001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018package org.apache.commons.net.io; 019 020import java.io.BufferedReader; 021import java.io.IOException; 022import java.io.Reader; 023 024/** 025 * DotTerminatedMessageReader is a class used to read messages from a 026 * server that are terminated by a single dot followed by a 027 * <CR><LF> 028 * sequence and with double dots appearing at the begining of lines which 029 * do not signal end of message yet start with a dot. Various Internet 030 * protocols such as NNTP and POP3 produce messages of this type. 031 * <p> 032 * This class handles stripping of the duplicate period at the beginning 033 * of lines starting with a period, and ensures you cannot read past the end of the message. 034 * <p> 035 * Note: versions since 3.0 extend BufferedReader rather than Reader, 036 * and no longer change the CRLF into the local EOL. Also only DOT CR LF 037 * acts as EOF. 038 * @version $Id: DotTerminatedMessageReader.java 1301276 2012-03-15 23:51:31Z sebb $ 039 */ 040public final class DotTerminatedMessageReader extends BufferedReader 041{ 042 private static final char LF = '\n'; 043 private static final char CR = '\r'; 044 private static final int DOT = '.'; 045 046 private boolean atBeginning; 047 private boolean eof; 048 private boolean seenCR; // was last character CR? 049 050 /** 051 * Creates a DotTerminatedMessageReader that wraps an existing Reader 052 * input source. 053 * @param reader The Reader input source containing the message. 054 */ 055 public DotTerminatedMessageReader(Reader reader) 056 { 057 super(reader); 058 // Assumes input is at start of message 059 atBeginning = true; 060 eof = false; 061 } 062 063 /** 064 * Reads and returns the next character in the message. If the end of the 065 * message has been reached, returns -1. Note that a call to this method 066 * may result in multiple reads from the underlying input stream to decode 067 * the message properly (removing doubled dots and so on). All of 068 * this is transparent to the programmer and is only mentioned for 069 * completeness. 070 * @return The next character in the message. Returns -1 if the end of the 071 * message has been reached. 072 * @exception IOException If an error occurs while reading the underlying 073 * stream. 074 */ 075 @Override 076 public int read() throws IOException { 077 synchronized (lock) { 078 if (eof) { 079 return -1; // Don't allow read past EOF 080 } 081 int chint = super.read(); 082 if (chint == -1) { // True EOF 083 eof = true; 084 return -1; 085 } 086 if (atBeginning) { 087 atBeginning = false; 088 if (chint == DOT) { // Have DOT 089 mark(2); // need to check for CR LF or DOT 090 chint = super.read(); 091 if (chint == -1) { // Should not happen 092 // new Throwable("Trailing DOT").printStackTrace(); 093 eof = true; 094 return DOT; // return the trailing DOT 095 } 096 if (chint == DOT) { // Have DOT DOT 097 // no need to reset as we want to lose the first DOT 098 return chint; // i.e. DOT 099 } 100 if (chint == CR) { // Have DOT CR 101 chint = super.read(); 102 if (chint == -1) { // Still only DOT CR - should not happen 103 //new Throwable("Trailing DOT CR").printStackTrace(); 104 reset(); // So CR is picked up next time 105 return DOT; // return the trailing DOT 106 } 107 if (chint == LF) { // DOT CR LF 108 atBeginning = true; 109 eof = true; 110 // Do we need to clear the mark somehow? 111 return -1; 112 } 113 } 114 // Should not happen - lone DOT at beginning 115 //new Throwable("Lone DOT followed by "+(char)chint).printStackTrace(); 116 reset(); 117 return DOT; 118 } // have DOT 119 } // atBeginning 120 121 // Handle CRLF in normal flow 122 if (seenCR) { 123 seenCR = false; 124 if (chint == LF) { 125 atBeginning = true; 126 } 127 } 128 if (chint == CR) { 129 seenCR = true; 130 } 131 return chint; 132 } 133 } 134 135 136 /** 137 * Reads the next characters from the message into an array and 138 * returns the number of characters read. Returns -1 if the end of the 139 * message has been reached. 140 * @param buffer The character array in which to store the characters. 141 * @return The number of characters read. Returns -1 if the 142 * end of the message has been reached. 143 * @exception IOException If an error occurs in reading the underlying 144 * stream. 145 */ 146 @Override 147 public int read(char[] buffer) throws IOException 148 { 149 return read(buffer, 0, buffer.length); 150 } 151 152 /** 153 * Reads the next characters from the message into an array and 154 * returns the number of characters read. Returns -1 if the end of the 155 * message has been reached. The characters are stored in the array 156 * starting from the given offset and up to the length specified. 157 * @param buffer The character array in which to store the characters. 158 * @param offset The offset into the array at which to start storing 159 * characters. 160 * @param length The number of characters to read. 161 * @return The number of characters read. Returns -1 if the 162 * end of the message has been reached. 163 * @exception IOException If an error occurs in reading the underlying 164 * stream. 165 */ 166 @Override 167 public int read(char[] buffer, int offset, int length) throws IOException 168 { 169 if (length < 1) 170 { 171 return 0; 172 } 173 int ch; 174 synchronized (lock) 175 { 176 if ((ch = read()) == -1) 177 { 178 return -1; 179 } 180 181 int off = offset; 182 183 do 184 { 185 buffer[offset++] = (char) ch; 186 } 187 while (--length > 0 && (ch = read()) != -1); 188 189 return (offset - off); 190 } 191 } 192 193 /** 194 * Closes the message for reading. This doesn't actually close the 195 * underlying stream. The underlying stream may still be used for 196 * communicating with the server and therefore is not closed. 197 * <p> 198 * If the end of the message has not yet been reached, this method 199 * will read the remainder of the message until it reaches the end, 200 * so that the underlying stream may continue to be used properly 201 * for communicating with the server. If you do not fully read 202 * a message, you MUST close it, otherwise your program will likely 203 * hang or behave improperly. 204 * @exception IOException If an error occurs while reading the 205 * underlying stream. 206 */ 207 @Override 208 public void close() throws IOException 209 { 210 synchronized (lock) 211 { 212 if (!eof) 213 { 214 while (read() != -1) 215 { 216 // read to EOF 217 } 218 } 219 eof = true; 220 atBeginning = false; 221 } 222 } 223 224 /** 225 * Read a line of text. 226 * A line is considered to be terminated by carriage return followed immediately by a linefeed. 227 * This contrasts with BufferedReader which also allows other combinations. 228 * @since 3.0 229 */ 230 @Override 231 public String readLine() throws IOException { 232 StringBuilder sb = new StringBuilder(); 233 int intch; 234 synchronized(lock) { // make thread-safe (hopefully!) 235 while((intch = read()) != -1) 236 { 237 if (intch == LF && atBeginning) { 238 return sb.substring(0, sb.length()-1); 239 } 240 sb.append((char) intch); 241 } 242 } 243 String string = sb.toString(); 244 if (string.length() == 0) { // immediate EOF 245 return null; 246 } 247 // Should not happen - EOF without CRLF 248 //new Throwable(string).printStackTrace(); 249 return string; 250 } 251}