factor: improve gmp-related buffering

Previously, the code used stdio buffers for gmp numbers,
and did its own buffering for smaller numbers.  This meant
for more flushing than was needed.  The code now uses its
own buffering for all standard output, which makes for
less flushing and fewer writes.
* src/factor.c (lbuf_half_flush): New function, taken from the
body of lbuf_putnl.
(lbuf_putnl): Use it.
(lbuf_putmpz): New function, to output an mpz without using stdio.
(print_factors): Output via functions instead of via stdio.

diff --git a/src/factor.c b/src/factor.c
index f947022e1dc35e937e22013c26f30043cad6ad8c..e463186deda7e85e061d4785494000fd78d3c638 100644 (file)
--- a/src/factor.c
+++ b/src/factor.c
@@ -2343,6 +2343,25 @@ lbuf_flush (void)
     write_error ();
 }
 
+/* Write LBUF to standard output.
+   LBUF should contain at least FACTOR_PIPE_BUF bytes.
+   If possible, write a prefix of LBUF that is newline terminated
+   and contains <= FACTOR_PIPE_BUF bytes, so consumers can read atomically.
+   But if the first FACTOR_PIPE_BUF bytes contain no newlines,
+   give up on atomicity and just write the first FACTOR_PIPE_BUF bytes.  */
+static void
+lbuf_half_flush (void)
+{
+  char *nl = memrchr (lbuf_buf, '\n', FACTOR_PIPE_BUF);
+  char *suffix = nl ? nl + 1 : lbuf_buf + FACTOR_PIPE_BUF;
+  idx_t prefix_size = suffix - lbuf_buf;
+  idx_t suffix_size = lbuffered - prefix_size;
+  lbuffered = prefix_size;
+  lbuf_flush ();
+  lbuffered = suffix_size;
+  memmove (lbuf_buf, suffix, suffix_size);
+}
+
 /* Add a character C to lbuf_buf.  */
 static void
 lbuf_putc (char c)
@@ -2365,24 +2384,7 @@ lbuf_putnl (void)
   if (line_buffered)
     lbuf_flush ();
   else if (FACTOR_PIPE_BUF <= lbuffered)
-    {
-      /* Write output in <= PIPE_BUF chunks
-         so consumers can read atomically.  */
-
-      /* Since a umaxint_t's factors must fit in FACTOR_PIPE_BUF
-         we're guaranteed to find a newline here.  */
-      char *trailing_newline = memrchr (lbuf_buf, '\n', FACTOR_PIPE_BUF);
-      char *suffix = trailing_newline + 1;
-      idx_t prefix_size = suffix - lbuf_buf;
-      idx_t suffix_size = lbuffered - prefix_size;
-
-      lbuffered = prefix_size;
-      lbuf_flush ();
-
-      /* Buffer the remainder.  */
-      lbuffered = suffix_size;
-      memcpy (lbuf_buf, suffix, suffix_size);
-    }
+    lbuf_half_flush ();
 }
 
 /* Buffer an int to the internal LBUF.  */
@@ -2422,6 +2424,33 @@ print_uintmaxes (uintmax_t t1, uintmax_t t0)
     }
 }
 
+/* Buffer an mpz to the internal LBUF, possibly writing if it is long.  */
+static void
+lbuf_putmpz (mpz_t const i)
+{
+  idx_t sizeinbase = mpz_sizeinbase (i, 10);
+  char *lbuf_bufend = lbuf_buf + sizeof lbuf_buf;
+  char *p = lbuf_buf + lbuffered;
+  if (sizeinbase < lbuf_bufend - p)
+    {
+      mpz_get_str (p, 10, i);
+      p += sizeinbase;
+      lbuffered = p - !p[-1] - lbuf_buf;
+      while (FACTOR_PIPE_BUF <= lbuffered)
+        lbuf_half_flush ();
+    }
+  else
+    {
+      lbuf_flush ();
+      char *istr = ximalloc (sizeinbase + 1);
+      mpz_get_str (istr, 10, i);
+      idx_t istrlen = sizeinbase - !istr[sizeinbase - 1];
+      if (full_write (STDOUT_FILENO, istr, istrlen) != istrlen)
+        write_error ();
+      free (istr);
+    }
+}
+
 /* Single-precision factoring */
 static void
 print_factors_single (uintmax_t t1, uintmax_t t0)
@@ -2503,26 +2532,26 @@ print_factors (char const *input)
 
   mpz_init_set_str (t, str, 10);
 
-  mpz_out_str (stdout, 10, t);
-  putchar (':');
+  lbuf_putmpz (t);
+  lbuf_putc (':');
   mp_factor (t, &factors);
 
   for (idx_t j = 0; j < factors.nfactors; j++)
     for (unsigned long int k = 0; k < factors.e[j]; k++)
       {
-        putchar (' ');
-        mpz_out_str (stdout, 10, factors.p[j]);
+        lbuf_putc (' ');
+        lbuf_putmpz (factors.p[j]);
         if (print_exponents && factors.e[j] > 1)
           {
-            printf ("^%lu", factors.e[j]);
+            lbuf_putc ('^');
+            lbuf_putint (factors.e[j], 0);
             break;
           }
       }
 
   mp_factor_clear (&factors);
   mpz_clear (t);
-  putchar ('\n');
-  fflush (stdout);
+  lbuf_putnl ();
   return true;
 }
 
@@ -2588,7 +2617,6 @@ main (int argc, char **argv)
   textdomain (PACKAGE);
 
   atexit (close_stdout);
-  atexit (lbuf_flush);
 
   int c;
   while ((c = getopt_long (argc, argv, "h", long_options, nullptr)) != -1)
@@ -2612,6 +2640,8 @@ main (int argc, char **argv)
         }
     }
 
+  atexit (lbuf_flush);
+
 #if STAT_SQUFOF
   memset (q_freq, 0, sizeof (q_freq));
 #endif