Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. * <p> * 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. * <p> * <p> ***/ 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. * <p> * @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. * <p> * @param ch The character to write. * @exception IOException If an error occurs while writing to the * underlying output. ***/ @Override 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. * <p> * @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. ***/ @Override 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. * <p> * @param buffer The character array to write. * @exception IOException If an error occurs while writing to the underlying * output. ***/ @Override public void write(char[] buffer) throws IOException { write(buffer, 0, buffer.length); } /*** * Writes a String to the output. * <p> * @param string The String to write. * @exception IOException If an error occurs while writing to the underlying * output. ***/ @Override public void write(String string) throws IOException { write(string.toCharArray()); } /*** * Writes part of a String to the output starting from a given offset. * <p> * @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. ***/ @Override public void write(String string, int offset, int length) throws IOException { write(string.toCharArray(), offset, length); } /*** * Flushes the underlying output, writing all buffered output. * <p> * @exception IOException If an error occurs while writing to the underlying * output. ***/ @Override 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. * <p> * @exception IOException If an error occurs while writing to the underlying * output or closing the Writer. ***/ @Override 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; } } }