ToNetASCIIInputStream.java

/*
 * 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 com.myjavaworld.ftp;

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.
 * <p>
 * <p>
 ***/

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;
	}
}