Function rt_slab_realloc

src/slab.c:669–727

* @brief This function will change the size of previously allocated memory block. * * @param m the slab memory management object. * * @param ptr is the previously allocated memory block. * * @param size is the new size of memory block. * * @return the allocated memory. */

 * @return the allocated memory.
 */
void *rt_slab_realloc(rt_slab_t m, void *ptr, rt_size_t size)
{
    void *nptr;
    struct rt_slab_zone *z;
    struct rt_slab_memusage *kup;
    struct rt_slab *slab = (struct rt_slab *)m;

    if (ptr == RT_NULL)
        return rt_slab_alloc(m, size);

    if (size == 0)
    {
        rt_slab_free(m, ptr);
        return RT_NULL;
    }

    /*
     * Get the original allocation's zone.  If the new request winds up
     * using the same chunk size we do not have to do anything.
     */
    kup = btokup((rt_uintptr_t)ptr & ~RT_MM_PAGE_MASK);
    if (kup->type == PAGE_TYPE_LARGE)
    {
        rt_size_t osize;

        osize = kup->size << RT_MM_PAGE_BITS;
        if ((nptr = rt_slab_alloc(m, size)) == RT_NULL)
            return RT_NULL;
        rt_memcpy(nptr, ptr, size > osize ? osize : size);
        rt_slab_free(m, ptr);

        return nptr;
    }
    else if (kup->type == PAGE_TYPE_SMALL)
    {
        z = (struct rt_slab_zone *)(((rt_uintptr_t)ptr & ~RT_MM_PAGE_MASK) -
                          kup->size * RT_MM_PAGE_SIZE);
        RT_ASSERT(z->z_magic == ZALLOC_SLAB_MAGIC);

        zoneindex(&size);
        if (z->z_chunksize == size)
            return (ptr); /* same chunk */

        /*
         * Allocate memory for the new request size.  Note that zoneindex has
         * already adjusted the request size to the appropriate chunk size, which
         * should optimize our bcopy().  Then copy and return the new pointer.
         */
        if ((nptr = rt_slab_alloc(m, size)) == RT_NULL)
            return RT_NULL;

        rt_memcpy(nptr, ptr, size > z->z_chunksize ? z->z_chunksize : size);
        rt_slab_free(m, ptr);

        return nptr;
    }

    return RT_NULL;