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Handle events received by dispatch_block()
#include <sys/iofunc.h>
#include <sys/dispatch.h>
int dispatch_handler( dispatch_context_t * ctp );
- ctp
- A pointer to a dispatch_context_t structure that
was allocated by
dispatch_context_alloc().
libc
Use the -l c option to
qcc
to link against this library.
This library is usually included automatically.
The dispatch_handler() function
handles events received by
dispatch_block().
This function is part of the dispatch layer of a resource manager.
For more information, see
“Layers in a resource manager”
in the Bones of a Resource Manager chapter of Writing a Resource Manager.
Depending on the blocking type,
dispatch_handler() does one of the following:
- Calls the
message_*
subsystem.
A search is made (based upon the message type or pulse code) for a matching function
(that was attached with
message_attach() or
pulse_attach()).
If a match is found, the attached function is called.
- If the message type is in the range handled by the resource manager
(e.g. I/O messages) and pathnames were attached using
resmgr_attach(), then the
resmgr_*
subsystem is called and handles the resource manager messages.
- If a pulse is received, it may be dispatched to the
resmgr_*
subsystem if it's one of the codes (unblock and disconnect pulses)
handled by the resource manager.
If a
select_attach()
was done and the pulse matches the one used by select_attach(),
then the
select_* subsystem is called and dispatches that event.
- If a message is received, and no matching handler is found for that message type,
MsgError()
returns ENOSYS to the sender.
- If a SignalWaitinfo()
blocking type is used,
then a search is made based upon the signal number for a matching function attached by the program
(using the sigwait_attach() function, not currently implemented).
If a match is found, that function is called.
- 0
- Success.
- -1
- One of the following occurred:
- The message was a
_PULSE_CODE_THREADDEATH
pulse message (see ChannelCreate()) for which there's no default handler function.
- The message length was less than 2 bytes.
A 2-byte message type is required at the beginning of the message so that
a handler function can be found or identified.
- The message wasn't in native endian format and there were no handler functions that specified
MSG_FLAG_CROSS_ENDIAN on this range,
even though a handler was registered for it using
message_attach().
The MSG_FLAG_CROSS_ENDIAN flag wasn't given to message_attach().
- A handler was found for the message, but the handler determined that there was a problem.
In any case, if the message wasn't a pulse, then the client will be
replied to with an appropriate
errno.
#include <stdlib.h>
#include <sys/dispatch.h>
int main( int argc, char **argv ) {
dispatch_context_t *ctp;
…
for(;;) {
if( ctp = dispatch_block( ctp ) ) {
dispatch_handler( ctp );
}
}
return EXIT_SUCCESS;
}
For examples using the dispatch interface, see
dispatch_create(),
message_attach(),
resmgr_attach(), and
thread_pool_create().
QNX Neutrino
Safety: | |
Cancellation point |
Read the Caveats |
Interrupt handler |
No |
Signal handler |
No |
Thread |
Yes |
This function might or might not be a cancellation point, depending on
the implementation of the handler.
dispatch_block(),
dispatch_create(),
dispatch_create_channel(),
dispatch_timeout()
“Layers in a resource manager”
in the Bones of a Resource Manager chapter of Writing a Resource Manager
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