From 0619c4a49130a9ea09ca8ac7774d6810f641aab5 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Fri, 27 Sep 2024 16:16:43 -0700
Subject: [PATCH] factor: eliminate print_uuint recursion
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* src/factor.c (lbuf_putint_append): New function, with
most of the old lbuf_putint body.  Do the umaxtostr stuff
by hand so that we needn’t worry about the trailing NUL.a
Do the string copy by hand since the string is so short.
(lbuf_putint): Reimplement in terms of lbuf_putint_append.
Omit last arg, which is no longer needed.  All callers changed.
(print_uuint): Rewrite to avoid recursion, using
lbuf_putint_append for the usual case.
---
 src/factor.c | 54 +++++++++++++++++++++++++++++++++-------------------
 1 file changed, 34 insertions(+), 20 deletions(-)

diff --git a/src/factor.c b/src/factor.c
index 5ccc9376a7..cba32d8743 100644
--- a/src/factor.c
+++ b/src/factor.c
@@ -2389,41 +2389,55 @@ lbuf_putnl (void)
     lbuf_half_flush ();
 }
 
-/* Buffer an int to the internal LBUF.  */
+/* Append the string representation of I to lbuf_buf, followed by
+   everything from BUFEND to lbuf_buf's end.  Use the area just before
+   BUFEND temporarily.  */
 static void
-lbuf_putint (uintmax_t i, int min_width)
+lbuf_putint_append (uintmax_t i, char *bufend)
 {
-  char *lbuf_bufend = lbuf_buf + sizeof lbuf_buf;
-  char *buf = lbuf_bufend - INT_BUFSIZE_BOUND (uintmax_t);
-  char const *umaxstr = umaxtostr (i, buf);
-  int width = lbuf_bufend - 1 - umaxstr;
-  assume (0 < width);
+  char *istr = bufend;
+  do
+    {
+      *--istr = '0' + i % 10;
+      i /= 10;
+    }
+  while (i);
 
   char *p = lbuf_buf + lbuffered;
-  for (int zeros = min_width - width; 0 < zeros; zeros--)
-    *p++ = '0';
+  do
+    *p++ = *istr++;
+  while (istr < lbuf_buf + sizeof lbuf_buf);
 
-  p = mempcpy (p, umaxstr, width);
   lbuffered = p - lbuf_buf;
 }
 
+/* Append the string representation of I to lbuf_buf.  */
+static void
+lbuf_putint (uintmax_t i)
+{
+  return lbuf_putint_append (i, lbuf_buf + sizeof lbuf_buf);
+}
+
+/* Append the string representation of T to lbuf_buf.  */
 static void
 print_uuint (uuint t)
 {
   uintmax_t t1 = hi (t), t0 = lo (t);
+  char *bufend = lbuf_buf + sizeof lbuf_buf;
 
-  if (t1 == 0)
-    lbuf_putint (t0, 0);
-  else
+  while (t1)
     {
-      /* Use very plain code here since it seems hard to write fast code
-         without assuming a specific word size.  */
-      uintmax_t q = t1 / BIG_POWER_OF_10;
       uintmax_t r = t1 % BIG_POWER_OF_10;
+      t1 /= BIG_POWER_OF_10;
       udiv_qrnnd (t0, r, r, t0, BIG_POWER_OF_10);
-      print_uuint (make_uuint (q, t0));
-      lbuf_putint (r, LOG_BIG_POWER_OF_10);
+      for (int i = 0; i < LOG_BIG_POWER_OF_10; i++)
+        {
+          *--bufend = '0' + r % 10;
+          r /= 10;
+        }
     }
+
+  lbuf_putint_append (t0, bufend);
 }
 
 /* Buffer an mpz to the internal LBUF, possibly writing if it is long.  */
@@ -2472,7 +2486,7 @@ print_factors_single (uintmax_t t1, uintmax_t t0)
         if (print_exponents && factors.e[j] > 1)
           {
             lbuf_putc ('^');
-            lbuf_putint (factors.e[j], 0);
+            lbuf_putint (factors.e[j]);
             break;
           }
       }
@@ -2546,7 +2560,7 @@ print_factors (char const *input)
         if (print_exponents && factors.e[j] > 1)
           {
             lbuf_putc ('^');
-            lbuf_putint (factors.e[j], 0);
+            lbuf_putint (factors.e[j]);
             break;
           }
       }
-- 
2.47.2