Getting Started with QNX Neutrino - QNX Software Systems

© 2009, QNX Software Systems GmbH & Co. KG. The resource manager library
• POSIX library helper functions
While you certainly could write resource managers “from scratch” (as was done in the
QNX 4 world), that’s far more hassle than it’s worth.
Just to show you the utility of the library approach, here’s the source for a
single-threaded version of “/dev/null”:
/*
* resmgr1.c
*
* /dev/null using the resource manager library
*/
#include
#include
#include
#include
#include
int
main (int argc, char **argv)
{
dispatch_t
*dpp;
resmgr_attr_t
resmgr_attr;
dispatch_context_t *ctp;
resmgr_connect_funcs_t connect_func;
resmgr_io_funcs_t io_func;
iofunc_attr_t
attr;
// create the dispatch structure
if ((dpp = dispatch_create ()) == NULL) {
perror ("Unable to dispatch_create\n");
exit (EXIT_FAILURE);
}
// initialize the various data structures
memset (&resmgr_attr, 0, sizeof (resmgr_attr));
resmgr_attr.nparts_max = 1;
resmgr_attr.msg_max_size = 2048;
// bind default functions into the outcall tables
iofunc_func_init (_RESMGR_CONNECT_NFUNCS, &connect_func,
_RESMGR_IO_NFUNCS, &io_func);
iofunc_attr_init (&attr, S_IFNAM | 0666, 0, 0);
// establish a name in the pathname space
if (resmgr_attach (dpp, &resmgr_attr, "/dev/mynull",
_FTYPE_ANY, 0, &connect_func, &io_func,
&attr) == -1) {
perror ("Unable to resmgr_attach\n");
exit (EXIT_FAILURE);
}
ctp = dispatch_context_alloc (dpp);
// wait here forever, handling messages
while (1) {
if ((ctp = dispatch_block (ctp)) == NULL) {
perror ("Unable to dispatch_block\n");
exit (EXIT_FAILURE);
}
April 30, 2009 Chapter 5 • Resource Managers 201