Add two missing data management functions

While we provided macros for these purposes, it turns out that the logic in implementing those macros is somewhat more complex that originally realized and better suited to an actual function call. This RFC adds to functions to the Data Management chapter:

- PMIx_Data_load transfers a data "blob" from a pmix_byte_object_t structure to a pmix_data_buffer_t

- PMIx_Data_unload transfers the payload in a pmix_data_buffer_t to a pmix_byte_object_t structure

Signed-off-by: Ralph Castain <rhc@pmix.org>

Chap_API_Data_Mgmt.tex

@@ -420,4 +420,106 @@ \subsection{\code{PMIx_Data_copy_payload}}
 This function will append a copy of the payload in one buffer into another buffer. Note that this is \textit{not} a destructive procedure --- the source buffer's payload will remain intact, as will any pre-existing payload in the destination's buffer. Only the unpacked portion of the source payload will be copied.
 
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\subsection{\code{PMIx_Data_load}}
+\declareapi{PMIx_Data_load}
+
+%%%%
+\summary
+
+Load a buffer with the provided payload
+
+%%%%
+\format
+
+\versionMarker{4.1}
+\cspecificstart
+\begin{codepar}
+pmix_status_t
+PMIx_Data_load(pmix_data_buffer_t *dest,
+               pmix_byte_object_t *src);
+\end{codepar}
+\cspecificend
+
+\begin{arglist}
+\argin{dest}{Pointer to the destination \refstruct{pmix_data_buffer_t} (handle)}
+\argin{src}{Pointer to the source \refstruct{pmix_byte_object_t} (handle)}
+\end{arglist}
+
+Returns one of the following:
+\begin{constantdesc}
+\item \refconst{PMIX_SUCCESS} The data has been loaded as requested
+\item \refconst{PMIX_ERR_BAD_PARAM} The \refarg{dest} structure pointer is \code{NULL}
+\item \refconst{PMIX_ERR_NOT_SUPPORTED} The \ac{PMIx} implementation does not support this function.
+\end{constantdesc}
+
+%%%%
+\descr
+
+The load function allows the caller to transfer the contents of the \refarg{src}
+\refstruct{pmix_byte_object_t} to the \refarg{dest} target buffer. If a payload
+already exists in the buffer, the function will "free" the existing data to
+release it, and then replace the data payload with the one provided
+by the caller.
+
+\adviceuserstart
+The buffer must be allocated or constructed in advance - failing to do so
+will cause the load function to return an error code or fail.
+
+The caller is responsible for pre-packing the provided
+payload - the load function cannot convert to network byte order
+any data contained in the provided payload.
+\adviceuserend
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\subsection{\code{PMIx_Data_unload}}
+\declareapi{PMIx_Data_unload}
+
+%%%%
+\summary
+
+Unload a buffer into a byte object
+
+%%%%
+\format
+
+\versionMarker{4.1}
+\cspecificstart
+\begin{codepar}
+pmix_status_t
+PMIx_Data_unload(pmix_data_buffer_t *src,
+                 pmix_byte_object_t *dest);
+\end{codepar}
+\cspecificend
+
+\begin{arglist}
+\argin{src}{Pointer to the source \refstruct{pmix_data_buffer_t} (handle)}
+\argin{dest}{Pointer to the destination \refstruct{pmix_byte_object_t} (handle)}
+\end{arglist}
+
+Returns one of the following:
+\begin{constantdesc}
+\item \refconst{PMIX_SUCCESS} The data has been copied as requested
+\item \refconst{PMIX_ERR_BAD_PARAM} The destination and/or source pointer is \code{NULL}
+\item \refconst{PMIX_ERR_NOT_SUPPORTED} The \ac{PMIx} implementation does not support this function.
+\end{constantdesc}
+
+%%%%
+\descr
+
+The unload function provides the caller with a pointer to the
+portion of the data payload within the buffer that has not yet been
+unpacked, along with the size of that region. Any portion of
+the payload that was previously unpacked using the \refapi{PMIx_Data_unpack}
+routine will be ignored. This allows the user to directly access the payload.
+
+\adviceuserstart
+This is a destructive operation. While the payload returned in the
+destination \refstruct{pmix_byte_object_t} is
+undisturbed, the function will clear the \refarg{src}'s pointers to the
+payload. Thus, the \refarg{src} and the payload are completely separated,
+leaving the caller able to free or destruct the \refarg{src}.
+\adviceuserend
+
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%