+ :param ptr: pointer to an initialized `memcached_st` struct
+ :param mem: pointer to previously allocated memory
+ :param context: pointer to the user supplied context
+
+.. type:: void * (*memcached_calloc_fn) (memcached_st *ptr, size_t nelem, const size_t elsize, void *context)
+
+ :param ptr: pointer to an initialized `memcached_st` struct
+ :param nelem: number of elements to allocate
+ :param elsize: the number of bytes to allocate per element
+ :param context: pointer to the user supplied context
+ :returns: pointer to at least `elsize` \* `nelem` bytes of allocated and zeroed memory