basic: add set_equal() helper

3 files changed, 107 insertions, 0 deletions

diff --git a/src/basic/hashmap.c b/src/basic/hashmap.c
index c118289b99..e354c67adc 100644
--- a/src/basic/hashmap.c
+++ b/src/basic/hashmap.c
@@ -2036,3 +2036,35 @@ int set_strjoin(Set *s, const char *separator, bool wrap_with_separator, char **
         *ret = TAKE_PTR(str);
         return 0;
 }
+
+bool set_equal(Set *a, Set *b) {
+        void *p;
+
+        /* Checks whether each entry of 'a' is also in 'b' and vice versa, i.e. the two sets contain the same
+         * entries */
+
+        if (a == b)
+                return true;
+
+        if (set_isempty(a) && set_isempty(b))
+                return true;
+
+        if (set_size(a) != set_size(b)) /* Cheap check that hopefully catches a lot of inequality cases
+                                         * already */
+                return false;
+
+        SET_FOREACH(p, a)
+                if (!set_contains(b, p))
+                        return false;
+
+        /* If we have the same hashops, then we don't need to check things backwards given we compared the
+         * size and that all of a is in b. */
+        if (a->b.hash_ops == b->b.hash_ops)
+                return true;
+
+        SET_FOREACH(p, b)
+                if (!set_contains(a, p))
+                        return false;
+
+        return true;
+}
diff --git a/src/basic/set.h b/src/basic/set.h
index 57ff713039..52b6f4984c 100644
--- a/src/basic/set.h
+++ b/src/basic/set.h
@@ -152,3 +152,5 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(Set*, set_free_free);
 #define _cleanup_set_free_free_ _cleanup_(set_free_freep)
 
 int set_strjoin(Set *s, const char *separator, bool wrap_with_separator, char **ret);
+
+bool set_equal(Set *a, Set *b);
diff --git a/src/test/test-set.c b/src/test/test-set.c
index b4d07b2078..f89c968f21 100644
--- a/src/test/test-set.c
+++ b/src/test/test-set.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include "random-util.h"
 #include "set.h"
 #include "strv.h"
 
@@ -227,6 +228,77 @@ static void test_set_strjoin(void) {
         assert_se(STR_IN_SET(joined, "xxxaaaxxxbbbxxx", "xxxbbbxxxaaaxxx"));
 }
 
+static void test_set_equal(void) {
+        _cleanup_set_free_ Set *a = NULL, *b = NULL;
+        void *p;
+        int r;
+
+        assert_se(a = set_new(NULL));
+        assert_se(b = set_new(NULL));
+
+        assert_se(set_equal(a, a));
+        assert_se(set_equal(b, b));
+        assert_se(set_equal(a, b));
+        assert_se(set_equal(b, a));
+        assert_se(set_equal(NULL, a));
+        assert_se(set_equal(NULL, b));
+        assert_se(set_equal(a, NULL));
+        assert_se(set_equal(b, NULL));
+        assert_se(set_equal(NULL, NULL));
+
+        for (unsigned i = 0; i < 333; i++) {
+                p = INT32_TO_PTR(1 + (random_u32() & 0xFFFU));
+
+                r = set_put(a, p);
+                assert_se(r >= 0 || r == -EEXIST);
+        }
+
+        assert_se(set_put(a, INT32_TO_PTR(0x1000U)) >= 0);
+
+        assert_se(set_size(a) >= 2);
+        assert_se(set_size(a) <= 334);
+
+        assert_se(!set_equal(a, b));
+        assert_se(!set_equal(b, a));
+        assert_se(!set_equal(a, NULL));
+
+        SET_FOREACH(p, a)
+                assert_se(set_put(b, p) >= 0);
+
+        assert_se(set_equal(a, b));
+        assert_se(set_equal(b, a));
+
+        assert_se(set_remove(a, INT32_TO_PTR(0x1000U)) == INT32_TO_PTR(0x1000U));
+
+        assert_se(!set_equal(a, b));
+        assert_se(!set_equal(b, a));
+
+        assert_se(set_remove(b, INT32_TO_PTR(0x1000U)) == INT32_TO_PTR(0x1000U));
+
+        assert_se(set_equal(a, b));
+        assert_se(set_equal(b, a));
+
+        assert_se(set_put(b, INT32_TO_PTR(0x1001U)) >= 0);
+
+        assert_se(!set_equal(a, b));
+        assert_se(!set_equal(b, a));
+
+        assert_se(set_put(a, INT32_TO_PTR(0x1001U)) >= 0);
+
+        assert_se(set_equal(a, b));
+        assert_se(set_equal(b, a));
+
+        set_clear(a);
+
+        assert_se(!set_equal(a, b));
+        assert_se(!set_equal(b, a));
+
+        set_clear(b);
+
+        assert_se(set_equal(a, b));
+        assert_se(set_equal(b, a));
+}
+
 int main(int argc, const char *argv[]) {
         test_set_steal_first();
         test_set_free_with_destructor();
@@ -238,6 +310,7 @@ int main(int argc, const char *argv[]) {
         test_set_ensure_put();
         test_set_ensure_consume();
         test_set_strjoin();
+        test_set_equal();
 
         return 0;
 }