CODEWITHSUNDEEP
carrayspointersdynamic-arrays
Luis Valdez
Luis Valdez

Reputation: 2429

Returning Two Pointers to Dynamic Arrays

I am having a bunch of problems with pointers and dynamic arrays here. I have a function that I call, that does a bunch a stuff, like removing an ellement from the dynamic array , which leads me to reallocating memory to one of those dynamic arrays. The problem is I call functions within functions, and I can't return all my values properly to the Main. Since I can't return 2 values, how can I do this?

structure1* register(structure1 *registerArray,structure2 *waitingList, int counter){
    //Bunch of code in here
    registerArray = realloc(inspecao, (counter)+1);
    waitingList = eliminate(waitingList, 5, counter); //Doesn't matter what it does really

    return registerArray;
}


structure1* eliminate(structure1 *arrayToEliminateFrom, int positionToEliminate, int *counter){

    //The code for this doesn't matter
    //All I do is eliminate an ellement and reallocate it
    arrayToEliminateFrom = realloc(arrayToEliminateFrom, (*counter-1)*sizeof(structure1))
    return arrayToEliminateFrom;
}

As you can see , I don't know how to return the pointer to the waitingList dynamic array to the Main. How can I do this? I have searched everywhere. Help

Upvotes: 2

Views: 94

Answers (2)

Craig Estey
Craig Estey

Reputation: 33666

Okay, here are two ways to do it.

The first is, based upon your comment, what you think your instructor would want:

void
xregister(structure1 **registerArray, int *arrayCount,
    structure1 **waitingList, int *waitCount)
{

    // Bunch of code in here

    *arrayCount += 1;
    *registerArray = realloc(inspecao, *arrayCount * sizeof(structure1));

    // Doesn't matter what it does really
    eliminate(waitingList, 5, waitCount)
}

void
eliminate(structure1 **arrayToEliminateFrom, int positionToEliminate,
int *count)
{

    // The code for this doesn't matter

    *count -= 1;

    // All I do is eliminate an ellement and reallocate it
    *arrayToEliminateFrom = realloc(*arrayToEliminateFrom,
        *count * sizeof(structure1))
}

Here is what Roberto and I were suggesting. Actually, mine's a general variable length array approach that can be fully generalized with some slight field changes. In a way, since you're already using a struct, I can't see why your instructor would object to this as it's a standard way to do it. Less cumbersome and cleaner.

struct vector {
    int vec_count;
    structure1 *vec_base;
};

void
xregister(vector *registerArray,vector *waitingList)
{

    // Bunch of code in here

    registerArray->vec_count += 1;
    registerArray->vec_base = realloc(registerArray->vec_base,
        registerArray->vec_count * sizeof(structure1));

    // Doesn't matter what it does really
    eliminate(waitingList, 5)
}

void
eliminate(vector *arrayToEliminateFrom, int positionToEliminate)
{

    // The code for this doesn't matter

    arrayToEliminateFrom->vec_count -= 1;

    // All I do is eliminate an ellement and reallocate it
    arrayToEliminateFrom->vec_base = realloc(arrayToEliminateFrom->vec_base,
        arrayToEliminateFrom->vec_count * sizeof(structure1))
}

Here's an even more compact way:

struct vector {
    int vec_count;
    structure1 *vec_base;
};

void
vecgrow(vector *vec,int inc)
{

    vec->vec_count += inc;
    vec->vec_base = realloc(vec->vec_base,vec->vec_count * sizeof(structure1));
}

void
xregister(vector *registerArray,vector *waitingList)
{

    // Bunch of code in here

    vecgrow(registerArray,1);

    // Doesn't matter what it does really
    eliminate(waitingList, 5)
}

void
eliminate(vector *arrayToEliminateFrom, int positionToEliminate)
{

    // The code for this doesn't matter

    vecgrow(arrayToEliminateFrom,-1);
}

Upvotes: 3

Roberto Zanichelli
Roberto Zanichelli

Reputation: 66

you should try to do an higher structure that contains both pointers and pass and return that structure beetween your functions, because function can return only one object/structure, but your structure/object can contain more objects/structures

Upvotes: 0

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