Thread: Need help with basic enumeration

So I really haven't used enumeration since my intro to c class and now have to for this program. I'm having trouble understanding how to go about using it.

In a header file that was given to me i have:

Code:

typedef enum { LOGON_EVT = 0, SIO_EVT, WIO_EVT, EIO_EVT, END_EVT, TIMER_EVT, SEGFAULT_EVT, ADRFAULT_EVT, NUM_EVENTS } event_type;

And i want to use it in a get_event_id function.

How do I access this properly though?


I need to compare a char* that will be the first half of each of those strings (LOGON, SIO, WIO, EIO, and so on)

then if they are equal return the value that it represents.

this is the best i can come up with but it gives me a syntax error before event_type:

Code:

for(j =0; j<NUM_EVENTS; j++)
            {
                    if(event_name == event_type[j])
                    {
                       return j;
                    }
                    else j++;
                    
            }

also while im at it, if i just strcmp LOGON with LOGON_EVT how can i know that is a match? or should i concatenate _EVT onto each one then compare?

Originally Posted by MK27

You refer to the individual members by name (SIO_EVT, WIO_EVT, EIO_EVT), like they were #defines. The point of an enum is to just create a sequential list of values.

so i would just have 9 string compares in the for loop checking for each one individually? if so then how do i return the integer value of the event just return LOGON_EVT; ?

Originally Posted by MK27

You refer to the individual members by name (SIO_EVT, WIO_EVT, EIO_EVT), like they were #defines. The point of an enum is to just create a sequential list of values.



No dice there. Enums are integers, not strings. You cannot use strcmp, nor can you do anything with the label at runtime (unless you create a parallel array of char*, but that would be pretty bizarre).

I think you are confused slightly about whatever API it is you are using.

Here is the function description:

Capitalize event name so that case does not matter
Verify that name's length is shorter than constant the EVENT_NAME_LENGTH_MAX
For event ID = 0 to NUM_EVENTS
Compare event name to Event_Names[ event ID ]
If they are equal
Return event ID
Otherwise,
Continue in loop
Report error if no event matched
\endverbatim


event name is a char* and the other one is the enumeration from what i understand, guess i should just ask the professor

tried this:

Code:

   	
	int i =0, len = strlen(event_name[1]);

if (!strcmp(event_name[1], "LOGON")) return LOGON_EVT;
	if (!strcmp(event_name[1], "SIO")) return SIO_EVT;
	if (!strcmp(event_name[1], "WIO")) return WIO_EVT;
	if (!strcmp(event_name[1], "EIO")) return EIO_EVT;
	if (!strcmp(event_name[1], "END")) return END_EVT;
	if (!strcmp(event_name[1], "TIMER")) return TIMER_EVT;
	if (!strcmp(event_name[1], "SEGFAULT")) return SEGFAULT_EVT;
	if (!strcmp(event_name[1], "ADRFAULT")) return ADRFAULT_EVT;
	printf("Error: No such Event.");
	return NUM_EVENTS;

but every line had a warning passing arg1 of strcmp (strlen for first line) makes pointer from integer without a cast. did i do something wrong? (note i already have the words the case i need so i didn't include the for loop)

Originally Posted by DaNxTh3xMaNx

so i would just have 9 string compares in the for loop checking for each one individually? if so then how do i return the integer value of the event just return LOGON_EVT; ?

You don't have access to the text names in an enum, except to use them as variable names. They work like #defines as already explained...

Code:

printf("%d\n", SIO_EVT);   // ok
if (problem == SIO_EVT)    // ok
if (string == SIO_EVT)   // not ok

Originally Posted by MK27

Post the declaration of event_name. Sounds like event_name[1] may be a single char (which is an integer value). If you are trying to use that as a pointer into the string (so you skip the first byte) use &event_name[1].

i changed it to: if (!strcmp(event_name, "LOGON")) return LOGON_EVT;

(took out the [1] completely and it did what i wanted. so thanks for the help)