[PATCH 1/2] libsepol: Create function ebitmap_highest_set_bit()

[James Carter <jwcart2@gmail.com>]

Create the function ebitmap_highest_set_bit() which returns the position
of the highest bit set in the ebitmap.

The return value is valid only if the ebitmap is not empty. An empty
ebitmap will return 0.

Signed-off-by: James Carter <jwcart2@gmail.com>
---
 libsepol/include/sepol/policydb/ebitmap.h |  1 +
 libsepol/src/ebitmap.c                    | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/libsepol/include/sepol/policydb/ebitmap.h b/libsepol/include/sepol/policydb/ebitmap.h
index 910834dd..634436f6 100644
--- a/libsepol/include/sepol/policydb/ebitmap.h
+++ b/libsepol/include/sepol/policydb/ebitmap.h
@@ -94,6 +94,7 @@ extern int ebitmap_contains(const ebitmap_t * e1, const ebitmap_t * e2);
 extern int ebitmap_match_any(const ebitmap_t *e1, const ebitmap_t *e2);
 extern int ebitmap_get_bit(const ebitmap_t * e, unsigned int bit);
 extern int ebitmap_set_bit(ebitmap_t * e, unsigned int bit, int value);
+extern unsigned int ebitmap_highest_set_bit(ebitmap_t * e);
 extern void ebitmap_destroy(ebitmap_t * e);
 extern int ebitmap_read(ebitmap_t * e, void *fp);
 
diff --git a/libsepol/src/ebitmap.c b/libsepol/src/ebitmap.c
index 963b8080..7f425349 100644
--- a/libsepol/src/ebitmap.c
+++ b/libsepol/src/ebitmap.c
@@ -344,6 +344,26 @@ int ebitmap_set_bit(ebitmap_t * e, unsigned int bit, int value)
 	return 0;
 }
 
+unsigned int ebitmap_highest_set_bit(ebitmap_t * e)
+{
+	ebitmap_node_t *n;
+	MAPTYPE map;
+	unsigned int pos = 0;
+
+	n = e->node;
+	if (!n)
+		return 0;
+
+	while (n->next)
+		n = n->next;
+
+	map = n->map;
+	while (map >>= 1)
+		pos++;
+
+	return n->startbit + pos;
+}
+
 void ebitmap_destroy(ebitmap_t * e)
 {
 	ebitmap_node_t *n, *temp;
-- 
2.26.2