bitmap: fix bitmap_equal on bitmaps with unset bits

Given two bitmaps and the following code:

Bitmap *a = bitmap_new(), *b = bitmap_new();
bitmap_set(a, 0);
bitmap_unset(a, 0);

These two bitmaps should now have the same bits set and they should be
equal but bitmap_equal() will return false in this case because the
bitmaps array in a is larger because of the bit which was previously
set.

Fix this by comparing only the bits which exists in both bitmaps and
then check that the rest of the bits (if any) is all zero.

This also adds test code for this issue.

diff --git a/src/basic/bitmap.c b/src/basic/bitmap.c
index bf9d8d4d7c7f08e46d03a53e31eb50a19eb808d1..e7e19b3b6696dfcd82d86d0738e5caf2cbfcf550 100644 (file)
--- a/src/basic/bitmap.c
+++ b/src/basic/bitmap.c
@@ -184,6 +184,9 @@ bool bitmap_iterate(Bitmap *b, Iterator *i, unsigned *n) {
 }
 
 bool bitmap_equal(Bitmap *a, Bitmap *b) {
+        size_t common_n_bitmaps;
+        Bitmap *c;
+        unsigned i;
 
         if (!a ^ !b)
                 return false;
@@ -191,8 +194,14 @@ bool bitmap_equal(Bitmap *a, Bitmap *b) {
         if (!a)
                 return true;
 
-        if (a->n_bitmaps != b->n_bitmaps)
+        common_n_bitmaps = MIN(a->n_bitmaps, b->n_bitmaps);
+        if (memcmp(a->bitmaps, b->bitmaps, sizeof(uint64_t) * common_n_bitmaps) != 0)
                 return false;
 
-        return memcmp(a->bitmaps, b->bitmaps, sizeof(uint64_t) * a->n_bitmaps) == 0;
+        c = a->n_bitmaps > b->n_bitmaps ? a : b;
+        for (i = common_n_bitmaps; i < c->n_bitmaps; i++)
+                if (c->bitmaps[i] != 0)
+                        return false;
+
+        return true;
 }

diff --git a/src/test/test-bitmap.c b/src/test/test-bitmap.c
index 96deeded7e500663d9dd166d5f8539ca6b3ce4e4..cb9e4a41f6e2c6aab197477998a9072f2cedf531 100644 (file)
--- a/src/test/test-bitmap.c
+++ b/src/test/test-bitmap.c
@@ -20,7 +20,7 @@
 #include "bitmap.h"
 
 int main(int argc, const char *argv[]) {
-        _cleanup_bitmap_free_ Bitmap *b = NULL;
+        _cleanup_bitmap_free_ Bitmap *b = NULL, *b2 = NULL;
         Iterator it;
         unsigned n = (unsigned) -1, i = 0;
 
@@ -101,5 +101,15 @@ int main(int argc, const char *argv[]) {
 
         assert_se(bitmap_set(b, (unsigned) -1) == -ERANGE);
 
+        bitmap_free(b);
+        b = NULL;
+        assert_se(bitmap_ensure_allocated(&b) == 0);
+        assert_se(bitmap_ensure_allocated(&b2) == 0);
+
+        assert_se(bitmap_equal(b, b2));
+        assert_se(bitmap_set(b, 0) == 0);
+        bitmap_unset(b, 0);
+        assert_se(bitmap_equal(b, b2));
+
         return 0;
 }