BINInputStream.java

/***
 * Copyright 2002-2010 jamod development team
 *
 * 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.
 ***/

package net.wimpi.modbus.io;

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

/**
 * Class implementing a specialized <tt>InputStream</tt> which
 * handles binary transmitted messages.
 *
 * @author Dieter Wimberger
 * @version @version@ (@date@)
 *
 * @see ModbusBINTransport#FRAME_START
 * @see ModbusBINTransport#FRAME_END
 */
public class BINInputStream extends FilterInputStream {

    /**
     * Constructs a new <tt>BINInputStream</tt> instance
     * reading from the given <tt>InputStream</tt>.
     *
     * @param in a base input stream to be wrapped.
     */
    public BINInputStream(InputStream in) {
        super(in);
        if (!in.markSupported()) {
            throw new RuntimeException("Accepts only input streams that support marking.");
        }
    }// constructor

    /**
     * Reads a byte from the BIN encoded stream.
     *
     * @return int the byte read from the stream.
     * @throws java.io.IOException if an I/O error occurs.
     */
    @Override
    public int read() throws IOException {
        int ch = in.read();
        if (ch == -1) {
            return -1;
        } else if (ch == ModbusBINTransport.FRAME_START_TOKEN) {
            in.mark(1);
            // read next
            ch = in.read();
            if (ch == ModbusBINTransport.FRAME_START_TOKEN) {
                return ch;
            } else {
                in.reset();
                return ModbusBINTransport.FRAME_START;
            }
        } else if (ch == ModbusBINTransport.FRAME_END_TOKEN) {
            in.mark(1);
            // read next
            ch = in.read();
            if (ch == ModbusBINTransport.FRAME_END_TOKEN) {
                return ch;
            } else {
                in.reset();
                return ModbusBINTransport.FRAME_END;
            }
        } else {
            return ch;
        }
    }// read

}// class BINInputStream