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    1   package org.apache.commons.net.io;
    2
    3   /* ====================================================================
    4    * The Apache Software License, Version 1.1
    5    *
    6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
    7    * reserved.
    8    *
    9    * Redistribution and use in source and binary forms, with or without
    10   * modification, are permitted provided that the following conditions
    11   * are met:
    12   *
    13   * 1. Redistributions of source code must retain the above copyright
    14   *    notice, this list of conditions and the following disclaimer.
    15   *
    16   * 2. Redistributions in binary form must reproduce the above copyright
    17   *    notice, this list of conditions and the following disclaimer in
    18   *    the documentation and/or other materials provided with the
    19   *    distribution.
    20   *
    21   * 3. The end-user documentation included with the redistribution,
    22   *    if any, must include the following acknowledgment:
    23   *       "This product includes software developed by the
    24   *        Apache Software Foundation (http://www.apache.org/)."
    25   *    Alternately, this acknowledgment may appear in the software itself,
    26   *    if and wherever such third-party acknowledgments normally appear.
    27   *
    28   * 4. The names "Apache" and "Apache Software Foundation" and
    29   *    "Apache Commons" must not be used to endorse or promote products
    30   *    derived from this software without prior written permission. For
    31   *    written permission, please contact apache@apache.org.
    32   *
    33   * 5. Products derived from this software may not be called "Apache",
    34   *    nor may "Apache" appear in their name, without
    35   *    prior written permission of the Apache Software Foundation.
    36   *
    37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    38   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    39   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    40   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
    41   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    42   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    43   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    44   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    45   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    46   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    47   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    48   * SUCH DAMAGE.
    49   * ====================================================================
    50   *
    51   * This software consists of voluntary contributions made by many
    52   * individuals on behalf of the Apache Software Foundation.  For more
    53   * information on the Apache Software Foundation, please see
    54   * <http://www.apache.org/>;.
    55   */
    56
    57  import java.io.IOException;
    58  import java.io.Writer;
    59
    60  /****
    61   * DotTerminatedMessageWriter is a class used to write messages to a
    62   * server that are terminated by a single dot followed by a
    63   * <CR><LF>
    64   * sequence and with double dots appearing at the begining of lines which
    65   * do not signal end of message yet start with a dot.  Various Internet
    66   * protocols such as NNTP and POP3 produce messages of this type.
    67   * <p>
    68   * This class handles the doubling of line-starting periods,
    69   * converts single linefeeds to NETASCII newlines, and on closing
    70   * will send the final message terminator dot and NETASCII newline
    71   * sequence.
    72   * <p>
    73   * <p>
    74   * @author Daniel F. Savarese
    75   ***/
    76
    77  public final class DotTerminatedMessageWriter extends Writer
    78  {
    79      private static final int __NOTHING_SPECIAL_STATE = 0;
    80      private static final int __LAST_WAS_CR_STATE = 1;
    81      private static final int __LAST_WAS_NL_STATE = 2;
    82
    83      private int __state;
    84      private Writer __output;
    85
    86
    87      /****
    88       * Creates a DotTerminatedMessageWriter that wraps an existing Writer
    89       * output destination.
    90       * <p>
    91       * @param output  The Writer output destination to write the message.
    92       ***/
    93      public DotTerminatedMessageWriter(Writer output)
    94      {
    95          super(output);
    96          __output = output;
    97          __state = __NOTHING_SPECIAL_STATE;
    98      }
    99
    100
    101     /****
    102      * Writes a character to the output.  Note that a call to this method
    103      * may result in multiple writes to the underling Writer in order to
    104      * convert naked linefeeds to NETASCII line separators and to double
    105      * line-leading periods.  This is transparent to the programmer and
    106      * is only mentioned for completeness.
    107      * <p>
    108      * @param ch  The character to write.
    109      * @exception IOException  If an error occurs while writing to the
    110      *            underlying output.
    111      ***/
    112     public void write(int ch) throws IOException
    113     {
    114         synchronized (lock)
    115         {
    116             switch (ch)
    117             {
    118             case '\r':
    119                 __state = __LAST_WAS_CR_STATE;
    120                 __output.write('\r');
    121                 return ;
    122             case '\n':
    123                 if (__state != __LAST_WAS_CR_STATE)
    124                     __output.write('\r');
    125                 __output.write('\n');
    126                 __state = __LAST_WAS_NL_STATE;
    127                 return ;
    128             case '.':
    129                 // Double the dot at the beginning of a line
    130                 if (__state == __LAST_WAS_NL_STATE)
    131                     __output.write('.');
    132                 // Fall through
    133             default:
    134                 __state = __NOTHING_SPECIAL_STATE;
    135                 __output.write(ch);
    136                 return ;
    137             }
    138         }
    139     }
    140
    141
    142     /****
    143      * Writes a number of characters from a character array to the output
    144      * starting from a given offset.
    145      * <p>
    146      * @param buffer  The character array to write.
    147      * @param offset  The offset into the array at which to start copying data.
    148      * @param length  The number of characters to write.
    149      * @exception IOException If an error occurs while writing to the underlying
    150      *            output.
    151      ***/
    152     public void write(char[] buffer, int offset, int length) throws IOException
    153     {
    154         synchronized (lock)
    155         {
    156             while (length-- > 0)
    157                 write(buffer[offset++]);
    158         }
    159     }
    160
    161
    162     /****
    163      * Writes a character array to the output.
    164      * <p>
    165      * @param buffer  The character array to write.
    166      * @exception IOException If an error occurs while writing to the underlying
    167      *            output.
    168      ***/
    169     public void write(char[] buffer) throws IOException
    170     {
    171         write(buffer, 0, buffer.length);
    172     }
    173
    174
    175     /****
    176      * Writes a String to the output.
    177      * <p>
    178      * @param string  The String to write.
    179      * @exception IOException If an error occurs while writing to the underlying
    180      *            output.
    181      ***/
    182     public void write(String string) throws IOException
    183     {
    184         write(string.toCharArray());
    185     }
    186
    187
    188     /****
    189      * Writes part of a String to the output starting from a given offset.
    190      * <p>
    191      * @param string  The String to write.
    192      * @param offset  The offset into the String at which to start copying data.
    193      * @param length  The number of characters to write.
    194      * @exception IOException If an error occurs while writing to the underlying
    195      *            output.
    196      ***/
    197     public void write(String string, int offset, int length) throws IOException
    198     {
    199         write(string.toCharArray(), offset, length);
    200     }
    201
    202
    203     /****
    204      * Flushes the underlying output, writing all buffered output.
    205      * <p>
    206      * @exception IOException If an error occurs while writing to the underlying
    207      *            output.
    208      ***/
    209     public void flush() throws IOException
    210     {
    211         synchronized (lock)
    212         {
    213             __output.flush();
    214         }
    215     }
    216
    217
    218     /****
    219      * Flushes the underlying output, writing all buffered output, but doesn't
    220      * actually close the underlying stream.  The underlying stream may still
    221      * be used for communicating with the server and therefore is not closed.
    222      * <p>
    223      * @exception IOException If an error occurs while writing to the underlying
    224      *            output or closing the Writer.
    225      ***/
    226     public void close() throws IOException
    227     {
    228         synchronized (lock)
    229         {
    230             if (__output == null)
    231                 return ;
    232
    233             if (__state == __LAST_WAS_CR_STATE)
    234                 __output.write('\n');
    235             else if (__state != __LAST_WAS_NL_STATE)
    236                 __output.write("\r\n");
    237
    238             __output.write(".\r\n");
    239
    240             __output.flush();
    241             __output = null;
    242         }
    243     }
    244
    245 }

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