1 /* 2 * Copyright (c) 1994, 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 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; 28 29 /** 30 * A <code>BufferedInputStream</code> adds 31 * functionality to another input stream-namely, 32 * the ability to buffer the input and to 33 * support the <code>mark</code> and <code>reset</code> 34 * methods. When the <code>BufferedInputStream</code> 35 * is created, an internal buffer array is 36 * created. As bytes from the stream are read 37 * or skipped, the internal buffer is refilled 38 * as necessary from the contained input stream, 39 * many bytes at a time. The <code>mark</code> 40 * operation remembers a point in the input 41 * stream and the <code>reset</code> operation 42 * causes all the bytes read since the most 43 * recent <code>mark</code> operation to be 44 * reread before new bytes are taken from 45 * the contained input stream. 46 * 47 * @author Arthur van Hoff 48 * @since JDK1.0 49 */ 50 public 51 class BufferedInputStream extends FilterInputStream { 52 53 // Android-changed: made final 54 private static final int DEFAULT_BUFFER_SIZE = 8192; 55 56 /** 57 * The maximum size of array to allocate. 58 * Some VMs reserve some header words in an array. 59 * Attempts to allocate larger arrays may result in 60 * OutOfMemoryError: Requested array size exceeds VM limit 61 */ 62 // Android-changed: made final 63 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8; 64 65 /** 66 * The internal buffer array where the data is stored. When necessary, 67 * it may be replaced by another array of 68 * a different size. 69 */ 70 protected volatile byte buf[]; 71 72 /** 73 * Atomic updater to provide compareAndSet for buf. This is 74 * necessary because closes can be asynchronous. We use nullness 75 * of buf[] as primary indicator that this stream is closed. (The 76 * "in" field is also nulled out on close.) 77 */ 78 private static final 79 AtomicReferenceFieldUpdater<BufferedInputStream, byte[]> bufUpdater = 80 AtomicReferenceFieldUpdater.newUpdater 81 (BufferedInputStream.class, byte[].class, "buf"); 82 83 /** 84 * The index one greater than the index of the last valid byte in 85 * the buffer. 86 * This value is always 87 * in the range <code>0</code> through <code>buf.length</code>; 88 * elements <code>buf[0]</code> through <code>buf[count-1] 89 * </code>contain buffered input data obtained 90 * from the underlying input stream. 91 */ 92 protected int count; 93 94 /** 95 * The current position in the buffer. This is the index of the next 96 * character to be read from the <code>buf</code> array. 97 * <p> 98 * This value is always in the range <code>0</code> 99 * through <code>count</code>. If it is less 100 * than <code>count</code>, then <code>buf[pos]</code> 101 * is the next byte to be supplied as input; 102 * if it is equal to <code>count</code>, then 103 * the next <code>read</code> or <code>skip</code> 104 * operation will require more bytes to be 105 * read from the contained input stream. 106 * 107 * @see java.io.BufferedInputStream#buf 108 */ 109 protected int pos; 110 111 /** 112 * The value of the <code>pos</code> field at the time the last 113 * <code>mark</code> method was called. 114 * <p> 115 * This value is always 116 * in the range <code>-1</code> through <code>pos</code>. 117 * If there is no marked position in the input 118 * stream, this field is <code>-1</code>. If 119 * there is a marked position in the input 120 * stream, then <code>buf[markpos]</code> 121 * is the first byte to be supplied as input 122 * after a <code>reset</code> operation. If 123 * <code>markpos</code> is not <code>-1</code>, 124 * then all bytes from positions <code>buf[markpos]</code> 125 * through <code>buf[pos-1]</code> must remain 126 * in the buffer array (though they may be 127 * moved to another place in the buffer array, 128 * with suitable adjustments to the values 129 * of <code>count</code>, <code>pos</code>, 130 * and <code>markpos</code>); they may not 131 * be discarded unless and until the difference 132 * between <code>pos</code> and <code>markpos</code> 133 * exceeds <code>marklimit</code>. 134 * 135 * @see java.io.BufferedInputStream#mark(int) 136 * @see java.io.BufferedInputStream#pos 137 */ 138 protected int markpos = -1; 139 140 /** 141 * The maximum read ahead allowed after a call to the 142 * <code>mark</code> method before subsequent calls to the 143 * <code>reset</code> method fail. 144 * Whenever the difference between <code>pos</code> 145 * and <code>markpos</code> exceeds <code>marklimit</code>, 146 * then the mark may be dropped by setting 147 * <code>markpos</code> to <code>-1</code>. 148 * 149 * @see java.io.BufferedInputStream#mark(int) 150 * @see java.io.BufferedInputStream#reset() 151 */ 152 protected int marklimit; 153 154 /** 155 * Check to make sure that underlying input stream has not been 156 * nulled out due to close; if not return it; 157 */ getInIfOpen()158 private InputStream getInIfOpen() throws IOException { 159 InputStream input = in; 160 if (input == null) 161 throw new IOException("Stream closed"); 162 return input; 163 } 164 165 /** 166 * Check to make sure that buffer has not been nulled out due to 167 * close; if not return it; 168 */ getBufIfOpen()169 private byte[] getBufIfOpen() throws IOException { 170 byte[] buffer = buf; 171 if (buffer == null) 172 throw new IOException("Stream closed"); 173 return buffer; 174 } 175 176 /** 177 * Creates a <code>BufferedInputStream</code> 178 * and saves its argument, the input stream 179 * <code>in</code>, for later use. An internal 180 * buffer array is created and stored in <code>buf</code>. 181 * 182 * @param in the underlying input stream. 183 */ BufferedInputStream(InputStream in)184 public BufferedInputStream(InputStream in) { 185 this(in, DEFAULT_BUFFER_SIZE); 186 } 187 188 /** 189 * Creates a <code>BufferedInputStream</code> 190 * with the specified buffer size, 191 * and saves its argument, the input stream 192 * <code>in</code>, for later use. An internal 193 * buffer array of length <code>size</code> 194 * is created and stored in <code>buf</code>. 195 * 196 * @param in the underlying input stream. 197 * @param size the buffer size. 198 * @exception IllegalArgumentException if {@code size <= 0}. 199 */ BufferedInputStream(InputStream in, int size)200 public BufferedInputStream(InputStream in, int size) { 201 super(in); 202 if (size <= 0) { 203 throw new IllegalArgumentException("Buffer size <= 0"); 204 } 205 buf = new byte[size]; 206 } 207 208 /** 209 * Fills the buffer with more data, taking into account 210 * shuffling and other tricks for dealing with marks. 211 * Assumes that it is being called by a synchronized method. 212 * This method also assumes that all data has already been read in, 213 * hence pos > count. 214 */ fill()215 private void fill() throws IOException { 216 byte[] buffer = getBufIfOpen(); 217 if (markpos < 0) 218 pos = 0; /* no mark: throw away the buffer */ 219 else if (pos >= buffer.length) /* no room left in buffer */ 220 if (markpos > 0) { /* can throw away early part of the buffer */ 221 int sz = pos - markpos; 222 System.arraycopy(buffer, markpos, buffer, 0, sz); 223 pos = sz; 224 markpos = 0; 225 } else if (buffer.length >= marklimit) { 226 markpos = -1; /* buffer got too big, invalidate mark */ 227 pos = 0; /* drop buffer contents */ 228 } else if (buffer.length >= MAX_BUFFER_SIZE) { 229 throw new OutOfMemoryError("Required array size too large"); 230 } else { /* grow buffer */ 231 int nsz = (pos <= MAX_BUFFER_SIZE - pos) ? 232 pos * 2 : MAX_BUFFER_SIZE; 233 if (nsz > marklimit) 234 nsz = marklimit; 235 byte nbuf[] = new byte[nsz]; 236 System.arraycopy(buffer, 0, nbuf, 0, pos); 237 if (!bufUpdater.compareAndSet(this, buffer, nbuf)) { 238 // Can't replace buf if there was an async close. 239 // Note: This would need to be changed if fill() 240 // is ever made accessible to multiple threads. 241 // But for now, the only way CAS can fail is via close. 242 // assert buf == null; 243 throw new IOException("Stream closed"); 244 } 245 buffer = nbuf; 246 } 247 count = pos; 248 int n = getInIfOpen().read(buffer, pos, buffer.length - pos); 249 if (n > 0) 250 count = n + pos; 251 } 252 253 /** 254 * See 255 * the general contract of the <code>read</code> 256 * method of <code>InputStream</code>. 257 * 258 * @return the next byte of data, or <code>-1</code> if the end of the 259 * stream is reached. 260 * @exception IOException if this input stream has been closed by 261 * invoking its {@link #close()} method, 262 * or an I/O error occurs. 263 * @see java.io.FilterInputStream#in 264 */ read()265 public synchronized int read() throws IOException { 266 if (pos >= count) { 267 fill(); 268 if (pos >= count) 269 return -1; 270 } 271 return getBufIfOpen()[pos++] & 0xff; 272 } 273 274 /** 275 * Read characters into a portion of an array, reading from the underlying 276 * stream at most once if necessary. 277 */ read1(byte[] b, int off, int len)278 private int read1(byte[] b, int off, int len) throws IOException { 279 int avail = count - pos; 280 if (avail <= 0) { 281 /* If the requested length is at least as large as the buffer, and 282 if there is no mark/reset activity, do not bother to copy the 283 bytes into the local buffer. In this way buffered streams will 284 cascade harmlessly. */ 285 if (len >= getBufIfOpen().length && markpos < 0) { 286 return getInIfOpen().read(b, off, len); 287 } 288 fill(); 289 avail = count - pos; 290 if (avail <= 0) return -1; 291 } 292 int cnt = (avail < len) ? avail : len; 293 System.arraycopy(getBufIfOpen(), pos, b, off, cnt); 294 pos += cnt; 295 return cnt; 296 } 297 298 /** 299 * Reads bytes from this byte-input stream into the specified byte array, 300 * starting at the given offset. 301 * 302 * <p> This method implements the general contract of the corresponding 303 * <code>{@link InputStream#read(byte[], int, int) read}</code> method of 304 * the <code>{@link InputStream}</code> class. As an additional 305 * convenience, it attempts to read as many bytes as possible by repeatedly 306 * invoking the <code>read</code> method of the underlying stream. This 307 * iterated <code>read</code> continues until one of the following 308 * conditions becomes true: <ul> 309 * 310 * <li> The specified number of bytes have been read, 311 * 312 * <li> The <code>read</code> method of the underlying stream returns 313 * <code>-1</code>, indicating end-of-file, or 314 * 315 * <li> The <code>available</code> method of the underlying stream 316 * returns zero, indicating that further input requests would block. 317 * 318 * </ul> If the first <code>read</code> on the underlying stream returns 319 * <code>-1</code> to indicate end-of-file then this method returns 320 * <code>-1</code>. Otherwise this method returns the number of bytes 321 * actually read. 322 * 323 * <p> Subclasses of this class are encouraged, but not required, to 324 * attempt to read as many bytes as possible in the same fashion. 325 * 326 * @param b destination buffer. 327 * @param off offset at which to start storing bytes. 328 * @param len maximum number of bytes to read. 329 * @return the number of bytes read, or <code>-1</code> if the end of 330 * the stream has been reached. 331 * @exception IOException if this input stream has been closed by 332 * invoking its {@link #close()} method, 333 * or an I/O error occurs. 334 */ read(byte b[], int off, int len)335 public synchronized int read(byte b[], int off, int len) 336 throws IOException 337 { 338 getBufIfOpen(); // Check for closed stream 339 if ((off | len | (off + len) | (b.length - (off + len))) < 0) { 340 throw new IndexOutOfBoundsException(); 341 } else if (len == 0) { 342 return 0; 343 } 344 345 int n = 0; 346 for (;;) { 347 int nread = read1(b, off + n, len - n); 348 if (nread <= 0) 349 return (n == 0) ? nread : n; 350 n += nread; 351 if (n >= len) 352 return n; 353 // if not closed but no bytes available, return 354 InputStream input = in; 355 if (input != null && input.available() <= 0) 356 return n; 357 } 358 } 359 360 /** 361 * See the general contract of the <code>skip</code> 362 * method of <code>InputStream</code>. 363 * 364 * @exception IOException if the stream does not support seek, 365 * or if this input stream has been closed by 366 * invoking its {@link #close()} method, or an 367 * I/O error occurs. 368 */ skip(long n)369 public synchronized long skip(long n) throws IOException { 370 getBufIfOpen(); // Check for closed stream 371 if (n <= 0) { 372 return 0; 373 } 374 long avail = count - pos; 375 376 if (avail <= 0) { 377 // If no mark position set then don't keep in buffer 378 if (markpos <0) 379 return getInIfOpen().skip(n); 380 381 // Fill in buffer to save bytes for reset 382 fill(); 383 avail = count - pos; 384 if (avail <= 0) 385 return 0; 386 } 387 388 long skipped = (avail < n) ? avail : n; 389 pos += skipped; 390 return skipped; 391 } 392 393 /** 394 * Returns an estimate of the number of bytes that can be read (or 395 * skipped over) from this input stream without blocking by the next 396 * invocation of a method for this input stream. The next invocation might be 397 * the same thread or another thread. A single read or skip of this 398 * many bytes will not block, but may read or skip fewer bytes. 399 * <p> 400 * This method returns the sum of the number of bytes remaining to be read in 401 * the buffer (<code>count - pos</code>) and the result of calling the 402 * {@link java.io.FilterInputStream#in in}.available(). 403 * 404 * @return an estimate of the number of bytes that can be read (or skipped 405 * over) from this input stream without blocking. 406 * @exception IOException if this input stream has been closed by 407 * invoking its {@link #close()} method, 408 * or an I/O error occurs. 409 */ available()410 public synchronized int available() throws IOException { 411 int n = count - pos; 412 int avail = getInIfOpen().available(); 413 return n > (Integer.MAX_VALUE - avail) 414 ? Integer.MAX_VALUE 415 : n + avail; 416 } 417 418 /** 419 * See the general contract of the <code>mark</code> 420 * method of <code>InputStream</code>. 421 * 422 * @param readlimit the maximum limit of bytes that can be read before 423 * the mark position becomes invalid. 424 * @see java.io.BufferedInputStream#reset() 425 */ mark(int readlimit)426 public synchronized void mark(int readlimit) { 427 marklimit = readlimit; 428 markpos = pos; 429 } 430 431 /** 432 * See the general contract of the <code>reset</code> 433 * method of <code>InputStream</code>. 434 * <p> 435 * If <code>markpos</code> is <code>-1</code> 436 * (no mark has been set or the mark has been 437 * invalidated), an <code>IOException</code> 438 * is thrown. Otherwise, <code>pos</code> is 439 * set equal to <code>markpos</code>. 440 * 441 * @exception IOException if this stream has not been marked or, 442 * if the mark has been invalidated, or the stream 443 * has been closed by invoking its {@link #close()} 444 * method, or an I/O error occurs. 445 * @see java.io.BufferedInputStream#mark(int) 446 */ reset()447 public synchronized void reset() throws IOException { 448 getBufIfOpen(); // Cause exception if closed 449 if (markpos < 0) 450 throw new IOException("Resetting to invalid mark"); 451 pos = markpos; 452 } 453 454 /** 455 * Tests if this input stream supports the <code>mark</code> 456 * and <code>reset</code> methods. The <code>markSupported</code> 457 * method of <code>BufferedInputStream</code> returns 458 * <code>true</code>. 459 * 460 * @return a <code>boolean</code> indicating if this stream type supports 461 * the <code>mark</code> and <code>reset</code> methods. 462 * @see java.io.InputStream#mark(int) 463 * @see java.io.InputStream#reset() 464 */ markSupported()465 public boolean markSupported() { 466 return true; 467 } 468 469 /** 470 * Closes this input stream and releases any system resources 471 * associated with the stream. 472 * Once the stream has been closed, further read(), available(), reset(), 473 * or skip() invocations will throw an IOException. 474 * Closing a previously closed stream has no effect. 475 * 476 * @exception IOException if an I/O error occurs. 477 */ close()478 public void close() throws IOException { 479 byte[] buffer; 480 while ( (buffer = buf) != null) { 481 if (bufUpdater.compareAndSet(this, buffer, null)) { 482 InputStream input = in; 483 in = null; 484 if (input != null) 485 input.close(); 486 return; 487 } 488 // Else retry in case a new buf was CASed in fill() 489 } 490 } 491 } 492