Tribblix: manual page: ct_event

CT_EVENT_READ(3CONTRACT) Contract Management Library Functions

NAME

ct_event_read, ct_event_read_critical, ct_event_reset,
ct_event_reliable, ct_event_free, ct_event_get_flags,
ct_event_get_ctid, ct_event_get_evid, ct_event_get_type,
ct_event_get_nevid, ct_event_get_newct - common contract event
functions

SYNOPSIS

cc [ flag... ] file... -D_LARGEFILE64_SOURCE -lcontract [ library... ]
#include <libcontract.h>

int ct_event_read(int fd, ct_evthdl_t *evthndlp);

int ct_event_read_critical(int fd, ct_evthdl_t *evthndlp);

int ct_event_reset(int fd);

int ct_event_reliable(int fd);

void ct_event_free(ct_evthdl_t evthndl);

ctid_t ct_event_get_ctid(ct_evthdl_t evthndl);

ctevid_t ct_event_get_evid(ct_evthdl_t evthndl);

uint_t ct_event_get_flags(ct_evthdl_t evthndl);

uint_t ct_event_get_type(ct_evthdl_t evthndl);

int ct_event_get_nevid(ct_evthdl_t evthndl, ctevid_t *evidp);

int ct_event_get_newct(ct_evthdl_t evthndl, ctid_t *ctidp);

DESCRIPTION

These functions operate on contract event endpoint file descriptors
obtained from the contract(5) file system and event object handles
returned by ct_event_read() and ct_event_read_critical().

The ct_event_read() function reads the next event from the queue
referenced by the file descriptor fd and initializes the event object
handle pointed to by evthndlp. After a successful call to
ct_event_read(), the caller is responsible for calling
ct_event_free() on this event object handle when it has finished
using it.

The ct_event_read_critical() function behaves like ct_event_read()
except that it reads the next critical event from the queue, skipping
any intermediate events.

The ct_event_reset() function resets the location of the listener to
the beginning of the queue. This function can be used to re-read
events, or read events that were sent before the event endpoint was
opened. Informative and acknowledged critical events, however, might
have been removed from the queue.

The ct_event_reliable() function indicates that no event published to
the specified event queue should be dropped by the system until the
specified listener has read the event. This function requires that
the caller have the {PRIV_CONTRACT_EVENT} privilege in its effective
set.

The ct_event_free() function frees any storage associated with the
event object handle specified by evthndl.

The ct_event_get_ctid() function returns the ID of the contract that
sent the specified event.

The ct_event_get_evid() function returns the ID of the specified
event.

The ct_event_get_flags() function returns the event flags for the
specified event. Valid event flags are:

CTE_INFO
The event is an informative event.

CTE_ACK
The event has been acknowledged (for critical and
negotiation messages).

CTE_NEG
The message represents an exit negotiation.

The ct_event_get_type() function reads the event type. The value is
one of the event types described in contract(5) or the contract
type's manual page.

The ct_event_get_nevid() function reads the negotiation ID from an
CT_EV_NEGEND event.

The ct_event_get_newct() function obtains the ID of the contract
created when the negotiation referenced by the CT_EV_NEGEND event
succeeded. If no contract was created, ctidp will be 0. If the
operation was cancelled, *ctidp will equal the ID of the existing
contract.

RETURN VALUES

Upon successful completion, ct_event_read(),
ct_event_read_critical(), ct_event_reset(), ct_event_reliable(),
ct_event_get_nevid(), and ct_event_get_newct() return 0. Otherwise,
they return a non-zero error value.

The ct_event_get_flags(), ct_event_get_ctid(), ct_event_get_evid(),
and ct_event_get_type() functions return data as described in the
DESCRIPTION.

ERRORS

The ct_event_reliable() function will fail if:

EPERM
The caller does not have {PRIV_CONTRACT_EVENT} in its
effective set.

The ct_event_read() and ct_event_read_critical() functions will fail
if:

EAGAIN
The event endpoint was opened O_NONBLOCK and no applicable
events were available to be read.

The ct_event_get_nevid() and ct_event_get_newct() functions will fail
if:

EINVAL
The evthndl argument is not a CT_EV_NEGEND event object.