patch 9.2.0351: repeat_string() can be improved

Problem:  repeat_string() can be improved
Solution: Replace the for() loop by an exponential growing while loop
          (Yasuhiro Matsumoto)

closes: #19977

Signed-off-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/evalfunc.c

@@ -10584,7 +10584,7 @@ repeat_string(typval_T *str_tv, int n, typval_T *rettv)
     int		slen;
     int		len;
     char_u	*r;
-    int		i;
+    int		done;
 
     p = tv_get_string(str_tv);
     rettv->v_type = VAR_STRING;
@@ -10599,8 +10599,17 @@ repeat_string(typval_T *str_tv, int n, typval_T *rettv)
     if (r == NULL)
 	return;
 
-    for (i = 0; i < n; i++)
-	mch_memmove(r + i * slen, p, (size_t)slen);
+    mch_memmove(r, p, (size_t)slen);
+    done = slen;
+    while (done < len)
+    {
+	int copy_len = done;
+
+	if (copy_len > len - done)
+	    copy_len = len - done;
+	mch_memmove(r + done, r, (size_t)copy_len);
+	done += copy_len;
+    }
     r[len] = NUL;
 
     rettv->vval.v_string = r;

src/version.c

@@ -734,6 +734,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    351,
 /**/
     350,
 /**/