src/java/com/oroinc/io/FromNetASCIIInputStream.java

/***
 * $Id: FromNetASCIIInputStream.java,v 1.1 2002/04/03 01:04:41 brekke Exp $
 *
 * NetComponents Internet Protocol Library
 * Copyright (C) 1997-2002  Daniel F. Savarese
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library in the LICENSE file; if not, write
 * to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA  02111-1307  USA
 ***/

package com.oroinc.io;

import java.io.*;

/***
 * This class wraps an input stream, replacing all occurrences
 * of <CR><LF> (carriage return followed by a linefeed),
 * which is the NETASCII standard for representing a newline, with the
 * local line separator representation.  You would use this class to 
 * implement ASCII file transfers requiring conversion from NETASCII.
 * <p>
 * <p>
 * @author Daniel F. Savarese
 ***/

public final class FromNetASCIIInputStream extends PushbackInputStream {
  static final boolean _noConversionRequired;
  static final String _lineSeparator;
  static final byte[] _lineSeparatorBytes;

  static {
    _lineSeparator        = System.getProperty("line.separator");
    _noConversionRequired = _lineSeparator.equals("\r\n");
    _lineSeparatorBytes   = _lineSeparator.getBytes();
  }

  private int __length = 0;

  /***
   * Returns true if the NetASCII line separator differs from the system
   * line separator, false if they are the same.  This method is useful
   * to determine whether or not you need to instantiate a
   * FromNetASCIIInputStream object.
   * <p>
   * @return True if the NETASCII line separator differs from the local
   *   system line separator, false if they are the same.
   ***/
  public static final boolean isConversionRequired() {
    return !_noConversionRequired;
  }

  /***
   * Creates a FromNetASCIIInputStream instance that wraps an existing
   * InputStream.
   ***/
  public FromNetASCIIInputStream(InputStream input) {
    super(input, _lineSeparatorBytes.length + 1);
  }


  private int __read() throws IOException {
    int ch;

    ch = super.read();

    if(ch == '\r') {
      ch = super.read();
      if(ch == '\n') {
	unread(_lineSeparatorBytes);
	ch = super.read();
	// This is a kluge for read(byte[], ...) to read the right amount
	--__length;
      } else {
	if(ch != -1)
	  unread(ch);
	return '\r';
      }
    }

    return ch;
  }


  /***
   * Reads and returns the next byte in the stream.  If the end of the
   * message has been reached, returns -1.  Note that a call to this method
   * may result in multiple reads from the underlying input stream in order
   * to convert NETASCII line separators to the local line separator format.
   * This is transparent to the programmer and is only mentioned for
   * completeness.
   * <p>
   * @return The next character in the stream. Returns -1 if the end of the
   *          stream has been reached.
   * @exception IOException If an error occurs while reading the underlying
   *            stream.
   ***/
  public int read() throws IOException {
    if(_noConversionRequired)
      return super.read();

    return __read();
  }


  /***
   * Reads the next number of bytes from the stream into an array and
   * returns the number of bytes read.  Returns -1 if the end of the
   * stream has been reached.
   * <p>
   * @param buffer  The byte array in which to store the data.
   * @return The number of bytes read. Returns -1 if the
   *          end of the message has been reached.
   * @exception IOException If an error occurs in reading the underlying
   *            stream.
   ***/
  public int read(byte buffer[]) throws IOException {
    return read(buffer, 0, buffer.length);
  }                 


  /***
   * Reads the next number of bytes from the stream into an array and returns
   * the number of bytes read.  Returns -1 if the end of the
   * message has been reached.  The characters are stored in the array
   * starting from the given offset and up to the length specified.
   * <p>
   * @param buffer The byte array in which to store the data.
   * @param offset  The offset into the array at which to start storing data.
   * @param length   The number of bytes to read.
   * @return The number of bytes read. Returns -1 if the
   *          end of the stream has been reached.
   * @exception IOException If an error occurs while reading the underlying
   *            stream.
   ***/
  public int read(byte buffer[], int offset, int length) throws IOException {
    int ch, off;

    if(length < 1)
      return 0;

    ch = available();

    __length = (length > ch ? ch : length);

    // If nothing is available, block to read only one character
    if(__length < 1)
      __length = 1;

    if(_noConversionRequired)
      return super.read(buffer, offset, __length);

    if((ch = __read()) == -1)
      return -1;

    off = offset;

    do {
      buffer[offset++] = (byte)ch;
    } while(--__length > 0 && (ch = __read()) != -1);


    return (offset - off);
  }


  // PushbackInputStream in JDK 1.1.3 returns the wrong thing
  /***
   * Returns the number of bytes that can be read without blocking EXCEPT
   * when newline conversions have to be made somewhere within the
   * available block of bytes.  In other words, you really should not
   * rely on the value returned by this method if you are trying to avoid 
   * blocking.
   ***/
  public int available() throws IOException {
    return (buf.length - pos) + in.available();
  }

}