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			804 lines
		
	
	
		
			29 KiB
		
	
	
	
		
			Java
		
	
	
	
			
		
		
	
	
			804 lines
		
	
	
		
			29 KiB
		
	
	
	
		
			Java
		
	
	
	
/* DataInputStream.java -- FilteredInputStream that implements DataInput
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   Copyright (C) 1998, 1999, 2000, 2001, 2003  Free Software Foundation
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING.  If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library.  Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module.  An independent module is a module which is not derived from
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or based on this library.  If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so.  If you do not wish to do so, delete this
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exception statement from your version. */
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package java.io;
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/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
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 * "The Java Language Specification", ISBN 0-201-63451-1
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 * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
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 * Status:  Believed complete and correct.
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 */
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/**
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 * This subclass of <code>FilteredInputStream</code> implements the
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 * <code>DataInput</code> interface that provides method for reading primitive
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 * Java data types from a stream.
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 *
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 * @see DataInput
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 *
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 * @author Warren Levy <warrenl@cygnus.com>
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 * @author Aaron M. Renn <arenn@urbanophile.com>
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 * @date October 20, 1998.  
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 */
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public class DataInputStream extends FilterInputStream implements DataInput
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{
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  // readLine() hack to ensure that an '\r' not followed by an '\n' is
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  // handled correctly. If set, readLine() will ignore the first char it sees
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  // if that char is a '\n'
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  boolean ignoreInitialNewline = false;
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  // Byte buffer, used to make primitive read calls more efficient.
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  byte[] buf = new byte [8];
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  /**
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   * This constructor initializes a new <code>DataInputStream</code>
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   * to read from the specified subordinate stream.
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   *
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   * @param in The subordinate <code>InputStream</code> to read from
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   */
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  public DataInputStream (InputStream in)
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  {
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    super (in);
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  }
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  /**
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   * This method reads bytes from the underlying stream into the specified
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   * byte array buffer.  It will attempt to fill the buffer completely, but
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   * may return a short count if there is insufficient data remaining to be
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   * read to fill the buffer.
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   *
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   * @param b The buffer into which bytes will be read.
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   * 
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   * @return The actual number of bytes read, or -1 if end of stream reached 
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   * before reading any bytes.
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   *
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   * @exception IOException If an error occurs.
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   */
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  public final int read (byte[] b) throws IOException
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  {
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    return in.read (b, 0, b.length);
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  }
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  /**
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   * This method reads bytes from the underlying stream into the specified
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   * byte array buffer.  It will attempt to read <code>len</code> bytes and
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   * will start storing them at position <code>off</code> into the buffer.
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   * This method can return a short count if there is insufficient data
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   * remaining to be read to complete the desired read length.
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   *
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   * @param b The buffer into which bytes will be read.
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   * @param off The offset into the buffer to start storing bytes.
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   * @param len The requested number of bytes to read.
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   *
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   * @return The actual number of bytes read, or -1 if end of stream reached
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   * before reading any bytes.
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   *
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   * @exception IOException If an error occurs.
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   */
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  public final int read (byte[] b, int off, int len) throws IOException
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  {
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    return in.read (b, off, len);
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  }
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  /**
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   * This method reads a Java boolean value from an input stream.  It does
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   * so by reading a single byte of data.  If that byte is zero, then the
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   * value returned is <code>false</code>.  If the byte is non-zero, then
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   * the value returned is <code>true</code>.
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   * <p>
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   * This method can read a <code>boolean</code> written by an object
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   * implementing the <code>writeBoolean()</code> method in the
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   * <code>DataOutput</code> interface. 
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   *
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   * @return The <code>boolean</code> value read
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   *
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   * @exception EOFException If end of file is reached before reading
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   * the boolean
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   * @exception IOException If any other error occurs
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   *
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   * @see DataOutput#writeBoolean
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   */
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  public final boolean readBoolean () throws IOException
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  {
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    return convertToBoolean (in.read ());
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  }
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  /**
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   * This method reads a Java byte value from an input stream.  The value
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   * is in the range of -128 to 127.
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   * <p>
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   * This method can read a <code>byte</code> written by an object
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   * implementing the <code>writeByte()</code> method in the
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   * <code>DataOutput</code> interface.
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   *
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   * @return The <code>byte</code> value read
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   *
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   * @exception EOFException If end of file is reached before reading the byte
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   * @exception IOException If any other error occurs
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   *
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   * @see DataOutput#writeByte
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   */
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  public final byte readByte () throws IOException
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  {
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    return convertToByte (in.read ());
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  }
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  /**
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   * This method reads a Java <code>char</code> value from an input stream.  
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   * It operates by reading two bytes from the stream and converting them to 
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   * a single 16-bit Java <code>char</code>.  The two bytes are stored most
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   * significant byte first (i.e., "big endian") regardless of the native
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   * host byte ordering. 
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   * <p>
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   * As an example, if <code>byte1</code> and <code>byte2</code>
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   * represent the first and second byte read from the stream
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   * respectively, they will be transformed to a <code>char</code> in
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   * the following manner: 
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   * <p>
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   * <code>(char)(((byte1 & 0xFF) << 8) | (byte2 & 0xFF)</code>
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   * <p>
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   * This method can read a <code>char</code> written by an object
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   * implementing the <code>writeChar()</code> method in the
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   * <code>DataOutput</code> interface. 
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   *
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   * @return The <code>char</code> value read 
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   *
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   * @exception EOFException If end of file is reached before reading the char
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   * @exception IOException If any other error occurs
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   *
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   * @see DataOutput#writeChar
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   */
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  public final char readChar () throws IOException
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  {
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    readFully (buf, 0, 2);
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    return convertToChar (buf);
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  }
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  /**
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   * This method reads a Java double value from an input stream.  It operates
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   * by first reading a <code>long</code> value from the stream by calling the
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   * <code>readLong()</code> method in this interface, then converts
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   * that <code>long</code> to a <code>double</code> using the
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   * <code>longBitsToDouble</code> method in the class
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   * <code>java.lang.Double</code> 
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   * <p>
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   * This method can read a <code>double</code> written by an object
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   * implementing the <code>writeDouble()</code> method in the
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   * <code>DataOutput</code> interface.
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   *
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   * @return The <code>double</code> value read
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   *
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   * @exception EOFException If end of file is reached before reading
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   * the double
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   * @exception IOException If any other error occurs
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   *
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   * @see DataOutput#writeDouble
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   * @see java.lang.Double#longBitsToDouble
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   */
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  public final double readDouble () throws IOException
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  {
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    return Double.longBitsToDouble (readLong ());
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  }
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  /**
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   * This method reads a Java float value from an input stream.  It
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   * operates by first reading an <code>int</code> value from the
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   * stream by calling the <code>readInt()</code> method in this
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   * interface, then converts that <code>int</code> to a
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   * <code>float</code> using the <code>intBitsToFloat</code> method
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   * in the class <code>java.lang.Float</code>
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   * <p>
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   * This method can read a <code>float</code> written by an object
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   * implementing the <code>writeFloat()</code> method in the
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   * <code>DataOutput</code> interface.
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   *
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   * @return The <code>float</code> value read
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   *
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   * @exception EOFException If end of file is reached before reading the float
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   * @exception IOException If any other error occurs
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   *
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   * @see DataOutput#writeFloat 
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   * @see java.lang.Float#intBitsToFloat
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   */
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  public final float readFloat () throws IOException
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  {
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    return Float.intBitsToFloat (readInt ());
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  }
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  /**
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   * This method reads raw bytes into the passed array until the array is
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   * full.  Note that this method blocks until the data is available and
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   * throws an exception if there is not enough data left in the stream to
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   * fill the buffer.  Note also that zero length buffers are permitted.
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   * In this case, the method will return immediately without reading any
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   * bytes from the stream.
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   *
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   * @param b The buffer into which to read the data
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   *
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   * @exception EOFException If end of file is reached before filling the
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   * buffer
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   * @exception IOException If any other error occurs
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   */
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  public final void readFully (byte[] b) throws IOException
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  {
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    readFully (b, 0, b.length);
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  }
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  /**
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   * This method reads raw bytes into the passed array <code>buf</code>
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   * starting
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   * <code>offset</code> bytes into the buffer.  The number of bytes read
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   * will be
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   * exactly <code>len</code>.  Note that this method blocks until the data is
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   * available and throws an exception if there is not enough data left in
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   * the stream to read <code>len</code> bytes.  Note also that zero length
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   * buffers are permitted.  In this case, the method will return immediately
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   * without reading any bytes from the stream.
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   *
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   * @param buf The buffer into which to read the data
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   * @param offset The offset into the buffer to start storing data
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   * @param len The number of bytes to read into the buffer
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   *
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   * @exception EOFException If end of file is reached before filling the
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   * buffer
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   * @exception IOException If any other error occurs
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   */
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  public final void readFully (byte[] buf, int offset, int len) throws IOException
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  {
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    if (len < 0)
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      throw new IndexOutOfBoundsException("Negative length: " + len);
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    while (len > 0)
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      {
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	// in.read will block until some data is available.
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	int numread = in.read (buf, offset, len);
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	if (numread < 0)
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	  throw new EOFException ();
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	len -= numread;
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	offset += numread;
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      }
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  }
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  /**
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   * This method reads a Java <code>int</code> value from an input stream
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   * It operates by reading four bytes from the stream and converting them to
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   * a single Java <code>int</code>.  The bytes are stored most
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   * significant byte first (i.e., "big endian") regardless of the native
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   * host byte ordering.
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   * <p>
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   * As an example, if <code>byte1</code> through <code>byte4</code> represent
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   * the first four bytes read from the stream, they will be
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   * transformed to an <code>int</code> in the following manner:
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   * <p>
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   * <code>(int)(((byte1 & 0xFF) << 24) + ((byte2 & 0xFF) << 16) +
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   * ((byte3 & 0xFF)<< 8) + (byte4 & 0xFF)))</code>
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   * <p>
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   * The value returned is in the range of -2147483648 to 2147483647.
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   * <p>
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   * This method can read an <code>int</code> written by an object
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   * implementing the <code>writeInt()</code> method in the
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   * <code>DataOutput</code> interface.
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   *
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   * @return The <code>int</code> value read
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   *
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   * @exception EOFException If end of file is reached before reading the int
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   * @exception IOException If any other error occurs
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   *
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   * @see DataOutput#writeInt
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   */
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  public final int readInt () throws IOException
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  {
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    readFully (buf, 0, 4);
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    return convertToInt (buf);
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  }
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  /**
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   * This method reads the next line of text data from an input
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   * stream.  It operates by reading bytes and converting those bytes
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   * to <code>char</code> values by treating the byte read as the low
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   * eight bits of the <code>char</code> and using 0 as the high eight
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   * bits.  Because of this, it does not support the full 16-bit
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   * Unicode character set.
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   * <p>
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   * The reading of bytes ends when either the end of file or a line
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   * terminator is encountered.  The bytes read are then returned as a
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   * <code>String</code> A line terminator is a byte sequence
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   * consisting of either <code>\r</code>, <code>\n</code> or
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   * <code>\r\n</code>.  These termination charaters are discarded and
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   * are not returned as part of the string.
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   * <p>
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   * This method can read data that was written by an object implementing the
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   * <code>writeLine()</code> method in <code>DataOutput</code>.
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   *
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   * @return The line read as a <code>String</code>
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   *
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   * @exception IOException If an error occurs
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   *
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   * @see DataOutput
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   *
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   * @deprecated
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   */
 | 
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  public final String readLine () throws IOException
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  {
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    StringBuffer strb = new StringBuffer ();
 | 
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    readloop: while (true)
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      {
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        int c = 0;
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        char ch = ' ';
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        boolean getnext = true;
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        while (getnext)
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          {
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	    getnext = false;
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	    c = in.read();
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	    if (c < 0)	// got an EOF
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	      return strb.length () > 0 ? strb.toString () : null;
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	    ch = (char) c;
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	    if ((ch &= 0xFF) == '\n')
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	      // hack to correctly handle '\r\n' sequences
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	      if (ignoreInitialNewline)
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		{
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		  ignoreInitialNewline = false;
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		  getnext = true;
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		}
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	      else
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		break readloop;
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	  }
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	if (ch == '\r')
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	  {
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	    // FIXME: The following code tries to adjust the stream back one
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	    // character if the next char read is '\n'.  As a last resort,
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	    // it tries to mark the position before reading but the bottom
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	    // line is that it is possible that this method will not properly
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	    // deal with a '\r' '\n' combination thus not fulfilling the
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	    // DataInput contract for readLine.  It's not a particularly
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	    // safe approach threadwise since it is unsynchronized and
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	    // since it might mark an input stream behind the users back.
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	    // Along the same vein it could try the same thing for
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	    // ByteArrayInputStream and PushbackInputStream, but that is
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	    // probably overkill since this is deprecated & BufferedInputStream
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	    // is the most likely type of input stream.
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	    //
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	    // The alternative is to somehow push back the next byte if it
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	    // isn't a '\n' or to have the reading methods of this class
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	    // keep track of whether the last byte read was '\r' by readLine
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	    // and then skip the very next byte if it is '\n'.  Either way,
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	    // this would increase the complexity of the non-deprecated methods
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	    // and since it is undesirable to make non-deprecated methods
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	    // less efficient, the following seems like the most reasonable
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	    // approach.
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	    int next_c = 0;
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            char next_ch = ' ';
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						|
	    if (in instanceof BufferedInputStream)
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	      {
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	        next_c = in.read();
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	        next_ch = (char) (next_c & 0xFF);
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		if ((next_ch != '\n') && (next_c >= 0)) 
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		  {
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	            BufferedInputStream bin = (BufferedInputStream) in;
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		    if (bin.pos > 0)
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                      bin.pos--;
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		  }
 | 
						|
	      }
 | 
						|
	    else if (markSupported())
 | 
						|
	      {
 | 
						|
	        next_c = in.read();
 | 
						|
	        next_ch = (char) (next_c & 0xFF);
 | 
						|
		if ((next_ch != '\n') && (next_c >= 0)) 
 | 
						|
		  {
 | 
						|
		    mark(1);
 | 
						|
		    if ((in.read() & 0xFF) != '\n')
 | 
						|
		      reset();
 | 
						|
		  }
 | 
						|
	      } 
 | 
						|
	    // In order to catch cases where 'in' isn't a BufferedInputStream
 | 
						|
	    // and doesn't support mark() (such as reading from a Socket), set 
 | 
						|
	    // a flag that instructs readLine() to ignore the first character 
 | 
						|
	    // it sees _if_ that character is a '\n'.
 | 
						|
	    else ignoreInitialNewline = true;
 | 
						|
	    break;
 | 
						|
	  }
 | 
						|
	strb.append(ch);
 | 
						|
      }
 | 
						|
 | 
						|
    return strb.length() > 0 ? strb.toString() : "";
 | 
						|
  }
 | 
						|
 | 
						|
  /**
 | 
						|
   * This method reads a Java <code>long</code> 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)(((byte1 & 0xFF) << 56) + ((byte2 & 0xFF) << 48) +
 | 
						|
   * ((byte3 & 0xFF) << 40) + ((byte4 & 0xFF) << 32) +
 | 
						|
   * ((byte5 & 0xFF) << 24) + ((byte6 & 0xFF) << 16) +
 | 
						|
   * ((byte7 & 0xFF) << 8) + (byte8 & 0xFF)))
 | 
						|
   * </code>
 | 
						|
   * <p>
 | 
						|
   * The value returned is in the range of -9223372036854775808 to
 | 
						|
   * 9223372036854775807.
 | 
						|
   * <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#writeLong
 | 
						|
   */
 | 
						|
  public final long readLong () throws IOException
 | 
						|
  {
 | 
						|
    readFully (buf, 0, 8);
 | 
						|
    return convertToLong (buf);
 | 
						|
  }
 | 
						|
 | 
						|
  /**
 | 
						|
   * 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#writeShort
 | 
						|
   */
 | 
						|
  public final short readShort () throws IOException
 | 
						|
  {
 | 
						|
    readFully (buf, 0, 2);
 | 
						|
    return convertToShort (buf);
 | 
						|
  }
 | 
						|
  
 | 
						|
  /**
 | 
						|
   * 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#writeByte
 | 
						|
   */
 | 
						|
  public final int readUnsignedByte () throws IOException
 | 
						|
  {
 | 
						|
    return convertToUnsignedByte (in.read ());
 | 
						|
  }
 | 
						|
 | 
						|
  /**
 | 
						|
   * 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
 | 
						|
   *
 | 
						|
   * @see DataOutput#writeShort
 | 
						|
   */
 | 
						|
  public final int readUnsignedShort () throws IOException
 | 
						|
  {
 | 
						|
    readFully (buf, 0, 2);
 | 
						|
    return convertToUnsignedShort (buf);
 | 
						|
  }
 | 
						|
 | 
						|
  /**
 | 
						|
   * 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 110 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 1110 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 10 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#writeUTF
 | 
						|
   */
 | 
						|
  public final String readUTF () throws IOException
 | 
						|
  {
 | 
						|
    return readUTF (this);
 | 
						|
  }
 | 
						|
 | 
						|
  /**
 | 
						|
   * This method reads a String encoded in UTF-8 format from the 
 | 
						|
   * specified <code>DataInput</code> source.
 | 
						|
   *
 | 
						|
   * @param in The <code>DataInput</code> source to read from
 | 
						|
   *
 | 
						|
   * @return The String read from the source
 | 
						|
   *
 | 
						|
   * @exception IOException If an error occurs
 | 
						|
   *
 | 
						|
   * @see DataInput#readUTF
 | 
						|
   */
 | 
						|
  public static final String readUTF(DataInput in) throws IOException
 | 
						|
  {
 | 
						|
    final int UTFlen = in.readUnsignedShort ();
 | 
						|
    byte[] buf = new byte [UTFlen];
 | 
						|
 | 
						|
    // This blocks until the entire string is available rather than
 | 
						|
    // doing partial processing on the bytes that are available and then
 | 
						|
    // blocking.  An advantage of the latter is that Exceptions
 | 
						|
    // could be thrown earlier.  The former is a bit cleaner.
 | 
						|
    in.readFully (buf, 0, UTFlen);
 | 
						|
 | 
						|
    return convertFromUTF (buf);
 | 
						|
  }
 | 
						|
 | 
						|
  /**
 | 
						|
   * This method attempts to skip and discard the specified number of bytes 
 | 
						|
   * in the input stream.  It may actually skip fewer bytes than requested. 
 | 
						|
   * This method will not skip any bytes if passed a negative number of bytes 
 | 
						|
   * to skip. 
 | 
						|
   *
 | 
						|
   * @param n The requested number of bytes to skip.
 | 
						|
   *
 | 
						|
   * @return The requested number of bytes to skip.
 | 
						|
   *
 | 
						|
   * @exception IOException If an error occurs.
 | 
						|
   * @specnote The JDK docs claim that this returns the number of bytes 
 | 
						|
   *  actually skipped. The JCL claims that this method can throw an 
 | 
						|
   *  EOFException. Neither of these appear to be true in the JDK 1.3's
 | 
						|
   *  implementation. This tries to implement the actual JDK behaviour.
 | 
						|
   */
 | 
						|
  public final int skipBytes (int n) throws IOException
 | 
						|
  {
 | 
						|
    if (n <= 0)
 | 
						|
      return 0;    
 | 
						|
    try
 | 
						|
      {
 | 
						|
        return (int) in.skip (n);
 | 
						|
      }
 | 
						|
    catch (EOFException x)
 | 
						|
      {
 | 
						|
        // do nothing.
 | 
						|
      }         
 | 
						|
    return n;
 | 
						|
  }
 | 
						|
  
 | 
						|
  static boolean convertToBoolean (int b) throws EOFException
 | 
						|
  {
 | 
						|
    if (b < 0)
 | 
						|
      throw new EOFException ();
 | 
						|
    
 | 
						|
    return (b != 0);
 | 
						|
  }
 | 
						|
 | 
						|
  static byte convertToByte (int i) throws EOFException
 | 
						|
  {
 | 
						|
    if (i < 0)
 | 
						|
      throw new EOFException ();
 | 
						|
    
 | 
						|
    return (byte) i;
 | 
						|
  }
 | 
						|
 | 
						|
  static int convertToUnsignedByte (int i) throws EOFException
 | 
						|
  {
 | 
						|
    if (i < 0)
 | 
						|
      throw new EOFException ();
 | 
						|
    
 | 
						|
    return (i & 0xFF);
 | 
						|
  }
 | 
						|
 | 
						|
  static char convertToChar (byte[] buf)
 | 
						|
  {
 | 
						|
    return (char) ((buf [0] << 8)
 | 
						|
		    | (buf [1] & 0xff));  
 | 
						|
  }  
 | 
						|
 | 
						|
  static short convertToShort (byte[] buf)
 | 
						|
  {
 | 
						|
    return (short) ((buf [0] << 8)
 | 
						|
		    | (buf [1] & 0xff));  
 | 
						|
  }  
 | 
						|
 | 
						|
  static int convertToUnsignedShort (byte[] buf)
 | 
						|
  {
 | 
						|
    return (((buf [0] & 0xff) << 8)
 | 
						|
	    | (buf [1] & 0xff));  
 | 
						|
  }
 | 
						|
 | 
						|
  static int convertToInt (byte[] buf)
 | 
						|
  {
 | 
						|
    return (((buf [0] & 0xff) << 24)
 | 
						|
	    | ((buf [1] & 0xff) << 16)
 | 
						|
	    | ((buf [2] & 0xff) << 8)
 | 
						|
	    | (buf [3] & 0xff));  
 | 
						|
  }
 | 
						|
 | 
						|
  static long convertToLong (byte[] buf)
 | 
						|
  {
 | 
						|
    return (((long)(buf [0] & 0xff) << 56) |
 | 
						|
	    ((long)(buf [1] & 0xff) << 48) |
 | 
						|
	    ((long)(buf [2] & 0xff) << 40) |
 | 
						|
	    ((long)(buf [3] & 0xff) << 32) |
 | 
						|
	    ((long)(buf [4] & 0xff) << 24) |
 | 
						|
	    ((long)(buf [5] & 0xff) << 16) |
 | 
						|
	    ((long)(buf [6] & 0xff) <<  8) |
 | 
						|
	    ((long)(buf [7] & 0xff)));  
 | 
						|
  }
 | 
						|
 | 
						|
  // FIXME: This method should be re-thought.  I suspect we have multiple
 | 
						|
  // UTF-8 decoders floating around.  We should use the standard charset
 | 
						|
  // converters, maybe and adding a direct call into one of the new
 | 
						|
  // NIO converters for a super-fast UTF8 decode.
 | 
						|
  static String convertFromUTF (byte[] buf) 
 | 
						|
    throws EOFException, UTFDataFormatException
 | 
						|
  {
 | 
						|
    // Give StringBuffer an initial estimated size to avoid 
 | 
						|
    // enlarge buffer frequently
 | 
						|
    StringBuffer strbuf = new StringBuffer (buf.length / 2 + 2);
 | 
						|
 | 
						|
    for (int i = 0; i < buf.length; )
 | 
						|
      {
 | 
						|
	if ((buf [i] & 0x80) == 0)		// bit pattern 0xxxxxxx
 | 
						|
	  strbuf.append ((char) (buf [i++] & 0xFF));
 | 
						|
	else if ((buf [i] & 0xE0) == 0xC0)	// bit pattern 110xxxxx
 | 
						|
	  {
 | 
						|
	    if (i + 1 >= buf.length
 | 
						|
		|| (buf [i + 1] & 0xC0) != 0x80)
 | 
						|
	      throw new UTFDataFormatException ();
 | 
						|
 | 
						|
	    strbuf.append((char) (((buf [i++] & 0x1F) << 6)
 | 
						|
				  | (buf [i++] & 0x3F)));
 | 
						|
	  }
 | 
						|
	else if ((buf [i] & 0xF0) == 0xE0)	// bit pattern 1110xxxx
 | 
						|
	  {
 | 
						|
	    if (i + 2 >= buf.length
 | 
						|
		|| (buf [i + 1] & 0xC0) != 0x80
 | 
						|
		|| (buf [i + 2] & 0xC0) != 0x80)
 | 
						|
	      throw new UTFDataFormatException ();
 | 
						|
 | 
						|
	    strbuf.append ((char) (((buf [i++] & 0x0F) << 12)
 | 
						|
				   | ((buf [i++] & 0x3F) << 6)
 | 
						|
				   | (buf [i++] & 0x3F)));
 | 
						|
	  }
 | 
						|
	else // must be ((buf [i] & 0xF0) == 0xF0 || (buf [i] & 0xC0) == 0x80)
 | 
						|
	  throw new UTFDataFormatException ();	// bit patterns 1111xxxx or
 | 
						|
						// 		10xxxxxx
 | 
						|
      }
 | 
						|
 | 
						|
    return strbuf.toString ();
 | 
						|
  }
 | 
						|
}
 |