[SOLVED] A question about assigning structs to 2d struct array...

trist007 · 10-01-2014, 02:56 PM

Code:

struct Init {
        struct Domains *Dptr;
};

typedef struct Init Init;

struct Domains {
    u_int count;
    struct Domain **dptr;
};

typedef struct Domains Domains;

struct Domain {
        u_int GET, POST;
        u_int num_requests;
        char name[32];
        struct Request *requests[1];
};

typedef struct Domain Domain;

void AddDomain(Init *init, char *host)
{
    Domain *domain = calloc(1, sizeof(struct Domain));
    init->Dptr->dptr = domain;
    strncpy(init->Dptr->dptr[0]->name, host, 32);
}

Init *Initialize()
{
    Init *init = calloc(1, sizeof(Init));
    Domains *domains = calloc(1, sizeof(struct Domain));
    init->Dptr = domains;
    init->Dptr->count = 0;

    return init;
}

In the AddDomain(), how can I assign the dptr in struct Domains with the new struct Domain pointer?

This is the part is where I need help.

Code:

init->Dptr->dptr = domain;
strncpy(init->Dptr->dptr[0]->name, host, 32);

Basically when I add a new domain I want to dynamically grow the struct Domain dtpr, which is in struct Domains, array by 1.

trist007 · 10-01-2014, 06:20 PM

Ah nevermind, I need an array of struct domain pointers

Code:

struct Domains {
    u_int count;
    struct Domain *dptr[1];
};

trist007 · 10-09-2014, 11:48 AM

I need your help with syntax and maybe logic.

My struct looks like this

Code:

struct Domains {
    u_int count;
    struct Domain *dptr[];

};

I want the *dptr[] to be an array holding pointers to struct Domain. That way in my program as I see a new domain I can dynamically add an element to the array *dptr[]. The element will simply be a struct pointer pointing to a Domain struct.

So I am thinking that I would do a malloc for the struct pointer to increase the *dptr[] array by 1 and another malloc for the actual Domain struct. Is that correct?

My pseudo ish code so far.

Code:

Domain *domain = calloc(1, sizeof(struct Domain *));  // allocate memory for struct pointer
init->Dptr->dptr[count] = &domain;                    // How do I put that pointer into init->Dtpr->dtpr[count]?

Domain *domain = calloc(1, sizeof(struct Domain));    // allocate memory for an actual Domain struct
init->Dptr->dptr[count] = domain;                     // I think this part is correct

Here is the Domain struct.

Code:

struct Domain {
        u_int GET, POST;
        u_int num_requests;
        u_int total_requests;
        char name[32];
        struct Request *requests[];
       
};

The same would apply to the *requests[] array in the Domain struct.

ntubski · 10-09-2014, 12:52 PM

Quote:

Originally Posted by trist007

I would do a malloc for the struct pointer to increase the *dptr[] array by 1 ... Is that correct?

No, a malloc of size 1 element only gives you space for another element that isn't adjacent to your existing array, so it's useless for growing your array. You need to allocate a new array which is one element larger, copy all the old elements, and then copy the new one into the last place. The realloc() function can do the first part for you.

trist007 · 10-09-2014, 01:30 PM

Awesome! Thank you for pointing me in the right direction.