Need help with array of pointers to structure
Quote:
> I could sure use a hand (or some talented fingers.) Here is the situation.
> I have a structure defined which includes some pointers, counters and
> a buffer.
> I also have an array of pointers to twelve of these structures. As an
> example, if I want to clear each of the buffers and set a pointer to the
> beginning of the
> buffer plus set a counter to zero, I need to know how to address and
> manipulate the elements of the structure. I thought I understood the
> mechanism but I keep getting error messages from the compiler. Here is
> basically what I thought was proper. vtable is define as
> struct *vtable [] = {&v1, &v2, &v3,......v12};
Well, vtable is defined wrong. If the struct is declared to be "struct
mystruct", then vtable should be "struct mystruct *vtable[]", etc.
Quote:
> I was trying to do something like this:
> for (i=0; i < 12; i++) {
> vtable[i]->ptr = vtable[i]->buf;
> for (j=0; j<80; j++)
> vtable[i]->*ptr = -1;
> }
> where the intent is to place -1 into the 80 positions of the buffer and to do
> this for each of the 12 structures.
> Can anyone tell me what I'm doing wrong or if there is a better way. Even if
> there is a better way, I'd like to know what my misunderstanding is here.
Yes, there is a better way. Try using a table of structures rather than
naming each structure "v1", "v2", ..., "v12". The names you are using suggest
an array. Here is one way to do it:
#define BUFSIZE 80
#define NUM 12
struct mystruct {
char buf[BUFSIZE];
char *ptr;
int cnt;
Quote:
} vtable[NUM];
main()
{
int i, j;
struct mystruct *vptr;
for (i = 0; i < NUM; i++) {
vptr = &vtable[i];
vptr->ptr = vptr->buf;
for (j = 0; j < BUFSIZE; j++)
vptr->buf[j] = -1;
vptr->cnt = 0;
}
Quote:
}
Note the definition of vptr above; this is how to declare a pointer to a
structure. The code shows how to use it to avoid the awkward appearance of
"vtable[i].member".
Consider whether you really need to fill the buffer with negative ones. I
don't know your application, but this kind of thing is rarely necessary.
Hope this helps.
--G. Guy Greenwald II
