X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=src%2Fshared%2Fpath-util.c;h=d193494afb266b94d771d2fc44128c45c47f7e4d;hb=7d8da2c9641c584ff977493eeb8148300dce8759;hp=8bf9a3cf96c1cc809c01b192df6ed7cfd426a044;hpb=12ed81d9c88406234c20e9261ae8c8b992d8bc4d;p=elogind.git

diff --git a/src/shared/path-util.c b/src/shared/path-util.c
index 8bf9a3cf9..d193494af 100644
--- a/src/shared/path-util.c
+++ b/src/shared/path-util.c
@@ -132,6 +132,91 @@ char *path_make_absolute_cwd(const char *p) {
         return path_make_absolute(p, cwd);
 }
 
+int path_make_relative(const char *from_dir, const char *to_path, char **_r) {
+        char *r, *p;
+        unsigned n_parents;
+
+        assert(from_dir);
+        assert(to_path);
+        assert(_r);
+
+        /* Strips the common part, and adds ".." elements as necessary. */
+
+        if (!path_is_absolute(from_dir))
+                return -EINVAL;
+
+        if (!path_is_absolute(to_path))
+                return -EINVAL;
+
+        /* Skip the common part. */
+        for (;;) {
+                size_t a;
+                size_t b;
+
+                from_dir += strspn(from_dir, "/");
+                to_path += strspn(to_path, "/");
+
+                if (!*from_dir) {
+                        if (!*to_path)
+                                /* from_dir equals to_path. */
+                                r = strdup(".");
+                        else
+                                /* from_dir is a parent directory of to_path. */
+                                r = strdup(to_path);
+
+                        if (!r)
+                                return -ENOMEM;
+
+                        path_kill_slashes(r);
+
+                        *_r = r;
+                        return 0;
+                }
+
+                if (!*to_path)
+                        break;
+
+                a = strcspn(from_dir, "/");
+                b = strcspn(to_path, "/");
+
+                if (a != b)
+                        break;
+
+                if (memcmp(from_dir, to_path, a) != 0)
+                        break;
+
+                from_dir += a;
+                to_path += b;
+        }
+
+        /* If we're here, then "from_dir" has one or more elements that need to
+         * be replaced with "..". */
+
+        /* Count the number of necessary ".." elements. */
+        for (n_parents = 0;;) {
+                from_dir += strspn(from_dir, "/");
+
+                if (!*from_dir)
+                        break;
+
+                from_dir += strcspn(from_dir, "/");
+                n_parents++;
+        }
+
+        r = malloc(n_parents * 3 + strlen(to_path) + 1);
+        if (!r)
+                return -ENOMEM;
+
+        for (p = r; n_parents > 0; n_parents--, p += 3)
+                memcpy(p, "../", 3);
+
+        strcpy(p, to_path);
+        path_kill_slashes(r);
+
+        *_r = r;
+        return 0;
+}
+
 char **path_strv_make_absolute_cwd(char **l) {
         char **s;
 
@@ -153,7 +238,7 @@ char **path_strv_make_absolute_cwd(char **l) {
         return l;
 }
 
-char **path_strv_canonicalize_absolute(char **l, const char *prefix) {
+char **path_strv_resolve(char **l, const char *prefix) {
         char **s;
         unsigned k = 0;
         bool enomem = false;
@@ -238,12 +323,12 @@ char **path_strv_canonicalize_absolute(char **l, const char *prefix) {
         return l;
 }
 
-char **path_strv_canonicalize_absolute_uniq(char **l, const char *prefix) {
+char **path_strv_resolve_uniq(char **l, const char *prefix) {
 
         if (strv_isempty(l))
                 return l;
 
-        if (!path_strv_canonicalize_absolute(l, prefix))
+        if (!path_strv_resolve(l, prefix))
                 return NULL;
 
         return strv_uniq(l);
@@ -441,12 +526,18 @@ int path_is_os_tree(const char *path) {
         char *p;
         int r;
 
-        /* We use /etc/os-release as flag file if something is an OS */
+        /* We use /usr/lib/os-release as flag file if something is an OS */
+        p = strappenda(path, "/usr/lib/os-release");
+        r = access(p, F_OK);
+
+        if (r >= 0)
+                return 1;
 
+        /* Also check for the old location in /etc, just in case. */
         p = strappenda(path, "/etc/os-release");
         r = access(p, F_OK);
 
-        return r < 0 ? 0 : 1;
+        return r >= 0;
 }
 
 int find_binary(const char *name, char **filename) {