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authorTanu Kaskinen <tanu.kaskinen@linux.intel.com>2014-05-03 11:52:12 +0300
committerLennart Poettering <lennart@poettering.net>2014-05-16 18:47:34 +0200
commit7cb9c51ce81818c200f27de4db4a4076cbe4265b (patch)
treee7f350750c6cda8e02ae585629214d150afaf39c
parentf1f0198cb61a3398557cc9ec596e1e90ac731ed3 (diff)
path-util: add path_make_relative()
In user_dirs() in path-lookup.c, I want to replace this: symlink("../../../.config/systemd/user", data_home); with symlink(config_home, data_home); to avoid hardcoding .config when XDG_CONFIG_HOME is set. The problem is that config_home is an absolute path, and it's better to make the symlink relative. path_make_relative() is an utility function that converts an absolute path into a relative one.
-rw-r--r--src/shared/path-util.c90
-rw-r--r--src/shared/path-util.h1
2 files changed, 91 insertions, 0 deletions
diff --git a/src/shared/path-util.c b/src/shared/path-util.c
index 8bf9a3cf96..2f38c1096b 100644
--- a/src/shared/path-util.c
+++ b/src/shared/path-util.c
@@ -132,6 +132,96 @@ 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;
+ size_t to_path_len;
+
+ 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;
+
+ *_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++;
+ }
+
+ to_path_len = strlen(to_path);
+
+ r = malloc(n_parents * 3 + to_path_len);
+ if (!r)
+ return -ENOMEM;
+
+ for (p = r; n_parents > 0; n_parents--, p += 3)
+ memcpy(p, "../", 3);
+
+ if (to_path_len > 0)
+ memcpy(p, to_path, to_path_len);
+ else
+ /* "to_path" is a parent directory of "from_dir". Let's remove
+ * the redundant slash from the end of the result. */
+ *(p - 1) = 0;
+
+ *_r = r;
+ return 0;
+}
+
char **path_strv_make_absolute_cwd(char **l) {
char **s;
diff --git a/src/shared/path-util.h b/src/shared/path-util.h
index fdf1f6b000..6882d7866b 100644
--- a/src/shared/path-util.h
+++ b/src/shared/path-util.h
@@ -41,6 +41,7 @@ int path_get_parent(const char *path, char **parent);
bool path_is_absolute(const char *p) _pure_;
char* path_make_absolute(const char *p, const char *prefix);
char* path_make_absolute_cwd(const char *p);
+int path_make_relative(const char *from_dir, const char *to_path, char **_r);
char* path_kill_slashes(char *path);
char* path_startswith(const char *path, const char *prefix) _pure_;
bool path_equal(const char *a, const char *b) _pure_;