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.BufferedReader;
21 import java.io.IOException;
22 import java.io.Reader;
23
24 import org.apache.commons.net.util.NetConstants;
25
26 /**
27 * CRLFLineReader implements a readLine() method that requires exactly CRLF to terminate an input line. This is required for IMAP, which allows bare CR and LF.
28 *
29 * @since 3.0
30 */
31 public final class CRLFLineReader extends BufferedReader {
32 private static final char LF = '\n';
33 private static final char CR = '\r';
34
35 /**
36 * Creates a CRLFLineReader that wraps an existing Reader input source.
37 *
38 * @param reader The Reader input source.
39 */
40 public CRLFLineReader(final Reader reader) {
41 super(reader);
42 }
43
44 /**
45 * Read a line of text. A line is considered to be terminated by carriage return followed immediately by a linefeed. This contrasts with BufferedReader
46 * which also allows other combinations.
47 *
48 * @since 3.0
49 */
50 @Override
51 public String readLine() throws IOException {
52 final StringBuilder sb = new StringBuilder();
53 int intch;
54 boolean prevWasCR = false;
55 synchronized (lock) { // make thread-safe (hopefully!)
56 while ((intch = read()) != NetConstants.EOS) {
57 if (prevWasCR && intch == LF) {
58 return sb.substring(0, sb.length() - 1);
59 }
60 prevWasCR = intch == CR;
61 sb.append((char) intch);
62 }
63 }
64 final String string = sb.toString();
65 if (string.isEmpty()) { // immediate EOF
66 return null;
67 }
68 return string;
69 }
70 }