path: root/java/io/LineNumberInputStream.java

/* LineNumberInputStream.java -- An input stream which counts line numbers
   Copyright (C) 1998 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.

As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */


package java.io;

/**
  * This class functions like a standard <code>InputStream</code> except that it
  * counts line numbers, and canonicalizes newline characters.  As data
  * is read, whenever the byte sequences "\r", "\n", or "\r\n" are encountered,
  * the running line count is incremeted by one.  Additionally, the whatever
  * line termination sequence was encountered will be converted to a "\n"
  * byte.  Note that this class numbers lines from 0.  When the first
  * line terminator is encountered, the line number is incremented to 1, and
  * so on.
  * <p>
  * This class counts only line termination characters.  If the last line
  * read from the stream does not end in a line termination sequence, it
  * will not be counted as a line.
  * <p>
  * Note that since this class operates as a filter on an underlying stream,
  * it has the same mark/reset functionality as the underlying stream.  The
  * <code>mark()</code> and <code>reset()</code> methods in this class handle line numbers
  * correctly.  Calling @code{reset()} resets the line number to the point
  * at which <code>mark()</code> was called if the subordinate stream supports
  * that functionality.
  * <p>
  * This class is deprecated in favor if <code>LineNumberReader</code> because
  * it operates on ASCII bytes instead of an encoded character stream.  This
  * class is for backward compatibility only and should not be used in
  * new applications.
  *
  * @deprecated
  *
  * @version 0.0
  *
  * @author Aaron M. Renn (arenn@urbanophile.com)
  */
public class LineNumberInputStream extends FilterInputStream
{

/*************************************************************************/

/*
 * Instance Variables
 */

/**
  * This variable is used to keep track of the current line number
  */
private int line_number;

/**
  * This variable is used to keep track of the line number that was
  * current when the <code>mark()</code> method was called.
  */
private int marked_line_number;

/*************************************************************************/

/*
 * Constructors
 */

/**
  * Create a new <code>LineNumberInputStream</code> that reads from the 
  * specified subordinate <code>InputStream</code>
  *
  * @param in The subordinate <code>InputStream</code> to read from
  */
public
LineNumberInputStream(InputStream in)
{
  super(in);

  // Override this.in with another filter
  this.in = new PushbackInputStream(in);
}

/*************************************************************************/

/*
 * Instance Methods
 */

/**
  * This method returns the current line number
  *
  * @returns The current line number
  */
public int 
getLineNumber()
{
  return(line_number);
}

/*************************************************************************/

/**
  * This method sets the current line number to the specified value.
  * 
  * @param line_number The new line number
  */
public void
setLineNumber(int line_number)
{
  this.line_number = line_number;
}

/*************************************************************************/

/**
  * This method returns the number of bytes that can be read from the 
  * stream before the stream can block.  This method is tricky because
  * the subordinate <code>InputStream</code> might return only "\r\n" characters,
  * which are replaced by a single "\n" character by the <code>read()</code> method
  * of this class.  So this method can only guarantee that
  * <code>in.available() / 2</code> bytes can actually be read before blocking.
  * In practice, considerably more bytes might be read before blocking
  * <p>
  * Note that the stream may not block if additional bytes beyond the count
  * returned by this method are read.
  *
  * @return The number of bytes that can be read before blocking could occur
  *
  * @exception IOException If an error occurs
  */
public int
available() throws IOException
{
  return(in.available() / 2);
}

/*************************************************************************/

/**
  * This method marks a position in the input to which the stream can be
  * "reset" byte calling the <code>reset()</code> method.  The parameter
  * <code>readlimit</code> is the number of bytes that can be read from the
  * stream after setting the mark before the mark becomes invalid.   For
  * example, if <code>mark()</code> is called with a read limit of 10, then when
  * 11 bytes of data are read from the stream before the <code>reset()</code>
  * method is called, then the mark is invalid and the stream object
  * instance is not required to remember the mark.
  * <p>
  * In this class, this method will remember the current line number as well
  * as the current position in the stream.  When the <code>reset()</code> method 
  * is called, the line number will be restored to the saved line number in
  * addition to the stream position.
  * <p>
  * This method only works if the subordinate stream supports mark/reset
  * functionality.
  *
  * @param readlimit The number of bytes that can be read before the mark becomes invalid
  */
public synchronized void
mark(int readlimit)
{
  in.mark(readlimit);

  marked_line_number = line_number;
}

/*************************************************************************/

/**
  * This method resets a stream to the point where the <code>mark()</code> method
  * was called.  Any bytes that were read after the mark point was set will
  * be re-read during subsequent reads.
  * <p>
  * In this class, this method will also restore the line number that was
  * current when the <code>mark()</code> method was called.
  *  <p>
  * This method only works if the subordinate stream supports mark/reset
  * functionality.
  *
  * @exception IOException If an error occurs
  */
public synchronized void
reset() throws IOException
{
  in.reset();

  line_number = marked_line_number;
}

/*************************************************************************/

/**
  * This method reads an unsigned byte from the input stream and returns it
  * as an int in the range of 0-255.  This method will return -1 if the
  * end of the stream has been reached.
  * <p>
  * Note that if a line termination sequence is encountered (ie, "\r",
  * "\n", or "\r\n") then that line termination sequence is converted to
  * a single "\n" value which is returned from this method.  This means
  * that it is possible this method reads two bytes from the subordinate
  * stream instead of just one.
  * <p>
  * Note that this method will block until a byte of data is available
  * to be read.
  *
  * @return The byte read or -1 if end of stream
  * 
  * @exception IOException If an error occurs
  */
public synchronized int
read() throws IOException
{
  int byte_read = in.read();

  if (byte_read == '\n')
    ++line_number;

  if (byte_read == '\r')
    {
      int extra_byte_read = in.read();

      if ((extra_byte_read != '\n') && (extra_byte_read != -1))
        ((PushbackInputStream)in).unread(extra_byte_read);

      byte_read = '\n';
      ++line_number;
    }

  return(byte_read);
}

/*************************************************************************/

/**
  * This method reads bytes from a stream and stores them into a caller
  * supplied buffer.  It starts storing data at index <code>offset</code> into
  * the buffer and attemps to read <code>len</code> bytes.  This method can
  * return before reading the number of bytes requested.  The actual number
  * of bytes read is returned as an int.  A -1 is returned to indicated the
  * end of the stream.
  * <p>
  * This method will block until some data can be read.
  * <p>
  * Note that if a line termination sequence is encountered (ie, "\r",
  * "\n", or "\r\n") then that line termination sequence is converted to
  * a single "\n" value which is stored in the buffer.  Only a single
  * byte is counted towards the number of bytes read in this case.
  *
  * @param buf The array into which the bytes read should be stored
  * @param offset The offset 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 stream
  *
  * @exception IOException If an error occurs.
  */
public synchronized int
read(byte[] buf, int offset, int len) throws IOException
{
  if (len == 0)
    return(0);

  // Read the first byte here in order to allow IOException's to 
  // propagate up
  int byte_read = read();
  if (byte_read == -1)
    return(-1);
  buf[offset] = (byte)byte_read;

  int total_read = 1;

  // Read the rest of the bytes.  We do this in a single read() loop
  // like a raw InputStream. That's ok in my book since this class is
  // deprecated anyway.
  try
    {
      for (int i = 1; i < len; i++)
        {
          byte_read = read();
          if (byte_read == -1)
            return(total_read);

          buf[offset + i] = (byte)byte_read;
          
          ++total_read;  
        }
    }
  catch (IOException e)
    {
      return(total_read);
    }

  return(total_read);
}

/*************************************************************************/

/**
  * This method skips up to the requested number of bytes in the 
  * input stream.  The actual number of bytes skipped is returned.  If the
  * desired number of bytes to skip is negative, no bytes are skipped.
  *
  * @param num_byte The requested number of bytes to skip.
  *
  * @return The actual number of bytes skipped.
  *
  * @exception IOException If an error occurs.
  */
public long
skip(long num_bytes) throws IOException
{
  return(super.skip(num_bytes));
}

} // class LineNumberInputStream