    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.io.UnsupportedEncodingException;
    024
    025/***
    026 * This class wraps an input stream, replacing all occurrences
    027 * of &lt;CR&gt;&lt;LF&gt; (carriage return followed by a linefeed),
    028 * which is the NETASCII standard for representing a newline, with the
    029 * local line separator representation.  You would use this class to
    030 * implement ASCII file transfers requiring conversion from NETASCII.
    031 * <p>
    032 * <p>
    033 ***/
    034
    035public 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        try {
    045            _lineSeparatorBytes = _lineSeparator.getBytes("US-ASCII");
    046        } catch (UnsupportedEncodingException e) {
    047           throw new RuntimeException("Broken JVM - cannot find US-ASCII charset!",e);
    048        }
    049    }
    050
    051    private int __length = 0;
    052
    053    /***
    054     * Returns true if the NetASCII line separator differs from the system
    055     * line separator, false if they are the same.  This method is useful
    056     * to determine whether or not you need to instantiate a
    057     * FromNetASCIIInputStream object.
    058     * <p>
    059     * @return True if the NETASCII line separator differs from the local
    060     *   system line separator, false if they are the same.
    061     ***/
    062    public static final boolean isConversionRequired()
    063    {
    064        return !_noConversionRequired;
    065    }
    066
    067    /***
    068     * Creates a FromNetASCIIInputStream instance that wraps an existing
    069     * InputStream.
    070     ***/
    071    public FromNetASCIIInputStream(InputStream input)
    072    {
    073        super(input, _lineSeparatorBytes.length + 1);
    074    }
    075
    076
    077    private int __read() throws IOException
    078    {
    079        int ch;
    080
    081        ch = super.read();
    082
    083        if (ch == '\r')
    084        {
    085            ch = super.read();
    086            if (ch == '\n')
    087            {
    088                unread(_lineSeparatorBytes);
    089                ch = super.read();
    090                // This is a kluge for read(byte[], ...) to read the right amount
    091                --__length;
    092            }
    093            else
    094            {
    095                if (ch != -1) {
    096                    unread(ch);
    097                }
    098                return '\r';
    099            }
    100        }
    101
    102        return ch;
    103    }
    104
    105
    106    /***
    107     * Reads and returns the next byte in the stream.  If the end of the
    108     * message has been reached, returns -1.  Note that a call to this method
    109     * may result in multiple reads from the underlying input stream in order
    110     * to convert NETASCII line separators to the local line separator format.
    111     * This is transparent to the programmer and is only mentioned for
    112     * completeness.
    113     * <p>
    114     * @return The next character in the stream. Returns -1 if the end of the
    115     *          stream has been reached.
    116     * @exception IOException If an error occurs while reading the underlying
    117     *            stream.
    118     ***/
    119    @Override
    120    public int read() throws IOException
    121    {
    122        if (_noConversionRequired) {
    123            return super.read();
    124        }
    125
    126        return __read();
    127    }
    128
    129
    130    /***
    131     * Reads the next number of bytes from the stream into an array and
    132     * returns the number of bytes read.  Returns -1 if the end of the
    133     * stream has been reached.
    134     * <p>
    135     * @param buffer  The byte array in which to store the data.
    136     * @return The number of bytes read. Returns -1 if the
    137     *          end of the message has been reached.
    138     * @exception IOException If an error occurs in reading the underlying
    139     *            stream.
    140     ***/
    141    @Override
    142    public int read(byte buffer[]) throws IOException
    143    {
    144        return read(buffer, 0, buffer.length);
    145    }
    146
    147
    148    /***
    149     * Reads the next number of bytes from the stream into an array and returns
    150     * the number of bytes read.  Returns -1 if the end of the
    151     * message has been reached.  The characters are stored in the array
    152     * starting from the given offset and up to the length specified.
    153     * <p>
    154     * @param buffer The byte array in which to store the data.
    155     * @param offset  The offset into the array at which to start storing data.
    156     * @param length   The number of bytes to read.
    157     * @return The number of bytes read. Returns -1 if the
    158     *          end of the stream has been reached.
    159     * @exception IOException If an error occurs while reading the underlying
    160     *            stream.
    161     ***/
    162    @Override
    163    public int read(byte buffer[], int offset, int length) throws IOException
    164    {
    165        if (_noConversionRequired) {
    166            return super.read(buffer, offset, length);
    167        }
    168
    169        if (length < 1) {
    170            return 0;
    171        }
    172
    173        int ch, off;
    174
    175        ch = available();
    176
    177        __length = (length > ch ? ch : length);
    178
    179        // If nothing is available, block to read only one character
    180        if (__length < 1) {
    181            __length = 1;
    182        }
    183
    184
    185        if ((ch = __read()) == -1) {
    186            return -1;
    187        }
    188
    189        off = offset;
    190
    191        do
    192        {
    193            buffer[offset++] = (byte)ch;
    194        }
    195        while (--__length > 0 && (ch = __read()) != -1);
    196
    197
    198        return (offset - off);
    199    }
    200
    201
    202    // PushbackInputStream in JDK 1.1.3 returns the wrong thing
    203    // TODO - can we delete this override now?
    204    /***
    205     * Returns the number of bytes that can be read without blocking EXCEPT
    206     * when newline conversions have to be made somewhere within the
    207     * available block of bytes.  In other words, you really should not
    208     * rely on the value returned by this method if you are trying to avoid
    209     * blocking.
    210     ***/
    211    @Override
    212    public int available() throws IOException
    213    {
    214        if (in == null) {
    215            throw new IOException("Stream closed");
    216        }
    217        return (buf.length - pos) + in.available();
    218    }
    219
    220}