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 }