/*
-FIFO.C
*/

/*****************FIFO.C stuff*********************************/
#define FifoSize 10		// number of 8 bit data in the Fifo
#define START_CRITICAL() asm(" tpa\n staa %SaveSP\n sei")
#define END_CRITICAL() asm(" ldaa %SaveSP\n tap")

char *PUTPT;			// Pointer of where to put next
char *GETPT;			// Pointer of where to get next
// FIFO is empty if PUTPT=GETPT
// FIFO is full if PUTPT+1=GETPT
char Fifo[FifoSize];	// The statically allocated fifo data



void InitFifo(void)
{
	unsigned char SaveSP;
    START_CRITICAL();		// make atomic, entering critical section
    PUTPT=GETPT=&Fifo[0];	// Empty when PUTPT=GETPT
    END_CRITICAL();			// end critical section
}


int PutFifo (char data)
{
	char *Ppt; // Temporary put pointer
	unsigned char SaveSP;
    START_CRITICAL();	// make atomic, entering critical section
    Ppt=PUTPT;			// Copy of put pointer
    *(Ppt++)=data;		// Try to put data into fifo [MIDE comments - isn this kinda stupid???
						// cuz it writes data to a mem location that might have something valuable]
    if (Ppt == &Fifo[FifoSize])
		Ppt = &Fifo[0]; // Wrap
    if (Ppt == GETPT )
	{ 
        END_CRITICAL(); // end critical section
        return(0);		// Failed, fifo was full  [MIDE comments -this will like happen if u keep
						// putting stuff in and not getting it out. PUTPT will loop round to meet GETPT]
	}   
    else
	{ 
        PUTPT=Ppt;
        END_CRITICAL();	// end critical section
        return(-1);		// Successful 
    }
}



int GetFifo (char *datapt)
{
	unsigned char SaveSP;
    if (PUTPT == GETPT)
		return(0);		// Empty if PUTPT=GETPT
    else
	{ 
        START_CRITICAL();	// make atomic, entering critical section
        *datapt = *(GETPT++);
        if (GETPT == &Fifo[FifoSize])
            GETPT = &Fifo[0];
        END_CRITICAL();		// end critical section
        return(-1);
    }
}
/***************************************************************/