CacheService Object

Introduction

The CacheService object creates and handles a thread that helps update the Controller’s status cache. The CacheService object is a convenient way to have a program periodically update the Controller’s status cache, allowing the MPI methods to avoid the occasional performance penalty of explicitly updating the cache.

Thread handling is implemented differently on every operating system. CacheService objects may therefore have different behaviors on different operating systems. Programmers experienced in multi-threaded application programming will probably want to program their own threads that will call mpiControlStatusCacheRefresh(…).

Note: The CacheService object is not part of the standard MPI. In order to use the CacheService Object, the apputil.h header file needs to be included by your code and the apputil library linked to your application.

Methods

Create, Delete, Validate Methods
	cacheServiceCreate	Creates a Cache Service thread
	cacheServiceDelete	Deletes a Cache Service thread

Configuration and Information Methods
	cacheServiceConfigGet	Gets the configuration of a CacheService object
	cacheServiceConfigSet	Sets the configuration of a CacheService object
	cacheServiceEnable	Enables or disables the thread belonging to a Cache Service.
	cacheServiceStatus	Returns status structure for a CacheService object.
	cacheServiceErrorCountReset	Resets a CacheService object’s error count

Data Types

	CacheService	Type define for the CacheService handle
	CacheServiceConfig	Configuration structure used to configure CacheService objects
	CacheServiceConfigDEFAULT	Default configuration values for the CacheService configuration structure.
	CacheServiceErrorHandler	Type define for a CacheService object error handler function
	CacheServiceErrorParams	Error structure used when CacheService encounters an MPI error
	CacheServiceStatus	Structure that holds the status information for a CacheService object

Sample Code

/* Create and initialize MPI objects */
void programInit(MPIControl         *control,
                 MPIControlType      controlType,
                 MPIControlAddress  *controlAddress,
                 CacheService       *cacheService)
{
    CacheServiceConfig cacheServiceConfig = CacheServiceConfigDEFAULT;
    long			        returnValue;
 
    /* Create motion controller object */
    *control =
        mpiControlCreate(controlType, controlAddress);
    msgCHECK(mpiControlValidate(*control));
 
    /* Initialize motion controller */
    returnValue =
        mpiControlInit(*control);
    msgCHECK(returnValue);
 
       /* Set the MPIControl object's client connection count */
       returnValue =
           mpiControlClientCountSet(*control, 2);
       msgCHECK(returnValue);

    /* Create CacheService thread */
    cacheServiceConfig.sleepTime = 20; /* milliseconds */

    *cacheService =
        cacheServiceCreate(*control, &cacheServiceConfig);
    if (*cacheService == NULL)
    {
        msgCHECK(MPIMessageHANDLE_INVALID);
    }
}
 
/* Perform certain cleanup actions and delete MPI objects */
void programCleanup(MPIControl   *control,
                    CacheService *cacheService)
{
    long            returnValue; 
 
    /* Delete service thread */
    returnValue =
        cacheServiceDelete(*cacheService);
    msgCHECK(returnValue);
    *cacheService = MPIHandleVOID;
 
    /* Delete motion controller object */
    returnValue =
        mpiControlDelete(*control);
    msgCHECK(returnValue);
    *control = MPIHandleVOID;
}