string: provide strends()

Implement a function for checking if a string ends with a different
string and add its kunit test cases.

Acked-by: Linus Walleij <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bartosz Golaszewski <[e-mail]>

include/linux/string.h

···
 	return strncmp(str, prefix, strlen(prefix)) == 0;
 }
 
+/**
+ * strends - Check if a string ends with another string.
+ * @str - NULL-terminated string to check against @suffix
+ * @suffix - NULL-terminated string defining the suffix to look for in @str
+ *
+ * Returns:
+ * True if @str ends with @suffix. False in all other cases.
+ */
+static inline bool strends(const char *str, const char *suffix)
+{
+	unsigned int str_len = strlen(str), suffix_len = strlen(suffix);
+
+	if (str_len < suffix_len)
+		return false;
+
+	return !(strcmp(str + str_len - suffix_len, suffix));
+}
+
 #endif /* _LINUX_STRING_H_ */

lib/tests/string_kunit.c

···
 	KUNIT_EXPECT_EQ(test, dest[7], '\0');
 }
 
+static void string_test_strends(struct kunit *test)
+{
+	KUNIT_EXPECT_TRUE(test, strends("foo-bar", "bar"));
+	KUNIT_EXPECT_TRUE(test, strends("foo-bar", "-bar"));
+	KUNIT_EXPECT_TRUE(test, strends("foobar", "foobar"));
+	KUNIT_EXPECT_TRUE(test, strends("foobar", ""));
+	KUNIT_EXPECT_FALSE(test, strends("bar", "foobar"));
+	KUNIT_EXPECT_FALSE(test, strends("", "foo"));
+	KUNIT_EXPECT_FALSE(test, strends("foobar", "ba"));
+	KUNIT_EXPECT_TRUE(test, strends("", ""));
+}
+
 static struct kunit_case string_test_cases[] = {
 	KUNIT_CASE(string_test_memset16),
 	KUNIT_CASE(string_test_memset32),
···
 	KUNIT_CASE(string_test_strlcat),
 	KUNIT_CASE(string_test_strtomem),
 	KUNIT_CASE(string_test_memtostr),
+	KUNIT_CASE(string_test_strends),
 	{}
 };