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 int ch, off;
160
161 if (length < 1)
162 return 0;
163
164 ch = available();
165
166 __length = (length > ch ? ch : length);
167
168 // If nothing is available, block to read only one character
169 if (__length < 1)
170 __length = 1;
171
172 if (_noConversionRequired)
173 return super.read(buffer, offset, __length);
174
175 if ((ch = __read()) == -1)
176 return -1;
177
178 off = offset;
179
180 do
181 {
182 buffer[offset++] = (byte)ch;
183 }
184 while (--__length > 0 && (ch = __read()) != -1);
185
186
187 return (offset - off);
188 }
189
190
191 // PushbackInputStream in JDK 1.1.3 returns the wrong thing
192 /***
193 * Returns the number of bytes that can be read without blocking EXCEPT
194 * when newline conversions have to be made somewhere within the
195 * available block of bytes. In other words, you really should not
196 * rely on the value returned by this method if you are trying to avoid
197 * blocking.
198 ***/
199 @Override
200 public int available() throws IOException
201 {
202 return (buf.length - pos) + in.available();
203 }
204
205 }