Getting Started with QNX Neutrino - QNX Software Systems

Porting philosophy
© 2009, QNX Software Systems GmbH & Co. KG.
qnx_name_attach()
In this case, you have two choices. You can try to retain the global namespace idiom,
or you can modify your client and server to act like a standard resource manager. If
you wish to retain the global namespace, then you should look at the name_attach()
and name_detach() functions for your server, and name_open() and name_close() for
your clients.
However, I’d recommend that you do the latter; it’s “the Neutrino way” to do
everything with resource managers, rather than try to bolt a resource manager
“kludge” onto the side of a global namespace server.
The modification is actually reasonably simple. Chances are that the client side calls a
function that returns either the process ID of the server or uses the “VC” (Virtual
Circuit) approach to create a VC from the client’s node to a remote server’s node. In
both cases, the process ID or the VC to the remote process ID was found based on
calling qnx_name_locate().
Here, the “magic cookie” that binds the client to the server is some form of process ID
(we’re considering the VC to be a process ID, because VCs are taken from the same
number space, and for all intents and purposes, they look just like process IDs).
If you were to return a connection ID instead of a process ID, you’d have conquered
the major difference. Since the QNX 4 client probably doesn’t examine the process ID
in any way (what meaning would it have, anyway? — it’s just a number), you can
probably trick the QNX 4 client into performing an open() on the “global name.”
In this case, however, the global name would be the pathname that the resource
manager attached as its “id.” For example, the following is typical QNX 4 client code,
stolen from my caller ID (CLID) server library:
/*
* CLID_Attach (serverName)
*
* This routine is responsible for establishing a connection to
* the CLID server.
*
* Returns the process ID or VC to the CLID server.
*/
// a place to store the name, for other library calls
static char CLID_serverName [MAX_CLID_SERVER_NAME + 1];
// a place to store the clid server id
static int clid_pid = -1;
int
CLID_Attach (char *serverName)
{
if (serverName == NULL) {
sprintf (CLID_serverName, "/PARSE/CLID");
} else {
strcpy (CLID_serverName, serverName);
}
clid_pid = qnx_name_locate (0, CLID_serverName,
sizeof (CLID_ServerIPC), NULL);
292 Appendix: A • QNX 4 to Neutrino April 30, 2009