From dd92ba8a7a69016116e14d309829efff1e3c3d34 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 13 Mar 2024 23:17:11 +0100
Subject: [PATCH] path-util: add helper that checks if a path definitely refers
 to a dir

---
 src/basic/path-util.c     | 14 ++++++++++++++
 src/basic/path-util.h     |  2 ++
 src/test/test-path-util.c | 24 ++++++++++++++++++++++++
 3 files changed, 40 insertions(+)

diff --git a/src/basic/path-util.c b/src/basic/path-util.c
index 6810bf66aa..05a21f8f8e 100644
--- a/src/basic/path-util.c
+++ b/src/basic/path-util.c
@@ -1336,6 +1336,20 @@ bool dot_or_dot_dot(const char *path) {
         return path[2] == 0;
 }
 
+bool path_implies_directory(const char *path) {
+
+        /* Sometimes, if we look at a path we already know it must refer to a directory, because it is
+         * suffixed with a slash, or its last component is "." or ".." */
+
+        if (!path)
+                return false;
+
+        if (dot_or_dot_dot(path))
+                return true;
+
+        return ENDSWITH_SET(path, "/", "/.", "/..");
+}
+
 bool empty_or_root(const char *path) {
 
         /* For operations relative to some root directory, returns true if the specified root directory is
diff --git a/src/basic/path-util.h b/src/basic/path-util.h
index 39b6714525..052bbd7031 100644
--- a/src/basic/path-util.h
+++ b/src/basic/path-util.h
@@ -201,6 +201,8 @@ bool valid_device_allow_pattern(const char *path);
 
 bool dot_or_dot_dot(const char *path);
 
+bool path_implies_directory(const char *path);
+
 static inline const char *skip_dev_prefix(const char *p) {
         const char *e;
 
diff --git a/src/test/test-path-util.c b/src/test/test-path-util.c
index f5a425689a..ca11bf3a29 100644
--- a/src/test/test-path-util.c
+++ b/src/test/test-path-util.c
@@ -1305,4 +1305,28 @@ TEST(print_MAX) {
         assert_cc(FILENAME_MAX == PATH_MAX);
 }
 
+TEST(path_implies_directory) {
+        assert_se(!path_implies_directory(NULL));
+        assert_se(!path_implies_directory(""));
+        assert_se(path_implies_directory("/"));
+        assert_se(path_implies_directory("////"));
+        assert_se(path_implies_directory("////.///"));
+        assert_se(path_implies_directory("////./"));
+        assert_se(path_implies_directory("////."));
+        assert_se(path_implies_directory("."));
+        assert_se(path_implies_directory("./"));
+        assert_se(path_implies_directory("/."));
+        assert_se(path_implies_directory(".."));
+        assert_se(path_implies_directory("../"));
+        assert_se(path_implies_directory("/.."));
+        assert_se(!path_implies_directory("a"));
+        assert_se(!path_implies_directory("ab"));
+        assert_se(path_implies_directory("ab/"));
+        assert_se(!path_implies_directory("ab/a"));
+        assert_se(path_implies_directory("ab/a/"));
+        assert_se(path_implies_directory("ab/a/.."));
+        assert_se(path_implies_directory("ab/a/."));
+        assert_se(path_implies_directory("ab/a//"));
+}
+
 DEFINE_TEST_MAIN(LOG_DEBUG);
-- 
2.25.1