nes-proj/doc/example-service.c

116 lines
3.7 KiB
C
Raw Normal View History

/*
* This file is an example of how to implement a service in
* Contiki. The header file example-service.h defines a service called
* "example_service", which we implement in this file.
*
* This example shows how to define an instance of a service, and how
* to write the service's controlling process.
*
* See the file example-use-service.c for an example of how to call a
* service.
*/
#include <stdio.h>
#include "example-service.h"
#include "contiki.h"
/*---------------------------------------------------------------------------*/
/*
* We start by implementing all the functions that the service
* offers. In this case, there is only a single function (called
* example_function()) and we implement it here. We give it the name
* example() and declare it with the "static" keyword to keep the
* scope local to this file.
*/
static void
example(void) {
printf("Example service called\n");
}
/*---------------------------------------------------------------------------*/
/*
* This is the instantiation of the service called
* "example_service". The service interface is defined in the header
* file example-service.h.
*
* This statement defines the name of this implementation of the
* service - example_service_implementation - and defines the
* functions that actually implement the functions offered by the
* service. In this example, the service consists of a single function
* called "example_function()". We implement this function in the
* function called "example()" defined above.
*
*/
SERVICE(example_service_implementation, /* The name of this instance
of the service - used with
SERVICE_REGISTER(). */
example_service, /* The name of the serivce
that is instantiated. */
{ example }); /* The list of functions
required by the
service. In this case, we
only have one function. */
/*
* All services needs a controlling process. The controlling process
* registers the service with the system when it starts, and is also
* notified if the service is removed or replaced.
*
* We simply call the process "example_service_process" and gives it a
* similar textual name.
*/
PROCESS(example_service_process, "Example service process");
/*
* For this example, we use a timer to remove the service after a
* certain time. We declare the timer here.
*/
static struct etimer timer;
/*
* Finally, we implement the controlling process.
*/
PROCESS_THREAD(example_service_process, ev, data)
{
/*
* A process thread starts with PROCESS_BEGIN() and ends with
* PROCESS_END().
*/
PROCESS_EXITHANDLER(goto exit);
PROCESS_BEGIN();
/*
* We register the service instance with a SERVICE_REGISTER()
* statement.
*/
printf("Registering example service\n");
SERVICE_REGISTER(example_service_implementation);
/*
* We set a timer for four seconds and wait for it to expire - or
* for the process to receive an event which requests it to exit.
*
* The only purpose for the timer is to demonstrate how a service is
* removed - it is not something that is commonly done.
*/
etimer_set(&timer, 4 * CLOCK_SECOND);
PROCESS_YIELD_UNTIL(ev == PROCESS_EVENT_SERVICE_REMOVED ||
etimer_expired(&timer));
/*
* And we remove the service before the process ends. This is a
* *very* important step - if the process exits and is unloaded
* without first removing its services, the system may crash!
*/
printf("Removing example service\n");
/*
* And finally the process ends.
*/
exit:
SERVICE_REMOVE(example_service_implementation);
PROCESS_END();
}
/*---------------------------------------------------------------------------*/