libnm: add NMUtilsStrStrDictKey utility

When having a hash-of-hashes where each hash is indexed by a name,
(such as GKeyFile), you can either implement it as a hash-of-hashes
or define your own version of indexes that pack both levels of names
into one key.

This is an implementation of such a key. Use it as:

  GHashTable *hash = g_hash_table_new_full (_nm_utils_strstrdictkey_hash,
                                            _nm_utils_strstrdictkey_equal,
                                            g_free, _destroy_value);

and create keys via:

  NMUtilsStrStrDictKey *k = _nm_utils_strstrdictkey_create (s1, s2);

For lookup you can use static strings (note that the static string
might increase the size of the binary):

  g_hash_table_contains (hash, _nm_utils_strstrdictkey_static ("outer", "inner"))

libnm-core/nm-core-internal.h

@@ -202,4 +202,14 @@ int         _nm_utils_dns_option_find_idx (GPtrArray *array, const char *option)
 
 /***********************************************************/
 
+typedef struct _NMUtilsStrStrDictKey NMUtilsStrStrDictKey;
+guint                 _nm_utils_strstrdictkey_hash   (gconstpointer a);
+gboolean              _nm_utils_strstrdictkey_equal  (gconstpointer a, gconstpointer b);
+NMUtilsStrStrDictKey *_nm_utils_strstrdictkey_create (const char *v1, const char *v2);
+
+#define _nm_utils_strstrdictkey_static(v1, v2) \
+    ( (NMUtilsStrStrDictKey *) ("\03" v1 "\0" v2 "") )
+
+/***********************************************************/
+
 #endif

libnm-core/nm-utils.c

@@ -3488,6 +3488,105 @@ nm_utils_bond_mode_string_to_int (const char *mode)
 
 /**********************************************************************************************/
 
+#define STRSTRDICTKEY_V1_SET  0x01
+#define STRSTRDICTKEY_V2_SET  0x02
+#define STRSTRDICTKEY_ALL_SET 0x03
+
+struct _NMUtilsStrStrDictKey {
+	char type;
+	char data[1];
+};
+
+guint
+_nm_utils_strstrdictkey_hash (gconstpointer a)
+{
+	const NMUtilsStrStrDictKey *k = a;
+	const signed char *p;
+	guint32 h = 5381;
+
+	if (k) {
+		if (((int) k->type) & ~STRSTRDICTKEY_ALL_SET)
+			g_return_val_if_reached (0);
+
+		h = (h << 5) + h + k->type;
+		if (k->type & STRSTRDICTKEY_ALL_SET) {
+			p = (void *) k->data;
+			for (; *p != '\0'; p++)
+				h = (h << 5) + h + *p;
+			if (k->type == STRSTRDICTKEY_ALL_SET) {
+				/* the key contains two strings. Continue... */
+				h = (h << 5) + h + '\0';
+				for (p++; *p != '\0'; p++)
+					h = (h << 5) + h + *p;
+			}
+		}
+	}
+
+	return h;
+}
+
+gboolean
+_nm_utils_strstrdictkey_equal  (gconstpointer a, gconstpointer b)
+{
+	const NMUtilsStrStrDictKey *k1 = a;
+	const NMUtilsStrStrDictKey *k2 = b;
+
+	if (k1 == k2)
+		return TRUE;
+	if (!k1 || !k2)
+		return FALSE;
+
+	if (k1->type != k2->type)
+		return FALSE;
+
+	if (k1->type & STRSTRDICTKEY_ALL_SET) {
+		if (strcmp (k1->data, k2->data) != 0)
+			return FALSE;
+
+		if (k1->type == STRSTRDICTKEY_ALL_SET) {
+			gsize l = strlen (k1->data) + 1;
+
+			return strcmp (&k1->data[l], &k2->data[l]) == 0;
+		}
+	}
+
+	return TRUE;
+}
+
+NMUtilsStrStrDictKey *
+_nm_utils_strstrdictkey_create (const char *v1, const char *v2)
+{
+	char type = 0;
+	gsize l1 = 0, l2 = 0;
+	NMUtilsStrStrDictKey *k;
+
+	if (!v1 && !v2)
+		return g_malloc0 (1);
+
+	/* we need to distinguish between ("",NULL) and (NULL,"").
+	 * Thus, in @type we encode which strings we have present
+	 * as not-NULL. */
+	if (v1) {
+		type |= STRSTRDICTKEY_V1_SET;
+		l1 = strlen (v1) + 1;
+	}
+	if (v2) {
+		type |= STRSTRDICTKEY_V2_SET;
+		l2 = strlen (v2) + 1;
+	}
+
+	k = g_malloc (G_STRUCT_OFFSET (NMUtilsStrStrDictKey, data) + l1 + l2);
+	k->type = type;
+	if (v1)
+		memcpy (&k->data[0], v1, l1);
+	if (v2)
+		memcpy (&k->data[l1], v2, l2);
+
+	return k;
+}
+
+/**********************************************************************************************/
+
 /* _nm_utils_ascii_str_to_int64:
  *
  * A wrapper for g_ascii_strtoll, that checks whether the whole string

libnm-core/tests/test-general.c

@@ -4281,6 +4281,54 @@ test_nm_utils_ascii_str_to_int64 (void)
 
 /******************************************************************************/
 
+static void
+test_nm_utils_strstrdictkey ()
+{
+#define _VALUES_STATIC(_v1, _v2) { .v1 = _v1, .v2 = _v2, .v_static = _nm_utils_strstrdictkey_static (_v1, _v2), }
+	const struct {
+		const char *v1;
+		const char *v2;
+		NMUtilsStrStrDictKey *v_static;
+	} *val1, *val2, values[] = {
+		{ NULL, NULL },
+		{ "", NULL },
+		{ NULL, "" },
+		{ "a", NULL },
+		{ NULL, "a" },
+		_VALUES_STATIC ("", ""),
+		_VALUES_STATIC ("a", ""),
+		_VALUES_STATIC ("", "a"),
+		_VALUES_STATIC ("a", "b"),
+	};
+	guint i, j;
+
+	for (i = 0; i < G_N_ELEMENTS (values); i++) {
+		gs_free NMUtilsStrStrDictKey *key1 = NULL;
+
+		val1 = &values[i];
+
+		key1 = _nm_utils_strstrdictkey_create (val1->v1, val1->v2);
+		if (val1->v_static) {
+			g_assert (_nm_utils_strstrdictkey_equal (key1, val1->v_static));
+			g_assert (_nm_utils_strstrdictkey_equal (val1->v_static, key1));
+			g_assert_cmpint (_nm_utils_strstrdictkey_hash (key1), ==, _nm_utils_strstrdictkey_hash (val1->v_static));
+		}
+
+		for (j = 0; j < G_N_ELEMENTS (values); j++) {
+			gs_free NMUtilsStrStrDictKey *key2 = NULL;
+
+			val2 = &values[j];
+			key2 = _nm_utils_strstrdictkey_create (val2->v1, val2->v2);
+			if (i != j) {
+				g_assert (!_nm_utils_strstrdictkey_equal (key1, key2));
+				g_assert (!_nm_utils_strstrdictkey_equal (key2, key1));
+			}
+		}
+	}
+}
+
+/******************************************************************************/
+
 static void
 test_nm_utils_dns_option_validate_do (char *option, gboolean ipv6, const NMUtilsDNSOptionDesc *descs,
                                       gboolean exp_result, char *exp_name, gboolean exp_value)
@@ -4764,6 +4812,7 @@ int main (int argc, char **argv)
 	g_test_add_func ("/core/general/nm_utils_is_power_of_two", test_nm_utils_is_power_of_two);
 	g_test_add_func ("/core/general/_glib_compat_g_ptr_array_insert", test_g_ptr_array_insert);
 	g_test_add_func ("/core/general/_nm_utils_ptrarray_find_binary_search", test_nm_utils_ptrarray_find_binary_search);
+	g_test_add_func ("/core/general/_nm_utils_strstrdictkey", test_nm_utils_strstrdictkey);
 
 	g_test_add_func ("/core/general/_nm_utils_dns_option_validate", test_nm_utils_dns_option_validate);
 	g_test_add_func ("/core/general/_nm_utils_dns_option_find_idx", test_nm_utils_dns_option_find_idx);