util: add a helper to find substrings in a strv

Returns true and optionally the first index of any string in strv that
contains the given substring.

Part-of: <https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/1204>

src/util-strings.c

@@ -311,6 +311,27 @@ strv_find(char **strv, const char *needle, size_t *index_out)
 	return false;
 }
 
+bool
+strv_find_substring(char **strv, const char *needle, size_t *index_out)
+{
+	if (!strv || !needle)
+		return false;
+
+	size_t index = 0;
+	char **s = strv;
+	while (*s != NULL) {
+		if (strstr(*s, needle)) {
+			if (index_out)
+				*index_out = index;
+			return true;
+		}
+		s++;
+		index++;
+	}
+
+	return false;
+}
+
 /**
  * Return a pointer to the basename within filename.
  * If the filename the empty string or a directory (i.e. the last char of

src/util-strings.h

@@ -299,6 +299,7 @@ __attribute__ ((format (printf, 2, 0)))
 char **strv_append_vprintf(char **strv, const char *fmt, va_list args);
 
 bool strv_find(char **strv, const char *needle, size_t *index_out);
+bool strv_find_substring(char **strv, const char *needle, size_t *index_out);
 
 typedef int (*strv_foreach_callback_t)(const char *str, size_t index, void *data);
 int strv_for_each(const char **strv, strv_foreach_callback_t func, void *data);

test/test-utils.c

@@ -1328,6 +1328,50 @@ START_TEST(strv_find_test)
 }
 END_TEST
 
+START_TEST(strv_find_substring_test)
+{
+	char *strv[] = {"a", "bc", "cccc", NULL};
+
+	bool rc;
+	size_t index;
+
+	rc = strv_find_substring(strv, "a", &index);
+	litest_assert(rc);
+	litest_assert_int_eq(index, 0U);
+
+	rc = strv_find_substring(strv, "b", &index);
+	litest_assert(rc);
+	litest_assert_int_eq(index, 1U);
+
+	rc = strv_find_substring(strv, "c", &index);
+	litest_assert(rc);
+	litest_assert_int_eq(index, 1U);
+
+	rc = strv_find_substring(strv, "a", NULL);
+	litest_assert(rc);
+
+	index = 0xffff;
+	rc = strv_find_substring(strv, "d", &index);
+	litest_assert(!rc);
+	litest_assert_int_eq(index, 0xffffU);
+
+	rc = strv_find_substring(strv, "d", NULL);
+	litest_assert(!rc);
+
+	rc = strv_find_substring(NULL, "a", &index);
+	litest_assert(!rc);
+	litest_assert_int_eq(index, 0xffffU);
+
+	rc = strv_find_substring(NULL, NULL, &index);
+	litest_assert(!rc);
+	litest_assert_int_eq(index, 0xffffU);
+
+	rc = strv_find_substring(strv, NULL, &index);
+	litest_assert(!rc);
+	litest_assert_int_eq(index, 0xffffU);
+}
+END_TEST
+
 START_TEST(double_array_from_string_test)
 {
 	struct double_array_from_string_test {
@@ -2297,6 +2341,7 @@ int main(void)
 	ADD_TEST(strv_for_each_test);
 	ADD_TEST(strv_append_test);
 	ADD_TEST(strv_find_test);
+	ADD_TEST(strv_find_substring_test);
 	ADD_TEST(double_array_from_string_test);
 	ADD_TEST(strargv_test);
 	ADD_TEST(kvsplit_double_test);