DynamicArraySet

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azenris
Posts: 16
Joined: Thu Nov 26, 2009 5:44 pm

DynamicArraySet

Post by azenris » Sun Oct 10, 2010 4:01 pm

I mentioned it on irc, but just wanted to post here to. If it is a bug, heres a reminder! If its not, my bad!
In 1.4.6 the return value of realloc is only checked to see if it successfully allocated and ignores whether or not a new memory block is allocated.

Code: Select all

-----
1.4.6

bool DynamicArraySet(DynamicArray *v, unsigned int index, void* item)
{
    if(v == NULL)
    {
        return false;
    }

    if(index >= v->cur_size)
    {
        //resize the array, making sure it is bigger than index.
        unsigned int newSize = (v->cur_size * 2 > index ? v->cur_size * 2: index + 1);

        void** temp = (void**)realloc(v->data, sizeof(void*) * newSize);
        if(temp == NULL)
        {
            return false;
        }
        memset(v->data + v->cur_size, 0, sizeof(void*) * (newSize - v->cur_size));
        v->cur_size = newSize;
    }

    v->data[index] = item;
    return true;
}

-----
1.4.5

void DynamicArraySet(DynamicArray *v, int index, void* item)
{
    if(index >= v->cur_size)
    {
        v->data = (void**)realloc(v->data, sizeof(void*) * v->cur_size * 2);
        memset(v->data + v->cur_size, 0, sizeof(void*) * v->cur_size);
        v->cur_size *= 2;
    }
    
    v->data[index] = item;
}
Solution ( I hope )

Code: Select all

bool DynamicArraySet(DynamicArray *v, unsigned int index, void* item)
{
    // check the array is valid
    if(v == NULL)
    {
        return false;
    }

    // see if the array can handle the index or whether new memory is required
    if(index >= v->cur_size)
    {
        // double the array size (if enough) or increase the size to handle the index
        unsigned int newSize = (v->cur_size * 2 > index ? v->cur_size * 2: index + 1);

        // realloc memory, check return for newp (same as oldp if the old memory block could be grown (or shrunk))
        v->data = (void**)realloc(v->data, sizeof(void*) * newSize);

        // check no problems with the allocation
        if(v->data == NULL)
        {
            return false;
        }

        // zero the data newly allocated
        memset(v->data + v->cur_size, 0, sizeof(void*) * (newSize - v->cur_size));

        // record the new size of the array
        v->cur_size = newSize;
    }

    // set the array
    v->data[index] = item;

    // return its success
    return true;
}

WinterMute
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Posts: 1478
Joined: Tue Aug 09, 2005 3:21 am
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Re: DynamicArraySet

Post by WinterMute » Sun Oct 10, 2010 5:06 pm

I ended up doing it this way a few hours ago - http://devkitpro.svn.sourceforge.net/vi ... threv=4409

The way you're doing it will destroy the current array pointer & leak memory if realloc fails.
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azenris
Posts: 16
Joined: Thu Nov 26, 2009 5:44 pm

Re: DynamicArraySet

Post by azenris » Sun Oct 10, 2010 5:26 pm

Ahh, I see it now. Ty.

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