; 518 } 519 } 520 521 public void close() throws IOException { 522 synchronized (lock) { 523 if (in == null) 524 return; 525 try { 526 in.close(); 527 } finally { 528 in = null; 529 cb = null; 530 } 531 } 532 } 533 534 /** 535 * Returns a {@code Stream}, the elements of which are lines read from 536 * this {@code BufferedReader}. The {@link Stream} is lazily populated, 537 * i.e., read only occurs during the 538 * <a href="../util/stream/package-summary.html#StreamOps">terminal 539 * stream operation</a>. 540 * 541 * <p> The reader must not be operated on during the execution of the 542 * terminal stream operation. Otherwise, the result of the terminal stream 543 * operation is undefined. 544 * 545 * <p> After execution of the terminal stream operation there are no 546 * guarantees that the reader will be at a specific position from which to 547 * read the next character or line. 548 * 549 * <p> If an {@link IOException} is thrown when accessing the underlying 550 * {@code BufferedReader}, it is wrapped in an {@link 551 * UncheckedIOException} which will be thrown from the {@code Stream} 552 * method that caused the read to take place. This method will return a 553 * Stream if invoked on a BufferedReader that is closed. Any operation on 554 * that stream that requires reading from the BufferedReader after it is 555 * closed, will cause an UncheckedIOException to be thrown. 556 * 557 * @return a {@code Stream<String>} providing the lines of text 558 * described by this {@code BufferedReader} 559 * 560 * @since 1.8 561 */ 562 public Stream<String> lines() { 563 Iterator<String> iter = new Iterator<String>() { 564 String nextLine = null; 565 566 @Override 567 public boolean hasNext() { 568 if (nextLine != null) { 569 return true; 570 } else { 571 try { 572 nextLine = readLine(); 573 return (nextLine != null); 574 } catch (IOException e) { 575 throw new UncheckedIOException(e); 576 } 577 } 578 } 579 580 @Override 581 public String next() { 582 if (nextLine != null || hasNext()) { 583 String line = nextLine; 584 nextLine = null; 585 return line; 586 } else { 587 throw new NoSuchElementException(); 588 } 589 } 590 }; 591 return StreamSupport.stream(Spliterators.spliteratorUnknownSize( 592 iter, Spliterator.ORDERED | Spliterator.NONNULL), false); 593 } 594 }