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The source code

/*
 * Copyright 2001-2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.net.io;
import java.io.IOException;
import java.io.Writer;

/***
 * DotTerminatedMessageWriter is a class used to write messages to a
 * server that are terminated by a single dot followed by a
 * <CR><LF>
 * sequence and with double dots appearing at the begining of lines which
 * do not signal end of message yet start with a dot.  Various Internet
 * protocols such as NNTP and POP3 produce messages of this type.
 * 

* This class handles the doubling of line-starting periods, * converts single linefeeds to NETASCII newlines, and on closing * will send the final message terminator dot and NETASCII newline * sequence. *

*

* @author Daniel F. Savarese ***/ public final class DotTerminatedMessageWriter extends Writer { private static final int __NOTHING_SPECIAL_STATE = 0; private static final int __LAST_WAS_CR_STATE = 1; private static final int __LAST_WAS_NL_STATE = 2; private int __state; private Writer __output; /*** * Creates a DotTerminatedMessageWriter that wraps an existing Writer * output destination. *

* @param output The Writer output destination to write the message. ***/ public DotTerminatedMessageWriter(Writer output) { super(output); __output = output; __state = __NOTHING_SPECIAL_STATE; } /*** * Writes a character to the output. Note that a call to this method * may result in multiple writes to the underling Writer in order to * convert naked linefeeds to NETASCII line separators and to double * line-leading periods. This is transparent to the programmer and * is only mentioned for completeness. *

* @param ch The character to write. * @exception IOException If an error occurs while writing to the * underlying output. ***/ public void write(int ch) throws IOException { synchronized (lock) { switch (ch) { case '\r': __state = __LAST_WAS_CR_STATE; __output.write('\r'); return ; case '\n': if (__state != __LAST_WAS_CR_STATE) __output.write('\r'); __output.write('\n'); __state = __LAST_WAS_NL_STATE; return ; case '.': // Double the dot at the beginning of a line if (__state == __LAST_WAS_NL_STATE) __output.write('.'); // Fall through default: __state = __NOTHING_SPECIAL_STATE; __output.write(ch); return ; } } } /*** * Writes a number of characters from a character array to the output * starting from a given offset. *

* @param buffer The character array to write. * @param offset The offset into the array at which to start copying data. * @param length The number of characters to write. * @exception IOException If an error occurs while writing to the underlying * output. ***/ public void write(char[] buffer, int offset, int length) throws IOException { synchronized (lock) { while (length-- > 0) write(buffer[offset++]); } } /*** * Writes a character array to the output. *

* @param buffer The character array to write. * @exception IOException If an error occurs while writing to the underlying * output. ***/ public void write(char[] buffer) throws IOException { write(buffer, 0, buffer.length); } /*** * Writes a String to the output. *

* @param string The String to write. * @exception IOException If an error occurs while writing to the underlying * output. ***/ public void write(String string) throws IOException { write(string.toCharArray()); } /*** * Writes part of a String to the output starting from a given offset. *

* @param string The String to write. * @param offset The offset into the String at which to start copying data. * @param length The number of characters to write. * @exception IOException If an error occurs while writing to the underlying * output. ***/ public void write(String string, int offset, int length) throws IOException { write(string.toCharArray(), offset, length); } /*** * Flushes the underlying output, writing all buffered output. *

* @exception IOException If an error occurs while writing to the underlying * output. ***/ public void flush() throws IOException { synchronized (lock) { __output.flush(); } } /*** * Flushes the underlying output, writing all buffered output, but doesn't * actually close the underlying stream. The underlying stream may still * be used for communicating with the server and therefore is not closed. *

* @exception IOException If an error occurs while writing to the underlying * output or closing the Writer. ***/ public void close() throws IOException { synchronized (lock) { if (__output == null) return ; if (__state == __LAST_WAS_CR_STATE) __output.write('\n'); else if (__state != __LAST_WAS_NL_STATE) __output.write("\r\n"); __output.write(".\r\n"); __output.flush(); __output = null; } } }

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