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1: /* RandomAccessFile.java -- Class supporting random file I/O 2: Copyright (C) 1998, 1999, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package java.io; 40: 41: import gnu.java.nio.channels.FileChannelImpl; 42: 43: import java.nio.channels.FileChannel; 44: 45: /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3 46: * "The Java Language Specification", ISBN 0-201-63451-1 47: * Status: Believe complete and correct to 1.1. 48: */ 49: 50: /** 51: * This class allows reading and writing of files at random locations. 52: * Most Java I/O classes are either pure sequential input or output. This 53: * class fulfills the need to be able to read the bytes of a file in an 54: * arbitrary order. In addition, this class implements the 55: * <code>DataInput</code> and <code>DataOutput</code> interfaces to allow 56: * the reading and writing of Java primitives. 57: * 58: * @author Aaron M. Renn (arenn@urbanophile.com) 59: * @author Tom Tromey (tromey@cygnus.com) 60: */ 61: public class RandomAccessFile implements DataOutput, DataInput 62: { 63: 64: // The underlying file. 65: private FileChannelImpl ch; 66: private FileDescriptor fd; 67: // The corresponding input and output streams. 68: private DataOutputStream out; 69: private DataInputStream in; 70: 71: 72: /** 73: * This method initializes a new instance of <code>RandomAccessFile</code> 74: * to read from the specified <code>File</code> object with the specified 75: * access mode. The access mode is either "r" for read only access or "rw" 76: * for read-write access. 77: * <p> 78: * Note that a <code>SecurityManager</code> check is made prior to 79: * opening the file to determine whether or not this file is allowed to 80: * be read or written. 81: * 82: * @param file The <code>File</code> object to read and/or write. 83: * @param mode "r" for read only or "rw" for read-write access to the file 84: * 85: * @exception IllegalArgumentException If <code>mode</code> has an 86: * illegal value 87: * @exception SecurityException If the requested access to the file 88: * is not allowed 89: * @exception FileNotFoundException If the file is a directory, or 90: * any other error occurs 91: */ 92: public RandomAccessFile (File file, String mode) 93: throws FileNotFoundException 94: { 95: int fdmode; 96: if (mode.equals("r")) 97: fdmode = FileChannelImpl.READ; 98: else if (mode.equals("rw")) 99: fdmode = FileChannelImpl.READ | FileChannelImpl.WRITE; 100: else if (mode.equals("rws")) 101: { 102: fdmode = (FileChannelImpl.READ | FileChannelImpl.WRITE 103: | FileChannelImpl.SYNC); 104: } 105: else if (mode.equals("rwd")) 106: { 107: fdmode = (FileChannelImpl.READ | FileChannelImpl.WRITE 108: | FileChannelImpl.DSYNC); 109: } 110: else 111: throw new IllegalArgumentException ("invalid mode: " + mode); 112: 113: final String fileName = file.getPath(); 114: 115: // The obligatory SecurityManager stuff 116: SecurityManager s = System.getSecurityManager(); 117: if (s != null) 118: { 119: s.checkRead(fileName); 120: 121: if ((fdmode & FileChannelImpl.WRITE) != 0) 122: s.checkWrite(fileName); 123: } 124: 125: ch = FileChannelImpl.create(file, fdmode); 126: fd = new FileDescriptor(ch); 127: out = new DataOutputStream (new FileOutputStream (fd)); 128: in = new DataInputStream (new FileInputStream (fd)); 129: } 130: 131: /** 132: * This method initializes a new instance of <code>RandomAccessFile</code> 133: * to read from the specified file name with the specified access mode. 134: * The access mode is either "r" for read only access, "rw" for read 135: * write access, "rws" for synchronized read/write access of both 136: * content and metadata, or "rwd" for read/write access 137: * where only content is required to be synchronous. 138: * <p> 139: * Note that a <code>SecurityManager</code> check is made prior to 140: * opening the file to determine whether or not this file is allowed to 141: * be read or written. 142: * 143: * @param fileName The name of the file to read and/or write 144: * @param mode "r", "rw", "rws", or "rwd" 145: * 146: * @exception IllegalArgumentException If <code>mode</code> has an 147: * illegal value 148: * @exception SecurityException If the requested access to the file 149: * is not allowed 150: * @exception FileNotFoundException If the file is a directory or 151: * any other error occurs 152: */ 153: public RandomAccessFile (String fileName, String mode) 154: throws FileNotFoundException 155: { 156: this (new File(fileName), mode); 157: } 158: 159: /** 160: * This method closes the file and frees up all file related system 161: * resources. Since most operating systems put a limit on how many files 162: * may be opened at any given time, it is a good idea to close all files 163: * when no longer needed to avoid hitting this limit 164: */ 165: public void close () throws IOException 166: { 167: ch.close(); 168: } 169: 170: /** 171: * This method returns a <code>FileDescriptor</code> object that 172: * represents the native file handle for this file. 173: * 174: * @return The <code>FileDescriptor</code> object for this file 175: * 176: * @exception IOException If an error occurs 177: */ 178: public final FileDescriptor getFD () throws IOException 179: { 180: synchronized (this) 181: { 182: if (fd == null) 183: fd = new FileDescriptor (ch); 184: return fd; 185: } 186: } 187: 188: /** 189: * This method returns the current offset in the file at which the next 190: * read or write will occur 191: * 192: * @return The current file position 193: * 194: * @exception IOException If an error occurs 195: */ 196: public long getFilePointer () throws IOException 197: { 198: return ch.position(); 199: } 200: 201: /** 202: * This method sets the length of the file to the specified length. 203: * If the currently length of the file is longer than the specified 204: * length, then the file is truncated to the specified length (the 205: * file position is set to the end of file in this case). If the 206: * current length of the file is shorter than the specified length, 207: * the file is extended with bytes of an undefined value (the file 208: * position is unchanged in this case). 209: * <p> 210: * The file must be open for write access for this operation to succeed. 211: * 212: * @param newLen The new length of the file 213: * 214: * @exception IOException If an error occurs 215: */ 216: public void setLength (long newLen) throws IOException 217: { 218: // FIXME: Extending a file should probably be done by one method call. 219: 220: // FileChannel.truncate() can only shrink a file. 221: // To expand it we need to seek forward and write at least one byte. 222: if (newLen < length()) 223: ch.truncate (newLen); 224: else if (newLen > length()) 225: { 226: long pos = getFilePointer(); 227: seek(newLen - 1); 228: write(0); 229: seek(pos); 230: } 231: } 232: 233: /** 234: * This method returns the length of the file in bytes 235: * 236: * @return The length of the file 237: * 238: * @exception IOException If an error occurs 239: */ 240: public long length () throws IOException 241: { 242: return ch.size(); 243: } 244: 245: /** 246: * This method reads a single byte of data from the file and returns it 247: * as an integer. 248: * 249: * @return The byte read as an int, or -1 if the end of the file was reached. 250: * 251: * @exception IOException If an error occurs 252: */ 253: public int read () throws IOException 254: { 255: return in.read(); 256: } 257: 258: /** 259: * This method reads bytes from the file into the specified array. The 260: * bytes are stored starting at the beginning of the array and up to 261: * <code>buf.length</code> bytes can be read. 262: * 263: * @param buffer The buffer to read bytes from the file into 264: * 265: * @return The actual number of bytes read or -1 if end of file 266: * 267: * @exception IOException If an error occurs 268: */ 269: public int read (byte[] buffer) throws IOException 270: { 271: return in.read (buffer); 272: } 273: 274: /** 275: * This methods reads up to <code>len</code> bytes from the file into the 276: * specified array starting at position <code>offset</code> into the array. 277: * 278: * @param buffer The array to read the bytes into 279: * @param offset The index into the array to start storing bytes 280: * @param len The requested number of bytes to read 281: * 282: * @return The actual number of bytes read, or -1 if end of file 283: * 284: * @exception IOException If an error occurs 285: */ 286: public int read (byte[] buffer, int offset, int len) throws IOException 287: { 288: return in.read (buffer, offset, len); 289: } 290: 291: /** 292: * This method reads a Java boolean value from an input stream. It does 293: * so by reading a single byte of data. If that byte is zero, then the 294: * value returned is <code>false</code> If the byte is non-zero, then 295: * the value returned is <code>true</code> 296: * <p> 297: * This method can read a <code>boolean</code> written by an object 298: * implementing the 299: * <code>writeBoolean()</code> method in the <code>DataOutput</code> 300: * interface. 301: * 302: * @return The <code>boolean</code> value read 303: * 304: * @exception EOFException If end of file is reached before reading the 305: * boolean 306: * @exception IOException If any other error occurs 307: */ 308: public final boolean readBoolean () throws IOException 309: { 310: return in.readBoolean (); 311: } 312: 313: /** 314: * This method reads a Java byte value from an input stream. The value 315: * is in the range of -128 to 127. 316: * <p> 317: * This method can read a <code>byte</code> written by an object 318: * implementing the 319: * <code>writeByte()</code> method in the <code>DataOutput</code> interface. 320: * 321: * @return The <code>byte</code> value read 322: * 323: * @exception EOFException If end of file is reached before reading the byte 324: * @exception IOException If any other error occurs 325: * 326: * @see DataOutput 327: */ 328: public final byte readByte () throws IOException 329: { 330: return in.readByte (); 331: } 332: 333: /** 334: * This method reads a Java <code>char</code> value from an input stream. 335: * It operates by reading two bytes from the stream and converting them to 336: * a single 16-bit Java <code>char</code> The two bytes are stored most 337: * significant byte first (i.e., "big endian") regardless of the native 338: * host byte ordering. 339: * <p> 340: * As an example, if <code>byte1</code> and <code>byte2</code> represent 341: * the first 342: * and second byte read from the stream respectively, they will be 343: * transformed to a <code>char</code> in the following manner: 344: * <p> 345: * <code>(char)(((byte1 & 0xFF) << 8) | (byte2 & 0xFF)</code> 346: * <p> 347: * This method can read a <code>char</code> written by an object 348: * implementing the 349: * <code>writeChar()</code> method in the <code>DataOutput</code> interface. 350: * 351: * @return The <code>char</code> value read 352: * 353: * @exception EOFException If end of file is reached before reading the char 354: * @exception IOException If any other error occurs 355: * 356: * @see DataOutput 357: */ 358: public final char readChar () throws IOException 359: { 360: return in.readChar(); 361: } 362: 363: /** 364: * This method reads a Java double value from an input stream. It operates 365: * by first reading a <code>logn</code> value from the stream by calling the 366: * <code>readLong()</code> method in this interface, then 367: * converts that <code>long</code> 368: * to a <code>double</code> using the <code>longBitsToDouble</code> 369: * method in the class <code>java.lang.Double</code> 370: * <p> 371: * This method can read a <code>double</code> written by an object 372: * implementing the 373: * <code>writeDouble()</code> method in the <code>DataOutput</code> 374: * interface. 375: * 376: * @return The <code>double</code> value read 377: * 378: * @exception EOFException If end of file is reached before reading 379: * the double 380: * @exception IOException If any other error occurs 381: * 382: * @see java.lang.Double 383: * @see DataOutput 384: */ 385: public final double readDouble () throws IOException 386: { 387: return in.readDouble (); 388: } 389: 390: /** 391: * This method reads a Java float value from an input stream. It operates 392: * by first reading an <code>int</code> value from the stream by calling the 393: * <code>readInt()</code> method in this interface, then converts 394: * that <code>int</code> 395: * to a <code>float</code> using the <code>intBitsToFloat</code> method in 396: * the class <code>java.lang.Float</code> 397: * <p> 398: * This method can read a <code>float</code> written by an object 399: * implementing the 400: * <code>writeFloat()</code> method in the <code>DataOutput</code> interface. 401: * 402: * @return The <code>float</code> value read 403: * 404: * @exception EOFException If end of file is reached before reading the float 405: * @exception IOException If any other error occurs 406: * 407: * @see java.lang.Float 408: * @see DataOutput 409: */ 410: public final float readFloat () throws IOException 411: { 412: return in.readFloat(); 413: } 414: 415: /** 416: * This method reads raw bytes into the passed array until the array is 417: * full. Note that this method blocks until the data is available and 418: * throws an exception if there is not enough data left in the stream to 419: * fill the buffer 420: * 421: * @param buffer The buffer into which to read the data 422: * 423: * @exception EOFException If end of file is reached before filling the 424: * buffer 425: * @exception IOException If any other error occurs 426: */ 427: public final void readFully (byte[] buffer) throws IOException 428: { 429: in.readFully(buffer); 430: } 431: 432: /** 433: * This method reads raw bytes into the passed array <code>buf</code> 434: * starting 435: * <code>offset</code> bytes into the buffer. The number of bytes read 436: * will be 437: * exactly <code>len</code> Note that this method blocks until the data is 438: * available and throws an exception if there is not enough data left in 439: * the stream to read <code>len</code> bytes. 440: * 441: * @param buffer The buffer into which to read the data 442: * @param offset The offset into the buffer to start storing data 443: * @param count The number of bytes to read into the buffer 444: * 445: * @exception EOFException If end of file is reached before filling 446: * the buffer 447: * @exception IOException If any other error occurs 448: */ 449: public final void readFully (byte[] buffer, int offset, int count) 450: throws IOException 451: { 452: in.readFully (buffer, offset, count); 453: } 454: 455: /** 456: * This method reads a Java <code>int</code> value from an input stream 457: * It operates by reading four bytes from the stream and converting them to 458: * a single Java <code>int</code> The bytes are stored most 459: * significant byte first (i.e., "big endian") regardless of the native 460: * host byte ordering. 461: * <p> 462: * As an example, if <code>byte1</code> through <code>byte4</code> 463: * represent the first 464: * four bytes read from the stream, they will be 465: * transformed to an <code>int</code> in the following manner: 466: * <p> 467: * <code>(int)(((byte1 & 0xFF) << 24) + ((byte2 & 0xFF) << 16) + 468: * ((byte3 & 0xFF) << 8) + (byte4 & 0xFF)))</code> 469: * <p> 470: * The value returned is in the range of 0 to 65535. 471: * <p> 472: * This method can read an <code>int</code> written by an object 473: * implementing the 474: * <code>writeInt()</code> method in the <code>DataOutput</code> interface. 475: * 476: * @return The <code>int</code> value read 477: * 478: * @exception EOFException If end of file is reached before reading the int 479: * @exception IOException If any other error occurs 480: * 481: * @see DataOutput 482: */ 483: public final int readInt () throws IOException 484: { 485: return in.readInt(); 486: } 487: 488: /** 489: * This method reads the next line of text data from an input stream. 490: * It operates by reading bytes and converting those bytes to 491: * <code>char</code> 492: * values by treating the byte read as the low eight bits of the 493: * <code>char</code> 494: * and using <code>0</code> as the high eight bits. Because of this, it does 495: * not support the full 16-bit Unicode character set. 496: * <p> 497: * The reading of bytes ends when either the end of file or a line terminator 498: * is encountered. The bytes read are then returned as a <code>String</code> 499: * A line terminator is a byte sequence consisting of either 500: * <code>\r</code> <code>\n</code> or <code>\r\n</code> These 501: * termination charaters are 502: * discarded and are not returned as part of the string. 503: * <p> 504: * This method can read data that was written by an object implementing the 505: * <code>writeLine()</code> method in <code>DataOutput</code> 506: * 507: * @return The line read as a <code>String</code> 508: * 509: * @exception IOException If an error occurs 510: * 511: * @see DataOutput 512: */ 513: public final String readLine () throws IOException 514: { 515: return in.readLine (); 516: } 517: 518: /** 519: * This method reads a Java long value from an input stream 520: * It operates by reading eight bytes from the stream and converting them to 521: * a single Java <code>long</code> The bytes are stored most 522: * significant byte first (i.e., "big endian") regardless of the native 523: * host byte ordering. 524: * <p> 525: * As an example, if <code>byte1</code> through <code>byte8</code> 526: * represent the first 527: * eight bytes read from the stream, they will be 528: * transformed to an <code>long</code> in the following manner: 529: * <p> 530: * <code> 531: * (long)((((long)byte1 & 0xFF) << 56) + (((long)byte2 & 0xFF) << 48) + 532: * (((long)byte3 & 0xFF) << 40) + (((long)byte4 & 0xFF) << 32) + 533: * (((long)byte5 & 0xFF) << 24) + (((long)byte6 & 0xFF) << 16) + 534: * (((long)byte7 & 0xFF) << 8) + ((long)byte9 & 0xFF)))</code> 535: * <p> 536: * The value returned is in the range of 0 to 65535. 537: * <p> 538: * This method can read an <code>long</code> written by an object 539: * implementing the 540: * <code>writeLong()</code> method in the <code>DataOutput</code> interface. 541: * 542: * @return The <code>long</code> value read 543: * 544: * @exception EOFException If end of file is reached before reading the long 545: * @exception IOException If any other error occurs 546: * 547: * @see DataOutput 548: */ 549: public final long readLong () throws IOException 550: { 551: return in.readLong(); 552: } 553: 554: /** 555: * This method reads a signed 16-bit value into a Java in from the stream. 556: * It operates by reading two bytes from the stream and converting them to 557: * a single 16-bit Java <code>short</code> The two bytes are stored most 558: * significant byte first (i.e., "big endian") regardless of the native 559: * host byte ordering. 560: * <p> 561: * As an example, if <code>byte1</code> and <code>byte2</code> 562: * represent the first 563: * and second byte read from the stream respectively, they will be 564: * transformed to a <code>short</code> in the following manner: 565: * <p> 566: * <code>(short)(((byte1 & 0xFF) << 8) | (byte2 & 0xFF)</code> 567: * <p> 568: * The value returned is in the range of -32768 to 32767. 569: * <p> 570: * This method can read a <code>short</code> written by an object 571: * implementing the 572: * <code>writeShort()</code> method in the <code>DataOutput</code> interface. 573: * 574: * @return The <code>short</code> value read 575: * 576: * @exception EOFException If end of file is reached before reading the value 577: * @exception IOException If any other error occurs 578: * 579: * @see DataOutput 580: */ 581: public final short readShort () throws IOException 582: { 583: return in.readShort(); 584: } 585: 586: /** 587: * This method reads 8 unsigned bits into a Java <code>int</code> value 588: * from the 589: * stream. The value returned is in the range of 0 to 255. 590: * <p> 591: * This method can read an unsigned byte written by an object implementing 592: * the <code>writeUnsignedByte()</code> method in the 593: * <code>DataOutput</code> interface. 594: * 595: * @return The unsigned bytes value read as a Java <code>int</code> 596: * 597: * @exception EOFException If end of file is reached before reading the value 598: * @exception IOException If any other error occurs 599: * 600: * @see DataOutput 601: */ 602: public final int readUnsignedByte () throws IOException 603: { 604: return in.readUnsignedByte(); 605: } 606: 607: /** 608: * This method reads 16 unsigned bits into a Java int value from the stream. 609: * It operates by reading two bytes from the stream and converting them to 610: * a single Java <code>int</code> The two bytes are stored most 611: * significant byte first (i.e., "big endian") regardless of the native 612: * host byte ordering. 613: * <p> 614: * As an example, if <code>byte1</code> and <code>byte2</code> 615: * represent the first 616: * and second byte read from the stream respectively, they will be 617: * transformed to an <code>int</code> in the following manner: 618: * <p> 619: * <code>(int)(((byte1 & 0xFF) << 8) + (byte2 & 0xFF))</code> 620: * <p> 621: * The value returned is in the range of 0 to 65535. 622: * <p> 623: * This method can read an unsigned short written by an object implementing 624: * the <code>writeUnsignedShort()</code> method in the 625: * <code>DataOutput</code> interface. 626: * 627: * @return The unsigned short value read as a Java <code>int</code> 628: * 629: * @exception EOFException If end of file is reached before reading the value 630: * @exception IOException If any other error occurs 631: */ 632: public final int readUnsignedShort () throws IOException 633: { 634: return in.readUnsignedShort(); 635: } 636: 637: /** 638: * This method reads a <code>String</code> from an input stream that 639: * is encoded in 640: * a modified UTF-8 format. This format has a leading two byte sequence 641: * that contains the remaining number of bytes to read. This two byte 642: * sequence is read using the <code>readUnsignedShort()</code> method of this 643: * interface. 644: * <p> 645: * After the number of remaining bytes have been determined, these bytes 646: * are read an transformed into <code>char</code> values. 647: * These <code>char</code> values 648: * are encoded in the stream using either a one, two, or three byte format. 649: * The particular format in use can be determined by examining the first 650: * byte read. 651: * <p> 652: * If the first byte has a high order bit of 0 then 653: * that character consists on only one byte. This character value consists 654: * of seven bits that are at positions 0 through 6 of the byte. As an 655: * example, if <code>byte1</code> is the byte read from the stream, it would 656: * be converted to a <code>char</code> like so: 657: * <p> 658: * <code>(char)byte1</code> 659: * <p> 660: * If the first byte has <code>110</code> as its high order bits, then the 661: * character consists of two bytes. The bits that make up the character 662: * value are in positions 0 through 4 of the first byte and bit positions 663: * 0 through 5 of the second byte. (The second byte should have 664: * 10 as its high order bits). These values are in most significant 665: * byte first (i.e., "big endian") order. 666: * <p> 667: * As an example, if <code>byte1</code> and <code>byte2</code> 668: * are the first two bytes 669: * read respectively, and the high order bits of them match the patterns 670: * which indicate a two byte character encoding, then they would be 671: * converted to a Java <code>char</code> like so: 672: * <p> 673: * <code>(char)(((byte1 & 0x1F) << 6) | (byte2 & 0x3F))</code> 674: * <p> 675: * If the first byte has a <code>1110</code> as its high order bits, then the 676: * character consists of three bytes. The bits that make up the character 677: * value are in positions 0 through 3 of the first byte and bit positions 678: * 0 through 5 of the other two bytes. (The second and third bytes should 679: * have <code>10</code> as their high order bits). These values are in most 680: * significant byte first (i.e., "big endian") order. 681: * <p> 682: * As an example, if <code>byte1</code> <code>byte2</code> 683: * and <code>byte3</code> are the 684: * three bytes read, and the high order bits of them match the patterns 685: * which indicate a three byte character encoding, then they would be 686: * converted to a Java <code>char</code> like so: 687: * <p> 688: * <code>(char)(((byte1 & 0x0F) << 12) | ((byte2 & 0x3F) << 6) | 689: * (byte3 & 0x3F))</code> 690: * <p> 691: * Note that all characters are encoded in the method that requires the 692: * fewest number of bytes with the exception of the character with the 693: * value of <code>\u0000</code> which is encoded as two bytes. This is 694: * a modification of the UTF standard used to prevent C language style 695: * <code>NUL</code> values from appearing in the byte stream. 696: * <p> 697: * This method can read data that was written by an object implementing the 698: * <code>writeUTF()</code> method in <code>DataOutput</code> 699: * 700: * @return The <code>String</code> read 701: * 702: * @exception EOFException If end of file is reached before reading the 703: * String 704: * @exception UTFDataFormatException If the data is not in UTF-8 format 705: * @exception IOException If any other error occurs 706: * 707: * @see DataOutput 708: */ 709: public final String readUTF () throws IOException 710: { 711: return in.readUTF(); 712: } 713: 714: /** 715: * This method sets the current file position to the specified offset 716: * from the beginning of the file. Note that some operating systems will 717: * allow the file pointer to be set past the current end of the file. 718: * 719: * @param pos The offset from the beginning of the file at which to set 720: * the file pointer 721: * 722: * @exception IOException If an error occurs 723: */ 724: public void seek (long pos) throws IOException 725: { 726: ch.position(pos); 727: } 728: 729: /** 730: * This method attempts to skip and discard the specified number of bytes 731: * in the input stream. It may actually skip fewer bytes than requested. 732: * The actual number of bytes skipped is returned. This method will not 733: * skip any bytes if passed a negative number of bytes to skip. 734: * 735: * @param numBytes The requested number of bytes to skip. 736: * 737: * @return The number of bytes actually skipped. 738: * 739: * @exception IOException If an error occurs. 740: */ 741: public int skipBytes (int numBytes) throws IOException 742: { 743: if (numBytes < 0) 744: throw new IllegalArgumentException ("Can't skip negative bytes: " + 745: numBytes); 746: 747: if (numBytes == 0) 748: return 0; 749: 750: long oldPos = ch.position(); 751: long newPos = oldPos + numBytes; 752: long size = ch.size(); 753: if (newPos > size) 754: newPos = size; 755: ch.position(newPos); 756: return (int) (ch.position() - oldPos); 757: } 758: 759: /** 760: * This method writes a single byte of data to the file. The file must 761: * be open for read-write in order for this operation to succeed. 762: * 763: * @param oneByte The byte of data to write, passed as an int. 764: * 765: * @exception IOException If an error occurs 766: */ 767: public void write (int oneByte) throws IOException 768: { 769: out.write(oneByte); 770: } 771: 772: /** 773: * This method writes all the bytes in the specified array to the file. 774: * The file must be open read-write in order for this operation to succeed. 775: * 776: * @param buffer The array of bytes to write to the file 777: */ 778: public void write (byte[] buffer) throws IOException 779: { 780: out.write(buffer); 781: } 782: 783: /** 784: * This method writes <code>len</code> bytes to the file from the specified 785: * array starting at index <code>offset</code> into the array. 786: * 787: * @param buffer The array of bytes to write to the file 788: * @param offset The index into the array to start writing file 789: * @param len The number of bytes to write 790: * 791: * @exception IOException If an error occurs 792: */ 793: public void write (byte[] buffer, int offset, int len) throws IOException 794: { 795: out.write (buffer, offset, len); 796: } 797: 798: /** 799: * This method writes a Java <code>boolean</code> to the underlying output 800: * stream. For a value of <code>true</code>, 1 is written to the stream. 801: * For a value of <code>false</code>, 0 is written. 802: * 803: * @param val The <code>boolean</code> value to write to the stream 804: * 805: * @exception IOException If an error occurs 806: */ 807: public final void writeBoolean (boolean val) throws IOException 808: { 809: out.writeBoolean(val); 810: } 811: 812: /** 813: * This method writes a Java <code>byte</code> value to the underlying 814: * output stream. 815: * 816: * @param val The <code>byte</code> to write to the stream, passed 817: * as an <code>int</code>. 818: * 819: * @exception IOException If an error occurs 820: */ 821: public final void writeByte (int val) throws IOException 822: { 823: out.writeByte(val); 824: } 825: 826: /** 827: * This method writes a Java <code>short</code> to the stream, high byte 828: * first. This method requires two bytes to encode the value. 829: * 830: * @param val The <code>short</code> value to write to the stream, 831: * passed as an <code>int</code>. 832: * 833: * @exception IOException If an error occurs 834: */ 835: public final void writeShort (int val) throws IOException 836: { 837: out.writeShort(val); 838: } 839: 840: /** 841: * This method writes a single <code>char</code> value to the stream, 842: * high byte first. 843: * 844: * @param val The <code>char</code> value to write, passed as 845: * an <code>int</code>. 846: * 847: * @exception IOException If an error occurs 848: */ 849: public final void writeChar (int val) throws IOException 850: { 851: out.writeChar(val); 852: } 853: 854: /** 855: * This method writes a Java <code>int</code> to the stream, high bytes 856: * first. This method requires four bytes to encode the value. 857: * 858: * @param val The <code>int</code> value to write to the stream. 859: * 860: * @exception IOException If an error occurs 861: */ 862: public final void writeInt (int val) throws IOException 863: { 864: out.writeInt(val); 865: } 866: 867: /** 868: * This method writes a Java <code>long</code> to the stream, high bytes 869: * first. This method requires eight bytes to encode the value. 870: * 871: * @param val The <code>long</code> value to write to the stream. 872: * 873: * @exception IOException If an error occurs 874: */ 875: public final void writeLong (long val) throws IOException 876: { 877: out.writeLong(val); 878: } 879: 880: /** 881: * This method writes a Java <code>float</code> value to the stream. This 882: * value is written by first calling the method 883: * <code>Float.floatToIntBits</code> 884: * to retrieve an <code>int</code> representing the floating point number, 885: * then writing this <code>int</code> value to the stream exactly the same 886: * as the <code>writeInt()</code> method does. 887: * 888: * @param val The floating point number to write to the stream. 889: * 890: * @exception IOException If an error occurs 891: * 892: * @see #writeInt(int) 893: */ 894: public final void writeFloat (float val) throws IOException 895: { 896: out.writeFloat(val); 897: } 898: 899: /** 900: * This method writes a Java <code>double</code> value to the stream. This 901: * value is written by first calling the method 902: * <code>Double.doubleToLongBits</code> 903: * to retrieve an <code>long</code> representing the floating point number, 904: * then writing this <code>long</code> value to the stream exactly the same 905: * as the <code>writeLong()</code> method does. 906: * 907: * @param val The double precision floating point number to write to the 908: * stream. 909: * 910: * @exception IOException If an error occurs 911: * 912: * @see #writeLong(long) 913: */ 914: public final void writeDouble (double val) throws IOException 915: { 916: out.writeDouble(val); 917: } 918: 919: /** 920: * This method writes all the bytes in a <code>String</code> out to the 921: * stream. One byte is written for each character in the <code>String</code>. 922: * The high eight bits of each character are discarded. 923: * 924: * @param val The <code>String</code> to write to the stream 925: * 926: * @exception IOException If an error occurs 927: */ 928: public final void writeBytes (String val) throws IOException 929: { 930: out.writeBytes(val); 931: } 932: 933: /** 934: * This method writes all the characters in a <code>String</code> to the 935: * stream. There will be two bytes for each character value. The high 936: * byte of the character will be written first. 937: * 938: * @param val The <code>String</code> to write to the stream. 939: * 940: * @exception IOException If an error occurs 941: */ 942: public final void writeChars (String val) throws IOException 943: { 944: out.writeChars(val); 945: } 946: 947: /** 948: * This method writes a Java <code>String</code> to the stream in a modified 949: * UTF-8 format. First, two bytes are written to the stream indicating the 950: * number of bytes to follow. Note that this is the number of bytes in the 951: * encoded <code>String</code> not the <code>String</code> length. Next 952: * come the encoded characters. Each character in the <code>String</code> 953: * is encoded as either one, two or three bytes. For characters in the 954: * range of <code>\u0001</code> to <code>\u007F</code>, 955: * one byte is used. The character 956: * value goes into bits 0-7 and bit eight is 0. For characters in the range 957: * of <code>\u0080</code> to <code>\u007FF</code>, two 958: * bytes are used. Bits 959: * 6-10 of the character value are encoded bits 0-4 of the first byte, with 960: * the high bytes having a value of "110". Bits 0-5 of the character value 961: * are stored in bits 0-5 of the second byte, with the high bits set to 962: * "10". This type of encoding is also done for the null character 963: * <code>\u0000</code>. This eliminates any C style NUL character values 964: * in the output. All remaining characters are stored as three bytes. 965: * Bits 12-15 of the character value are stored in bits 0-3 of the first 966: * byte. The high bits of the first bytes are set to "1110". Bits 6-11 967: * of the character value are stored in bits 0-5 of the second byte. The 968: * high bits of the second byte are set to "10". And bits 0-5 of the 969: * character value are stored in bits 0-5 of byte three, with the high bits 970: * of that byte set to "10". 971: * 972: * @param val The <code>String</code> to write to the output in UTF format 973: * 974: * @exception IOException If an error occurs 975: */ 976: public final void writeUTF (String val) throws IOException 977: { 978: out.writeUTF(val); 979: } 980: 981: /** 982: * This method creates a java.nio.channels.FileChannel. 983: * Nio does not allow one to create a file channel directly. 984: * A file channel must be created by first creating an instance of 985: * Input/Output/RandomAccessFile and invoking the getChannel() method on it. 986: */ 987: public final synchronized FileChannel getChannel () 988: { 989: return ch; 990: } 991: }
GNU Classpath (0.19) |