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.IOException; 021 import java.io.InputStream; 022 import java.io.PushbackInputStream; 023 024 /*** 025 * This class wraps an input stream, replacing all occurrences 026 * of <CR><LF> (carriage return followed by a linefeed), 027 * which is the NETASCII standard for representing a newline, with the 028 * local line separator representation. You would use this class to 029 * implement ASCII file transfers requiring conversion from NETASCII. 030 * <p> 031 * <p> 032 * @author Daniel F. Savarese 033 ***/ 034 035 public final class FromNetASCIIInputStream extends PushbackInputStream 036 { 037 static final boolean _noConversionRequired; 038 static final String _lineSeparator; 039 static final byte[] _lineSeparatorBytes; 040 041 static { 042 _lineSeparator = System.getProperty("line.separator"); 043 _noConversionRequired = _lineSeparator.equals("\r\n"); 044 _lineSeparatorBytes = _lineSeparator.getBytes(); 045 } 046 047 private int __length = 0; 048 049 /*** 050 * Returns true if the NetASCII line separator differs from the system 051 * line separator, false if they are the same. This method is useful 052 * to determine whether or not you need to instantiate a 053 * FromNetASCIIInputStream object. 054 * <p> 055 * @return True if the NETASCII line separator differs from the local 056 * system line separator, false if they are the same. 057 ***/ 058 public static final boolean isConversionRequired() 059 { 060 return !_noConversionRequired; 061 } 062 063 /*** 064 * Creates a FromNetASCIIInputStream instance that wraps an existing 065 * InputStream. 066 ***/ 067 public FromNetASCIIInputStream(InputStream input) 068 { 069 super(input, _lineSeparatorBytes.length + 1); 070 } 071 072 073 private int __read() throws IOException 074 { 075 int ch; 076 077 ch = super.read(); 078 079 if (ch == '\r') 080 { 081 ch = super.read(); 082 if (ch == '\n') 083 { 084 unread(_lineSeparatorBytes); 085 ch = super.read(); 086 // This is a kluge for read(byte[], ...) to read the right amount 087 --__length; 088 } 089 else 090 { 091 if (ch != -1) 092 unread(ch); 093 return '\r'; 094 } 095 } 096 097 return ch; 098 } 099 100 101 /*** 102 * Reads and returns the next byte in the stream. If the end of the 103 * message has been reached, returns -1. Note that a call to this method 104 * may result in multiple reads from the underlying input stream in order 105 * to convert NETASCII line separators to the local line separator format. 106 * This is transparent to the programmer and is only mentioned for 107 * completeness. 108 * <p> 109 * @return The next character in the stream. Returns -1 if the end of the 110 * stream has been reached. 111 * @exception IOException If an error occurs while reading the underlying 112 * stream. 113 ***/ 114 @Override 115 public int read() throws IOException 116 { 117 if (_noConversionRequired) 118 return super.read(); 119 120 return __read(); 121 } 122 123 124 /*** 125 * Reads the next number of bytes from the stream into an array and 126 * returns the number of bytes read. Returns -1 if the end of the 127 * stream has been reached. 128 * <p> 129 * @param buffer The byte array in which to store the data. 130 * @return The number of bytes read. Returns -1 if the 131 * end of the message has been reached. 132 * @exception IOException If an error occurs in reading the underlying 133 * stream. 134 ***/ 135 @Override 136 public int read(byte buffer[]) throws IOException 137 { 138 return read(buffer, 0, buffer.length); 139 } 140 141 142 /*** 143 * Reads the next number of bytes from the stream into an array and returns 144 * the number of bytes read. Returns -1 if the end of the 145 * message has been reached. The characters are stored in the array 146 * starting from the given offset and up to the length specified. 147 * <p> 148 * @param buffer The byte array in which to store the data. 149 * @param offset The offset into the array at which to start storing data. 150 * @param length The number of bytes to read. 151 * @return The number of bytes read. Returns -1 if the 152 * end of the stream has been reached. 153 * @exception IOException If an error occurs while reading the underlying 154 * stream. 155 ***/ 156 @Override 157 public int read(byte buffer[], int offset, int length) throws IOException 158 { 159 if (_noConversionRequired) 160 return super.read(buffer, offset, length); 161 162 if (length < 1) 163 return 0; 164 165 int ch, off; 166 167 ch = available(); 168 169 __length = (length > ch ? ch : length); 170 171 // If nothing is available, block to read only one character 172 if (__length < 1) 173 __length = 1; 174 175 176 if ((ch = __read()) == -1) 177 return -1; 178 179 off = offset; 180 181 do 182 { 183 buffer[offset++] = (byte)ch; 184 } 185 while (--__length > 0 && (ch = __read()) != -1); 186 187 188 return (offset - off); 189 } 190 191 192 // PushbackInputStream in JDK 1.1.3 returns the wrong thing 193 // TODO - can we delete this override now? 194 /*** 195 * Returns the number of bytes that can be read without blocking EXCEPT 196 * when newline conversions have to be made somewhere within the 197 * available block of bytes. In other words, you really should not 198 * rely on the value returned by this method if you are trying to avoid 199 * blocking. 200 ***/ 201 @Override 202 public int available() throws IOException 203 { 204 if (in == null) { 205 throw new IOException("Stream closed"); 206 } 207 return (buf.length - pos) + in.available(); 208 } 209 210 }