[libvirt] [PATCH 2/3] util: Clear unused part of the map in virBitmapShrink

[Martin Kletzander]

Some of the other functions depend on the fact that unused bits and longs are
always zero and it's less error-prone to clear it than fix the other functions.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1540817

Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
---
 src/util/virbitmap.c  | 13 +++++++++++++
 tests/virbitmaptest.c |  5 +++++
 2 files changed, 18 insertions(+)

diff --git a/src/util/virbitmap.c b/src/util/virbitmap.c
index b2c5c7a6a5ac..b32342024e19 100644
--- a/src/util/virbitmap.c
+++ b/src/util/virbitmap.c
@@ -1213,9 +1213,22 @@ void
 virBitmapShrink(virBitmapPtr map,
                 size_t b)
 {
+    size_t nl = 0;
+    size_t nb = 0;
+
     if (!map)
         return;
 
     if (map->max_bit >= b)
         map->max_bit = b;
+
+    nl = map->max_bit / VIR_BITMAP_BITS_PER_UNIT;
+    nb = map->max_bit % VIR_BITMAP_BITS_PER_UNIT;
+    map->map[nl] &= ((1UL << nb) - 1);
+
+    nl++;
+    if (nl < map->map_len) {
+        memset(map->map + nl, 0,
+               (map->map_len - nl) * (VIR_BITMAP_BITS_PER_UNIT / CHAR_BIT));
+    }
 }
diff --git a/tests/virbitmaptest.c b/tests/virbitmaptest.c
index 9c0ffe70cb49..a3258dc0ebad 100644
--- a/tests/virbitmaptest.c
+++ b/tests/virbitmaptest.c
@@ -656,6 +656,11 @@ test12(const void *opaque ATTRIBUTE_UNUSED)
 
     TEST_MAP(1024, "34,1023");
 
+    virBitmapShrink(map, 35);
+    TEST_MAP(35, "34");
+    virBitmapShrink(map, 34);
+    TEST_MAP(34, "");
+
     ret = 0;
 
  cleanup:
-- 
2.16.1