2.5-18.1

1 files changed, 88 insertions, 0 deletions

diff --git a/stdlib/rshift.c b/stdlib/rshift.c
new file mode 100644
index 0000000000..9d0a9c4c0e
--- /dev/null
+++ b/stdlib/rshift.c
@@ -0,0 +1,88 @@
+/* mpn_rshift -- Shift right a low-level natural-number integer.
+
+Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or (at your
+option) any later version.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+MA 02111-1307, USA. */
+
+#include <gmp.h>
+#include "gmp-impl.h"
+
+/* Shift U (pointed to by UP and USIZE limbs long) CNT bits to the right
+   and store the USIZE least significant limbs of the result at WP.
+   The bits shifted out to the right are returned.
+
+   Argument constraints:
+   1. 0 < CNT < BITS_PER_MP_LIMB
+   2. If the result is to be written over the input, WP must be <= UP.
+*/
+
+mp_limb_t
+#if __STDC__
+mpn_rshift (register mp_ptr wp,
+	    register mp_srcptr up, mp_size_t usize,
+	    register unsigned int cnt)
+#else
+mpn_rshift (wp, up, usize, cnt)
+     register mp_ptr wp;
+     register mp_srcptr up;
+     mp_size_t usize;
+     register unsigned int cnt;
+#endif
+{
+  register mp_limb_t high_limb, low_limb;
+  register unsigned sh_1, sh_2;
+  register mp_size_t i;
+  mp_limb_t retval;
+
+#ifdef DEBUG
+  if (usize == 0 || cnt == 0)
+    abort ();
+#endif
+
+  sh_1 = cnt;
+
+#if 0
+  if (sh_1 == 0)
+    {
+      if (wp != up)
+	{
+	  /* Copy from low end to high end, to allow specified input/output
+	     overlapping.  */
+	  for (i = 0; i < usize; i++)
+	    wp[i] = up[i];
+	}
+      return usize;
+    }
+#endif
+
+  wp -= 1;
+  sh_2 = BITS_PER_MP_LIMB - sh_1;
+  high_limb = up[0];
+  retval = high_limb << sh_2;
+  low_limb = high_limb;
+
+  for (i = 1; i < usize; i++)
+    {
+      high_limb = up[i];
+      wp[i] = (low_limb >> sh_1) | (high_limb << sh_2);
+      low_limb = high_limb;
+    }
+  wp[i] = low_limb >> sh_1;
+
+  return retval;
+}