Systems and methods for managing data in complex containers permit atomic addition of a plurality of data items to the containers. Each data item can occupy contiguous memory locations, although the plurality of data items may be mutually discontiguous. The method comprises creating a package object, which comprises an externally accessible array of pointer and associated integers. Each pointer points to the start of a memory location holding a distinct data item and the associated integer represents the size of the data item referenced by the pointer. A function associated with an external interface of the container determines a quantity of memory to hold the plurality of data items and invokes an externally accessible write function in the package object to add the plurality of individual data items to the container at specified locations if there is adequate memory available to hold the plurality of data items.