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(4) 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(4) 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.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Evolving |
+--------------------+-----------------+
|MT-Level | Safe |
+--------------------+-----------------+

SEE ALSO


libcontract(3LIB), contract(4), attributes(5), lfcompile(5)


April 9, 2016 CT_EVENT_READ(3CONTRACT)