Add a method for ebitmaps that computes the relative complement.
All bits set in the second ebitmap are set to zero in the first one.
Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
v3:
- rename from ebitmap_subtract() to ebitmap_relative_complement()
v2:
- add shortcut for empty ebitmaps
---
libsepol/include/sepol/policydb/ebitmap.h | 1 +
libsepol/src/ebitmap.c | 18 ++++++++++++++++++
2 files changed, 19 insertions(+)
diff --git a/libsepol/include/sepol/policydb/ebitmap.h b/libsepol/include/sepol/policydb/ebitmap.h
index 81d0c7a6..076b9341 100644
--- a/libsepol/include/sepol/policydb/ebitmap.h
+++ b/libsepol/include/sepol/policydb/ebitmap.h
@@ -83,6 +83,7 @@ static inline int ebitmap_node_get_bit(const ebitmap_node_t * n, unsigned int bi
extern int ebitmap_cmp(const ebitmap_t * e1, const ebitmap_t * e2);
extern int ebitmap_or(ebitmap_t * dst, const ebitmap_t * e1, const ebitmap_t * e2);
extern int ebitmap_union(ebitmap_t * dst, const ebitmap_t * e1);
+extern int ebitmap_relative_complement(ebitmap_t *dst, const ebitmap_t *e1);
extern int ebitmap_and(ebitmap_t *dst, const ebitmap_t *e1, const ebitmap_t *e2);
extern int ebitmap_xor(ebitmap_t *dst, const ebitmap_t *e1, const ebitmap_t *e2);
extern int ebitmap_not(ebitmap_t *dst, const ebitmap_t *e1, unsigned int maxbit);
diff --git a/libsepol/src/ebitmap.c b/libsepol/src/ebitmap.c
index 1de3816a..5f166e8c 100644
--- a/libsepol/src/ebitmap.c
+++ b/libsepol/src/ebitmap.c
@@ -72,6 +72,24 @@ int ebitmap_union(ebitmap_t * dst, const ebitmap_t * e1)
return 0;
}
+int ebitmap_relative_complement(ebitmap_t *dst, const ebitmap_t *e1)
+{
+ unsigned int i, length;
+
+ if (ebitmap_is_empty(dst) || ebitmap_is_empty(e1))
+ return 0;
+
+ length = min(ebitmap_length(dst), ebitmap_length(e1));
+ for (i=0; i < length; i++) {
+ if (ebitmap_get_bit(e1, i)) {
+ int rc = ebitmap_set_bit(dst, i, 0);
+ if (rc < 0)
+ return rc;
+ }
+ }
+ return 0;
+}
+
int ebitmap_and(ebitmap_t *dst, const ebitmap_t *e1, const ebitmap_t *e2)
{
unsigned int i, length = min(ebitmap_length(e1), ebitmap_length(e2));
--
2.34.1
