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EvmFilterCreate(3)
NAME
  EvmFilterCreate, EvmFilterSet, EvmFilterTest, EvmFilterIsFile,
  EvmFilterReadFile, EvmFilterDestroy - Event filter evaluator routines

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
  filter_evaluator
      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.

  filter_string
      The filter string to be used by the filter evaluator in subsequent
      matches. See the EvmFilter(5) reference page for the syntax.

  event
      The event to be compared with the filter string currently associated
      with the filter evaluator.

  matchFlag
      The result obtained when the supplied event is compared with the filter
      string currently associated with the filter evaluator. Possible return
      values are as follows:

      EvmTRUE The event matches the filter_string.

      EvmFALSE
	      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:

  EvmTRUE
      The event matches the filter_string.

  EvmFALSE
      The event does not match the filter_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
  EvmFilterReadFile() 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
  EvmERROR_NONE
      The operation was completed without error.

  EvmERROR_FILTER_NOT_VALID
      A filter string passed to the filter evaluator was syntactically
      invalid.

  EvmERROR_INVALID_ARGUMENT
      One of the arguments to the function was 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_NOT_INITIALIZED
      An attempt was made to use a filter evaluator without first calling
      EvmFilterSet() to provide an initial filter string.

  EvmERROR_FILTER_NOT_VALID
      A filter string passed to the filter evaluator was syntactically
      invalid.

  NULL
      An attempt to read a filter file failed.

ERRORS
  None

LIBRARY
  EVM Support Library (libevm.so, libevm.a)

FILES
  None

SEE ALSO
  Files: kevm(7)

  Event Management: EVM(5)

  EVM Events: EvmEvent(5)

  Event Filter: EvmFilter(5)

Index for Section 3

Alphabetical listing for E

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