hash-func: add generic hash_ops implementation for hashing paths

This is similar to string_hash_ops but operates one file system paths
specifically. It will ensure that "/foo//bar" and "///foo/bar" are
considered to be the same path for hashmap purposes.

This makes use of the existing path_compare() API, and adds a matching
hashing function for it.

Note that relative and absolute paths will hash to different values,
however whether the path is suffixed with a slash or not is not
detected. This matches the existing path_compare() behaviour, and
follows the logic that on Linux there can't be two different objects at
path /foo/bar and /foo/bar/ either.

2 files changed, 37 insertions, 3 deletions

diff --git a/src/basic/hash-funcs.h b/src/basic/hash-funcs.h
index c31ef0cc3..945b4c251 100644
--- a/src/basic/hash-funcs.h
+++ b/src/basic/hash-funcs.h
@@ -36,9 +36,12 @@ void string_hash_func(const void *p, struct siphash *state);
 int string_compare_func(const void *a, const void *b) _pure_;
 extern const struct hash_ops string_hash_ops;
 
-/* This will compare the passed pointers directly, and will not
- * dereference them. This is hence not useful for strings or
- * suchlike. */
+void path_hash_func(const void *p, struct siphash *state);
+int path_compare_func(const void *a, const void *b) _pure_;
+extern const struct hash_ops path_hash_ops;
+
+/* This will compare the passed pointers directly, and will not dereference them. This is hence not useful for strings
+ * or suchlike. */
 void trivial_hash_func(const void *p, struct siphash *state);
 int trivial_compare_func(const void *a, const void *b) _const_;
 extern const struct hash_ops trivial_hash_ops;
diff --git a/src/test/test-hashmap.c b/src/test/test-hashmap.c
index 16ca27cd5..ad0b7390e 100644
--- a/src/test/test-hashmap.c
+++ b/src/test/test-hashmap.c
@@ -137,6 +137,34 @@ static void test_iterated_cache(void) {
         assert_se(iterated_cache_free(c) == NULL);
 }
 
+static void test_path_hashmap(void) {
+        _cleanup_(hashmap_freep) Hashmap *h = NULL;
+
+        assert_se(h = hashmap_new(&path_hash_ops));
+
+        assert_se(hashmap_put(h, "foo", INT_TO_PTR(1)) >= 0);
+        assert_se(hashmap_put(h, "/foo", INT_TO_PTR(2)) >= 0);
+        assert_se(hashmap_put(h, "//foo", INT_TO_PTR(3)) == -EEXIST);
+        assert_se(hashmap_put(h, "//foox/", INT_TO_PTR(4)) >= 0);
+        assert_se(hashmap_put(h, "/foox////", INT_TO_PTR(5)) == -EEXIST);
+        assert_se(hashmap_put(h, "foo//////bar/quux//", INT_TO_PTR(6)) >= 0);
+        assert_se(hashmap_put(h, "foo/bar//quux/", INT_TO_PTR(8)) == -EEXIST);
+
+        assert_se(hashmap_get(h, "foo") == INT_TO_PTR(1));
+        assert_se(hashmap_get(h, "foo/") == INT_TO_PTR(1));
+        assert_se(hashmap_get(h, "foo////") == INT_TO_PTR(1));
+        assert_se(hashmap_get(h, "/foo") == INT_TO_PTR(2));
+        assert_se(hashmap_get(h, "//foo") == INT_TO_PTR(2));
+        assert_se(hashmap_get(h, "/////foo////") == INT_TO_PTR(2));
+        assert_se(hashmap_get(h, "/////foox////") == INT_TO_PTR(4));
+        assert_se(hashmap_get(h, "/foox/") == INT_TO_PTR(4));
+        assert_se(hashmap_get(h, "/foox") == INT_TO_PTR(4));
+        assert_se(!hashmap_get(h, "foox"));
+        assert_se(hashmap_get(h, "foo/bar/quux") == INT_TO_PTR(6));
+        assert_se(hashmap_get(h, "foo////bar////quux/////") == INT_TO_PTR(6));
+        assert_se(!hashmap_get(h, "/foo////bar////quux/////"));
+}
+
 int main(int argc, const char *argv[]) {
         test_hashmap_funcs();
         test_ordered_hashmap_funcs();
@@ -147,4 +175,7 @@ int main(int argc, const char *argv[]) {
         test_trivial_compare_func();
         test_string_compare_func();
         test_iterated_cache();
+        test_path_hashmap();
+
+        return 0;
 }