EvmFilterCreate(3) Library Functions Manual EvmFilterCreate(3)
NAME
EvmFilterCreate, EvmFilterSet, EvmFilterTest, EvmFilterIsFile, EvmFilterReadFile, EvmFilterDestroy - Event filter evaluator routines
LIBRARY
EVM Support Library (libevm.so, libevm.a)
SYNOPSIS
#include <evm/evm.h>
EvmStatus_t EvmFilterCreate (
EvmFilter_t *filter_evaluator);
EvmStatus_t EvmFilterSet (
EvmFilter_t filter_evaluator,
const EvmString_t filter_string);
EvmStatus_t EvmFilterTest (
EvmFilter_t filter_evaluator,
EvmEvent_t event,
EvmBoolean_t *matchFlag);
EvmBoolean_t EvmFilterIsFile (
const char *filter_string);
char * EvmFilterReadFile (
const char *filter_string);
EvmStatus_t EvmFilterDestroy (
EvmFilter_t filter_evaluator);
OPERANDS
For EvmFilterCreate() this is the return handle of the instance of a filter evaluator established.
For EvmFilterSet() this identifies the filter evaluator that will use the filter_string in subsequent matches.
For EvmFilterTest() this identifies the filter evaluator that will compare the supplied event with the filter string.
For EvmFilterDestroy() this identifies the filter evaluator to be destroyed. The filter string to be used by the filter evaluator
in subsequent matches. See the EvmFilter(5) reference page for the syntax. The event to be compared with the filter string cur-
rently associated with the filter evaluator. The result obtained when the supplied event is compared with the filter string cur-
rently associated with the filter evaluator. Possible return values are as follows: The event matches the filter_string. The event
does not match the filter_string.
DESCRIPTION
The filter evaluation routines are used to check whether an event matches a given event filter. Although most EVM clients do not need to
use these functions directly, they are useful to clients that pass a complex filter to the EVM daemon, and then test incoming events
against subcomponents of the filter to determine the appropriate action.
The EvmFilterCreate() routine establishes an instance of a filter evaluator, returning a handle in filter_evaluator.
The EvmFilterSet() routine passes a filter_string to the filter_evaluator to be used in subsequent matches.
The EvmFilterTest() routine compares the supplied event with the filter_string currently associated with the filter_evaluator. The result
is returned in matchFlag. Possible return values are as follows: The event matches the filter_string. The event does not match the fil-
ter_string.
The indirect filter syntax, @filename, is supported by the EvmFilterIsFile() and EvmFilterReadFile() routines. Programs which support
indirect filters may use EvmFilterIsFile() to determine whether a user-supplied filter string is indirect, and, if so, can then use EvmFil-
terReadFile() to expand the file to a regular filter string.
EvmFilterIsFile() returns EvmTRUE if the supplied filter_string uses indirect filter notation, and EvmFALSE otherwise.
EvmFilterReadFile() interprets the supplied filter_string, and attempts to open and read the referenced file, returning a pointer to heap
space memory containing the expanded filter string. The caller is responsible for freeing the memory when it is no longer needed. NULL is
returned if an error was encountered while reading the file. Note that EvmFilterReadFile() does not attempt to validate the filter string
contained in the file.
The EvmFilterDestroy() routine destroys the filter_evaluator, freeing all associated resources.
RESTRICTIONS
None
RETURN VALUES
The operation was completed without error. A filter string passed to the filter evaluator was syntactically invalid. One of the arguments
to the function was invalid. A value in a structure member is invalid. An operation failed because an attempt to acquire heap memory
failed. An attempt was made to use a filter evaluator without first calling EvmFilterSet() to provide an initial filter string. A filter
string passed to the filter evaluator was syntactically invalid. An attempt to read a filter file failed.
ERRORS
None
FILES
None
SEE ALSO
Event Management: EVM(5)
EVM Events: EvmEvent(5)
Event Filter: EvmFilter(5)
delim off
EvmFilterCreate(3)