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PMIX_DATA_BUFFER_T(5) OpenPMIx PMIX_DATA_BUFFER_T(5)

pmix_data_buffer_t — Describes a data buffer used for packing and unpacking

SYNTAX

C Syntax

#include <pmix_common.h>
typedef struct pmix_data_buffer {


    /** Start of my memory */


    char *base_ptr;


    /** Where the next data will be packed to (within the allocated


        memory starting at base_ptr) */


    char *pack_ptr;


    /** Where the next data will be unpacked from (within the


        allocated memory starting as base_ptr) */


    char *unpack_ptr;


    /** Number of bytes allocated (starting at base_ptr) */


    size_t bytes_allocated;


    /** Number of bytes used by the buffer (i.e., amount of data --


        including overhead -- packed in the buffer) */


    size_t bytes_used;
} pmix_data_buffer_t;


DESCRIPTION

The pmix_data_buffer_t structure describes a data buffer used for packing and unpacking of PMIx data. It provides an opaque, self-describing container into which typed data can be serialized (packed) for transmission or storage, and from which that data can subsequently be deserialized (unpacked).

The structure carries the following fields:

  • base_ptr — Pointer to the start of the memory region allocated for the buffer.
  • pack_ptr — Pointer to the location, within the memory region starting at base_ptr, at which the next data element will be packed.
  • unpack_ptr — Pointer to the location, within the memory region starting at base_ptr, from which the next data element will be unpacked.
  • bytes_allocated — The number of bytes allocated for the buffer, starting at base_ptr.
  • bytes_used — The number of bytes used by the buffer — that is, the amount of data (including overhead) currently packed in the buffer.

Callers should treat these fields as opaque and manipulate a pmix_data_buffer_t only through the provided support routines rather than by directly accessing or modifying the fields. A statically declared pmix_data_buffer_t may be initialized using the PMIX_DATA_BUFFER_STATIC_INIT initializer.

SUPPORT FUNCTIONS

PMIx provides a number of functions and macros to support constructing, destructing, allocating, releasing, loading, and unloading pmix_data_buffer_t structures, along with packing and unpacking their contents. These include:

  • PMIX_DATA_BUFFER_CREATE — Allocate and initialize a pmix_data_buffer_t object.
  • PMIX_DATA_BUFFER_RELEASE — Free a pmix_data_buffer_t object and the data it contains.
  • PMIX_DATA_BUFFER_CONSTRUCT — Initialize the fields of a statically declared pmix_data_buffer_t.
  • PMIX_DATA_BUFFER_DESTRUCT — Release the data held by a pmix_data_buffer_t (the companion to PMIX_DATA_BUFFER_CONSTRUCT).
  • PMIX_DATA_BUFFER_LOAD / PMIX_DATA_BUFFER_UNLOAD — Load a region of memory into, or extract it from, a pmix_data_buffer_t.
  • PMIx_Data_pack — Pack one or more values of a given type into a pmix_data_buffer_t.
  • PMIx_Data_unpack — Unpack one or more values of a given type from a pmix_data_buffer_t.

pmix_data_buffer_t is the buffer type manipulated by the PMIx_Data_pack, PMIx_Data_unpack, and PMIx_Data_buffer_* interfaces.

STATIC INITIALIZER

A statically declared pmix_data_buffer_t may be initialized with the PMIX_DATA_BUFFER_STATIC_INIT macro, which sets the base_ptr, pack_ptr, and unpack_ptr pointers to NULL and both bytes_allocated and bytes_used to 0:

pmix_data_buffer_t buffer = PMIX_DATA_BUFFER_STATIC_INIT;


See also:

PMIx_Data_pack(3) <#man3-pmix-data-pack>, PMIx_Data_unpack(3) <#man3-pmix-data-unpack>, pmix_value_t(5) <#man5-pmix-value-t>, pmix_byte_object_t(5) <#man5-pmix-byte-object-t>, pmix_data_type_t(5) <#man5-pmix-data-type-t>


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October 5, 2026