    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 *
    032 *
    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 (final 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     *
    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 boolean isConversionRequired()
    063    {
    064        return !_noConversionRequired;
    065    }
    066
    067    /***
    068     * Creates a FromNetASCIIInputStream instance that wraps an existing
    069     * InputStream.
    070     * @param input the stream to wrap
    071     ***/
    072    public FromNetASCIIInputStream(final InputStream input)
    073    {
    074        super(input, _lineSeparatorBytes.length + 1);
    075    }
    076
    077
    078    private int __read() throws IOException
    079    {
    080        int ch;
    081
    082        ch = super.read();
    083
    084        if (ch == '\r')
    085        {
    086            ch = super.read();
    087            if (ch == '\n')
    088            {
    089                unread(_lineSeparatorBytes);
    090                ch = super.read();
    091                // This is a kluge for read(byte[], ...) to read the right amount
    092                --length;
    093            }
    094            else
    095            {
    096                if (ch != -1) {
    097                    unread(ch);
    098                }
    099                return '\r';
    100            }
    101        }
    102
    103        return ch;
    104    }
    105
    106
    107    /***
    108     * Reads and returns the next byte in the stream.  If the end of the
    109     * message has been reached, returns -1.  Note that a call to this method
    110     * may result in multiple reads from the underlying input stream in order
    111     * to convert NETASCII line separators to the local line separator format.
    112     * This is transparent to the programmer and is only mentioned for
    113     * completeness.
    114     *
    115     * @return The next character in the stream. Returns -1 if the end of the
    116     *          stream has been reached.
    117     * @throws IOException If an error occurs while reading the underlying
    118     *            stream.
    119     ***/
    120    @Override
    121    public int read() throws IOException
    122    {
    123        if (_noConversionRequired) {
    124            return super.read();
    125        }
    126
    127        return __read();
    128    }
    129
    130
    131    /***
    132     * Reads the next number of bytes from the stream into an array and
    133     * returns the number of bytes read.  Returns -1 if the end of the
    134     * stream has been reached.
    135     *
    136     * @param buffer  The byte array in which to store the data.
    137     * @return The number of bytes read. Returns -1 if the
    138     *          end of the message has been reached.
    139     * @throws IOException If an error occurs in reading the underlying
    140     *            stream.
    141     ***/
    142    @Override
    143    public int read(final byte buffer[]) throws IOException
    144    {
    145        return read(buffer, 0, buffer.length);
    146    }
    147
    148
    149    /***
    150     * Reads the next number of bytes from the stream into an array and returns
    151     * the number of bytes read.  Returns -1 if the end of the
    152     * message has been reached.  The characters are stored in the array
    153     * starting from the given offset and up to the length specified.
    154     *
    155     * @param buffer The byte array in which to store the data.
    156     * @param offset  The offset into the array at which to start storing data.
    157     * @param length   The number of bytes to read.
    158     * @return The number of bytes read. Returns -1 if the
    159     *          end of the stream has been reached.
    160     * @throws IOException If an error occurs while reading the underlying
    161     *            stream.
    162     ***/
    163    @Override
    164    public int read(final byte buffer[], int offset, final int length) throws IOException
    165    {
    166        if (_noConversionRequired) {
    167            return super.read(buffer, offset, length);
    168        }
    169
    170        if (length < 1) {
    171            return 0;
    172        }
    173
    174        int ch, off;
    175
    176        ch = available();
    177
    178        this.length = length > ch ? ch : length;
    179
    180        // If nothing is available, block to read only one character
    181        if (this.length < 1) {
    182            this.length = 1;
    183        }
    184
    185
    186        if ((ch = __read()) == -1) {
    187            return -1;
    188        }
    189
    190        off = offset;
    191
    192        do
    193        {
    194            buffer[offset++] = (byte)ch;
    195        }
    196        while (--this.length > 0 && (ch = __read()) != -1);
    197
    198
    199        return offset - off;
    200    }
    201
    202
    203    // PushbackInputStream in JDK 1.1.3 returns the wrong thing
    204    // TODO - can we delete this override now?
    205    /***
    206     * Returns the number of bytes that can be read without blocking EXCEPT
    207     * when newline conversions have to be made somewhere within the
    208     * available block of bytes.  In other words, you really should not
    209     * rely on the value returned by this method if you are trying to avoid
    210     * blocking.
    211     ***/
    212    @Override
    213    public int available() throws IOException
    214    {
    215        if (in == null) {
    216            throw new IOException("Stream closed");
    217        }
    218        return buf.length - pos + in.available();
    219    }
    220
    221}