Add file-name-split

3 files changed, 48 insertions, 0 deletions

diff --git a/compat-29.el b/compat-29.el
index 6ecf0fc..e7bdba5 100644
--- a/compat-29.el
+++ b/compat-29.el
@@ -483,6 +483,33 @@ The variable list SPEC is the same as in `if-let'."
 
 ;;;; Defined in files.el
 
+(compat-defun file-name-split (filename) ;; <OK>
+  "Return a list of all the components of FILENAME.
+On most systems, this will be true:
+
+  (equal (string-join (file-name-split filename) \"/\") filename)"
+  (let ((components nil))
+    ;; If this is a directory file name, then we have a null file name
+    ;; at the end.
+    (when (directory-name-p filename)
+      (push "" components)
+      (setq filename (directory-file-name filename)))
+    ;; Loop, chopping off components.
+    (while (length> filename 0)
+      (push (file-name-nondirectory filename) components)
+      (let ((dir (file-name-directory filename)))
+        (setq filename (and dir (directory-file-name dir)))
+        ;; If there's nothing left to peel off, we're at the root and
+        ;; we can stop.
+        (when (and dir (equal dir filename))
+          (push (if (equal dir "") ""
+                  ;; On Windows, the first component might be "c:" or
+                  ;; the like.
+                  (substring dir 0 -1))
+                components)
+          (setq filename nil))))
+    components))
+
 (compat-defun file-attribute-file-identifier (attributes) ;; <OK>
   "The inode and device numbers in ATTRIBUTES returned by `file-attributes'.
 The value is a list of the form (INODENUM DEVICE), where DEVICE could be
diff --git a/compat-tests.el b/compat-tests.el
index 605b58e..18306bd 100644
--- a/compat-tests.el
+++ b/compat-tests.el
@@ -731,6 +731,13 @@
   (should-equal (file-name-concat "" "bar") "bar")
   (should-equal (file-name-concat "" "") ""))
 
+(ert-deftest file-name-split ()
+  (should-equal (file-name-split "foo/bar") '("foo" "bar"))
+  (should-equal (file-name-split "/foo/bar") '("" "foo" "bar"))
+  (should-equal (file-name-split "/foo/bar/zot") '("" "foo" "bar" "zot"))
+  (should-equal (file-name-split "/foo/bar/") '("" "foo" "bar" ""))
+  (should-equal (file-name-split "foo/bar/") '("foo" "bar" "")))
+
 (ert-deftest file-name-with-extension ()
   (should-equal "file.ext" (file-name-with-extension "file" "ext"))
   (should-equal "file.ext" (file-name-with-extension "file" ".ext"))
diff --git a/compat.texi b/compat.texi
index ffdadae..70b1041 100644
--- a/compat.texi
+++ b/compat.texi
@@ -2326,6 +2326,20 @@ generated by @code{file-attributes}.
 @end defun
 
 @c copied from lispref/files.texi
+@defun file-name-split filename
+This function splits a file name into its components, and can be
+thought of as the inverse of @code{string-join} with the appropriate
+directory separator.  For example,
+
+@example
+(file-name-split "/tmp/foo.txt")
+    @result{} ("" "tmp" "foo.txt")
+(string-join (file-name-split "/tmp/foo.txt") "/")
+    @result{} "/tmp/foo.txt"
+@end example
+@end defun
+
+@c copied from lispref/files.texi
 @defun file-name-parent-directory filename
 This function returns the directory name of the parent directory of
 @var{filename}.  If @var{filename} is at the root directory of the