Add cl-parse-integer based on parse-integer

* doc/misc/cl.texi (Predicates on Numbers): Document cl-digit-char-p.
(Numerical Functions): Document cl-parse-integer. 

* lisp/calendar/parse-time.el (parse-time-digits): Remove.
(digit-char-p, parse-integer) Moved to cl-lib.el.
(parse-time-tokenize, parse-time-rules, parse-time-string): Use
cl-parse-integer.

* lisp/emacs-lisp/cl-extra.el (cl-parse-integer): New function.

* lisp/emacs-lisp/cl-lib.el (cl-digit-char-table): New var.
(cl-digit-char-p): New function.

* test/automated/cl-lib.el (cl-digit-char-p, cl-parse-integer): New
tests.

Fixes: debbugs:18557

2 files changed, 54 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/cl-extra.el b/lisp/emacs-lisp/cl-extra.el
index 3761d04c2c2..c8404e0bc2d 100644
--- a/lisp/emacs-lisp/cl-extra.el
+++ b/lisp/emacs-lisp/cl-extra.el
@@ -383,6 +383,41 @@ With two arguments, return rounding and remainder of their quotient."
   "Return 1 if X is positive, -1 if negative, 0 if zero."
   (cond ((> x 0) 1) ((< x 0) -1) (t 0)))
 
+;;;###autoload
+(cl-defun cl-parse-integer (string &key start end radix junk-allowed)
+  "Parse integer from the substring of STRING from START to END.
+STRING may be surrounded by whitespace chars (chars with syntax ` ').
+Other non-digit chars are considered junk.
+RADIX is an integer between 2 and 36, the default is 10.  Signal
+an error if the substring between START and END cannot be parsed
+as an integer unless JUNK-ALLOWED is non-nil."
+  (cl-check-type string string)
+  (let* ((start (or start 0))
+	 (len	(length string))
+	 (end   (or end len))
+	 (radix (or radix 10)))
+    (or (<= start end len)
+	(error "Bad interval: [%d, %d)" start end))
+    (cl-flet ((skip-whitespace ()
+		(while (and (< start end)
+			    (= 32 (char-syntax (aref string start))))
+		  (setq start (1+ start)))))
+      (skip-whitespace)
+      (let ((sign (cl-case (and (< start end) (aref string start))
+		    (?+ (cl-incf start) +1)
+		    (?- (cl-incf start) -1)
+		    (t  +1)))
+	    digit sum)
+	(while (and (< start end)
+		    (setq digit (cl-digit-char-p (aref string start) radix)))
+	  (setq sum (+ (* (or sum 0) radix) digit)
+		start (1+ start)))
+	(skip-whitespace)
+	(cond ((and junk-allowed (null sum)) sum)
+	      (junk-allowed (* sign sum))
+	      ((/= start end) (error "Not an integer string: %s" string))
+	      (t (* sign sum)))))))
+
 
 ;; Random numbers.
 
diff --git a/lisp/emacs-lisp/cl-lib.el b/lisp/emacs-lisp/cl-lib.el
index c4b9673aa2a..09cc3eee985 100644
--- a/lisp/emacs-lisp/cl-lib.el
+++ b/lisp/emacs-lisp/cl-lib.el
@@ -279,6 +279,25 @@ so that they are registered at compile-time as well as run-time."
   "Return t if INTEGER is even."
   (eq (logand integer 1) 0))
 
+(defconst cl-digit-char-table
+  (let* ((digits (make-vector 256 nil))
+         (populate (lambda (start end base)
+                     (mapc (lambda (i)
+                             (aset digits i (+ base (- i start))))
+                           (number-sequence start end)))))
+    (funcall populate ?0 ?9 0)
+    (funcall populate ?A ?Z 10)
+    (funcall populate ?a ?z 10)
+    digits))
+
+(defun cl-digit-char-p (char &optional radix)
+  "Test if CHAR is a digit in the specified RADIX (default 10).
+If true return the decimal value of digit CHAR in RADIX."
+  (or (<= 2 (or radix 10) 36)
+      (signal 'args-out-of-range (list 'radix radix '(2 36))))
+  (let ((n (aref cl-digit-char-table char)))
+    (and n (< n (or radix 10)) n)))
+
 (defvar cl--random-state
   (vector 'cl--random-state-tag -1 30 (cl--random-time)))