On Thu, Nov 25, 2021 at 3:03 PM Christian Göttsche
<cgzones@xxxxxxxxxxxxxx> wrote:
>
> Add a subtract method for ebitmaps.
>
> Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
> ---
> 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..daca67a2 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_subtract(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..80f0e201 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_subtract(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));
> --
> 2.34.0
>
We already have ebitmap_andnot() which does the same thing (although
it does take three ebitmaps). Also, subtract is not a bit operation,
so it doesn't seem to fit.
Thanks,
Jim
