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