1 files changed, 51 insertions, 18 deletions

diff --git a/src/basic/hash-funcs.c b/src/basic/hash-funcs.c
index c3a4a011b..db48437be 100644
--- a/src/basic/hash-funcs.c
+++ b/src/basic/hash-funcs.c
@@ -1,24 +1,9 @@
-/***
-  This file is part of systemd.
+/* SPDX-License-Identifier: LGPL-2.1+ */
 
-  Copyright 2010 Lennart Poettering
-  Copyright 2014 Michal Schmidt
-
-  systemd is free software; you can redistribute it and/or modify it
-  under the terms of the GNU Lesser General Public License as published by
-  the Free Software Foundation; either version 2.1 of the License, or
-  (at your option) any later version.
-
-  systemd is distributed in the hope that it will be useful, but
-  WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-  Lesser General Public License for more details.
-
-  You should have received a copy of the GNU Lesser General Public License
-  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-***/
+#include <string.h>
 
 #include "hash-funcs.h"
+#include "path-util.h"
 
 void string_hash_func(const void *p, struct siphash *state) {
         siphash24_compress(p, strlen(p) + 1, state);
@@ -33,6 +18,54 @@ const struct hash_ops string_hash_ops = {
         .compare = string_compare_func
 };
 
+void path_hash_func(const void *p, struct siphash *state) {
+        const char *q = p;
+        size_t n;
+
+        assert(q);
+        assert(state);
+
+        /* Calculates a hash for a path in a way this duplicate inner slashes don't make a differences, and also
+         * whether there's a trailing slash or not. This fits well with the semantics of path_compare(), which does
+         * similar checks and also doesn't care for trailing slashes. Note that relative and absolute paths (i.e. those
+         * which begin in a slash or not) will hash differently though. */
+
+        n = strspn(q, "/");
+        if (n > 0) { /* Eat up initial slashes, and add one "/" to the hash for all of them */
+                siphash24_compress(q, 1, state);
+                q += n;
+        }
+
+        for (;;) {
+                /* Determine length of next component */
+                n = strcspn(q, "/");
+                if (n == 0) /* Reached the end? */
+                        break;
+
+                /* Add this component to the hash and skip over it */
+                siphash24_compress(q, n, state);
+                q += n;
+
+                /* How many slashes follow this component? */
+                n = strspn(q, "/");
+                if (q[n] == 0) /* Is this a trailing slash? If so, we are at the end, and don't care about the slashes anymore */
+                        break;
+
+                /* We are not add the end yet. Hash exactly one slash for all of the ones we just encountered. */
+                siphash24_compress(q, 1, state);
+                q += n;
+        }
+}
+
+int path_compare_func(const void *a, const void *b) {
+        return path_compare(a, b);
+}
+
+const struct hash_ops path_hash_ops = {
+        .hash = path_hash_func,
+        .compare = path_compare_func
+};
+
 void trivial_hash_func(const void *p, struct siphash *state) {
         siphash24_compress(&p, sizeof(p), state);
 }