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dispatch_create()

Allocate a dispatch handle

Synopsis:

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

dispatch_t *dispatch_create( void );

Library:

libc

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

Description:

The dispatch_create() function allocates and initializes a dispatch handle. The attach functions are:

• message_attach()
• pulse_attach()
• resmgr_attach()
• select_attach()

If you wish, you can do a resmgr_attach() with a NULL path. This has the effect of initializing dispatch to receive messages and creates the channel among other things.

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A channel is created only when you first attach something that requires a channel (indicating you will block receiving messages).

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This function is part of the dispatch layer of a resource manager. For more information, see "Components of a resource manager" in the Writing a Resource Manager chapter of the Neutrino Programmer's Guide.

Returns:

A handle to a dispatch structure, or NULL if an error occurs.

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The dispatch structure, dispatch_t, is an opaque data type; you can't access its contents directly.

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Errors:

ENOMEM

Insufficient memory to allocate context.

Examples:

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

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

   /* Do some useful stuff with data */
   i = read( fd, &c, 1 );
   fprintf( stderr, "activity on fd %d: read char %c,
                     return code %d\n", fd, c, i ); 
}

int main( int argc, char **argv ) {
   dispatch_t           *dpp;
   dispatch_context_t   *ctp;
   select_attr_t        attr;
   int                  fd, fd2;

   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 ) {
     return EXIT_FAILURE;
   }
   
   if( argc <= 2 || (fd2 = open( argv[2],
                    O_RDWR | O_NONBLOCK )) == -1 ) {
     return EXIT_FAILURE;
   }

   select_attach( dpp, &attr, fd,
      SELECT_FLAG_READ | SELECT_FLAG_REARM, my_func, NULL );
   select_attach( dpp, &attr, fd2,
      SELECT_FLAG_READ | SELECT_FLAG_REARM, my_func, NULL );
   ctp = dispatch_context_alloc( dpp );

   for(;;) {
     if( ctp = dispatch_block( ctp ) ) {
       dispatch_handler( ctp );
     }
   }
   return EXIT_SUCCESS;
}

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

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	No
Thread	Yes

See also:

dispatch_block(), dispatch_context_alloc(), dispatch_destroy(), dispatch_handler(), dispatch_timeout(), dispatch_unblock() message_attach(), pulse_attach(), resmgr_attach(), select_attach()

"Components of a resource manager" in the Writing a Resource Manager chapter of the Neutrino Programmer's Guide

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