From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001
From: Tobias Klauser <tklauser@distanz.ch>
Date: Sun, 27 Jan 2008 11:37:44 +0100
Subject: Initial import (2.0.2-6)

---
 reference/C/CONTRIB/SNIP/bigfac.c | 122 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)
 create mode 100755 reference/C/CONTRIB/SNIP/bigfac.c

(limited to 'reference/C/CONTRIB/SNIP/bigfac.c')

diff --git a/reference/C/CONTRIB/SNIP/bigfac.c b/reference/C/CONTRIB/SNIP/bigfac.c
new file mode 100755
index 0000000..5e51077
--- /dev/null
+++ b/reference/C/CONTRIB/SNIP/bigfac.c
@@ -0,0 +1,122 @@
+/*
+**  bigfac.c -- put into the public domain by Carl Declerck
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define BUFFLEN 8192
+#define BUFFER ((char *) malloc(BUFFLEN))
+
+void main (void);
+void multiply (char *, char *, char *);
+void zero_buffer (char *);
+void minus_one (char *);
+int  isnull (char *);
+void factorial (char *);
+
+void main (void)
+{
+      char *g = BUFFER;
+
+      printf ("Enter a number: ");
+      scanf ("%s", g);
+      printf ("Factorial of %s is: ", g);
+      factorial (g);
+      printf ("%s\n", g);
+      free (g);
+}
+
+void multiply (char *g1, char *g2, char *g3)
+{
+      int gp1, gp2, cumpos, respos, mod, div;
+      int cmod, cdiv, resoff, wdig1, wdig2, base;
+
+      zero_buffer (g3);
+      for (gp2 = strlen(g2) - 1; gp2 >= 0; gp2--)
+      {
+            wdig2 = *(g2 + gp2) - 48;
+            resoff = strlen(g2) - gp2 - 1;
+            respos = BUFFLEN - resoff - 2;
+            for (gp1 = strlen(g1) - 1; gp1 >= 0; gp1--)
+            {
+                  wdig1 = *(g1 + gp1) - 48;
+                  mod = (wdig1 * wdig2) % 10;
+                  div = (wdig1 * wdig2) / 10;
+                  base = *(g3 + respos) - 48;
+                  cmod = (base + mod) % 10;
+                  cdiv = (base + mod) / 10 + div;
+                  *(g3 + respos) = (char)(cmod + 48);
+                  cumpos = --respos;
+                  while (cdiv > 0)
+                  {
+                        base = *(g3 + cumpos) - 48;
+                        *(g3 + cumpos--) = (char)((base + cdiv) % 10 + 48);
+                        cdiv = (base + cdiv) / 10;
+                  }
+            }
+      }
+      for (respos = 0; *(g3 + respos) == '0'; respos++)
+            ;
+      strcpy (g3, (char *) (g3 + respos));
+      if (*g3 == 0)
+            strcpy (g3, "0");
+}
+
+void zero_buffer (char *buff)
+{
+      int cnt;
+
+      for (cnt= 0; cnt < BUFFLEN; cnt++)
+            *(buff + cnt) = '0';
+      *(buff + BUFFLEN - 1) = 0;
+}
+
+void minus_one (char *g)
+{
+      int p;
+      char digit;
+
+      p = strlen(g) - 1;
+      digit = *(g + p);
+      while (digit == '0')
+      {
+            *(g + p--) = '9';
+            digit = *(g + p);
+      }
+      *(g + p) -= 1;
+}
+
+int isnull (char *g)
+{
+      int p, ok = 1;
+
+      for (p = 0; p < (int)(strlen(g)); p++)
+            if (*(g + p) != '0')
+                  ok = 0;
+      return (ok);
+}
+
+void factorial (char *g)
+{
+      char *h1 = BUFFER, *h2 = BUFFER;
+
+      strcpy (h1, "1");
+      while (!isnull(g))
+      {
+            multiply (h1, g, h2);
+            strcpy (h1, h2);
+            minus_one (g);
+      }
+      strcpy (g, h1);
+      free (h1);
+      free (h2);
+}
+
+/*
+**  The principal function is multiply(), it 'multiplies' two
+**  character-strings of arbritrary length and puts the result
+**  into a third.  8192 bytes is enough for 1000!, beyond that
+**  the buffer-size may need to be incremented.
+*/
-- 
cgit v1.2.3-54-g00ecf