simpleeventhandler.c

来自「8051试验程序 基础教材」· C语言 代码 · 共 138 行

/*****************************************************************************
* visualSTATE Static Event Handler Source File (sample code)
*
* The file implements an event queue with a static size, specified by the
* value of the macro EVENT_QUEUE_SIZE.
*
* Whenever the queue runs full (by a call to SEQ_AddEvent), the event is ig-
* nored and an error is returned.
*
* A function is provided for initializing the queue, as well as functions for
* adding and retrieving events from the queue. See the associated header file
* for descriptions and use of those functions.
*
* The queue is a static variable in this file. If multiple queues are to be
* used, the static variable must be removed and the queue handling functions
* must be modified to take a parameter identifying a particular queue, for
* example a pointer to a queue.
*****************************************************************************/



/* *** include directives *** */
#include "simpleEventHandler.h"



/* *** macro definitions *** */

/** Event queue size. Defines the size of the event queue. */
#ifndef EVENT_QUEUE_SIZE
#define EVENT_QUEUE_SIZE 5
#endif



/* *** type definitions *** */

/** Event queue size type. Defines the type for indexes into the event queue.
    The type must be an unsigned ordinal type, capable of holding values in
    the range [0;EVENT_QUEUE_SIZE[. */
#if (EVENT_QUEUE_SIZE <= 0x0100)
typedef VS_UINT8 SEQ_SIZE_TYPE;
#elif (EVENT_QUEUE_SIZE <= 0x010000)
typedef VS_UINT16 SEQ_SIZE_TYPE;
#elif (EVENT_QUEUE_SIZE <= 0x01000000)
typedef VS_UINT32 SEQ_SIZE_TYPE;
#else
#error Cannot determine type of SEQ_SIZE_TYPE
#endif



/** Event queue type. Defines the internal structure of the event queue. */
typedef struct StaticEventQueue
{
  /** Event queue. The array stores events in the queue. */
  SEM_EVENT_TYPE queue[EVENT_QUEUE_SIZE];

  /** Front index into the queue. The front index specifies the index into the
      array, where the next event will be retrieved from. */
  SEQ_SIZE_TYPE front;

  /** Back index into the queue. The back index specifies the index into the
      array, where the next event will be stored. */
  SEQ_SIZE_TYPE back;
} StaticEventQueue;



/* *** variable definitions *** */

/** The event queue. If more than one event queue is needed (for example when
    a visualSTATE project contains more than one system), the event queue must
    be a parameter for all event queue handling functions instead of being a
    static variable. */
static StaticEventQueue eventQueue;



/* *** function definitions *** */

void SEQ_Initialize (void)
{
  SEQ_Clear();
}



UCC_TYPE SEQ_AddEvent (SEM_EVENT_TYPE event)
{
  /* If the queue indexes equals and the 'current' event is not undefined,
      the queue is full. */
  if (eventQueue.front == eventQueue.back && eventQueue.queue[eventQueue.back] != EVENT_UNDEFINED)
    return UCC_QUEUE_FULL;

  /* Store the event in the queue. */
  eventQueue.queue[eventQueue.back] = event;

  /* Increment the back queue index. */
  eventQueue.back = (SEQ_SIZE_TYPE) ((eventQueue.back + 1) % EVENT_QUEUE_SIZE);

  return UCC_OK;
}



UCC_TYPE SEQ_RetrieveEvent (SEM_EVENT_TYPE* pEvent)
{
  /* Retrieve event from queue. */
  if ((*pEvent = eventQueue.queue[eventQueue.front]) == EVENT_UNDEFINED)
    return UCC_QUEUE_EMPTY;

  /* Increment the front queue index. */
  eventQueue.front = (SEQ_SIZE_TYPE)((eventQueue.front + 1) % EVENT_QUEUE_SIZE);

  /* If queue is empty, indicate this by setting the 'current' event to the
     undefined value. */
  if (eventQueue.back == eventQueue.front)
    eventQueue.queue[eventQueue.back] = EVENT_UNDEFINED;

  return UCC_OK;
}



void SEQ_Clear (void)
{
  eventQueue.front = eventQueue.back = 0;
  eventQueue.queue[0] = EVENT_UNDEFINED;
}



VS_BOOL SEQ_EventPendingP (void)
{
  return (VS_BOOL)(eventQueue.front != eventQueue.back || eventQueue.queue[eventQueue.front] != EVENT_UNDEFINED);
}