"State Machine Shortcuts"  
Michael Kreiman
Embedded Systems Programming
July 2003

/*****************************************************
		  Figure #1 Code 
******************************************************/

typedef     unsigned char   unsigned8;

typedef enum {
		 NULL_EVENT = 0, 
		 EV_1, 
		 EV_2, 
		 EV_3, 
		 EV_4, 
		 EV_5, 
		 EV_6, 
		 EV_7, 
		 EV_8, 
		 EV_9 } event_type;

typedef void (*functionPointerType)(void);

#define NUM_MODES		 		 	 2

#define NO_NEW_STATE		 		 0
#define ANY_STATE		 		 	 1

#define SUPER_STATE_A		 		 2
#define STATE_B		 		 	 3

/* Substates */

#define SUB_STATE_A		 		 0
#define SUB_STATE_B		 		 1
#define SUB_STATE_C		 		 2
#define SUB_STATE_D		 		 3

typedef struct state_table_type
{
		 unsigned8		 		 current_state;
		 event_type		 		 received_event;
		 functionPointerType		 	 execute_function;
		 unsigned8		 		 next_state;
		 unsigned8		 		 next_mode;
};

static unsigned8 current_mode;
static unsigned8 current_state;

void null_function(void);
void Conditional_1(void);
void Guard_1(void);
void Entry_Action_B_C(void);
void Transition_Action_B(void);
void Entry_Action_A(void);
void Transition_Action_C(void);
void Entry_Action_D(void);
void Null_function(void);
void Transition_Action_A(void);


const struct state_table_type SUPER_STATE_A_STATE_TABLE[] =
{
		 {		 SUB_STATE_A,
		 		 EV_1,
		 		 Conditional_1,
		 		 NO_NEW_STATE,
		 		 SUPER_STATE_A 
		 },
		 {		 SUB_STATE_B,
		 		 EV_2,
		 		 Guard_1,
		 		 NO_NEW_STATE,
		 		 SUPER_STATE_A 
		 },
		 {		 ANY_STATE,
		 		 EV_4,
		 		 Entry_Action_B_C,
		 		 SUB_STATE_C,
		 		 SUPER_STATE_A 
		 },
		 {		 SUB_STATE_C,
		 		 EV_3,
		 		 Transition_Action_B,
		 		 SUB_STATE_D,
		 		 SUPER_STATE_A 
		 },
		 {		 SUB_STATE_D,
		 		 EV_5,
		 		 Entry_Action_A,
		 		 NO_NEW_STATE,
		 		 SUPER_STATE_A 
		 },
		 {		 ANY_STATE,
		 		 EV_7,
		 		 Null_function,
		 		 NO_NEW_STATE,
		 		 STATE_B 
		 },
		 {		 SUB_STATE_D,
		 		 EV_5,
		 		 Transition_Action_C,
		 		 NO_NEW_STATE,
		 		 SUPER_STATE_A
		 }
};

const struct state_table_type STATE_B_STATE_TABLE[] =
{
		 {		 ANY_STATE,
		 		 EV_8,
		 		 Entry_Action_D,
		 		 SUB_STATE_D,
		 		 SUPER_STATE_A 
		 },
		 {		 ANY_STATE,
		 		 EV_9,
		 		 Entry_Action_A,
		 		 SUB_STATE_A,
		 		 SUPER_STATE_A 
		 }
};


const struct state_table_type * MODE_TABLE[2] =
{
		 & SUPER_STATE_A_STATE_TABLE [0],
		 &STATE_B_STATE_TABLE[0],
};

const unsigned8 STATE_TABLE_SIZE[NUM_MODES] = 
{
		 9,
		 2,
};

/* Event receptor function */

void class_receive_event( event_type event )
{
		 unsigned8 i;
		 const struct state_table_type * thisTable = MODE_TABLE[current_mode];

		 /* Note: This generic table processor function can be pulled out and reused as a 
		 		 utility for many state machines, thus reusing the code */

		 for ( i = 0; i < STATE_TABLE_SIZE[current_mode]; i++ )
		 {
		 		 if ( ( event == thisTable->received_event ) &&
		 		 		  ( ( current_state == thisTable->current_state ) ||
		 		 		 ( thisTable->current_state == ANY_STATE ) ) )
		 		 {
		 		 		 (*thisTable->execute_function)();
		 		 		 if ( thisTable->next_state != NO_NEW_STATE )
		 		 		 {
		 		 		 		 current_state = thisTable->next_state;
		 		 		 }
		 		 		 current_mode = thisTable->next_mode;
		 		 		 break;
		 		 }
		 		 thisTable++;
		 }
}


void null_function(void)
{
}

void Conditional_1(void)
{
		 if ( case_X )
		 {
		 		 current_state = SUB_STATE_B;
		 		 /* Flesh out execute actions here */
		 }
		 else if ( case_Y )
		 {
		 		 current_state = SUB_STATE_C;
		 		 Transition_Action_A();
		 		 Entry_Action_B_C();
		 }
}

void Guard_1(void)
{
		 if ( case_Z )
		 {
		 		 current_state = SUB_STATE_C;
		 		 Entry_Action_B_C();
		 }
}

void Entry_Action_B_C(void)
{
		 /* Flesh out execute actions here */
}

void Transition_Action_A(void)
{
		 /* Flesh out execute actions here */
}


void Transition_Action_B(void)
{
		 /* Flesh out execute actions here */
}

void Entry_Action_A(void)
{
		 /* Flesh out execute actions here */
}

void Transition_Action_C(void)
{
		 /* Flesh out execute actions here */
}

void Entry_Action_D(void)
{
		 /* Flesh out execute actions here */
}