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                    return '\r';
093                }
094            }
095    
096            return ch;
097        }
098    
099    
100        /***
101         * Reads and returns the next byte in the stream.  If the end of the
102         * message has been reached, returns -1.  Note that a call to this method
103         * may result in multiple reads from the underlying input stream in order
104         * to convert NETASCII line separators to the local line separator format.
105         * This is transparent to the programmer and is only mentioned for
106         * completeness.
107         * <p>
108         * @return The next character in the stream. Returns -1 if the end of the
109         *          stream has been reached.
110         * @exception IOException If an error occurs while reading the underlying
111         *            stream.
112         ***/
113        @Override
114        public int read() throws IOException
115        {
116            if (_noConversionRequired)
117                return super.read();
118    
119            return __read();
120        }
121    
122    
123        /***
124         * Reads the next number of bytes from the stream into an array and
125         * returns the number of bytes read.  Returns -1 if the end of the
126         * stream has been reached.
127         * <p>
128         * @param buffer  The byte array in which to store the data.
129         * @return The number of bytes read. Returns -1 if the
130         *          end of the message has been reached.
131         * @exception IOException If an error occurs in reading the underlying
132         *            stream.
133         ***/
134        @Override
135        public int read(byte buffer[]) throws IOException
136        {
137            return read(buffer, 0, buffer.length);
138        }
139    
140    
141        /***
142         * Reads the next number of bytes from the stream into an array and returns
143         * the number of bytes read.  Returns -1 if the end of the
144         * message has been reached.  The characters are stored in the array
145         * starting from the given offset and up to the length specified.
146         * <p>
147         * @param buffer The byte array in which to store the data.
148         * @param offset  The offset into the array at which to start storing data.
149         * @param length   The number of bytes to read.
150         * @return The number of bytes read. Returns -1 if the
151         *          end of the stream has been reached.
152         * @exception IOException If an error occurs while reading the underlying
153         *            stream.
154         ***/
155        @Override
156        public int read(byte buffer[], int offset, int length) throws IOException
157        {
158            if (_noConversionRequired)
159                return super.read(buffer, offset, length);
160    
161            if (length < 1)
162                return 0;
163    
164            int ch, off;
165    
166            ch = available();
167    
168            __length = (length > ch ? ch : length);
169    
170            // If nothing is available, block to read only one character
171            if (__length < 1)
172                __length = 1;
173    
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        // TODO - can we delete this override now?
193        /***
194         * Returns the number of bytes that can be read without blocking EXCEPT
195         * when newline conversions have to be made somewhere within the
196         * available block of bytes.  In other words, you really should not
197         * rely on the value returned by this method if you are trying to avoid
198         * blocking.
199         ***/
200        @Override
201        public int available() throws IOException
202        {
203            if (in == null) {
204                throw new IOException("Stream closed");
205            }
206            return (buf.length - pos) + in.available();
207        }
208    
209    }