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Getting void * size to create a simple shared dynamically allocated array - C

I created a simple dynamic array in C.

typedef struct varray_t
{
    void **memory;
    size_t allocated;
    size_t used;
    int index;              
} varray;

void
varray_init(varray **array)
{
    *array = (varray*) malloc (sizeof(varray));    
    (*array)->memory = NULL;
    (*array)->allocated = 0;
    (*array)->used = 0;
    (*array)->index = -1;
}

void
varray_push(varray *array, void *data, size_t size)
{
    if ((array->allocated - array->used) < size) {
        array->memory = realloc(array->memory, array->allocated + size);
        array->allocated = array->allocated + size;
    }

    array->used = array->used + size;   
    array->memory[++array->index] = data;
}

int
varray_length(varray *array)
{
    return array->index + 1;
}

void
varray_clear(varray *array)
{
    int i;
    for(i = 0; i < varray_length(array); i++)
    {
        array->memory[i] = NULL;
    }    
    array->used = 0;
    array->index = -1;
}

void 
varray_free(varray *array)
{
    free(array->memory);
    free(array);
}

void*
varray_get(varray *array, int index)
{
    if (index < 0 || index > array->index)
        return NULL;

    return array->memory[index];
}

It works great. But in order to add an element to the array, the caller must pass the size of the added element. I can not find another way to get the size from the passed in void*. I am wondering if there is a better way for the design varray_push(varray *array, void *data, size_t size)to sizebe able to deduce?

Any help would be great

Edited code after sentences

My array will contain only pointer elements. I changed the code as suggested by Blastfurnace. The new code will use sizeof(void*)and resize the memory using a constant proposition to get the amortized constant time on the inserts.

void
varray_push(varray *array, void *data)
{
    size_t toallocate;
    size_t size = sizeof(void*);
    if ((array->allocated - array->used) < size) {
        toallocate = array->allocated == 0 ? size : (array->allocated * 2);
        array->memory = realloc(array->memory, toallocate);
        array->allocated = array->allocated + toallocate;
    }

    array->memory[++array->index] = data;
    array->used = array->used + size;
}
+5
2

, varray_init.

, , , 16 , , , realloc 16 + 16 = 32 . , malloc , mallocing .

EDIT: Blastfurnace, , memcpy , , , .

+2

, . , , : https://github.com/inorton/xrlist

#include <stdio.h>
#include "xrlist.h"

xr_list_t * mylist = xrlist_new();

xrlist_push(mylist, (void*) ptr1);
xrlist_push(mylist, (void*) ptr2);

: -

xr_list_item_t * iter = mylist->head;
while ( iter != NULL ) 
{
  printf(" * item [0x%x] contains [%s]\n",
    (unsigned int) iter->object, (char*) iter->object );
  iter = iter->next; 
}

remove/add/free. . .

, , https://github.com/inorton/xrhash

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