med_article_sm_5.c

#include "stdio.h"

typedef void (*ptStateFunc)(void);

/// Define all events
typedef enum eEvent {
    EVT_NO_EVENT,
    EVT_BUTTON_PRESSED,
    EVT_BEAN_CRUSHED,
    EVT_MILK_HEATED,
    EVT_WATER_MIXED,
    EVT_DISPENSED,
    EVT_NO_BEAN,
    EVT_NO_MILK,
    EVT_NO_WATER
} eEvent;


/// Define all states
void stateIdle(void);
void stateCrushBean(void);
void stateHeatMilk(void);
void stateMixWater(void);
void stateDispenseCofee(void);
void stateError(void); 

/// Define a row of STM
typedef struct stStmRow {
    ptStateFunc pSrcState;
    eEvent      eEvt;
    ptStateFunc pDestState;
} stStmRow;

void stateIdle(void)
{
    if(bIsStateFirstEntry)
    {
        /// Do stuff for first entry(state initialization stuff)
    }

    if(bIsStateAboutToExit)
    {
        /// Handle exit(i.e free up resources)
    }
}

void stateCrushBean(void)
{
    if(bIsStateFirstEntry)
    {
        /// Do stuff for first entry(state initialization stuff)
        /// TurnHeaterOn();
    }

    if(bIsStateAboutToExit)
    {
        /// Handle exit(i.e free up resources)
        /// TurnHeaterOff();
    }
}

void stateHeatMilk(void)
{

}

void stateMixWater(void)
{

}

void stateDispenseCofee(void)
{

}

void stateError(void)
{

} 


static eEvent      eCurrentEvent       = EVT_NO_EVENT;
static ptStateFunc stCurrentState      = stateIdle;
/// Used to flag first entry to a state
static bool        bIsStateFirstEntry  = false;
/// Used to flag an imminent exit from the state
static bool        bIsStateAboutToExit = false;

stStmRow stStm[] = {
{stateIdle     , EVT_BUTTON_PRESSED, stateCrushBean    },
{stateCrushBean, EVT_BEAN_CRUSHED  , stateHeatMilk     },
{stateCrushBean, EVT_NO_BEAN       , stateError        },
{stateHeatMilk , EVT_MILK_HEATED   , stateMixWater     },
{stateHeatMilk , EVT_NO_MILK       , stateError        },
{stateMixWater , EVT_WATER_MIXED   , stateDispenseCofee},
{stateMixWater , EVT_NO_WATER      , stateError        }
};

void StateMachineHandler()
{
    int idx = 0;
    if(EVT_NO_EVENT != eCurrentEvent)
    {
        for(;idx < sizeof(stStm)/sizeof(stStmRow); idx++)
        {
            if( (stStm[idx].pSrcState == stCurrentState) &&
                (stStm[idx].eEvt      == eCurrentEvent))
            {
                /// Clear event
                eCurrentEvent  = EVT_NO_EVENT;
                /// Notify the state that the exit is imminent;
                bIsStateAboutToExit = true;
                stCurrentState();
                /// Move to new state
                stCurrentState = stStm[idx].pDestState;
                /// Flag that this is the first entry to the state
                bIsStateFirstEntry = true;
            }
        }
    }

    if(NULL != stCurrentState)
    {
        /// Run the state
        stCurrentState();
        /// Unfllag first entry
        bIsStateFirstEntry = false;
    }
}


int main()
{
    while(true)
    {
        StateMachineHandler();    
    }
    
}