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