/* LineNumberReader.java -- A character 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>Reader</code> except that it
  * counts line numbers, and canonicalizes newline characters.  As data
  * is read, whenever the char 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"
  * char.  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.  Also note that actual "\r" and "\n" characters are looked for.
  * The system dependent line separator sequence is ignored.
  * <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.
  *
  * @version 0.0
  *
  * @author Aaron M. Renn (arenn@urbanophile.com)
  */
public class LineNumberReader extends BufferedReader
{

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

/*
 * 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;

/**
  * Determines whether or not a '\n' as the first character of a read
  * is the continuation of a '\r' as the last character of the previous
  * read or not
  */
private boolean continued_newline;

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

/*
 * Constructors
 */

/**
  * Create a new <code>LineNumberReader</code> that reads from the 
  * specified subordinate <code>Reader</code>.  A default 4096 char sized
  * buffer will be used for reads.
  *
  * @param in The subordinate <code>Reader</code> to read from
  */
public
LineNumberReader(Reader in)
{
  this(in, DEFAULT_BUFFER_SIZE);
}

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

/**
  * This method initializes a new <code>LineNumberReader</code> to read
  * from the specified subordinate <code>Reader</code> using the specified
  * read buffer size.
  *
  * @param in The subordinate <code>Reader</code> to read from
  * @param size The buffer size to use for reading
  */
public
LineNumberReader(Reader in, int size)
{
  super(new PushbackReader(in), size);
}

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

/*
 * 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 marks a position in the input to which the stream can be
  * "reset" char calling the <code>reset()</code> method.  The parameter
  * <code>readlimit</code> is the number of chars 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 chars 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.
  *
  * @param readlimit The number of chars that can be read before the mark becomes invalid
  *
  * @exception IOException If an error occurs
  */
public void
mark(int readlimit) throws IOException
{
  synchronized (lock) {

  super.mark(readlimit);

  marked_line_number = line_number;

  } // synchronized
}

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

/**
  * This method resets a stream to the point where the <code>mark()</code> method
  * was called.  Any chars 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.
  * 
  * @exception IOException If an error occurs
  */
public void
reset() throws IOException
{
  synchronized (lock) {

  super.reset();

  line_number = marked_line_number;

  } // synchronized
}

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

/**
  * This method reads an unsigned char 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 chars from the subordinate
  * stream instead of just one.
  * <p>
  * Note that this method will block until a char of data is available
  * to be read.
  *
  * @return The char read or -1 if end of stream
  * 
  * @exception IOException If an error occurs
  */
public int
read() throws IOException
{
  synchronized (lock) {

  int char_read = super.read();

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

  if (char_read == '\r')
    {
      int extra_char_read = super.read();

      if ((extra_char_read != '\n') && (extra_char_read != -1))
        ((PushbackReader)in).unread(extra_char_read);

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

  return(char_read);

  } // synchronized
}

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

/**
  * This method reads chars 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> chars.  This method can
  * return before reading the number of chars requested.  The actual number
  * of chars 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
  * char is counted towards the number of chars read in this case.
  *
  * @param buf The array into which the chars read should be stored
  * @param offset The offset into the array to start storing chars
  * @param len The requested number of chars to read
  *
  * @return The actual number of chars read, or -1 if end of stream
  *
  * @exception IOException If an error occurs.
  */
public int
read(char[] buf, int offset, int len) throws IOException
{
  if (len == 0)
    return(0);

  synchronized (lock) {

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

  int total_read = 1;

  // Read the rest of the chars.  We do this in a single char read() loop,
  // which is bad and should be fixed in the future. *****RECODE THIS****
  try
    {
      for (int i = 1; i < len; i++)
        {
          char_read = read();
          if (char_read == -1)
            return(total_read);

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

  return(total_read);

  } // synchronized
}

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

/**
  * This method reads a line of text from the input stream and returns
  * it as a <code>String</code>.  A line is considered to be terminated
  * by a "\r", "\n", or "\r\n" sequence, not by the system dependent line
  * separator.
  *
  * @return The line read as a <code>String</code> or <code>null</code> if end of stream.
  *
  * @exception IOException If an error occurs
  */
public String
readLine() throws IOException
{
  synchronized (lock) {

  String line = super.readLine();
  if (line != null)
    ++line_number;

  return(line);

  } // synchronized
}

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

/**
  * This method skips over characters in the stream.  This method will
  * skip the specified number of characters if possible, but is not required
  * to skip them all.  The actual number of characters skipped is returned.
  * This method returns 0 if the specified number of chars is less than 1.
  *
  * @param num_chars The specified number of chars to skip.
  *
  * @return The actual number of chars skipped. 
  *
  * @exception IOException If an error occurs
  */
public long
skip(long num_chars) throws IOException
{
  // The spec says to override this method so we do even though we
  // don't need to.  Assume we aren't counting lines in skipped chars.
  return(super.skip(num_chars));
}

} // class LineNumberReader