Combine archive-int-to-mode and tar-grind-file-mode

Add a new function, file-modes-number-to-symbolic.
Make archive-int-to-mode and obsolete alias of it; use it
to define tar-grind-file-mode (Bug#27952).

* lisp/files.el (file-modes-number-to-symbolic): New defun.
* lisp/arc-mode.el (archive-int-to-mode): Make it an obsolete alias.
* lisp/tar-mode.el (tar-grind-file-mode):
Use file-modes-number-to-symbolic.

* test/lisp/arc-mode-tests.el (arc-mode-test-archive-int-to-mode)
* test/lisp/tar-mode-tests.el (tar-mode-test-tar-grind-file-mode):
Update test.

* test/lisp/files-tests.el (files-tests-file-modes-symbolic-to-number)
(files-tests-file-modes-number-to-symbolic): New tests.

* doc/lispref/files.texi (Changing Files): Document the new funtion.
* etc/NEWS (Lisp Changes in Emacs 28.1): Announce it.

3 files changed, 26 insertions, 39 deletions

diff --git a/lisp/arc-mode.el b/lisp/arc-mode.el
index c918f06c80e..6ce64fe24b3 100644
--- a/lisp/arc-mode.el
+++ b/lisp/arc-mode.el
@@ -563,28 +563,8 @@ in which case a second argument, length LEN, should be supplied."
 		      (aref str (- len i)))))
     result))
 
-(defun archive-int-to-mode (mode)
-  "Turn an integer like 0700 (i.e., 448) into a mode string like -rwx------."
-  ;; FIXME: merge with tar-grind-file-mode.
-  (if (null mode)
-      "??????????"
-    (string
-     (if (zerop (logand  8192 mode))
-	 (if (zerop (logand 16384 mode)) ?- ?d)
-       ?c)                              ; completeness
-     (if (zerop (logand   256 mode)) ?- ?r)
-     (if (zerop (logand   128 mode)) ?- ?w)
-     (if (zerop (logand    64 mode))
-	 (if (zerop (logand  2048 mode)) ?- ?S)
-       (if (zerop (logand  2048 mode)) ?x ?s))
-     (if (zerop (logand    32 mode)) ?- ?r)
-     (if (zerop (logand    16 mode)) ?- ?w)
-     (if (zerop (logand     8 mode))
-	 (if (zerop (logand  1024 mode)) ?- ?S)
-       (if (zerop (logand  1024 mode)) ?x ?s))
-     (if (zerop (logand     4 mode)) ?- ?r)
-     (if (zerop (logand     2 mode)) ?- ?w)
-     (if (zerop (logand     1 mode)) ?- ?x))))
+(define-obsolete-function-alias 'archive-int-to-mode
+  'file-modes-number-to-symbolic "28.1")
 
 (defun archive-calc-mode (oldmode newmode)
   "From the integer OLDMODE and the string NEWMODE calculate a new file mode.
diff --git a/lisp/files.el b/lisp/files.el
index c34fe003880..dba704f7a4b 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -7552,6 +7552,27 @@ as in \"og+rX-w\"."
 	      op char-right)))
     num-rights))
 
+(defun file-modes-number-to-symbolic (mode)
+  (string
+   (if (zerop (logand  8192 mode))
+       (if (zerop (logand 16384 mode)) ?- ?d)
+     ?c) ; completeness
+   (if (zerop (logand   256 mode)) ?- ?r)
+   (if (zerop (logand   128 mode)) ?- ?w)
+   (if (zerop (logand    64 mode))
+       (if (zerop (logand  2048 mode)) ?- ?S)
+     (if (zerop (logand  2048 mode)) ?x ?s))
+   (if (zerop (logand    32 mode)) ?- ?r)
+   (if (zerop (logand    16 mode)) ?- ?w)
+   (if (zerop (logand     8 mode))
+       (if (zerop (logand  1024 mode)) ?- ?S)
+     (if (zerop (logand  1024 mode)) ?x ?s))
+   (if (zerop (logand     4 mode)) ?- ?r)
+   (if (zerop (logand     2 mode)) ?- ?w)
+   (if (zerop (logand 512 mode))
+       (if (zerop (logand   1 mode)) ?- ?x)
+     (if (zerop (logand   1 mode)) ?T ?t))))
+
 (defun file-modes-symbolic-to-number (modes &optional from)
   "Convert symbolic file modes to numeric file modes.
 MODES is the string to convert, it should match
diff --git a/lisp/tar-mode.el b/lisp/tar-mode.el
index a3c1715b1e1..73978ffc4a7 100644
--- a/lisp/tar-mode.el
+++ b/lisp/tar-mode.el
@@ -480,23 +480,9 @@ checksum before doing the check."
 
 (defun tar-grind-file-mode (mode)
   "Construct a `rw-r--r--' string indicating MODE.
-MODE should be an integer which is a file mode value."
-  (string
-   (if (zerop (logand 256 mode)) ?- ?r)
-   (if (zerop (logand 128 mode)) ?- ?w)
-   (if (zerop (logand 2048 mode))
-       (if (zerop (logand  64 mode)) ?- ?x)
-     (if (zerop (logand  64 mode)) ?S ?s))
-   (if (zerop (logand  32 mode)) ?- ?r)
-   (if (zerop (logand  16 mode)) ?- ?w)
-   (if (zerop (logand 1024 mode))
-       (if (zerop (logand   8 mode)) ?- ?x)
-     (if (zerop (logand   8 mode)) ?S ?s))
-   (if (zerop (logand   4 mode)) ?- ?r)
-   (if (zerop (logand   2 mode)) ?- ?w)
-   (if (zerop (logand 512 mode))
-       (if (zerop (logand   1 mode)) ?- ?x)
-     (if (zerop (logand   1 mode)) ?T ?t))))
+MODE should be an integer which is a file mode value.
+For instance, if mode is #o700, then it produces `rwx------'."
+  (substring (file-modes-number-to-symbolic mode) 1))
 
 (defun tar-header-block-summarize (tar-hblock &optional mod-p)
   "Return a line similar to the output of `tar -vtf'."