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
018package org.apache.commons.net.io;
019
020import java.io.IOException;
021import java.io.InputStream;
022import java.io.PushbackInputStream;
023import java.nio.charset.StandardCharsets;
024
025import org.apache.commons.net.util.NetConstants;
026
027/**
028 * This class wraps an input stream, replacing all occurrences of <CR><LF> (carriage return followed by a linefeed), which is the NETASCII standard
029 * for representing a newline, with the local line separator representation. You would use this class to implement ASCII file transfers requiring conversion
030 * from NETASCII.
031 */
032
033public final class FromNetASCIIInputStream extends PushbackInputStream {
034    static final boolean _noConversionRequired;
035    static final String _lineSeparator;
036    static final byte[] _lineSeparatorBytes;
037
038    static {
039        _lineSeparator = System.lineSeparator();
040        _noConversionRequired = _lineSeparator.equals("\r\n");
041        _lineSeparatorBytes = _lineSeparator.getBytes(StandardCharsets.US_ASCII);
042    }
043
044    /**
045     * Returns true if the NetASCII line separator differs from the system line separator, false if they are the same. This method is useful to determine
046     * whether or not you need to instantiate a FromNetASCIIInputStream object.
047     *
048     * @return True if the NETASCII line separator differs from the local system line separator, false if they are the same.
049     */
050    public static boolean isConversionRequired() {
051        return !_noConversionRequired;
052    }
053
054    private int length;
055
056    /**
057     * Creates a FromNetASCIIInputStream instance that wraps an existing InputStream.
058     *
059     * @param input the stream to wrap
060     */
061    public FromNetASCIIInputStream(final InputStream input) {
062        super(input, _lineSeparatorBytes.length + 1);
063    }
064
065    // PushbackInputStream in JDK 1.1.3 returns the wrong thing
066    // TODO - can we delete this override now?
067    /**
068     * Returns the number of bytes that can be read without blocking EXCEPT when newline conversions have to be made somewhere within the available block of
069     * bytes. In other words, you really should not rely on the value returned by this method if you are trying to avoid blocking.
070     */
071    @Override
072    public int available() throws IOException {
073        if (in == null) {
074            throw new IOException("Stream closed");
075        }
076        return buf.length - pos + in.available();
077    }
078
079    /**
080     * Reads and returns the next byte in the stream. If the end of the message has been reached, returns -1. Note that a call to this method may result in
081     * multiple reads from the underlying input stream in order to convert NETASCII line separators to the local line separator format. This is transparent to
082     * the programmer and is only mentioned for completeness.
083     *
084     * @return The next character in the stream. Returns -1 if the end of the stream has been reached.
085     * @throws IOException If an error occurs while reading the underlying stream.
086     */
087    @Override
088    public int read() throws IOException {
089        if (_noConversionRequired) {
090            return super.read();
091        }
092
093        return readInt();
094    }
095
096    /**
097     * Reads the next number of bytes from the stream into an array and returns the number of bytes read. Returns -1 if the end of the stream has been reached.
098     *
099     * @param buffer The byte array in which to store the data.
100     * @return The number of bytes read. Returns -1 if the end of the message has been reached.
101     * @throws IOException If an error occurs in reading the underlying stream.
102     */
103    @Override
104    public int read(final byte buffer[]) throws IOException {
105        return read(buffer, 0, buffer.length);
106    }
107
108    /**
109     * Reads the next number of bytes from the stream into an array and returns the number of bytes read. Returns -1 if the end of the message has been reached.
110     * The characters are stored in the array starting from the given offset and up to the length specified.
111     *
112     * @param buffer The byte array in which to store the data.
113     * @param offset The offset into the array at which to start storing data.
114     * @param length The number of bytes to read.
115     * @return The number of bytes read. Returns -1 if the end of the stream has been reached.
116     * @throws IOException If an error occurs while reading the underlying stream.
117     */
118    @Override
119    public int read(final byte buffer[], int offset, final int length) throws IOException {
120        if (_noConversionRequired) {
121            return super.read(buffer, offset, length);
122        }
123
124        if (length < 1) {
125            return 0;
126        }
127
128        int ch;
129        final int off;
130
131        ch = available();
132
133        this.length = Math.min(length, ch);
134
135        // If nothing is available, block to read only one character
136        if (this.length < 1) {
137            this.length = 1;
138        }
139
140        if ((ch = readInt()) == -1) {
141            return NetConstants.EOS;
142        }
143
144        off = offset;
145
146        do {
147            buffer[offset++] = (byte) ch;
148        } while (--this.length > 0 && (ch = readInt()) != -1);
149
150        return offset - off;
151    }
152
153    private int readInt() throws IOException {
154        int ch;
155
156        ch = super.read();
157
158        if (ch == '\r') {
159            ch = super.read();
160            if (ch != '\n') {
161                if (ch != -1) {
162                    unread(ch);
163                }
164                return '\r';
165            }
166            unread(_lineSeparatorBytes);
167            ch = super.read();
168            // This is a kluge for read(byte[], ...) to read the right amount
169            --length;
170        }
171
172        return ch;
173    }
174
175}