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 ***/
033
034 public final class FromNetASCIIInputStream extends PushbackInputStream
035 {
036 static final boolean _noConversionRequired;
037 static final String _lineSeparator;
038 static final byte[] _lineSeparatorBytes;
039
040 static {
041 _lineSeparator = System.getProperty("line.separator");
042 _noConversionRequired = _lineSeparator.equals("\r\n");
043 _lineSeparatorBytes = _lineSeparator.getBytes();
044 }
045
046 private int __length = 0;
047
048 /***
049 * Returns true if the NetASCII line separator differs from the system
050 * line separator, false if they are the same. This method is useful
051 * to determine whether or not you need to instantiate a
052 * FromNetASCIIInputStream object.
053 * <p>
054 * @return True if the NETASCII line separator differs from the local
055 * system line separator, false if they are the same.
056 ***/
057 public static final boolean isConversionRequired()
058 {
059 return !_noConversionRequired;
060 }
061
062 /***
063 * Creates a FromNetASCIIInputStream instance that wraps an existing
064 * InputStream.
065 ***/
066 public FromNetASCIIInputStream(InputStream input)
067 {
068 super(input, _lineSeparatorBytes.length + 1);
069 }
070
071
072 private int __read() throws IOException
073 {
074 int ch;
075
076 ch = super.read();
077
078 if (ch == '\r')
079 {
080 ch = super.read();
081 if (ch == '\n')
082 {
083 unread(_lineSeparatorBytes);
084 ch = super.read();
085 // This is a kluge for read(byte[], ...) to read the right amount
086 --__length;
087 }
088 else
089 {
090 if (ch != -1) {
091 unread(ch);
092 }
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
121 return __read();
122 }
123
124
125 /***
126 * Reads the next number of bytes from the stream into an array and
127 * returns the number of bytes read. Returns -1 if the end of the
128 * stream has been reached.
129 * <p>
130 * @param buffer The byte array in which to store the data.
131 * @return The number of bytes read. Returns -1 if the
132 * end of the message has been reached.
133 * @exception IOException If an error occurs in reading the underlying
134 * stream.
135 ***/
136 @Override
137 public int read(byte buffer[]) throws IOException
138 {
139 return read(buffer, 0, buffer.length);
140 }
141
142
143 /***
144 * Reads the next number of bytes from the stream into an array and returns
145 * the number of bytes read. Returns -1 if the end of the
146 * message has been reached. The characters are stored in the array
147 * starting from the given offset and up to the length specified.
148 * <p>
149 * @param buffer The byte array in which to store the data.
150 * @param offset The offset into the array at which to start storing data.
151 * @param length The number of bytes to read.
152 * @return The number of bytes read. Returns -1 if the
153 * end of the stream has been reached.
154 * @exception IOException If an error occurs while reading the underlying
155 * stream.
156 ***/
157 @Override
158 public int read(byte buffer[], int offset, int length) throws IOException
159 {
160 if (_noConversionRequired) {
161 return super.read(buffer, offset, length);
162 }
163
164 if (length < 1) {
165 return 0;
166 }
167
168 int ch, off;
169
170 ch = available();
171
172 __length = (length > ch ? ch : length);
173
174 // If nothing is available, block to read only one character
175 if (__length < 1) {
176 __length = 1;
177 }
178
179
180 if ((ch = __read()) == -1) {
181 return -1;
182 }
183
184 off = offset;
185
186 do
187 {
188 buffer[offset++] = (byte)ch;
189 }
190 while (--__length > 0 && (ch = __read()) != -1);
191
192
193 return (offset - off);
194 }
195
196
197 // PushbackInputStream in JDK 1.1.3 returns the wrong thing
198 // TODO - can we delete this override now?
199 /***
200 * Returns the number of bytes that can be read without blocking EXCEPT
201 * when newline conversions have to be made somewhere within the
202 * available block of bytes. In other words, you really should not
203 * rely on the value returned by this method if you are trying to avoid
204 * blocking.
205 ***/
206 @Override
207 public int available() throws IOException
208 {
209 if (in == null) {
210 throw new IOException("Stream closed");
211 }
212 return (buf.length - pos) + in.available();
213 }
214
215 }