SerialInputStream.java

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package com.freedomotic.plugins.devices.modbus.gateways;

import jssc.SerialPort;

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

/**
 * Class that wraps a {@link SerialPort} to provide {@link InputStream}
 * functionality. This stream also provides support for performing blocking
 * reads with timeouts.
 * <br>
 * It is instantiated by passing the constructor a {@link SerialPort} instance.
 * Do not create multiple streams for the same serial port unless you implement
 * your own synchronization.
 *
 * @author Charles Hache <chalz@member.fsf.org>
 *
 * Attribution: https://github.com/therealchalz/java-simple-serial-connector
 *
 */
public class SerialInputStream extends InputStream {

    private SerialPort serialPort;
    private int defaultTimeout = 0;

    /**
     * Instantiates a SerialInputStream for the given {@link SerialPort} Do not
     * create multiple streams for the same serial port unless you implement
     * your own synchronization.
     *
     * @param sp The serial port to stream.
     */
    public SerialInputStream(SerialPort sp) {
        serialPort = sp;
    }

    /**
     * Set the default timeout (ms) of this SerialInputStream. This affects
     * subsequent calls to {@link #read()}, {@link #blockingRead(int[])}, and
     * {@link #blockingRead(int[], int, int)} The default timeout can be 'unset'
     * by setting it to 0.
     *
     * @param time The timeout in milliseconds.
     */
    public void setTimeout(int time) {
        defaultTimeout = time;
    }

    /**
     * Reads the next byte from the port. If the timeout of this stream has been
     * set, then this method blocks until data is available or until the timeout
     * has been hit. If the timeout is not set or has been set to 0, then this
     * method blocks indefinitely.
     */
    @Override
    public int read() throws IOException {
        return read(defaultTimeout);
    }

    /**
     * The same contract as {@link #read()}, except overrides this stream's
     * default timeout with the given timeout in milliseconds.
     *
     * @param timeout The timeout in milliseconds.
     * @return The read byte.
     * @throws IOException On serial port error or timeout
     */
    public int read(int timeout) throws IOException {
        byte[] buf = new byte[1];
        try {
            if (timeout > 0) {
                buf = serialPort.readBytes(1, timeout);
            } else {
                buf = serialPort.readBytes(1);
            }
            return buf[0];
        } catch (Exception e) {
            throw new IOException(e);
        }
    }

    /**
     * Non-blocking read of up to buf.length bytes from the stream. This call
     * behaves as read(buf, 0, buf.length) would.
     *
     * @param buf The buffer to fill.
     * @return The number of bytes read, which can be 0.
     * @throws IOException on error.
     */
    @Override
    public int read(byte[] buf) throws IOException {
        return read(buf, 0, buf.length);
    }

    /**
     * Non-blocking read of up to length bytes from the stream. This method
     * returns what is immediately available in the input buffer.
     *
     * @param buf The buffer to fill.
     * @param offset The offset into the buffer to start copying data.
     * @param length The maximum number of bytes to read.
     * @return The actual number of bytes read, which can be 0.
     * @throws IOException on error.
     */
    @Override
    public int read(byte[] buf, int offset, int length) throws IOException {

        if (buf.length < offset + length) {
            length = buf.length - offset;
        }

        int available = this.available();

        if (available > length) {
            available = length;
        }

        try {
            byte[] readBuf = serialPort.readBytes(available);
            System.arraycopy(readBuf, 0, buf, offset, length);
            return readBuf.length;
        } catch (Exception e) {
            throw new IOException(e);
        }
    }

    /**
     * Blocks until buf.length bytes are read, an error occurs, or the default
     * timeout is hit (if specified). This behaves as blockingRead(buf, 0,
     * buf.length) would.
     *
     * @param buf The buffer to fill with data.
     * @return The number of bytes read.
     * @throws IOException On error or timeout.
     */
    public int blockingRead(byte[] buf) throws IOException {
        return blockingRead(buf, 0, buf.length, defaultTimeout);
    }

    /**
     * The same contract as {@link #blockingRead(byte[])} except overrides this
     * stream's default timeout with the given one.
     *
     * @param buf The buffer to fill.
     * @param timeout The timeout in milliseconds.
     * @return The number of bytes read.
     * @throws IOException On error or timeout.
     */
    public int blockingRead(byte[] buf, int timeout) throws IOException {
        return blockingRead(buf, 0, buf.length, timeout);
    }

    /**
     * Blocks until length bytes are read, an error occurs, or the default
     * timeout is hit (if specified). Saves the data into the given buffer at
     * the specified offset. If the stream's timeout is not set, behaves as
     * {@link #read(byte[], int, int)} would.
     *
     * @param buf The buffer to fill.
     * @param offset The offset in buffer to save the data.
     * @param length The number of bytes to read.
     * @return the number of bytes read.
     * @throws IOException on error or timeout.
     */
    public int blockingRead(byte[] buf, int offset, int length) throws IOException {
        return blockingRead(buf, offset, length, defaultTimeout);
    }

    /**
     * The same contract as {@link #blockingRead(byte[], int, int)} except
     * overrides this stream's default timeout with the given one.
     *
     * @param buf The buffer to fill.
     * @param offset Offset in the buffer to start saving data.
     * @param length The number of bytes to read.
     * @param timeout The timeout in milliseconds.
     * @return The number of bytes read.
     * @throws IOException On error or timeout.
     */
    public int blockingRead(byte[] buf, int offset, int length, int timeout) throws IOException {
        if (buf.length < offset + length) {
            throw new IOException("Not enough buffer space for serial data");
        }

        if (timeout < 1) {
            return read(buf, offset, length);
        }

        try {
            byte[] readBuf = serialPort.readBytes(length, timeout);
            System.arraycopy(readBuf, 0, buf, offset, length);
            return readBuf.length;
        } catch (Exception e) {
            throw new IOException(e);
        }
    }

    @Override
    public int available() throws IOException {
        int ret;
        try {
            ret = serialPort.getInputBufferBytesCount();
            if (ret >= 0) {
                return ret;
            }
            throw new IOException("Error checking available bytes from the serial port.");
        } catch (Exception e) {
            throw new IOException("Error checking available bytes from the serial port.");
        }
    }

}