1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package org.apache.commons.net.io; 19 20 import java.io.IOException; 21 import java.io.Writer; 22 23 /*** 24 * DotTerminatedMessageWriter is a class used to write messages to a 25 * server that are terminated by a single dot followed by a 26 * <CR><LF> 27 * sequence and with double dots appearing at the begining of lines which 28 * do not signal end of message yet start with a dot. Various Internet 29 * protocols such as NNTP and POP3 produce messages of this type. 30 * <p> 31 * This class handles the doubling of line-starting periods, 32 * converts single linefeeds to NETASCII newlines, and on closing 33 * will send the final message terminator dot and NETASCII newline 34 * sequence. 35 * <p> 36 * <p> 37 * @author Daniel F. Savarese 38 ***/ 39 40 public final class DotTerminatedMessageWriter extends Writer 41 { 42 private static final int __NOTHING_SPECIAL_STATE = 0; 43 private static final int __LAST_WAS_CR_STATE = 1; 44 private static final int __LAST_WAS_NL_STATE = 2; 45 46 private int __state; 47 private Writer __output; 48 49 50 /*** 51 * Creates a DotTerminatedMessageWriter that wraps an existing Writer 52 * output destination. 53 * <p> 54 * @param output The Writer output destination to write the message. 55 ***/ 56 public DotTerminatedMessageWriter(Writer output) 57 { 58 super(output); 59 __output = output; 60 __state = __NOTHING_SPECIAL_STATE; 61 } 62 63 64 /*** 65 * Writes a character to the output. Note that a call to this method 66 * may result in multiple writes to the underling Writer in order to 67 * convert naked linefeeds to NETASCII line separators and to double 68 * line-leading periods. This is transparent to the programmer and 69 * is only mentioned for completeness. 70 * <p> 71 * @param ch The character to write. 72 * @exception IOException If an error occurs while writing to the 73 * underlying output. 74 ***/ 75 @Override 76 public void write(int ch) throws IOException 77 { 78 synchronized (lock) 79 { 80 switch (ch) 81 { 82 case '\r': 83 __state = __LAST_WAS_CR_STATE; 84 __output.write('\r'); 85 return ; 86 case '\n': 87 if (__state != __LAST_WAS_CR_STATE) 88 __output.write('\r'); 89 __output.write('\n'); 90 __state = __LAST_WAS_NL_STATE; 91 return ; 92 case '.': 93 // Double the dot at the beginning of a line 94 if (__state == __LAST_WAS_NL_STATE) 95 __output.write('.'); 96 // Fall through 97 default: 98 __state = __NOTHING_SPECIAL_STATE; 99 __output.write(ch); 100 return ; 101 } 102 } 103 } 104 105 106 /*** 107 * Writes a number of characters from a character array to the output 108 * starting from a given offset. 109 * <p> 110 * @param buffer The character array to write. 111 * @param offset The offset into the array at which to start copying data. 112 * @param length The number of characters to write. 113 * @exception IOException If an error occurs while writing to the underlying 114 * output. 115 ***/ 116 @Override 117 public void write(char[] buffer, int offset, int length) throws IOException 118 { 119 synchronized (lock) 120 { 121 while (length-- > 0) 122 write(buffer[offset++]); 123 } 124 } 125 126 127 /*** 128 * Writes a character array to the output. 129 * <p> 130 * @param buffer The character array to write. 131 * @exception IOException If an error occurs while writing to the underlying 132 * output. 133 ***/ 134 @Override 135 public void write(char[] buffer) throws IOException 136 { 137 write(buffer, 0, buffer.length); 138 } 139 140 141 /*** 142 * Writes a String to the output. 143 * <p> 144 * @param string The String to write. 145 * @exception IOException If an error occurs while writing to the underlying 146 * output. 147 ***/ 148 @Override 149 public void write(String string) throws IOException 150 { 151 write(string.toCharArray()); 152 } 153 154 155 /*** 156 * Writes part of a String to the output starting from a given offset. 157 * <p> 158 * @param string The String to write. 159 * @param offset The offset into the String at which to start copying data. 160 * @param length The number of characters to write. 161 * @exception IOException If an error occurs while writing to the underlying 162 * output. 163 ***/ 164 @Override 165 public void write(String string, int offset, int length) throws IOException 166 { 167 write(string.toCharArray(), offset, length); 168 } 169 170 171 /*** 172 * Flushes the underlying output, writing all buffered output. 173 * <p> 174 * @exception IOException If an error occurs while writing to the underlying 175 * output. 176 ***/ 177 @Override 178 public void flush() throws IOException 179 { 180 synchronized (lock) 181 { 182 __output.flush(); 183 } 184 } 185 186 187 /*** 188 * Flushes the underlying output, writing all buffered output, but doesn't 189 * actually close the underlying stream. The underlying stream may still 190 * be used for communicating with the server and therefore is not closed. 191 * <p> 192 * @exception IOException If an error occurs while writing to the underlying 193 * output or closing the Writer. 194 ***/ 195 @Override 196 public void close() throws IOException 197 { 198 synchronized (lock) 199 { 200 if (__output == null) 201 return ; 202 203 if (__state == __LAST_WAS_CR_STATE) 204 __output.write('\n'); 205 else if (__state != __LAST_WAS_NL_STATE) 206 __output.write("\r\n"); 207 208 __output.write(".\r\n"); 209 210 __output.flush(); 211 __output = null; 212 } 213 } 214 215 }