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JCA is an EPICS Channel Access library for Java. For more information concerning EPICS or Channel Access please refer to the <a href="http://www.aps.anl.gov/epics">EPICS Web pages</a> or read the <a href="http://www.aps.anl.gov/epics/base/R3-14/8-docs/CAref.html">Channel Access manual (3.14)</a>. <p>This module also includes CAJ, A 100% pure Java implementation of the EPICS Channel Access library.</p>

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/*
 * Copyright (c) 2004 by Cosylab
 *
 * The full license specifying the redistribution, modification, usage and other
 * rights and obligations is included with the distribution of this project in
 * the file "LICENSE-CAJ". If the license is not included visit Cosylab web site,
 * .
 *
 * THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY OF ANY KIND, NOT EVEN THE
 * IMPLIED WARRANTY OF MERCHANTABILITY. THE AUTHOR OF THIS SOFTWARE, ASSUMES
 * _NO_ RESPONSIBILITY FOR ANY CONSEQUENCE RESULTING FROM THE USE, MODIFICATION,
 * OR REDISTRIBUTION OF THIS SOFTWARE.
 */

package com.cosylab.epics.caj.cas.util;

import gov.aps.jca.CAException;
import gov.aps.jca.CAStatus;
import gov.aps.jca.cas.ProcessVariable;
import gov.aps.jca.cas.ProcessVariableEventCallback;
import gov.aps.jca.cas.ProcessVariableReadCallback;
import gov.aps.jca.cas.ProcessVariableWriteCallback;
import gov.aps.jca.dbr.DBR;
import gov.aps.jca.dbr.DBRType;
import gov.aps.jca.dbr.DBR_String;
import gov.aps.jca.dbr.DBR_TIME_String;

/**
 * Abstract convenient string process variable implementation. 
 */
public abstract class StringProcessVariable extends ProcessVariable
{
	/**
	 * String PV constructor.
	 * @param name process variable name.
	 * @param eventCallback	event callback, can be null.
	 */
	public StringProcessVariable(String name, ProcessVariableEventCallback eventCallback)
	{
		super(name, eventCallback);
	}

	/**
	 * Return DBRType.STRING type as native type.
	 * @see gov.aps.jca.cas.ProcessVariable#getType()
	 */
	public DBRType getType() {
		return DBRType.STRING;
	}

	/**
	 * Casts DBR to DBR_TIME_String and
	 * delegates operation of reading a value to readValue method.
	 * @see gov.aps.jca.cas.ProcessVariable#read(gov.aps.jca.dbr.DBR, gov.aps.jca.cas.ProcessVariableReadCallback)
	 */
	public CAStatus read(DBR value, ProcessVariableReadCallback asyncReadCallback) throws CAException {

		// for STRING type input DBR is always DBR_TIME_String
		DBR_TIME_String stringValue = (DBR_TIME_String)value;

		// read value
		return readValue(stringValue, asyncReadCallback);
	}

	/**
	 * Read value.
	 * Reference implementation:
	 * 	 * 	{
	 * 
	 * 		// for async. completion, return null,
	 * 		// set value (and status) to enumValue and
	 * 		// report completion using asyncReadCallback callback.
	 * 		// return null;
	 * 	
	 *      {@code
	 * 		// BEGIN optional (to override defaults) 
	 * 		
	 * 		// set status and severity
	 * 		value.setStatus(gov.aps.jca.dbr.Status);
	 * 		value.setSeverity(gov.aps.jca.dbr.Severity);
	 * 		
	 * 		// set timestamp
	 * 		value.setTimestamp(timestamp);
	 * 		
	 * 		// END optional (to override defaults)
 	 * 		
	 * 		// set value to given DBR (example of copying value)
	 * 		// given DBR has already allocated an array of elements client has requested
	 * 		// it contains maximum number of elements to fill
	 * 		String[] arrayValue = value.getStringValue();
	 * 		int elementCount = Math.min(\.length, arrayValue.length);
	 * 		System.arraycopy(\, 0, arrayValue, 0, elementCount);
	 * 
	 * 		// return read completion status
	 * 		return CAStatus.NORMAL;
	 *      }
	 * 	} 
	 * 
	 * 
	 * @see gov.aps.jca.cas.ProcessVariable#read(gov.aps.jca.dbr.DBR, gov.aps.jca.cas.ProcessVariableReadCallback)
	 */
	protected abstract CAStatus readValue(DBR_TIME_String value,
			ProcessVariableReadCallback asyncReadCallback) throws CAException;
		
	
	/**
	 * Casts DBR to DBR_String and delegates operation of writing a value to writeValue method.
	 * @see gov.aps.jca.cas.ProcessVariable#write(gov.aps.jca.dbr.DBR, gov.aps.jca.cas.ProcessVariableWriteCallback)
	 */
	public CAStatus write(DBR value, ProcessVariableWriteCallback asyncWriteCallback) throws CAException {
		
		// for STRING type input DBR is always DBR_String
		DBR_String stringValue = (DBR_String)value;
		
		return writeValue(stringValue, asyncWriteCallback);
	}
	
    /**
     * Write value. Reference implementation:
     * 
     *      * {
     * 
     *     // for async. completion, return null,
     *     // set value (and status) from enumValue,
     *     // notify if there is an interest and
     *     // report completion using asyncWriteCallback callback.
     *     // return null;
     *     
     *     {@code
     *     // set value from given DBR here (scalar example)
     *     this.value = ((DBR_String) value).getStringValue()[0];
     * 
     *     // notify, set appropirate Monitor mask (VALUE, LOG, ALARM)
     *     if (status == CAStatus.NORMAL && interest) {
     *         DBR monitorDBR = AbstractCASResponseHandler.createDBRforReading(this);
     *         ((DBR_String) monitorDBR).getStringValue()[0] = this.value;
     *         fillInStatusAndTime((TIME) monitorDBR);
     * 
     *         eventCallback.postEvent(Monitor.VALUE | Monitor.LOG, value);
     *     }
     * 
     *     // return read completion status
     *     return CAStatus.NORMAL;
     *     }
     * }
     * 
     * 
     * @see gov.aps.jca.cas.ProcessVariable#write(gov.aps.jca.dbr.DBR,
     *      gov.aps.jca.cas.ProcessVariableWriteCallback)
     */
	protected abstract CAStatus writeValue(DBR_String value,
			ProcessVariableWriteCallback asyncWriteCallback) throws CAException;

}