NAME
EvmEventPost(), EvmEventPostVa() — post an EVM event
SYNOPSIS
#include <evm/evm.h>
EvmStatus_t EvmEventPost(
EvmConnection_t connection,
const EvmEvent_t event);
EvmStatus_t EvmEventPostVa(
EvmConnection_t connection,
const EvmEvent_t event);
[EvmItemId_t item_id",
const EvmItemValue_t item_id"]...,
EvmITEM_NONE );
Library
EVM Support Library
(libevm.so).
Parameters
- connection
The connection through which events are posted. See
EvmConnCreate(3).
- event
The event that is to be posted to the specified connection. See
EvmEventCreate(3).
- item_id
The identifier for the event data item to be set. See
EvmItemSet(3)
for possible values for this operand, and the data contained by the data item.
- item_value
The value to be stored in the associated item indicated by item_id.
DESCRIPTION
An EVM client program uses the routines described on this page to pass
events to the EVM daemon, for distribution to subscribers.
EvmEventPost()
posts an event that has already been created with
EvmEventCreate()
or
EvmEventCreateVa().
EvmEventPostVa()
creates, posts and destroys an event in a single call.
It first creates a new event, adding any data items
supplied in the call to it.
If the event operand is not NULL,
the contents of the supplied event are then merged into the new event,
and the new event is posted.
The new event is destroyed before the routine returns,
and the supplied event (if any) is unchanged.
See
EvmItemSetVa(3)
for details of the
item_ids
and
item_values
that may be passed as operands to this routine.
If NULL is passed as the connection operand to either of these routines,
the event is posted to the local daemon using a temporary connection.
The temporary connection is
destroyed before the routine returns.
Because of the overhead associated
with creating and destroying an EVM connection,
pass NULL only if your program rarely posts events.
If either routine is unable to pass the event to the daemon, the error is
reported immediately through the return code.
If the event is passed to the daemon,
the type of response depends on the response mode specified when
the connection was created.
Notes
- 1.
These routines do not destroy the event passed as the event operand.
Explicitly call
EvmEventDestroy()
to destroy the event and free its memory once it is no longer needed.
- 2.
Avoid posting a large number of events in rapid succession,
since this may cause the connection's send buffer to fill,
and the posting process to block until the EVM daemon has relieved some or all
of the data. Although this is a normal part of process synchronization,
some high-performance processes may prefer to block as infrequently as possible.
EvmConnControl()
can be used to increase the size of the send buffer.
See
EvmConnControl(3)
for more information.
- 3.
When using extended
item_ids
to supply names and values of variable items to
EvmEventPostVa(),
be sure to supply the correct number of operands for each.
A variable name and value is required for all such items,
and some variable types require an additional argument. See
EvmItemSetVa(3)
for more information.
RETURN VALUE
- EvmERROR_NONE
The operation completed without error.
- EvmERROR_EVENT_REJECTED
The EVM daemon rejected the event.
The most likely reasons are that no template
has been registered for the event, or
that the caller is not authorized to post the event. See
evmtemplate(4)
and
evm.auth(4)
for more information.
- EvmERROR_INVALID_ARGUMENT
One of the arguments to the function is invalid.
- EvmERROR_INVALID_VALUE
A value in a structure member is invalid.
- EvmERROR_NO_MEMORY
An operation failed because an attempt to acquire heap memory failed.
- EvmERROR_QUEUED
The connection's output buffer is full, and the event has
been queued in heap space.
Another attempt is made to flush the queue when the next call is made to
EvmEventPost(),
or when the caller invokes
EvmConnFlush().
This error code is only returned for connections for which
EvmConnControl()
has been invoked with the request argument set to
EvmCONN_POST_NONBLOCK_SET.
- EvmERROR_READ
A read error occurred while reading from the EVM daemon connection.
The connection is no longer usable.
The caller needs to invoke
EvmConnDestroy()
to destroy it.
- EvmERROR_WRITE
A write error occurred while writing to the EVM daemon connection.
The connection is no longer usable.
The caller needs to invoke
EvmConnDestroy()
to destroy it.
ERRORS
The value of
errno
is not set.
Printable version
