Make ucs-names a hash table (Bug#28302)

* etc/NEWS: Mention the type change.
* lisp/descr-text.el (describe-char): Use gethash to access ucs-names.
Hardcode BEL's name into the function instead of needlessly mapping
over the hash table in the spirit of rassoc.
* lisp/international/mule-cmds.el (ucs-names): Fix variable and
function docstrings.  Initialize a hash table for ucs-names--the
number of entries is 42845 here.  Switch to hash-table
getters/setters.
(mule--ucs-names-annotation): Use hash-table getter.
(char-from-name): Upcase the string if ignore-case is truthy.
* lisp/leim/quail/latin-ltx.el: Use maphash instead of dolist.

4 files changed, 43 insertions, 39 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 0889303f82e..d32b0e5bc89 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1155,6 +1155,9 @@ isn't compatible with previous Emacs versions.  This functionality can
 be disabled by setting 'byte-compile-cond-use-jump-table' to nil.
 
 ---
+** The alist 'ucs-names' is now a hash table.
+
+---
 ** 'C-up', 'C-down', 'C-left' and 'C-right' are now defined in term
 mode to send the same escape sequences that xterm does.  This makes
 things like forward-word in readline work.
diff --git a/lisp/descr-text.el b/lisp/descr-text.el
index 6f36bbed680..b3c96988dd6 100644
--- a/lisp/descr-text.el
+++ b/lisp/descr-text.el
@@ -617,16 +617,16 @@ relevant to POS."
                          (list
                           (let* ((names (ucs-names))
                                  (name
-                                  (or (when (= char 7)
+                                  (or (when (= char ?\a)
                                        ;; Special case for "BELL" which is
                                        ;; apparently the only char which
                                        ;; doesn't have a new name and whose
                                        ;; old-name is shadowed by a newer char
                                        ;; with that name (bug#25641).
-                                       (car (rassoc char names)))
+                                       "BELL (BEL)")
                                       (get-char-code-property char 'name)
                                       (get-char-code-property char 'old-name))))
-                            (if (and name (assoc-string name names))
+                            (if (and name (gethash name names))
                                 (format
                                  "type \"C-x 8 RET %x\" or \"C-x 8 RET %s\""
                                  char name)
diff --git a/lisp/international/mule-cmds.el b/lisp/international/mule-cmds.el
index 338ca6a6e3c..a596411eb78 100644
--- a/lisp/international/mule-cmds.el
+++ b/lisp/international/mule-cmds.el
@@ -2923,10 +2923,10 @@ on encoding."
 (make-obsolete-variable 'nonascii-translation-table "do not use it." "23.1")
 
 (defvar ucs-names nil
-  "Alist of cached (CHAR-NAME . CHAR-CODE) pairs.")
+  "Hash table of cached CHAR-NAME keys to CHAR-CODE values.")
 
 (defun ucs-names ()
-  "Return alist of (CHAR-NAME . CHAR-CODE) pairs cached in `ucs-names'."
+  "Return table of CHAR-NAME keys and CHAR-CODE values cached in `ucs-names'."
   (or ucs-names
       (let ((ranges
              '((#x0000 . #x33FF)
@@ -2954,38 +2954,39 @@ on encoding."
                ;; (#x20000 . #xDFFFF) CJK Ideograph Extension A, B, etc, unused
                (#xE0000 . #xE01FF)))
             (gc-cons-threshold 10000000)
-            names)
-        (dolist (range ranges)
-          (let ((c (car range))
-                (end (cdr range)))
-          (while (<= c end)
+            (names (make-hash-table :size 42943 :test #'equal)))
+        (dolist (range ranges)
+          (let ((c (car range))
+                (end (cdr range)))
+            (while (<= c end)
               (let ((new-name (get-char-code-property c 'name))
                     (old-name (get-char-code-property c 'old-name)))
-                ;; In theory this code could end up pushing an "old-name" that
-                ;; shadows a "new-name" but in practice every time an
-                ;; `old-name' conflicts with a `new-name', the newer one has a
-                ;; higher code, so it gets pushed later!
-                (if new-name (push (cons new-name c) names))
-                (if old-name (push (cons old-name c) names))
-                (setq c (1+ c))))))
-        ;; Special case for "BELL" which is apparently the only char which
-        ;; doesn't have a new name and whose old-name is shadowed by a newer
-        ;; char with that name.
-        (setq ucs-names `(("BELL (BEL)" . 7) ,@names)))))
+                ;; In theory this code could end up pushing an "old-name" that
+                ;; shadows a "new-name" but in practice every time an
+                ;; `old-name' conflicts with a `new-name', the newer one has a
+                ;; higher code, so it gets pushed later!
+                (if new-name (puthash new-name c names))
+                (if old-name (puthash old-name c names))
+                (setq c (1+ c))))))
+        ;; Special case for "BELL" which is apparently the only char which
+        ;; doesn't have a new name and whose old-name is shadowed by a newer
+        ;; char with that name.
+        (puthash "BELL (BEL)" ?\a names)
+        (setq ucs-names names))))
 
 (defun mule--ucs-names-annotation (name)
   ;; FIXME: It would be much better to add this annotation before rather than
   ;; after the char name, so the annotations are aligned.
   ;; FIXME: The default behavior of displaying annotations in italics
   ;; doesn't work well here.
-  (let ((char (assoc name ucs-names)))
-    (when char (format " (%c)" (cdr char)))))
+  (let ((char (gethash name ucs-names)))
+    (when char (format " (%c)" char))))
 
 (defun char-from-name (string &optional ignore-case)
   "Return a character as a number from its Unicode name STRING.
 If optional IGNORE-CASE is non-nil, ignore case in STRING.
 Return nil if STRING does not name a character."
-  (or (cdr (assoc-string string (ucs-names) ignore-case))
+  (or (gethash (if ignore-case (upcase string) string) (ucs-names))
       (let ((minus (string-match-p "-[0-9A-F]+\\'" string)))
         (when minus
           ;; Parse names like "VARIATION SELECTOR-17" and "CJK
diff --git a/lisp/leim/quail/latin-ltx.el b/lisp/leim/quail/latin-ltx.el
index 6c5afcd4f93..d8ea90ec3ec 100644
--- a/lisp/leim/quail/latin-ltx.el
+++ b/lisp/leim/quail/latin-ltx.el
@@ -75,20 +75,20 @@ system, including many technical ones.  Examples:
           (`(,seq ,re)
            (let ((count 0)
                  (re (eval re t)))
-             (dolist (pair (ucs-names))
-               (let ((name (car pair))
-                     (char (cdr pair)))
-                 (when (and (characterp char) ;; Ignore char-ranges.
-                            (string-match re name))
-                   (let ((keys (if (stringp seq)
-                                   (replace-match seq nil nil name)
-                                 (funcall seq name char))))
-                     (if (listp keys)
-                         (dolist (x keys)
-                           (setq count (1+ count))
-                           (push (list x char) newrules))
-                       (setq count (1+ count))
-                       (push (list keys char) newrules))))))
+             (maphash
+              (lambda (name char)
+                (when (and (characterp char) ;; Ignore char-ranges.
+                           (string-match re name))
+                  (let ((keys (if (stringp seq)
+                                  (replace-match seq nil nil name)
+                                (funcall seq name char))))
+                    (if (listp keys)
+                        (dolist (x keys)
+                          (setq count (1+ count))
+                          (push (list x char) newrules))
+                      (setq count (1+ count))
+                      (push (list keys char) newrules)))))
+               (ucs-names))
              ;; (message "latin-ltx: %d mappings for %S" count re)
              ))))
       (setq newrules (delete-dups newrules))
@@ -206,7 +206,7 @@ system, including many technical ones.  Examples:
 
  ((lambda (name char)
     (let* ((base (concat (match-string 1 name) (match-string 3 name)))
-           (basechar (cdr (assoc base (ucs-names)))))
+           (basechar (gethash base (ucs-names))))
       (when (latin-ltx--ascii-p basechar)
         (string (if (match-end 2) ?^ ?_) basechar))))
   "\\(.*\\)SU\\(?:B\\|\\(PER\\)\\)SCRIPT \\(.*\\)")