Styjun

Consider the following:

// main.h
struct

 uint16_t aChargeOption0;
 uint16_t aChargeOption1;
 oBattChargerInfo;

typedef struct CHGRRM

 uint16_t nRegIndex;
 uint8_t nDataType;
 uint32_t nDataWidth;
 uint32_t nRegAddress;
 bool IsWritable;
 bool HasBits;
 uint32_t nBitStoreStart;
 uint32_t nBitStoreEnd;
 int *ptrToData;
 chargerRegMap_t;

extern chargerRegMap_t charger_reg_map[];



// main.c

chargerRegMap_t charger_reg_map[] =

 &oBattChargerInfo.aChargeOption0 ,
 &oBattChargerInfo.aChargeOption1 ,
;




// code to store a variable to the de-referenced variable
uint16_t aFinalBuff=0x00;
aFinalBuff=buff[1]<<8; // buff[0] and buff[1] is uint8 
aFinalBuff=aFinalBuff+buff[0];
*charger_reg_map[nRegIndex].ptrToData=aFinalBuff;

When I store the first variable (charger_reg_map[0].ptrToData which in the first case is oBattChargerInfo.aChargeOption0) the 16 bit variable overwrites the adjacent variable oBattChargerInfo.aChargeOption1. Other than setting each variable in my oBattChargerInfo structure to 32 bits each, is there another solution? It seems strange that a dereferenced variable would work this way.

I tried *charger_reg_map[nRegIndex].ptrToData=(uint16_t)aFinalBuff;
to make clear my intention. Didn't matter.

What am I doing wrong here?

If you want differently-sized variables, there is no pointer type you can use to write to all of them.

The design is a bit brittle, since you would need to know which member your pointer is pointing to, or at least its type.

I think a better option would be to do the work with memcpy through a function, and add a 'size' member to chargerRegMap_t for sanity checking.

Something like

void write_data(chargerRegMap_t* map, void* data, size_t size)

 assert(size == map->data_size);
 memcpy(map->ptrToData, data, size);


/* ... */
uint16_t aFinalBuff = 0x00;
aFinalBuff = buff[1] << 8; 
aFinalBuff = aFinalBuff + buff[0];
write_data(charger_reg_map + nRegIndex, &aFinalBuff, sizeof(aFinalBuff)); 

I would probably add a macro to that as well, to eliminate sizeof typos and make it less tedious:

#define WRITE_DATA(map, data) write_data(map, &data, sizeof(data))
/* ... */
WRITE_DATA(charger_reg_map + nRegIndex, aFinalBuff);