ToNetASCIIInputStream.java

/*
 * Copyright 2010 netling project <http://netling.org>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * This file may incorporate work covered by the following copyright and
 * permission notice:
 *
 *     Licensed to the Apache Software Foundation (ASF) under one
 *     or more contributor license agreements.  See the NOTICE file
 *     distributed with this work for additional information
 *     regarding copyright ownership.  The ASF licenses this file
 *     to you under the Apache License, Version 2.0 (the
 *     "License"); you may not use this file except in compliance
 *     with the License.  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *      Unless required by applicable law or agreed to in writing,
 *      software distributed under the License is distributed on an
 *      "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *      KIND, either express or implied.  See the License for the
 *      specific language governing permissions and limitations
 *      under the License.
 */
package org.netling.io;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

/***
 * This class wraps an input stream, replacing all singly occurring
 * <LF> (linefeed) characters with <CR><LF> (carriage return
 * followed by linefeed), which is the NETASCII standard for representing
 * a newline.
 * You would use this class to implement ASCII file transfers requiring
 * conversion to NETASCII.
 ***/

public final class ToNetASCIIInputStream extends FilterInputStream
{
    private static final int NOTHING_SPECIAL = 0;
    private static final int LAST_WAS_CR = 1;
    private static final int LAST_WAS_NL = 2;
    private int status;

    /***
     * Creates a ToNetASCIIInputStream instance that wraps an existing
     * InputStream.
     * <p>
     * @param input  The InputStream to .
     ***/
    public ToNetASCIIInputStream(InputStream input)
    {
        super(input);
        status = NOTHING_SPECIAL;
    }


    /***
     * Reads and returns the next byte in the stream.  If the end of the
     * message has been reached, returns -1.
     * <p>
     * @return The next character in the stream. Returns -1 if the end of the
     *          stream has been reached.
     * @exception IOException If an error occurs while reading the underlying
     *            stream.
     ***/
    @Override
    public int read() throws IOException
    {
        int ch;

        if (status == LAST_WAS_NL)
        {
            status = NOTHING_SPECIAL;
            return '\n';
        }

        ch = in.read();

        switch (ch)
        {
        case '\r':
            status = LAST_WAS_CR;
            return '\r';
        case '\n':
            if (status != LAST_WAS_CR)
            {
                status = LAST_WAS_NL;
                return '\r';
            }
            //$FALL-THROUGH$
        default:
            status = NOTHING_SPECIAL;
            return ch;
        }
        // statement not reached
        //return ch;
    }


    /***
     * 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.
     * <p>
     * @param buffer  The byte array in which to store the data.
     * @return The number of bytes read. Returns -1 if the
     *          end of the message has been reached.
     * @exception IOException If an error occurs in reading the underlying
     *            stream.
     ***/
    @Override
    public int read(byte buffer[]) throws IOException
    {
        return read(buffer, 0, buffer.length);
    }


    /***
     * 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.  The characters are stored in the array
     * starting from the given offset and up to the length specified.
     * <p>
     * @param buffer The byte array in which to store the data.
     * @param offset  The offset into the array at which to start storing data.
     * @param length   The number of bytes to read.
     * @return The number of bytes read. Returns -1 if the
     *          end of the stream has been reached.
     * @exception IOException If an error occurs while reading the underlying
     *            stream.
     ***/
    @Override
    public int read(byte buffer[], int offset, int length) throws IOException
    {
        int ch, off;

        if (length < 1)
            return 0;

        ch = available();

        if (length > ch)
            length = ch;

        // If nothing is available, block to read only one character
        if (length < 1)
            length = 1;

        if ((ch = read()) == -1)
            return -1;

        off = offset;

        do
        {
            buffer[offset++] = (byte)ch;
        }
        while (--length > 0 && (ch = read()) != -1);

        return (offset - off);
    }

    /*** Returns false.  Mark is not supported. ***/
    @Override
    public boolean markSupported()
    {
        return false;
    }

    @Override
    public int available() throws IOException
    {
        int result;

        result = in.available();

        if (status == LAST_WAS_NL)
            return (result + 1);

        return result;
    }
}