From 3b703fe269a4a34f1b5ad1c3ce219c8c407e6fe1 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Wed, 17 Aug 2022 06:43:37 +0900
Subject: [PATCH] path-util: introduce path_glob_can_match()

---
 src/basic/path-util.c     | 62 +++++++++++++++++++++++++++++++++++++++
 src/basic/path-util.h     |  2 ++
 src/test/test-path-util.c | 38 ++++++++++++++++++++++++
 3 files changed, 102 insertions(+)

diff --git a/src/basic/path-util.c b/src/basic/path-util.c
index e40ab3f5b6f..88657d57750 100644
--- a/src/basic/path-util.c
+++ b/src/basic/path-util.c
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
 #include <errno.h>
+#include <fnmatch.h>
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -17,6 +18,7 @@
 #include "extract-word.h"
 #include "fd-util.h"
 #include "fs-util.h"
+#include "glob-util.h"
 #include "log.h"
 #include "macro.h"
 #include "path-util.h"
@@ -1310,3 +1312,63 @@ bool prefixed_path_strv_contains(char **l, const char *path) {
 
         return false;
 }
+
+int path_glob_can_match(const char *pattern, const char *prefix, char **ret) {
+        assert(pattern);
+        assert(prefix);
+
+        for (const char *a = pattern, *b = prefix;;) {
+                _cleanup_free_ char *g = NULL, *h = NULL;
+                const char *p, *q;
+                int r, s;
+
+                r = path_find_first_component(&a, /* accept_dot_dot = */ false, &p);
+                if (r < 0)
+                        return r;
+
+                s = path_find_first_component(&b, /* accept_dot_dot = */ false, &q);
+                if (s < 0)
+                        return s;
+
+                if (s == 0) {
+                        /* The pattern matches the prefix. */
+                        if (ret) {
+                                char *t;
+
+                                t = path_join(prefix, p);
+                                if (!t)
+                                        return -ENOMEM;
+
+                                *ret = t;
+                        }
+                        return true;
+                }
+
+                if (r == 0)
+                        break;
+
+                if (r == s && strneq(p, q, r))
+                        continue; /* common component. Check next. */
+
+                g = strndup(p, r);
+                if (!g)
+                        return -ENOMEM;
+
+                if (!string_is_glob(g))
+                        break;
+
+                /* We found a glob component. Check if the glob pattern matches the prefix component. */
+
+                h = strndup(q, s);
+                if (!h)
+                        return -ENOMEM;
+
+                if (fnmatch(g, h, 0) != 0)
+                        break;
+        }
+
+        /* The pattern does not match the prefix. */
+        if (ret)
+                *ret = NULL;
+        return false;
+}
diff --git a/src/basic/path-util.h b/src/basic/path-util.h
index bb200872216..757ed722d51 100644
--- a/src/basic/path-util.h
+++ b/src/basic/path-util.h
@@ -196,3 +196,5 @@ static inline const char *empty_to_root(const char *path) {
 
 bool path_strv_contains(char **l, const char *path);
 bool prefixed_path_strv_contains(char **l, const char *path);
+
+int path_glob_can_match(const char *pattern, const char *prefix, char **ret);
diff --git a/src/test/test-path-util.c b/src/test/test-path-util.c
index 4c56a7d5200..e0583cfbaba 100644
--- a/src/test/test-path-util.c
+++ b/src/test/test-path-util.c
@@ -1027,6 +1027,44 @@ TEST(path_startswith_strv) {
         assert_se(streq_ptr(path_startswith_strv("/foo2/bar", STRV_MAKE("/foo/quux", "", "/zzz")), NULL));
 }
 
+static void test_path_glob_can_match_one(const char *pattern, const char *prefix, const char *expected) {
+        _cleanup_free_ char *result = NULL;
+
+        log_debug("%s(%s, %s, %s)", __func__, pattern, prefix, strnull(expected));
+
+        assert_se(path_glob_can_match(pattern, prefix, &result) == !!expected);
+        assert_se(streq_ptr(result, expected));
+}
+
+TEST(path_glob_can_match) {
+        test_path_glob_can_match_one("/foo/hoge/aaa", "/foo/hoge/aaa/bbb", NULL);
+        test_path_glob_can_match_one("/foo/hoge/aaa", "/foo/hoge/aaa", "/foo/hoge/aaa");
+        test_path_glob_can_match_one("/foo/hoge/aaa", "/foo/hoge", "/foo/hoge/aaa");
+        test_path_glob_can_match_one("/foo/hoge/aaa", "/foo", "/foo/hoge/aaa");
+        test_path_glob_can_match_one("/foo/hoge/aaa", "/", "/foo/hoge/aaa");
+
+        test_path_glob_can_match_one("/foo/*/aaa", "/foo/hoge/aaa/bbb", NULL);
+        test_path_glob_can_match_one("/foo/*/aaa", "/foo/hoge/aaa", "/foo/hoge/aaa");
+        test_path_glob_can_match_one("/foo/*/aaa", "/foo/hoge", "/foo/hoge/aaa");
+        test_path_glob_can_match_one("/foo/*/aaa", "/foo", "/foo/*/aaa");
+        test_path_glob_can_match_one("/foo/*/aaa", "/", "/foo/*/aaa");
+
+        test_path_glob_can_match_one("/foo/*/*/aaa", "/foo/xxx/yyy/aaa/bbb", NULL);
+        test_path_glob_can_match_one("/foo/*/*/aaa", "/foo/xxx/yyy/aaa", "/foo/xxx/yyy/aaa");
+        test_path_glob_can_match_one("/foo/*/*/aaa", "/foo/xxx/yyy", "/foo/xxx/yyy/aaa");
+        test_path_glob_can_match_one("/foo/*/*/aaa", "/foo/xxx", "/foo/xxx/*/aaa");
+        test_path_glob_can_match_one("/foo/*/*/aaa", "/foo", "/foo/*/*/aaa");
+        test_path_glob_can_match_one("/foo/*/*/aaa", "/", "/foo/*/*/aaa");
+
+        test_path_glob_can_match_one("/foo/*/aaa/*", "/foo/xxx/aaa/bbb/ccc", NULL);
+        test_path_glob_can_match_one("/foo/*/aaa/*", "/foo/xxx/aaa/bbb", "/foo/xxx/aaa/bbb");
+        test_path_glob_can_match_one("/foo/*/aaa/*", "/foo/xxx/ccc", NULL);
+        test_path_glob_can_match_one("/foo/*/aaa/*", "/foo/xxx/aaa", "/foo/xxx/aaa/*");
+        test_path_glob_can_match_one("/foo/*/aaa/*", "/foo/xxx", "/foo/xxx/aaa/*");
+        test_path_glob_can_match_one("/foo/*/aaa/*", "/foo", "/foo/*/aaa/*");
+        test_path_glob_can_match_one("/foo/*/aaa/*", "/", "/foo/*/aaa/*");
+}
+
 TEST(print_MAX) {
         log_info("PATH_MAX=%zu\n"
                  "FILENAME_MAX=%zu\n"