HELP!!! how to return a value using pointer function?

[rob1012]

return value of pointer

i have a code like this


hal_usb_dev_req_resp_t device_req_cb(hal_usb_device_req* req, uint8_t** data_ptr) reentrant
{
hal_usb_dev_req_resp_t* resp;

hal_usb_hid_device_req_proc(req, &data_ptr, &resp);
return resp;
}

void hal_usb_hid_device_req_proc(hal_usb_device_req* req, uint8_t** data_ptr, hal_usb_dev_req_resp_t* resp)
{
*data_ptr = &string_of_data;
*resp = DATA;
}

this is pass by reference using pointers right? I cant pass the &string_of_data to the device_req_cb. im weirded out already.. please help.

 

[bobcat1]

return value from pointer

HI

Try this :

void FunctionCall(void)
{
//Define dat as variable
unsigned char Dat ;
//Send dat as ref
passByRef(&Dat);

//process the value of Dat
If(dat < 9)
{
Dat = Dat /2
}

}


void passByRef(unsigned char *Dat)
{
//Load Dat with new value
Dat = 9;

}

All the best

Bobi

 

[btbass]

return value or pointer

You can also view a pointer to a pointer as a pointer to an array of pointers, same thing. You dont have to de-reference it before passing it to your function.
You de-reference it in the function.
Either as an array, 'data_ptr[x]' or as an offset, '*(data_ptr + x)'
Code:

int main(void) 
{ 
char **data_ptr; 

data_ptr[0] = "hello";      /* Pointers to strings */ 
data_ptr[1] = "Goodbye"; 
data_ptr[2] = "World"; 

req_proc(data_ptr); 
return 0; 
} 

void req_proc(char **data_ptr) 
{ 
char *temp; 
char *Data = "Cruel"; /* Pointer to string */ 

data_ptr[0] = Data; 

Data = data_ptr[1]; 

temp = *(data_ptr + 2);   /* Another way */ 
}