NAME
af_initset, af_nrofkeys, af_setgkey, af_setaddkey, af_setrmkey,
af_setposrmkey, af_sortset, af_subset, af_copyset, af_intersect,
af_union, af_diff - AtFS operations on key sets
SYNOPSIS
#include <atfs.h>
int af_initset (Af_set *set)
int af_nrofkeys (Af_set *set)
int af_setgkey (Af_set *set, int position, Af_key *key)
int af_setaddkey (Af_set *set, int position, Af_key *key)
int af_setrmkey (Af_set *set, Af_key *key)
int af_setposrmkey (Af_set *set, int position)
int af_sortset (Af_set *set, char *attrname)
int af_subset (Af_set *set, Af_attrs *attrbuf, Af_set *subset)
int af_copyset (Af_set *source, Af_set *destination)
int af_intersect (Af_set *set1, Af_set *set2, Af_set *newset)
int af_union (Af_set *set1, Af_set *set2, Af_set *newset)
int af_diff (Af_set *set1, Af_set *set2, *Af_set newset)
DESCRIPTION
Sets in AtFS are ordered collections of keys. The structure of sets is
the following
typedef struct {
int af_nkeys;
int af_setlen;
Af_key *af_klist;
} Af_set;
The list of keys in a set is a linear list, residing in allocated
memory. The list has no holes, so that positions 0 through af_nkeys-1
are occupied with valid keys. Set functions returning a set require a
pointer to an empty set structure as argument.
af_initset initializes a set.
af_nrofkeys returns the number of valid keys in the given set.
af_setgkey delivers the filekey, stored at position position in the
identified set. The result is passed in the buffer key. Typically you
use af_setgkey to run through a set and perform a special action on
each key. The following code sequence does this job:
Af_key key;
Af_set set;
af_initset (&set);
...
for (i = 0; i < af_nrofkeys (&set); i++) {
af_setgkey (&set, i, &key);
/* process key */
...
}
af_setaddkey introduces a new filekey to an existing set at the given
position. All following keys are moved back by one position. The
constant AF_LASTPOS given as position argument leads to adding the new
filekey at the end of the set.
af_setrmkey (af_setposrmkey) removes the given filekey (the filekey at
position position) from the specified set. Holes generated by deleting
single keys from a set are eliminated by condensing the set. All
following keys are moved one position forth in the set.
af_sortset sorts a given set of object keys by the values of the named
attribute. The set is sorted in increasing order. Increasing order
means, that the lowest value occurs first in the set. Af_user
structures are compared by username first and by userdomain, if the
names are equal (user host will not be taken into account). Version
numbers are ordered in natural order, busy versions first.
In atfs.h you can find a list of attribute names naming the standard
attributes. All other attribute names are presumed to be user defined
attributes. While sorting by the values of an user defined attribute,
all ASOs that do not have the named attribute are added at the end of
the resulting (sorted) set. Sorting of user defined attributes with
multiple values bases on simple text comparison with the order of the
values taken as it is. The length of the given attribute name is
limited. This limit is defined by the constant AF_UDANAMLEN in atfs.h.
af_subset does a retrieve operation (similar to af_find - manual page
af_retrieve(3)) on a given set of object keys. Af_subset takes an
attribute buffer (attrbuf) with all desired attributes set to an
appropriate value as argument. The attribute buffer should be
initialized by af_initattrs (manual page af_retrieve(3)) beforehand.
af_subset returns it’s result in a new set, the original set remains
unchanged.
af_copyset for copying sets (really! =:-).
af_intersect, af_union and af_diff build intersections, unions, and
differences between two sets. The result is a new set, where all keys
taken from the first argument set (set1) occur first, and the keys from
the second argument set (set2) afterwards. You may gibe one of set1 or
set2 as resultset. In that case, the original set get lost and is
dropped implicitely.
Sets generated by af_copyset, af_subset, af_intersect, af_union, or
af_diff should be released by af_dropset as soon as they are not used
any longer.
SEE ALSO
af_retrieve(3)
DIAGNOSTICS
Upon error, -1 or a nil pointer (depending on the return type) is
returned and af_errno is set to the corresponding error number.