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 * https://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 server that are terminated by a single dot followed by a <CR><LF> sequence and
25 * with double dots appearing at the beginning of lines which do not signal end of message yet start with a dot. Various Internet protocols such as
26 * NNTP and POP3 produce messages of this type.
27 * <p>
28 * This class handles the doubling of line-starting periods, converts single linefeeds to NETASCII newlines, and on closing will send the final message
29 * terminator dot and NETASCII newline sequence.
30 * </p>
31 */
32 public final class DotTerminatedMessageWriter extends Writer {
33 private static final int NOTHING_SPECIAL_STATE = 0;
34 private static final int LAST_WAS_CR_STATE = 1;
35 private static final int LAST_WAS_NL_STATE = 2;
36
37 private int state;
38 private Writer output;
39
40 /**
41 * Creates a DotTerminatedMessageWriter that wraps an existing Writer output destination.
42 *
43 * @param output The Writer output destination to write the message.
44 */
45 public DotTerminatedMessageWriter(final Writer output) {
46 super(output);
47 this.output = output;
48 this.state = NOTHING_SPECIAL_STATE;
49 }
50
51 /**
52 * Flushes the underlying output, writing all buffered output, but doesn't actually close the underlying stream. The underlying stream may still be used for
53 * communicating with the server and therefore is not closed.
54 *
55 * @throws IOException If an error occurs while writing to the underlying output or closing the Writer.
56 */
57 @Override
58 public void close() throws IOException {
59 synchronized (lock) {
60 if (output == null) {
61 return;
62 }
63
64 if (state == LAST_WAS_CR_STATE) {
65 output.write('\n');
66 } else if (state != LAST_WAS_NL_STATE) {
67 output.write("\r\n");
68 }
69
70 output.write(".\r\n");
71
72 output.flush();
73 output = null;
74 }
75 }
76
77 /**
78 * Flushes the underlying output, writing all buffered output.
79 *
80 * @throws IOException If an error occurs while writing to the underlying output.
81 */
82 @Override
83 public void flush() throws IOException {
84 synchronized (lock) {
85 output.flush();
86 }
87 }
88
89 /**
90 * Writes a character array to the output.
91 *
92 * @param buffer The character array to write.
93 * @throws IOException If an error occurs while writing to the underlying output.
94 */
95 @Override
96 public void write(final char[] buffer) throws IOException {
97 write(buffer, 0, buffer.length);
98 }
99
100 /**
101 * Writes a number of characters from a character array to the output starting from a given offset.
102 *
103 * @param buffer The character array to write.
104 * @param offset The offset into the array at which to start copying data.
105 * @param length The number of characters to write.
106 * @throws IOException If an error occurs while writing to the underlying output.
107 */
108 @Override
109 public void write(final char[] buffer, int offset, int length) throws IOException {
110 synchronized (lock) {
111 while (length-- > 0) {
112 write(buffer[offset++]);
113 }
114 }
115 }
116
117 /**
118 * 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
119 * linefeeds to NETASCII line separators and to double line-leading periods. This is transparent to the programmer and is only mentioned for completeness.
120 *
121 * @param ch The character to write.
122 * @throws IOException If an error occurs while writing to the underlying output.
123 */
124 @Override
125 public void write(final int ch) throws IOException {
126 synchronized (lock) {
127 switch (ch) {
128 case '\r':
129 state = LAST_WAS_CR_STATE;
130 output.write('\r');
131 return;
132 case '\n':
133 if (state != LAST_WAS_CR_STATE) {
134 output.write('\r');
135 }
136 output.write('\n');
137 state = LAST_WAS_NL_STATE;
138 return;
139 case '.':
140 // Double the dot at the beginning of a line
141 if (state == LAST_WAS_NL_STATE) {
142 output.write('.');
143 }
144 // falls through$
145 default:
146 state = NOTHING_SPECIAL_STATE;
147 output.write(ch);
148 }
149 }
150 }
151
152 /**
153 * Writes a String to the output.
154 *
155 * @param string The String to write.
156 * @throws IOException If an error occurs while writing to the underlying output.
157 */
158 @Override
159 public void write(final String string) throws IOException {
160 write(string.toCharArray());
161 }
162
163 /**
164 * Writes part of a String to the output starting from a given offset.
165 *
166 * @param string The String to write.
167 * @param offset The offset into the String at which to start copying data.
168 * @param length The number of characters to write.
169 * @throws IOException If an error occurs while writing to the underlying output.
170 */
171 @Override
172 public void write(final String string, final int offset, final int length) throws IOException {
173 write(string.toCharArray(), offset, length);
174 }
175
176 }