Abstract Data Types in C

• Interface declares operations, not data structure
• Implementation is hidden from client (encapsulation)
• Use features of programming language to ensure encapsulation

Common practice

• Allocation and deallocation of data structure handled by module
• Names of functions and variables begin with <modulename>_
• Provide as much generality/flexibility in interface as possible
• Use void pointers to allow polymorphism

 

 

A simple exmaple is shown below for your reference, but a little change as we don't want to dynamic memory.

 

 

#ifndef COMMON_TIMER_H_
#define COMMON_TIMER_H_

#include <stdint.h>
#include <stdbool.h>

typedef struct
{
   uint32_t period;           /* unit ms */
   uint32_t endTick;          /* the tick of end */
}MsTimerT;

void timer_create(MsTimerT* timer, uint32_t period);
bool timer_expired(const MsTimerT* timer);
void timer_free(MsTimerT* timer);

#endif /* COMMON_TIMER_H_ */

#include "common/timer.h"

/* system tick every 10ms*/
#define SYSTEM_TICK_TIME (10)

uint32_t gSystemTick = 0;



void timer_create(MsTimerT* timer, uint32_t period)
{
   timer->endTick = gSystemTick + period/SYSTEM_TICK_TIME;
}

bool timer_expired(const MsTimerT* timer)
{
   return (gSystemTick >= timer->endTick);
}

void timer_free(MsTimerT* timer)
{
   timer->endTick = 0;
   timer->period = 0;
}

 

MsTimerT* timer,