Sorry, I've really forgot write a better comments to this structure because it is really trivial.
Updated:
/** Message pack MP_MAP or MP_ARRAY container descriptor. */
struct mp_frame {
/** MP frame type calculated with mp_typeof(). */
enum mp_type type;
/**
* Total items in MP_MAP or MP_ARRAY container
* calculated with mp_decode_map() or mp_decode_array().
*/
uint32_t size;
/**
* Count of items already processed. Must be less or
* equal to mp_frame::size member.
*/
uint32_t curr;
};
/**
* Stack of service contexts mp_frame to do complex msgpack parse.
* The structure is needed in order to facilitate the decoding
* nested MP_ARRAY and MP_MAP msgpack containers without
* recursion. This allows you to determine that the parsing of
* the current container is complete.
*/
struct mp_stack {
/** The maximum stack depth. */
uint32_t size;
/**
* Count of used stack frames. Corresponds to the index
* in the array to perform the push operation. Must be
* less or equal to mp_stack::size member.
*/
uint32_t used;
/**
* Array of mp_frames descriptors having at least
* mp_stack::size items.
*/
struct mp_frame *frames;
};