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nostrdb: ndb_filter_is_subset_of

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subset testing for filters. Can be used to see if one subset is
redundant in the presence of a another in the local relay model

Changelog-Added: Add ndb_filter_is_subset_of
Signed-off-by: William Casarin <jb55@jb55.com>
This commit is contained in:
William Casarin
2024-11-03 11:11:32 -08:00
committed by Daniel D’Aquino
parent 44ab702792
commit 573de6b881
2 changed files with 44 additions and 0 deletions
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41
nostrdb/src/nostrdb.c
View File

@@ -2672,6 +2672,47 @@ ndb_filter_find_elements(struct ndb_filter *filter, enum ndb_filter_fieldtype ty
return NULL;
}
int ndb_filter_is_subset_of(struct ndb_filter *a, struct ndb_filter *b)
{
int i;
struct ndb_filter_elements *b_field, *a_field;
// Everything is always a subset of {}
if (b->num_elements == 0)
return 1;
// We can't be a subset if the number of elements in the other
// filter is larger then the number of elements we have.
if (b->num_elements > a->num_elements)
return 0;
// If our filter count matches, we can only be a subset if we are
// equal
if (b->num_elements == a->num_elements)
return ndb_filter_eq(a, b);
// If our element count is larger than the other filter, then we
// must see if every element in the other filter exists in ours. If
// so, then we are a subset of the other.
//
// eg: B={k:1, a:b} <- A={t:x, k:1, a:b}
//
// A is a subset of B because `k:1` and `a:b` both exist in A
for (i = 0; i < b->num_elements; i++) {
b_field = ndb_filter_get_elements(b, i);
a_field = ndb_filter_find_elements(a, b_field->field.type);
if (a_field == NULL)
return 0;
if (!ndb_filter_field_eq(a, a_field, b, b_field))
return 0;
}
return 1;
}
int ndb_filter_eq(struct ndb_filter *a, struct ndb_filter *b)
{
int i;

3
nostrdb/src/nostrdb.h
View File

@@ -499,6 +499,9 @@ int ndb_filter_add_int_element(struct ndb_filter *, uint64_t integer);
int ndb_filter_add_str_element(struct ndb_filter *, const char *str);
int ndb_filter_eq(struct ndb_filter *, struct ndb_filter *);
/// is `a` a subset of `b`
int ndb_filter_is_subset_of(struct ndb_filter *a, struct ndb_filter *b);
// filters from json
int ndb_filter_from_json(const char *, int len, struct ndb_filter *filter, unsigned char *buf, int bufsize);