How to map a array of types over a struct with a sequence/list of the same types.

[WOGoos]

Hi guys, Hope some one can help me with this

I have defined an alarm struct of repeating struct memers that must manage various alarm massages and alarm audio signals.

I want to address these alarm's in the following way, for example

1) alarm.spray.stat

but also as

2) alarmlist[0].stat;

Both the struct and the array are in fact arrays of repeating alarm_t types and it should be possible to map them over eacht other having the same start address

For this I need to assign the alarm struct address to the alarmlist[] array address.

Tricky i know but on a 8bit controller like the ATmega 328 it should not be a problem. I also want to use this technique on STM32 controllers. How can i do this with out having conflicts at compile time.

I did try this :

alarmlist=(alarm_t)&alarm but that gave me a error.

typedef struct alarm_t {

char * msg;

uint8_t prio : 4;

uint8_t stat : 4;

uint8_t Buzzpattern;

uint8_t duration : 4;

uint8_t intermit : 4;

} alarm_t;

struct alarm_state_t {

alarm_t spray;

alarm_t stall;

alarm_t empty;

} alarm = { { },{ },{ } };

alarm_t alarmlist[];

[TDK]

alarm_t * alarmlist = alarm;

Actually this is a bit trickier since the struct could be padded.

This works but is probably compiler dependent:

typedef struct alarm_t {
  char * msg;
  uint8_t prio : 4;
  uint8_t stat : 4;
  uint8_t Buzzpattern;
  uint8_t duration : 4;
  uint8_t intermit : 4;
} alarm_t;
 
struct alarm_state_t {
  alarm_t spray;
  alarm_t stall;
  alarm_t empty;
} alarm = { { },{ },{ } };
 
alarm_t * alarmlist = (alarm_t *) &alarm.spray;
 
 
void main() {
 
  ASSERT_EQ((uint32_t) &alarmlist[0], (uint32_t) &alarm.spray);
  ASSERT_EQ((uint32_t) &alarmlist[1], (uint32_t) &alarm.stall);
  ASSERT_EQ((uint32_t) &alarmlist[2], (uint32_t) &alarm.empty);
 
}

[Piranha]

The requirement is strange...

I would drop the structure thing and use an array with named constants for indexes:

enum alarm {
	ALARM_SPRAY,
	ALARM_STALL,
	ALARM_EMPTY,
 
	ALARM_NUMBER
};
 
alarm_t alarmlist[ALARM_NUMBER];
 
alarmlist[ALARM_SPRAY].stat = 1;

[RMcCa]

Pointers?

One of the great things about 32bit arm programming is how everything on the chip is accessible thru a flat 32bit address space. With C, what that means is there is no real difference between a pointer and a uint32_t. You are free to manipulate the pointers (unsigned math & sizeof) and cast and reference/dereference as you need.​

[WOGoos]

Thanks Piranha, I agree that is possibility too and I will take it in considderation. however it's not an answer to my question. How to map an array of structs on a struct with a series of equal structs as used for the array

[WOGoos]

Sorry RMcCa but I think you missed the point, but thanks for responding