| /* RandomAccessFile.java -- Class supporting random file I/O |
| Copyright (C) 1998, 1999, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package java.io; |
| |
| import gnu.java.nio.channels.FileChannelImpl; |
| |
| import java.nio.channels.FileChannel; |
| |
| /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3 |
| * "The Java Language Specification", ISBN 0-201-63451-1 |
| * Status: Believe complete and correct to 1.1. |
| */ |
| |
| /** |
| * This class allows reading and writing of files at random locations. |
| * Most Java I/O classes are either pure sequential input or output. This |
| * class fulfills the need to be able to read the bytes of a file in an |
| * arbitrary order. In addition, this class implements the |
| * <code>DataInput</code> and <code>DataOutput</code> interfaces to allow |
| * the reading and writing of Java primitives. |
| * |
| * @author Aaron M. Renn (arenn@urbanophile.com) |
| * @author Tom Tromey (tromey@cygnus.com) |
| */ |
| public class RandomAccessFile implements DataOutput, DataInput |
| { |
| |
| // The underlying file. |
| private FileChannelImpl ch; |
| private FileDescriptor fd; |
| // The corresponding input and output streams. |
| private DataOutputStream out; |
| private DataInputStream in; |
| |
| |
| /** |
| * This method initializes a new instance of <code>RandomAccessFile</code> |
| * to read from the specified <code>File</code> object with the specified |
| * access mode. The access mode is either "r" for read only access or "rw" |
| * for read-write access. |
| * <p> |
| * Note that a <code>SecurityManager</code> check is made prior to |
| * opening the file to determine whether or not this file is allowed to |
| * be read or written. |
| * |
| * @param file The <code>File</code> object to read and/or write. |
| * @param mode "r" for read only or "rw" for read-write access to the file |
| * |
| * @exception IllegalArgumentException If <code>mode</code> has an |
| * illegal value |
| * @exception SecurityException If the requested access to the file |
| * is not allowed |
| * @exception IOException If any other error occurs |
| */ |
| public RandomAccessFile (File file, String mode) |
| throws FileNotFoundException |
| { |
| this (file.getPath(), mode); |
| } |
| |
| /** |
| * This method initializes a new instance of <code>RandomAccessFile</code> |
| * to read from the specified file name with the specified access mode. |
| * The access mode is either "r" for read only access, "rw" for read |
| * write access, "rws" for synchronized read/write access of both |
| * content and metadata, or "rwd" for read/write access |
| * where only content is required to be synchronous. |
| * <p> |
| * Note that a <code>SecurityManager</code> check is made prior to |
| * opening the file to determine whether or not this file is allowed to |
| * be read or written. |
| * |
| * @param fileName The name of the file to read and/or write |
| * @param mode "r", "rw", "rws", or "rwd" |
| * |
| * @exception IllegalArgumentException If <code>mode</code> has an |
| * illegal value |
| * @exception SecurityException If the requested access to the file |
| * is not allowed |
| * @exception FileNotFoundException If any other error occurs |
| */ |
| public RandomAccessFile (String fileName, String mode) |
| throws FileNotFoundException |
| { |
| int fdmode; |
| if (mode.equals("r")) |
| fdmode = FileChannelImpl.READ; |
| else if (mode.equals("rw")) |
| fdmode = FileChannelImpl.READ | FileChannelImpl.WRITE; |
| else if (mode.equals("rws")) |
| { |
| fdmode = (FileChannelImpl.READ | FileChannelImpl.WRITE |
| | FileChannelImpl.SYNC); |
| } |
| else if (mode.equals("rwd")) |
| { |
| fdmode = (FileChannelImpl.READ | FileChannelImpl.WRITE |
| | FileChannelImpl.DSYNC); |
| } |
| else |
| throw new IllegalArgumentException ("invalid mode: " + mode); |
| |
| // The obligatory SecurityManager stuff |
| SecurityManager s = System.getSecurityManager(); |
| if (s != null) |
| { |
| s.checkRead(fileName); |
| |
| if ((fdmode & FileChannelImpl.WRITE) != 0) |
| s.checkWrite(fileName); |
| } |
| |
| ch = new FileChannelImpl (fileName, fdmode); |
| fd = new FileDescriptor(ch); |
| out = new DataOutputStream (new FileOutputStream (fd)); |
| in = new DataInputStream (new FileInputStream (fd)); |
| } |
| |
| /** |
| * This method closes the file and frees up all file related system |
| * resources. Since most operating systems put a limit on how many files |
| * may be opened at any given time, it is a good idea to close all files |
| * when no longer needed to avoid hitting this limit |
| */ |
| public void close () throws IOException |
| { |
| ch.close(); |
| } |
| |
| /** |
| * This method returns a <code>FileDescriptor</code> object that |
| * represents the native file handle for this file. |
| * |
| * @return The <code>FileDescriptor</code> object for this file |
| * |
| * @exception IOException If an error occurs |
| */ |
| public final FileDescriptor getFD () throws IOException |
| { |
| synchronized (this) |
| { |
| if (fd == null) |
| fd = new FileDescriptor (ch); |
| return fd; |
| } |
| } |
| |
| /** |
| * This method returns the current offset in the file at which the next |
| * read or write will occur |
| * |
| * @return The current file position |
| * |
| * @exception IOException If an error occurs |
| */ |
| public long getFilePointer () throws IOException |
| { |
| return ch.position(); |
| } |
| |
| /** |
| * This method sets the length of the file to the specified length. |
| * If the currently length of the file is longer than the specified |
| * length, then the file is truncated to the specified length (the |
| * file position is set to the end of file in this case). If the |
| * current length of the file is shorter than the specified length, |
| * the file is extended with bytes of an undefined value (the file |
| * position is unchanged in this case). |
| * <p> |
| * The file must be open for write access for this operation to succeed. |
| * |
| * @param newLen The new length of the file |
| * |
| * @exception IOException If an error occurs |
| */ |
| public void setLength (long newLen) throws IOException |
| { |
| // FIXME: Extending a file should probably be done by one method call. |
| |
| // FileChannel.truncate() can only shrink a file. |
| // To expand it we need to seek forward and write at least one byte. |
| if (newLen < length()) |
| ch.truncate (newLen); |
| else if (newLen > length()) |
| { |
| long pos = getFilePointer(); |
| seek(newLen - 1); |
| write(0); |
| seek(pos); |
| } |
| } |
| |
| /** |
| * This method returns the length of the file in bytes |
| * |
| * @return The length of the file |
| * |
| * @exception IOException If an error occurs |
| */ |
| public long length () throws IOException |
| { |
| return ch.size(); |
| } |
| |
| /** |
| * This method reads a single byte of data from the file and returns it |
| * as an integer. |
| * |
| * @return The byte read as an int, or -1 if the end of the file was reached. |
| * |
| * @exception IOException If an error occurs |
| */ |
| public int read () throws IOException |
| { |
| return in.read(); |
| } |
| |
| /** |
| * This method reads bytes from the file into the specified array. The |
| * bytes are stored starting at the beginning of the array and up to |
| * <code>buf.length</code> bytes can be read. |
| * |
| * @param buffer The buffer to read bytes from the file into |
| * |
| * @return The actual number of bytes read or -1 if end of file |
| * |
| * @exception IOException If an error occurs |
| */ |
| public int read (byte[] buffer) throws IOException |
| { |
| return in.read (buffer); |
| } |
| |
| /** |
| * This methods reads up to <code>len</code> bytes from the file into the |
| * specified array starting at position <code>offset</code> into the array. |
| * |
| * @param buffer The array to read the bytes into |
| * @param offset The index into the array to start storing bytes |
| * @param len The requested number of bytes to read |
| * |
| * @return The actual number of bytes read, or -1 if end of file |
| * |
| * @exception IOException If an error occurs |
| */ |
| public int read (byte[] buffer, int offset, int len) throws IOException |
| { |
| return in.read (buffer, offset, len); |
| } |
| |
| /** |
| * This method reads a Java boolean value from an input stream. It does |
| * so by reading a single byte of data. If that byte is zero, then the |
| * value returned is <code>false</code> If the byte is non-zero, then |
| * the value returned is <code>true</code> |
| * <p> |
| * This method can read a <code>boolean</code> written by an object |
| * implementing the |
| * <code>writeBoolean()</code> method in the <code>DataOutput</code> |
| * interface. |
| * |
| * @return The <code>boolean</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the |
| * boolean |
| * @exception IOException If any other error occurs |
| */ |
| public final boolean readBoolean () throws IOException |
| { |
| return in.readBoolean (); |
| } |
| |
| /** |
| * This method reads a Java byte value from an input stream. The value |
| * is in the range of -128 to 127. |
| * <p> |
| * This method can read a <code>byte</code> written by an object |
| * implementing the |
| * <code>writeByte()</code> method in the <code>DataOutput</code> interface. |
| * |
| * @return The <code>byte</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the byte |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput |
| */ |
| public final byte readByte () throws IOException |
| { |
| return in.readByte (); |
| } |
| |
| /** |
| * This method reads a Java <code>char</code> value from an input stream. |
| * It operates by reading two bytes from the stream and converting them to |
| * a single 16-bit Java <code>char</code> The two bytes are stored most |
| * significant byte first (i.e., "big endian") regardless of the native |
| * host byte ordering. |
| * <p> |
| * As an example, if <code>byte1</code> and <code>byte2</code> represent |
| * the first |
| * and second byte read from the stream respectively, they will be |
| * transformed to a <code>char</code> in the following manner: |
| * <p> |
| * <code>(char)(((byte1 & 0xFF) << 8) | (byte2 & 0xFF)</code> |
| * <p> |
| * This method can read a <code>char</code> written by an object |
| * implementing the |
| * <code>writeChar()</code> method in the <code>DataOutput</code> interface. |
| * |
| * @return The <code>char</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the char |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput |
| */ |
| public final char readChar () throws IOException |
| { |
| return in.readChar(); |
| } |
| |
| /** |
| * This method reads a Java double value from an input stream. It operates |
| * by first reading a <code>logn</code> value from the stream by calling the |
| * <code>readLong()</code> method in this interface, then |
| * converts that <code>long</code> |
| * to a <code>double</code> using the <code>longBitsToDouble</code> |
| * method in the class <code>java.lang.Double</code> |
| * <p> |
| * This method can read a <code>double</code> written by an object |
| * implementing the |
| * <code>writeDouble()</code> method in the <code>DataOutput</code> |
| * interface. |
| * |
| * @return The <code>double</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading |
| * the double |
| * @exception IOException If any other error occurs |
| * |
| * @see java.lang.Double |
| * @see DataOutput |
| */ |
| public final double readDouble () throws IOException |
| { |
| return in.readDouble (); |
| } |
| |
| /** |
| * This method reads a Java float value from an input stream. It operates |
| * by first reading an <code>int</code> value from the stream by calling the |
| * <code>readInt()</code> method in this interface, then converts |
| * that <code>int</code> |
| * to a <code>float</code> using the <code>intBitsToFloat</code> method in |
| * the class <code>java.lang.Float</code> |
| * <p> |
| * This method can read a <code>float</code> written by an object |
| * implementing the |
| * <code>writeFloat()</code> method in the <code>DataOutput</code> interface. |
| * |
| * @return The <code>float</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the float |
| * @exception IOException If any other error occurs |
| * |
| * @see java.lang.Float |
| * @see DataOutput |
| */ |
| public final float readFloat () throws IOException |
| { |
| return in.readFloat(); |
| } |
| |
| /** |
| * This method reads raw bytes into the passed array until the array is |
| * full. Note that this method blocks until the data is available and |
| * throws an exception if there is not enough data left in the stream to |
| * fill the buffer |
| * |
| * @param buffer The buffer into which to read the data |
| * |
| * @exception EOFException If end of file is reached before filling the |
| * buffer |
| * @exception IOException If any other error occurs |
| */ |
| public final void readFully (byte[] buffer) throws IOException |
| { |
| in.readFully(buffer); |
| } |
| |
| /** |
| * This method reads raw bytes into the passed array <code>buf</code> |
| * starting |
| * <code>offset</code> bytes into the buffer. The number of bytes read |
| * will be |
| * exactly <code>len</code> Note that this method blocks until the data is |
| * available and throws an exception if there is not enough data left in |
| * the stream to read <code>len</code> bytes. |
| * |
| * @param buffer The buffer into which to read the data |
| * @param offset The offset into the buffer to start storing data |
| * @param count The number of bytes to read into the buffer |
| * |
| * @exception EOFException If end of file is reached before filling |
| * the buffer |
| * @exception IOException If any other error occurs |
| */ |
| public final void readFully (byte[] buffer, int offset, int count) |
| throws IOException |
| { |
| in.readFully (buffer, offset, count); |
| } |
| |
| /** |
| * This method reads a Java <code>int</code> value from an input stream |
| * It operates by reading four bytes from the stream and converting them to |
| * a single Java <code>int</code> The bytes are stored most |
| * significant byte first (i.e., "big endian") regardless of the native |
| * host byte ordering. |
| * <p> |
| * As an example, if <code>byte1</code> through <code>byte4</code> |
| * represent the first |
| * four bytes read from the stream, they will be |
| * transformed to an <code>int</code> in the following manner: |
| * <p> |
| * <code>(int)(((byte1 & 0xFF) << 24) + ((byte2 & 0xFF) << 16) + |
| * ((byte3 & 0xFF) << 8) + (byte4 & 0xFF)))</code> |
| * <p> |
| * The value returned is in the range of 0 to 65535. |
| * <p> |
| * This method can read an <code>int</code> written by an object |
| * implementing the |
| * <code>writeInt()</code> method in the <code>DataOutput</code> interface. |
| * |
| * @return The <code>int</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the int |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput |
| */ |
| public final int readInt () throws IOException |
| { |
| return in.readInt(); |
| } |
| |
| /** |
| * This method reads the next line of text data from an input stream. |
| * It operates by reading bytes and converting those bytes to |
| * <code>char</code> |
| * values by treating the byte read as the low eight bits of the |
| * <code>char</code> |
| * and using <code>0</code> as the high eight bits. Because of this, it does |
| * not support the full 16-bit Unicode character set. |
| * <p> |
| * The reading of bytes ends when either the end of file or a line terminator |
| * is encountered. The bytes read are then returned as a <code>String</code> |
| * A line terminator is a byte sequence consisting of either |
| * <code>\r</code> <code>\n</code> or <code>\r\n</code> These |
| * termination charaters are |
| * discarded and are not returned as part of the string. |
| * <p> |
| * This method can read data that was written by an object implementing the |
| * <code>writeLine()</code> method in <code>DataOutput</code> |
| * |
| * @return The line read as a <code>String</code> |
| * |
| * @exception IOException If an error occurs |
| * |
| * @see DataOutput |
| */ |
| public final String readLine () throws IOException |
| { |
| return in.readLine (); |
| } |
| |
| /** |
| * This method reads a Java long value from an input stream |
| * It operates by reading eight bytes from the stream and converting them to |
| * a single Java <code>long</code> The bytes are stored most |
| * significant byte first (i.e., "big endian") regardless of the native |
| * host byte ordering. |
| * <p> |
| * As an example, if <code>byte1</code> through <code>byte8</code> |
| * represent the first |
| * eight bytes read from the stream, they will be |
| * transformed to an <code>long</code> in the following manner: |
| * <p> |
| * <code> |
| * (long)((((long)byte1 & 0xFF) << 56) + (((long)byte2 & 0xFF) << 48) + |
| * (((long)byte3 & 0xFF) << 40) + (((long)byte4 & 0xFF) << 32) + |
| * (((long)byte5 & 0xFF) << 24) + (((long)byte6 & 0xFF) << 16) + |
| * (((long)byte7 & 0xFF) << 8) + ((long)byte9 & 0xFF)))</code> |
| * <p> |
| * The value returned is in the range of 0 to 65535. |
| * <p> |
| * This method can read an <code>long</code> written by an object |
| * implementing the |
| * <code>writeLong()</code> method in the <code>DataOutput</code> interface. |
| * |
| * @return The <code>long</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the long |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput |
| */ |
| public final long readLong () throws IOException |
| { |
| return in.readLong(); |
| } |
| |
| /** |
| * This method reads a signed 16-bit value into a Java in from the stream. |
| * It operates by reading two bytes from the stream and converting them to |
| * a single 16-bit Java <code>short</code> The two bytes are stored most |
| * significant byte first (i.e., "big endian") regardless of the native |
| * host byte ordering. |
| * <p> |
| * As an example, if <code>byte1</code> and <code>byte2</code> |
| * represent the first |
| * and second byte read from the stream respectively, they will be |
| * transformed to a <code>short</code> in the following manner: |
| * <p> |
| * <code>(short)(((byte1 & 0xFF) << 8) | (byte2 & 0xFF)</code> |
| * <p> |
| * The value returned is in the range of -32768 to 32767. |
| * <p> |
| * This method can read a <code>short</code> written by an object |
| * implementing the |
| * <code>writeShort()</code> method in the <code>DataOutput</code> interface. |
| * |
| * @return The <code>short</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the value |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput |
| */ |
| public final short readShort () throws IOException |
| { |
| return in.readShort(); |
| } |
| |
| /** |
| * This method reads 8 unsigned bits into a Java <code>int</code> value |
| * from the |
| * stream. The value returned is in the range of 0 to 255. |
| * <p> |
| * This method can read an unsigned byte written by an object implementing |
| * the <code>writeUnsignedByte()</code> method in the |
| * <code>DataOutput</code> interface. |
| * |
| * @return The unsigned bytes value read as a Java <code>int</code> |
| * |
| * @exception EOFException If end of file is reached before reading the value |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput |
| */ |
| public final int readUnsignedByte () throws IOException |
| { |
| return in.readUnsignedByte(); |
| } |
| |
| /** |
| * This method reads 16 unsigned bits into a Java int value from the stream. |
| * It operates by reading two bytes from the stream and converting them to |
| * a single Java <code>int</code> The two bytes are stored most |
| * significant byte first (i.e., "big endian") regardless of the native |
| * host byte ordering. |
| * <p> |
| * As an example, if <code>byte1</code> and <code>byte2</code> |
| * represent the first |
| * and second byte read from the stream respectively, they will be |
| * transformed to an <code>int</code> in the following manner: |
| * <p> |
| * <code>(int)(((byte1 & 0xFF) << 8) + (byte2 & 0xFF))</code> |
| * <p> |
| * The value returned is in the range of 0 to 65535. |
| * <p> |
| * This method can read an unsigned short written by an object implementing |
| * the <code>writeUnsignedShort()</code> method in the |
| * <code>DataOutput</code> interface. |
| * |
| * @return The unsigned short value read as a Java <code>int</code> |
| * |
| * @exception EOFException If end of file is reached before reading the value |
| * @exception IOException If any other error occurs |
| */ |
| public final int readUnsignedShort () throws IOException |
| { |
| return in.readUnsignedShort(); |
| } |
| |
| /** |
| * This method reads a <code>String</code> from an input stream that |
| * is encoded in |
| * a modified UTF-8 format. This format has a leading two byte sequence |
| * that contains the remaining number of bytes to read. This two byte |
| * sequence is read using the <code>readUnsignedShort()</code> method of this |
| * interface. |
| * <p> |
| * After the number of remaining bytes have been determined, these bytes |
| * are read an transformed into <code>char</code> values. |
| * These <code>char</code> values |
| * are encoded in the stream using either a one, two, or three byte format. |
| * The particular format in use can be determined by examining the first |
| * byte read. |
| * <p> |
| * If the first byte has a high order bit of 0 then |
| * that character consists on only one byte. This character value consists |
| * of seven bits that are at positions 0 through 6 of the byte. As an |
| * example, if <code>byte1</code> is the byte read from the stream, it would |
| * be converted to a <code>char</code> like so: |
| * <p> |
| * <code>(char)byte1</code> |
| * <p> |
| * If the first byte has <code>110</code> as its high order bits, then the |
| * character consists of two bytes. The bits that make up the character |
| * value are in positions 0 through 4 of the first byte and bit positions |
| * 0 through 5 of the second byte. (The second byte should have |
| * 10 as its high order bits). These values are in most significant |
| * byte first (i.e., "big endian") order. |
| * <p> |
| * As an example, if <code>byte1</code> and <code>byte2</code> |
| * are the first two bytes |
| * read respectively, and the high order bits of them match the patterns |
| * which indicate a two byte character encoding, then they would be |
| * converted to a Java <code>char</code> like so: |
| * <p> |
| * <code>(char)(((byte1 & 0x1F) << 6) | (byte2 & 0x3F))</code> |
| * <p> |
| * If the first byte has a <code>1110</code> as its high order bits, then the |
| * character consists of three bytes. The bits that make up the character |
| * value are in positions 0 through 3 of the first byte and bit positions |
| * 0 through 5 of the other two bytes. (The second and third bytes should |
| * have <code>10</code> as their high order bits). These values are in most |
| * significant byte first (i.e., "big endian") order. |
| * <p> |
| * As an example, if <code>byte1</code> <code>byte2</code> |
| * and <code>byte3</code> are the |
| * three bytes read, and the high order bits of them match the patterns |
| * which indicate a three byte character encoding, then they would be |
| * converted to a Java <code>char</code> like so: |
| * <p> |
| * <code>(char)(((byte1 & 0x0F) << 12) | ((byte2 & 0x3F) << 6) | |
| * (byte3 & 0x3F))</code> |
| * <p> |
| * Note that all characters are encoded in the method that requires the |
| * fewest number of bytes with the exception of the character with the |
| * value of <code>\u0000</code> which is encoded as two bytes. This is |
| * a modification of the UTF standard used to prevent C language style |
| * <code>NUL</code> values from appearing in the byte stream. |
| * <p> |
| * This method can read data that was written by an object implementing the |
| * <code>writeUTF()</code> method in <code>DataOutput</code> |
| * |
| * @return The <code>String</code> read |
| * |
| * @exception EOFException If end of file is reached before reading the |
| * String |
| * @exception UTFDataFormatException If the data is not in UTF-8 format |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput |
| */ |
| public final String readUTF () throws IOException |
| { |
| return in.readUTF(); |
| } |
| |
| /** |
| * This method sets the current file position to the specified offset |
| * from the beginning of the file. Note that some operating systems will |
| * allow the file pointer to be set past the current end of the file. |
| * |
| * @param pos The offset from the beginning of the file at which to set |
| * the file pointer |
| * |
| * @exception IOException If an error occurs |
| */ |
| public void seek (long pos) throws IOException |
| { |
| ch.position(pos); |
| } |
| |
| /** |
| * This method attempts to skip and discard the specified number of bytes |
| * in the input stream. It may actually skip fewer bytes than requested. |
| * The actual number of bytes skipped is returned. This method will not |
| * skip any bytes if passed a negative number of bytes to skip. |
| * |
| * @param numBytes The requested number of bytes to skip. |
| * |
| * @return The number of bytes actually skipped. |
| * |
| * @exception IOException If an error occurs. |
| */ |
| public int skipBytes (int numBytes) throws IOException |
| { |
| if (numBytes < 0) |
| throw new IllegalArgumentException ("Can't skip negative bytes: " + |
| numBytes); |
| |
| if (numBytes == 0) |
| return 0; |
| |
| long oldPos = ch.position(); |
| long newPos = oldPos + numBytes; |
| long size = ch.size(); |
| if (newPos > size) |
| newPos = size; |
| ch.position(newPos); |
| return (int) (ch.position() - oldPos); |
| } |
| |
| /** |
| * This method writes a single byte of data to the file. The file must |
| * be open for read-write in order for this operation to succeed. |
| * |
| * @param oneByte The byte of data to write, passed as an int. |
| * |
| * @exception IOException If an error occurs |
| */ |
| public void write (int oneByte) throws IOException |
| { |
| out.write(oneByte); |
| } |
| |
| /** |
| * This method writes all the bytes in the specified array to the file. |
| * The file must be open read-write in order for this operation to succeed. |
| * |
| * @param buffer The array of bytes to write to the file |
| */ |
| public void write (byte[] buffer) throws IOException |
| { |
| out.write(buffer); |
| } |
| |
| /** |
| * This method writes <code>len</code> bytes to the file from the specified |
| * array starting at index <code>offset</code> into the array. |
| * |
| * @param buffer The array of bytes to write to the file |
| * @param offset The index into the array to start writing file |
| * @param len The number of bytes to write |
| * |
| * @exception IOException If an error occurs |
| */ |
| public void write (byte[] buffer, int offset, int len) throws IOException |
| { |
| out.write (buffer, offset, len); |
| } |
| |
| /** |
| * This method writes a Java <code>boolean</code> to the underlying output |
| * stream. For a value of <code>true</code>, 1 is written to the stream. |
| * For a value of <code>false</code>, 0 is written. |
| * |
| * @param val The <code>boolean</code> value to write to the stream |
| * |
| * @exception IOException If an error occurs |
| */ |
| public final void writeBoolean (boolean val) throws IOException |
| { |
| out.writeBoolean(val); |
| } |
| |
| /** |
| * This method writes a Java <code>byte</code> value to the underlying |
| * output stream. |
| * |
| * @param val The <code>byte</code> to write to the stream, passed |
| * as an <code>int</code>. |
| * |
| * @exception IOException If an error occurs |
| */ |
| public final void writeByte (int val) throws IOException |
| { |
| out.writeByte(val); |
| } |
| |
| /** |
| * This method writes a Java <code>short</code> to the stream, high byte |
| * first. This method requires two bytes to encode the value. |
| * |
| * @param val The <code>short</code> value to write to the stream, |
| * passed as an <code>int</code>. |
| * |
| * @exception IOException If an error occurs |
| */ |
| public final void writeShort (int val) throws IOException |
| { |
| out.writeShort(val); |
| } |
| |
| /** |
| * This method writes a single <code>char</code> value to the stream, |
| * high byte first. |
| * |
| * @param val The <code>char</code> value to write, passed as |
| * an <code>int</code>. |
| * |
| * @exception IOException If an error occurs |
| */ |
| public final void writeChar (int val) throws IOException |
| { |
| out.writeChar(val); |
| } |
| |
| /** |
| * This method writes a Java <code>int</code> to the stream, high bytes |
| * first. This method requires four bytes to encode the value. |
| * |
| * @param val The <code>int</code> value to write to the stream. |
| * |
| * @exception IOException If an error occurs |
| */ |
| public final void writeInt (int val) throws IOException |
| { |
| out.writeInt(val); |
| } |
| |
| /** |
| * This method writes a Java <code>long</code> to the stream, high bytes |
| * first. This method requires eight bytes to encode the value. |
| * |
| * @param val The <code>long</code> value to write to the stream. |
| * |
| * @exception IOException If an error occurs |
| */ |
| public final void writeLong (long val) throws IOException |
| { |
| out.writeLong(val); |
| } |
| |
| /** |
| * This method writes a Java <code>float</code> value to the stream. This |
| * value is written by first calling the method |
| * <code>Float.floatToIntBits</code> |
| * to retrieve an <code>int</code> representing the floating point number, |
| * then writing this <code>int</code> value to the stream exactly the same |
| * as the <code>writeInt()</code> method does. |
| * |
| * @param val The floating point number to write to the stream. |
| * |
| * @exception IOException If an error occurs |
| * |
| * @see #writeInt(int) |
| */ |
| public final void writeFloat (float val) throws IOException |
| { |
| out.writeFloat(val); |
| } |
| |
| /** |
| * This method writes a Java <code>double</code> value to the stream. This |
| * value is written by first calling the method |
| * <code>Double.doubleToLongBits</code> |
| * to retrieve an <code>long</code> representing the floating point number, |
| * then writing this <code>long</code> value to the stream exactly the same |
| * as the <code>writeLong()</code> method does. |
| * |
| * @param val The double precision floating point number to write to the |
| * stream. |
| * |
| * @exception IOException If an error occurs |
| * |
| * @see #writeLong(long) |
| */ |
| public final void writeDouble (double val) throws IOException |
| { |
| out.writeDouble(val); |
| } |
| |
| /** |
| * This method writes all the bytes in a <code>String</code> out to the |
| * stream. One byte is written for each character in the <code>String</code>. |
| * The high eight bits of each character are discarded. |
| * |
| * @param val The <code>String</code> to write to the stream |
| * |
| * @exception IOException If an error occurs |
| */ |
| public final void writeBytes (String val) throws IOException |
| { |
| out.writeBytes(val); |
| } |
| |
| /** |
| * This method writes all the characters in a <code>String</code> to the |
| * stream. There will be two bytes for each character value. The high |
| * byte of the character will be written first. |
| * |
| * @param val The <code>String</code> to write to the stream. |
| * |
| * @exception IOException If an error occurs |
| */ |
| public final void writeChars (String val) throws IOException |
| { |
| out.writeChars(val); |
| } |
| |
| /** |
| * This method writes a Java <code>String</code> to the stream in a modified |
| * UTF-8 format. First, two bytes are written to the stream indicating the |
| * number of bytes to follow. Note that this is the number of bytes in the |
| * encoded <code>String</code> not the <code>String</code> length. Next |
| * come the encoded characters. Each character in the <code>String</code> |
| * is encoded as either one, two or three bytes. For characters in the |
| * range of <code>\u0001</code> to <code>\u007F</code>, |
| * one byte is used. The character |
| * value goes into bits 0-7 and bit eight is 0. For characters in the range |
| * of <code>\u0080</code> to <code>\u007FF</code>, two |
| * bytes are used. Bits |
| * 6-10 of the character value are encoded bits 0-4 of the first byte, with |
| * the high bytes having a value of "110". Bits 0-5 of the character value |
| * are stored in bits 0-5 of the second byte, with the high bits set to |
| * "10". This type of encoding is also done for the null character |
| * <code>\u0000</code>. This eliminates any C style NUL character values |
| * in the output. All remaining characters are stored as three bytes. |
| * Bits 12-15 of the character value are stored in bits 0-3 of the first |
| * byte. The high bits of the first bytes are set to "1110". Bits 6-11 |
| * of the character value are stored in bits 0-5 of the second byte. The |
| * high bits of the second byte are set to "10". And bits 0-5 of the |
| * character value are stored in bits 0-5 of byte three, with the high bits |
| * of that byte set to "10". |
| * |
| * @param val The <code>String</code> to write to the output in UTF format |
| * |
| * @exception IOException If an error occurs |
| */ |
| public final void writeUTF (String val) throws IOException |
| { |
| out.writeUTF(val); |
| } |
| |
| /** |
| * This method creates a java.nio.channels.FileChannel. |
| * Nio does not allow one to create a file channel directly. |
| * A file channel must be created by first creating an instance of |
| * Input/Output/RandomAccessFile and invoking the getChannel() method on it. |
| */ |
| public final synchronized FileChannel getChannel () |
| { |
| return ch; |
| } |
| } |