Getting Started with QNX Neutrino - QNX Software Systems

Porting philosophy
© 2009, QNX Software Systems GmbH & Co. KG.
}
/*
* CLID_IPC (IPC message number)
*
* This routine will call the server with the global buffer
* CLID_IPCData, and will stuff in the message number passed
* as the argument.
*
* Should the server not exist, this routine will stuff the
* .returnValue field with CLID_NoServer. Otherwise, no
* fields are affected.
*/
void
CLID_IPC (IPCMessage)
int IPCMessage;
{
if (clid_pid == -1) {
CLID_IPCData.returnValue = CLID_NoServer;
return;
}
CLID_IPCData.serverFunction = IPCMessage;
CLID_IPCData.type = 0x8001;
CLID_IPCData.subtype = 0;
if (Send (clid_pid, &CLID_IPCData, &CLID_IPCData,
sizeof (CLID_IPCData),
sizeof (CLID_IPCData))) {
CLID_IPCData.returnValue = CLID_IPCError;
return;
}
}
void
checkAttach ()
{
if (clid_pid == -1) {
CLID_Attach (NULL);
}
}
As you can see, the checkAttach() function is used to ensure that a connection exists to
the CLID server. If you didn’t have a connection, it would be like calling read() with
an invalid file descriptor. In my case here, the checkAttach() automagically creates the
connection. It would be like having the read() function determine that there is no valid
file descriptor and just create one out of the blue. Another style issue.
The customized messaging occurs in the CLID_IPC() function. It takes the global
variable CLID_IPCData and tries to send it to the server using the QNX 4 Send()
function.
The customized messages can be handled in one of two ways:
1 Functionally translate them into standard, file-descriptor-based POSIX calls.
Or:
2 Encapsulate them into either a devctl() or a customized message wrapper using
the _IO_MSG message type.
294 Appendix: A • QNX 4 to Neutrino April 30, 2009