19.3.14. pmix_data_array_t

pmix_data_array_t — Defines an array of like-typed values

19.3.14.1. SYNTAX

19.3.14.1.1. C Syntax

#include <pmix_common.h>

typedef struct pmix_data_array {
    pmix_data_type_t type;
    size_t size;
    void *array;
} pmix_data_array_t;

19.3.14.2. DESCRIPTION

The pmix_data_array_t structure defines an array data structure — a contiguous block of size elements, all of the same PMIx datatype type.

type — a pmix_data_type_t(5) value identifying the datatype of every element stored in array.
size — the number of elements in array.
array — pointer to the contiguous block of size elements. Each element is of the C type corresponding to type (for example, an array of pmix_info_t(5) when type is PMIX_INFO).

PMIX_DATA_ARRAY is itself a legal element type: when type is PMIX_DATA_ARRAY, array points at a contiguous block of size pmix_data_array_t structures, each a complete array in its own right (and each free to declare a different element type). The elements are stored inline in the block — they are not pointers to arrays elsewhere. Constructing such an array zeroes every element, so an element the caller does not fill in is a valid empty array (PMIX_UNDEF, size 0) rather than uninitialized memory, and destructing the outer array recursively releases every element.

Nesting is bounded. PMIx refuses to pack or unpack an array nested more deeply inside other arrays than the bfrops_base_max_array_depth MCA parameter permits — 100 levels by default, or unlimited if the parameter is set to zero. The limit counts every form of nesting, both an array whose element type is PMIX_DATA_ARRAY and the ordinary case of an array reached through a pmix_value_t, because each level of either costs the receiver a frame of recursion while costing the sender only a few bytes on the wire.

The pmix_data_array_t structure is the mechanism by which a collection of values is conveyed through a single pmix_value_t(5) or pmix_info_t(5): the containing structure references a pmix_data_array_t (via the darray union member of a pmix_value_t), which in turn points at the array of individual objects.

19.3.14.3. STATIC INITIALIZER

A statically declared pmix_data_array_t may be initialized with the PMIX_DATA_ARRAY_STATIC_INIT macro, which sets type to PMIX_UNDEF, size to 0, and array to NULL:

pmix_data_array_t array = PMIX_DATA_ARRAY_STATIC_INIT;