/usr/include/net-snmp/library/fd_event_manager.h is in libsnmp-dev 5.4.3~dfsg-2.4ubuntu1.3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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* UNIT: File Descriptor (FD) Event Manager
*
* OVERVIEW: This unit contains functions to register a FD with the FD
* event manager for callbacks when activity is received on that
* FD. Notification of read, write, and exception activity can
* all be registered for individually. Once a registered FD is
* closed by the user, the FD must be unregistered. To use
* the FD Event manager you need to make calls to
* netsnmp_external_event_info() and
* netsnmp_dispatch_external_events() in your event loop to receive
* callbacks for registered events. See snmpd.c and snmptrapd.c
* for examples.
*
* LIMITATIONS:
**************************************************************************/
#ifndef FD_EVENT_MANAGER_H
#define FD_EVENT_MANAGER_H
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#ifdef __cplusplus
extern "C" {
#endif
#define NUM_EXTERNAL_FDS 32
#define FD_REGISTERED_OK 0
#define FD_REGISTRATION_FAILED -2
#define FD_UNREGISTERED_OK 0
#define FD_NO_SUCH_REGISTRATION -1
/* Since the inception of netsnmp_external_event_info and
* netsnmp_dispatch_external_events, there is no longer a need for the data
* below to be globally visible. We will leave it global for now for
* compatibility purposes. */
extern int external_readfd[NUM_EXTERNAL_FDS], external_readfdlen;
extern int external_writefd[NUM_EXTERNAL_FDS], external_writefdlen;
extern int external_exceptfd[NUM_EXTERNAL_FDS], external_exceptfdlen;
extern void (*external_readfdfunc[NUM_EXTERNAL_FDS]) (int, void *);
extern void (*external_writefdfunc[NUM_EXTERNAL_FDS]) (int, void *);
extern void (*external_exceptfdfunc[NUM_EXTERNAL_FDS]) (int, void *);
extern void *external_readfd_data[NUM_EXTERNAL_FDS];
extern void *external_writefd_data[NUM_EXTERNAL_FDS];
extern void *external_exceptfd_data[NUM_EXTERNAL_FDS];
/* Here are the key functions of this unit. Use register_xfd to register
* a callback to be called when there is x activity on the register fd.
* x can be read, write, or except (for exception). When registering,
* you can pass in a pointer to some data that you have allocated that
* you would like to have back when the callback is called. */
int register_readfd(int, void (*func)(int, void *), void *);
int register_writefd(int, void (*func)(int, void *), void *);
int register_exceptfd(int, void (*func)(int, void *), void *);
/* Unregisters a given fd for events */
int unregister_readfd(int);
int unregister_writefd(int);
int unregister_exceptfd(int);
/*
* External Event Info
*
* Description:
* Call this function to add an external event fds to your read, write,
* exception fds that your application already has. When this function
* returns, your fd_sets will be ready for select(). It returns the
* biggest fd in the fd_sets so far.
*
* Input Parameters: None
*
* Output Parameters: None
*
* In/Out Parameters:
* numfds - The biggest fd so far. On exit to this function, numfds
* could of changed since we pass out the new biggest fd.
* readfds - Set of read FDs that we are monitoring. This function
* can modify this set to have more FDs that we are monitoring.
* writefds - Set of write FDs that we are monitoring. This function
* can modify this set to have more FDs that we are monitoring.
* exceptfds - Set of exception FDs that we are monitoring. This function
* can modify this set to have more FDs that we are monitoring.
*
* Return Value: None
*
* Side Effects: None
*/
void netsnmp_external_event_info(int *numfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds);
/*
* Dispatch External Events
*
* Description:
* Call this function after select returns with pending events. If any of
* them were NETSNMP external events, the registered callback will be called.
* The corresponding fd_set will have the FD cleared after the event is
* dispatched.
*
* Input Parameters: None
*
* Output Parameters: None
*
* In/Out Parameters:
* count - Number of FDs that have activity. In this function, we decrement
* count as we dispatch an event.
* readfds - Set of read FDs that have activity
* writefds - Set of write FDs that have activity
* exceptfds - Set of exception FDs that have activity
*
* Return Value: None
*
* Side Effects: None
*/
void netsnmp_dispatch_external_events(int *count, fd_set *readfds, fd_set *writefds, fd_set *exceptfds);
#ifdef __cplusplus
}
#endif
#endif
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