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 /**
25 * CRLFLineReader implements a readLine() method that requires
26 * exactly CRLF to terminate an input line.
27 * 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 {
33 private static final char LF = '\n';
34 private static final char CR = '\r';
35
36 /**
37 * Creates a CRLFLineReader that wraps an existing Reader
38 * input source.
39 * @param reader The Reader input source.
40 */
41 public CRLFLineReader(Reader reader)
42 {
43 super(reader);
44 }
45
46 /**
47 * Read a line of text.
48 * A line is considered to be terminated by carriage return followed immediately by a linefeed.
49 * This contrasts with BufferedReader which also allows other combinations.
50 * @since 3.0
51 */
52 @Override
53 public String readLine() throws IOException {
54 StringBuilder sb = new StringBuilder();
55 int intch;
56 boolean prevWasCR = false;
57 synchronized(lock) { // make thread-safe (hopefully!)
58 while((intch = read()) != -1)
59 {
60 if (prevWasCR && intch == LF) {
61 return sb.substring(0, sb.length()-1);
62 }
63 if (intch == CR) {
64 prevWasCR = true;
65 } else {
66 prevWasCR = false;
67 }
68 sb.append((char) intch);
69 }
70 }
71 String string = sb.toString();
72 if (string.length() == 0) { // immediate EOF
73 return null;
74 }
75 return string;
76 }
77 }