    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 *      https://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 &lt;CR&gt;&lt;LF&gt; (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 */
    032public final class FromNetASCIIInputStream extends PushbackInputStream {
    033
    034    static final boolean NO_CONVERSION_REQUIRED = System.lineSeparator().equals("\r\n");
    035    static final byte[] LINE_SEPARATOR_BYTES = System.lineSeparator().getBytes(StandardCharsets.US_ASCII);
    036
    037    /**
    038     * 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
    039     * whether or not you need to instantiate a FromNetASCIIInputStream object.
    040     *
    041     * @return True if the NETASCII line separator differs from the local system line separator, false if they are the same.
    042     */
    043    public static boolean isConversionRequired() {
    044        return !NO_CONVERSION_REQUIRED;
    045    }
    046
    047    private int length;
    048
    049    /**
    050     * Creates a FromNetASCIIInputStream instance that wraps an existing InputStream.
    051     *
    052     * @param input the stream to wrap
    053     */
    054    public FromNetASCIIInputStream(final InputStream input) {
    055        super(input, LINE_SEPARATOR_BYTES.length + 1);
    056    }
    057
    058    // PushbackInputStream in JDK 1.1.3 returns the wrong thing
    059    // TODO - can we delete this override now?
    060    /**
    061     * 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
    062     * bytes. In other words, you really should not rely on the value returned by this method if you are trying to avoid blocking.
    063     */
    064    @Override
    065    public int available() throws IOException {
    066        if (in == null) {
    067            throw new IOException("Stream closed");
    068        }
    069        return buf.length - pos + in.available();
    070    }
    071
    072    /**
    073     * 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
    074     * multiple reads from the underlying input stream in order to convert NETASCII line separators to the local line separator format. This is transparent to
    075     * the programmer and is only mentioned for completeness.
    076     *
    077     * @return The next character in the stream. Returns -1 if the end of the stream has been reached.
    078     * @throws IOException If an error occurs while reading the underlying stream.
    079     */
    080    @Override
    081    public int read() throws IOException {
    082        if (NO_CONVERSION_REQUIRED) {
    083            return super.read();
    084        }
    085        return readInt();
    086    }
    087
    088    /**
    089     * 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.
    090     *
    091     * @param buffer The byte array in which to store the data.
    092     * @return The number of bytes read. Returns -1 if the end of the message has been reached.
    093     * @throws IOException If an error occurs in reading the underlying stream.
    094     */
    095    @Override
    096    public int read(final byte buffer[]) throws IOException {
    097        return read(buffer, 0, buffer.length);
    098    }
    099
    100    /**
    101     * 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.
    102     * The characters are stored in the array starting from the given offset and up to the length specified.
    103     *
    104     * @param buffer The byte array in which to store the data.
    105     * @param offset The offset into the array at which to start storing data.
    106     * @param length The number of bytes to read.
    107     * @return The number of bytes read. Returns -1 if the end of the stream has been reached.
    108     * @throws IOException If an error occurs while reading the underlying stream.
    109     */
    110    @Override
    111    public int read(final byte buffer[], int offset, final int length) throws IOException {
    112        if (NO_CONVERSION_REQUIRED) {
    113            return super.read(buffer, offset, length);
    114        }
    115        if (length < 1) {
    116            return 0;
    117        }
    118        int ch;
    119        final int off;
    120        ch = available();
    121        this.length = Math.min(length, ch);
    122        // If nothing is available, block to read only one character
    123        if (this.length < 1) {
    124            this.length = 1;
    125        }
    126        if ((ch = readInt()) == -1) {
    127            return NetConstants.EOS;
    128        }
    129        off = offset;
    130        do {
    131            buffer[offset++] = (byte) ch;
    132        } while (--this.length > 0 && (ch = readInt()) != -1);
    133        return offset - off;
    134    }
    135
    136    private int readInt() throws IOException {
    137        int ch;
    138        ch = super.read();
    139        if (ch == '\r') {
    140            ch = super.read();
    141            if (ch != '\n') {
    142                if (ch != -1) {
    143                    unread(ch);
    144                }
    145                return '\r';
    146            }
    147            unread(LINE_SEPARATOR_BYTES);
    148            ch = super.read();
    149            // This is a kluge for read(byte[], ...) to read the right amount
    150            --length;
    151        }
    152        return ch;
    153    }
    154
    155}