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 */ 017 018 package org.apache.commons.net.io; 019 020 import java.io.BufferedReader; 021 import java.io.IOException; 022 import java.io.Reader; 023 024 /** 025 * CRLFLineReader implements a readLine() method that requires 026 * exactly CRLF to terminate an input line. 027 * This is required for IMAP, which allows bare CR and LF. 028 * 029 * @since 3.0 030 */ 031 public final class CRLFLineReader extends BufferedReader 032 { 033 private static final char LF = '\n'; 034 private static final char CR = '\r'; 035 036 /** 037 * Creates a CRLFLineReader that wraps an existing Reader 038 * input source. 039 * @param reader The Reader input source. 040 */ 041 public CRLFLineReader(Reader reader) 042 { 043 super(reader); 044 } 045 046 /** 047 * Read a line of text. 048 * A line is considered to be terminated by carriage return followed immediately by a linefeed. 049 * This contrasts with BufferedReader which also allows other combinations. 050 * @since 3.0 051 */ 052 @Override 053 public String readLine() throws IOException { 054 StringBuilder sb = new StringBuilder(); 055 int intch; 056 boolean prevWasCR = false; 057 synchronized(lock) { // make thread-safe (hopefully!) 058 while((intch = read()) != -1) 059 { 060 if (prevWasCR && intch == LF) { 061 return sb.substring(0, sb.length()-1); 062 } 063 if (intch == CR) { 064 prevWasCR = true; 065 } else { 066 prevWasCR = false; 067 } 068 sb.append((char) intch); 069 } 070 } 071 String string = sb.toString(); 072 if (string.length() == 0) { // immediate EOF 073 return null; 074 } 075 return string; 076 } 077 }