Designing structure with number of char array field in it

Question

I have following Structure in my Program.

#define WIFI_DEVICE_NAME 100
#define WIFI_SERIAL_NO 13       
#define WIFI_PROD_NAME 7


typedef struct WiFiDeviceInfo
{
    char name[WIFI_DEVICE_NAME];                
    char fullname [WIFI_DEVICE_NAME];               
    char productname[WIFI_PROD_NAME];               
    char serialnumber[WIFI_SERIAL_NO];              
};

This Struct is used in the various places. Some time some of the fields may remain empty. So while copying using strcpy_s() , it fails. So I tried with strlen() before doing any copy operation.

I modified the struct and came up with the following design.

typedef struct WiFiDeviceInfo
{
    char name[WIFI_DEVICE_NAME];    
    unsigned short nLenName;            
    char fullname [WIFI_DEVICE_NAME];   
    unsigned short nLenFullName;            
    char productname[WIFI_PROD_NAME];
    unsigned short nproductname;                            
    char serialnumber[WIFI_SERIAL_NO];              
};

I can't use STL here since its legacy code, which doesn't use STL. Is there any better way to design the structure.

Answer 1

This modification is good. Since you are now storing the actual length of string using the member variables, I would suggest that you use pointers to char and allocate required memory at runtime. This would be useful from memory perspective. I mean you should do this...

    typedef struct WiFiDeviceInfo
    {
          char* name;    
          unsigned short nLenName;            
          char* fullname;   
          unsigned short nLenFullName;            
          char* productname;
          unsigned short nproductname;                            
          char* serialnumber;    // Convert the serialnumber to a pointer as well
          unsigned short nserialnumber;
    };

Add constructor and destructor to the struct to handle memory, like setting to NULL, delete pointers etc.