gcc/libjava/java/io/RandomAccessFile.java

/* RandomAccessFile.java -- Class supporting random file I/O
   Copyright (C) 1998, 1999, 2001, 2002, 2003 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 java.nio.channels.FileChannel;
import gnu.java.nio.FileChannelImpl;

/* 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 FileDescriptor fd;
  // The corresponding input and output streams.
  private DataOutputStream out;
  private DataInputStream in;
  
  private FileChannel ch; /* cached associated file-channel */
  
  /**
   * 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 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 fileName The name of the file 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 FileNotFoundException If any other error occurs
   */
  public RandomAccessFile (String fileName, String mode)
    throws FileNotFoundException
  {
    // Check the mode
    if (!mode.equals("r") && !mode.equals("rw") && !mode.equals("rws") &&
        !mode.equals("rwd"))
      throw new IllegalArgumentException("Bad mode value: " + mode);
  
    int fdmode;
    if (mode.compareTo ("r") == 0)
      fdmode = FileDescriptor.READ;
    else if (mode.compareTo ("rw") == 0)
      fdmode = FileDescriptor.READ | FileDescriptor.WRITE;
    else
      throw new IllegalArgumentException ("invalid mode: " + mode);

    // The obligatory SecurityManager stuff
    SecurityManager s = System.getSecurityManager();
    if (s != null)
      {
        s.checkRead(fileName);

        if ((fdmode & FileDescriptor.WRITE) != 0)
          s.checkWrite(fileName);
      }

    fd = new FileDescriptor (fileName, fdmode);
    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
  {
    if (fd.valid())
      fd.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
  {
    if (! fd.valid())
      throw new IOException ();

    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 fd.getFilePointer();
  }

  /**
   * 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.  If the current
   * length of the file is shorter than the specified length, the file
   * is extended with bytes of an undefined value.
   *  <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 pos) throws IOException
  {
    fd.setLength(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 fd.length();
  }

  /**
   * 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 buf 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 buf 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 buf 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 buf The buffer into which to read the data
   * @param offset The offset into the buffer to start storing data
   * @param len 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
   *
   * @deprecated
   */
  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();
  }

  public final short readShort () throws IOException
  {
    return in.readShort();
  }

  public final int readUnsignedByte () throws IOException
  {
    return in.readUnsignedByte();
  }

  public final int readUnsignedShort () throws IOException
  {
    return in.readUnsignedShort();
  }

  public final String readUTF () throws IOException
  {
    return in.readUTF();
  }

  public void seek (long pos) throws IOException
  {
    fd.seek(pos, FileDescriptor.SET, false);
  }

  public int skipBytes (int count) throws IOException
  {
    if (count <= 0)
      return 0;
    long startPos = fd.getFilePointer();
    long endPos = fd.seek(count, FileDescriptor.CUR, true);
    return (int) (endPos - startPos);
  }

  public void write (int oneByte) throws IOException
  {
    out.write(oneByte);
  }

  public void write (byte[] buffer) throws IOException
  {
    out.write(buffer);
  }

  public void write (byte[] buffer, int offset, int count) throws IOException
  {
    out.write(buffer, offset, count);
  }

  public final void writeBoolean (boolean val) throws IOException
  {
    out.writeBoolean(val);
  }

  public final void writeByte (int v) throws IOException
  {
    out.writeByte(v);
  }

  public final void writeShort (int v) throws IOException
  {
    out.writeShort(v);
  }

  public final void writeChar (int v) throws IOException
  {
    out.writeChar(v);
  }

  public final void writeInt (int v) throws IOException
  {
    out.writeInt(v);
  }

  public final void writeLong (long v) throws IOException
  {
    out.writeLong(v);
  }

  public final void writeFloat (float v) throws IOException
  {
    out.writeFloat(v);
  }

  public final void writeDouble (double v) throws IOException
  {
    out.writeDouble(v);
  }

  public final void writeBytes (String s) throws IOException
  {
    out.writeBytes(s);
  }

  public final void writeChars (String s) throws IOException
  {
    out.writeChars(s);
  }
  
  /**
   * 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>&#92;u0001</code> to <code>&#92;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>&#92;u0080</code> to <code>&#92;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>&#92;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 s The <code>String</code> to write to the output in UTF format
   *
   * @exception IOException If an error occurs
   */
  public final void writeUTF(String s) throws IOException
  {
    out.writeUTF(s);
  }
  
  /**
   * 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 synchronized FileChannel getChannel() 
  {
    if (ch == null)
      ch = new FileChannelImpl (fd, true, this);

    return ch;
  }

} // class RandomAccessFile