shared: add path_compare(), an ordering path comparison

... and make path_equal() a simple wrapper around it.

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>

2 files changed, 28 insertions, 10 deletions

diff --git a/src/shared/path-util.c b/src/shared/path-util.c
index 92e3a8777e..26703836ad 100644
--- a/src/shared/path-util.c
+++ b/src/shared/path-util.c
@@ -280,12 +280,18 @@ char* path_startswith(const char *path, const char *prefix) {
         }
 }
 
-bool path_equal(const char *a, const char *b) {
+int path_compare(const char *a, const char *b) {
+        int d;
+
         assert(a);
         assert(b);
 
-        if ((a[0] == '/') != (b[0] == '/'))
-                return false;
+        /* A relative path and an abolute path must not compare as equal.
+         * Which one is sorted before the other does not really matter.
+         * Here a relative path is ordered before an absolute path. */
+        d = (a[0] == '/') - (b[0] == '/');
+        if (d)
+                return d;
 
         for (;;) {
                 size_t j, k;
@@ -294,25 +300,36 @@ bool path_equal(const char *a, const char *b) {
                 b += strspn(b, "/");
 
                 if (*a == 0 && *b == 0)
-                        return true;
+                        return 0;
 
-                if (*a == 0 || *b == 0)
-                        return false;
+                /* Order prefixes first: "/foo" before "/foo/bar" */
+                if (*a == 0)
+                        return -1;
+                if (*b == 0)
+                        return 1;
 
                 j = strcspn(a, "/");
                 k = strcspn(b, "/");
 
-                if (j != k)
-                        return false;
+                /* Alphabetical sort: "/foo/aaa" before "/foo/b" */
+                d = memcmp(a, b, MIN(j, k));
+                if (d)
+                        return (d > 0) - (d < 0); /* sign of d */
 
-                if (memcmp(a, b, j) != 0)
-                        return false;
+                /* Sort "/foo/a" before "/foo/aaa" */
+                d = (j > k) - (j < k);  /* sign of (j - k) */
+                if (d)
+                        return d;
 
                 a += j;
                 b += k;
         }
 }
 
+bool path_equal(const char *a, const char *b) {
+        return path_compare(a, b) == 0;
+}
+
 int path_is_mount_point(const char *t, bool allow_symlink) {
 
         union file_handle_union h = FILE_HANDLE_INIT;
diff --git a/src/shared/path-util.h b/src/shared/path-util.h
index e0cab15a3e..f5f5c36664 100644
--- a/src/shared/path-util.h
+++ b/src/shared/path-util.h
@@ -28,6 +28,7 @@ char* path_make_absolute(const char *p, const char *prefix);
 char* path_make_absolute_cwd(const char *p);
 char* path_kill_slashes(char *path);
 char* path_startswith(const char *path, const char *prefix) _pure_;
+int path_compare(const char *a, const char *b) _pure_;
 bool path_equal(const char *a, const char *b) _pure_;
 
 char** path_strv_resolve(char **l, const char *prefix);