ReadCoilsRequest.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.msg;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

import net.wimpi.modbus.Modbus;
import net.wimpi.modbus.ModbusCoupler;
import net.wimpi.modbus.procimg.DigitalOut;
import net.wimpi.modbus.procimg.IllegalAddressException;
import net.wimpi.modbus.procimg.ProcessImage;

/**
 * Class implementing a <tt>ReadCoilsRequest</tt>.
 * The implementation directly correlates with the class 1
 * function <i>read coils (FC 1)</i>. It encapsulates
 * the corresponding request message.
 * <p>
 * Coils are understood as bits that can be manipulated
 * (i.e. set or unset).
 *
 * @author Dieter Wimberger
 * @version @version@ (@date@)
 */
public final class ReadCoilsRequest extends ModbusRequest {

    // instance attributes
    private int m_Reference;
    private int m_BitCount;

    /**
     * Constructs a new <tt>ReadCoilsRequest</tt>
     * instance.
     */
    public ReadCoilsRequest() {
        super();
        setFunctionCode(Modbus.READ_COILS);
        // 4 bytes (unit id and function code is excluded)
        setDataLength(4);
    }// constructor

    /**
     * Constructs a new <tt>ReadCoilsRequest</tt>
     * instance with a given reference and count of coils
     * (i.e. bits) to be read.
     * <p>
     *
     * @param ref the reference number of the register
     *            to read from.
     * @param count the number of bits to be read.
     */
    public ReadCoilsRequest(int ref, int count) {
        super();
        setFunctionCode(Modbus.READ_COILS);
        // 4 bytes (unit id and function code is excluded)
        setDataLength(4);
        setReference(ref);
        setBitCount(count);
    }// constructor

    @Override
    public ModbusResponse createResponse() {
        ReadCoilsResponse response = null;
        DigitalOut[] douts = null;

        // 1. get process image
        ProcessImage procimg = ModbusCoupler.getReference().getProcessImage();
        // 2. get coil range
        try {
            douts = procimg.getDigitalOutRange(this.getReference(), this.getBitCount());
        } catch (IllegalAddressException iaex) {
            return createExceptionResponse(Modbus.ILLEGAL_ADDRESS_EXCEPTION);
        }
        response = new ReadCoilsResponse(douts.length);

        // transfer header data
        if (!isHeadless()) {
            response.setTransactionID(this.getTransactionID());
            response.setProtocolID(this.getProtocolID());
        } else {
            response.setHeadless();
        }
        response.setUnitID(this.getUnitID());
        response.setFunctionCode(this.getFunctionCode());

        for (int i = 0; i < douts.length; i++) {
            response.setCoilStatus(i, douts[i].isSet());
        }
        return response;
    }// createResponse

    /**
     * Sets the reference of the register to start reading
     * from with this <tt>ReadCoilsRequest</tt>.
     * <p>
     *
     * @param ref the reference of the register
     *            to start reading from.
     */
    public void setReference(int ref) {
        m_Reference = ref;
        // setChanged(true);
    }// setReference

    /**
     * Returns the reference of the register to to start
     * reading from with this <tt>ReadCoilsRequest</tt>.
     * <p>
     *
     * @return the reference of the register
     *         to start reading from as <tt>int</tt>.
     */
    public int getReference() {
        return m_Reference;
    }// getReference

    /**
     * Sets the number of bits (i.e. coils) to be read with
     * this <tt>ReadCoilsRequest</tt>.
     * <p>
     *
     * @param count the number of bits to be read.
     */
    public void setBitCount(int count) {
        if (count > Modbus.MAX_BITS) {
            throw new IllegalArgumentException("Maximum bitcount exceeded.");
        } else {
            m_BitCount = count;
        }
    }// setBitCount

    /**
     * Returns the number of bits (i.e. coils) to be
     * read with this <tt>ReadCoilsRequest</tt>.
     * <p>
     *
     * @return the number of bits to be read.
     */
    public int getBitCount() {
        return m_BitCount;
    }// getBitCount

    @Override
    public void writeData(DataOutput dout) throws IOException {
        dout.writeShort(m_Reference);
        dout.writeShort(m_BitCount);
    }// writeData

    @Override
    public void readData(DataInput din) throws IOException {
        m_Reference = din.readUnsignedShort();
        m_BitCount = din.readUnsignedShort();
    }// readData

}// class ReadCoilsRequest