select_query()

Decode the last select event

Synopsis:

#include <sys/iofunc.h>
#include <sys/dispatch.h>

int select_query
        ( select_context_t *ctp,
          int *fd,
          unsigned *flags,
          int (**func)( select_context_t *ctp,
                       int fd,
                       unsigned flags,
                       void *handle ),
          void **handle );

Arguments:

ctp

A pointer to a select_context_t structure that defines the context of the event that you want to get information about.

fd

A pointer to a location where the function can store the file descriptor that's associated with the event.

flags

A pointer to a location where the function can store the flags associated with the event; see “Flags” in the documentation for select_attach().

func

A pointer to a location where the function can store the function associated with the event; see “Function” in the documentation for select_attach().

handle

A pointer to a location where the function can store the address of any data that you arranged to pass to func.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The function select_query() stores the values of the last select event, for context ctp, in fd, flags, func, and handle.

Returns:

If an error occurs, the function returns -1. An error occurs if the received event doesn't belong to one of the file descriptors attached with select_attach().

Examples:

#include <sys/dispatch.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>

int my_func( select_context_t *ctp,
             int fd,
             unsigned flags,
             void *handle ) {

   …

}

int main( int argc, char **argv ) {
   dispatch_t           *dpp;
   dispatch_context_t   *ctp;
   int                  fd;
   unsigned             flag;
   void                 *handle;
   select_attr_t        *attr;
   int                  (*func)( select_context_t *,
                                 int, unsigned, void * );

   if( ( dpp = dispatch_create() ) == NULL ) {
     fprintf( stderr, "%s: Unable to allocate \
              dispatch handle.\n",argv[0] );
     return EXIT_FAILURE;
   }

   if( argc ≤ 2 || (fd = open( argv[1],
                    O_RDWR | O_NONBLOCK )) == -1 ) {
     exit(0);
   }
   
   select_attach( dpp, attr, fd,
      SELECT_FLAG_READ | SELECT_FLAG_REARM, &my_func, NULL );

   ctp = dispatch_context_alloc( dpp );

   …

   if( select_query( (select_context_t *)ctp, &fd, &flag, 
                      &func, &handle ) == -1 ) {
     fprintf( stderr, "Failed to decode last select event.\n");
     return 1;
   }
}

For more examples using the dispatch interface, see dispatch_create(), message_attach(), resmgr_attach(), and thread_pool_create().

Classification:

QNX Neutrino

See also:

select_attach(), select_detach()