Combine archive-int-to-mode and tar-grind-file-modebug27952_combine-tar-grind-file-mode_archive-int-to-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.

8 files changed, 74 insertions, 41 deletions

diff --git a/doc/lispref/files.texi b/doc/lispref/files.texi
index b3ad9b99649..686dbdb1caf 100644
--- a/doc/lispref/files.texi
+++ b/doc/lispref/files.texi
@@ -1909,6 +1909,11 @@ omitted or @code{nil}, it defaults to 0, i.e., no access rights at
 all.
 @end defun
 
+@defun file-modes-number-to-symbolic modes
+This function converts a numeric file mode specification in
+@var{modes} into the equivalent symbolic form.
+@end defun
+
 @defun set-file-times filename &optional time flag
 This function sets the access and modification times of @var{filename}
 to @var{time}.  The return value is @code{t} if the times are successfully
diff --git a/etc/NEWS b/etc/NEWS
index ae676a9bf83..8a1d51c18d7 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -400,6 +400,10 @@ Use macro 'with-current-buffer-window' with action alist entry 'body-function'.
 
 * Lisp Changes in Emacs 28.1
 
++++
+** New function 'file-modes-number-to-symbolic' to convert a numeric
+file mode specification into symbolic form.
+
 ** New macro 'dlet' to dynamically bind variables.
 
 ** The variable 'force-new-style-backquotes' has been removed.
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'."
diff --git a/test/lisp/arc-mode-tests.el b/test/lisp/arc-mode-tests.el
index df658b98139..22ca7e2ec55 100644
--- a/test/lisp/arc-mode-tests.el
+++ b/test/lisp/arc-mode-tests.el
@@ -28,7 +28,7 @@
   (let ((alist (list (cons 448 "-rwx------")
                      (cons 420 "-rw-r--r--")
                      (cons 292 "-r--r--r--")
-                     (cons 512 "----------")
+                     (cons 512 "---------T")
                      (cons 1024 "------S---") ; Bug#28092
                      (cons 2048 "---S------"))))
     (dolist (x alist)
diff --git a/test/lisp/files-tests.el b/test/lisp/files-tests.el
index 05d9ceebf1d..4b902fd82ae 100644
--- a/test/lisp/files-tests.el
+++ b/test/lisp/files-tests.el
@@ -1164,6 +1164,42 @@ works as expected if the default directory is quoted."
     (should-not (make-directory a/b t))
     (delete-directory dir 'recursive)))
 
+(ert-deftest files-tests-file-modes-symbolic-to-number ()
+  (let ((alist (list (cons "a=rwx" #o777)
+                     (cons "o=t" #o1000)
+                     (cons "o=xt" #o1001)
+                     (cons "o=tx" #o1001) ; Order doesn't matter.
+                     (cons "u=rwx,g=rx,o=rx" #o755)
+                     (cons "u=rwx,g=,o=" #o700)
+                     (cons "u=rwx" #o700) ; Empty permissions can be ignored.
+                     (cons "u=rw,g=r,o=r" #o644)
+                     (cons "u=rw,g=r,o=t" #o1640)
+                     (cons "u=rw,g=r,o=xt" #o1641)
+                     (cons "u=rwxs,g=rs,o=xt" #o7741)
+                     (cons "u=rws,g=rs,o=t" #o7640)
+                     (cons "u=rws,g=rs,o=r" #o6644)
+                     (cons "a=r" #o444)
+                     (cons "u=S" nil)
+                     (cons "u=T" nil)
+                     (cons "u=Z" nil))))
+    (dolist (x alist)
+      (if (cdr-safe x)
+          (should (equal (cdr x) (file-modes-symbolic-to-number (car x))))
+        (should-error (file-modes-symbolic-to-number (car x)))))))
+
+(ert-deftest files-tests-file-modes-number-to-symbolic ()
+  (let ((alist (list (cons #o755 "-rwxr-xr-x")
+                     (cons #o700 "-rwx------")
+                     (cons #o644 "-rw-r--r--")
+                     (cons #o1640 "-rw-r----T")
+                     (cons #o1641 "-rw-r----t")
+                     (cons #o7741 "-rwsr-S--t")
+                     (cons #o7640 "-rwSr-S--T")
+                     (cons #o6644 "-rwSr-Sr--")
+                     (cons #o444 "-r--r--r--"))))
+    (dolist (x alist)
+      (should (equal (cdr x) (file-modes-number-to-symbolic (car x)))))))
+
 (ert-deftest files-tests-no-file-write-contents ()
   "Test that `write-contents-functions' permits saving a file.
 Usually `basic-save-buffer' will prompt for a file name if the
diff --git a/test/lisp/tar-mode-tests.el b/test/lisp/tar-mode-tests.el
index bc41b863da7..f05389df60f 100644
--- a/test/lisp/tar-mode-tests.el
+++ b/test/lisp/tar-mode-tests.el
@@ -29,7 +29,8 @@
                      (cons 420 "rw-r--r--")
                      (cons 292 "r--r--r--")
                      (cons 512 "--------T")
-                     (cons 1024 "-----S---"))))
+                     (cons 1024 "-----S---")
+                     (cons 2048 "--S------"))))
     (dolist (x alist)
       (should (equal (cdr x) (tar-grind-file-mode (car x)))))))