2.5-18.1

1 files changed, 62 insertions, 0 deletions

diff --git a/stdlib/sub_n.c b/stdlib/sub_n.c
new file mode 100644
index 0000000000..987ad91eb1
--- /dev/null
+++ b/stdlib/sub_n.c
@@ -0,0 +1,62 @@
+/* mpn_sub_n -- Subtract two limb vectors of equal, non-zero length.
+
+Copyright (C) 1992, 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"
+
+mp_limb_t
+#if __STDC__
+mpn_sub_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr, mp_size_t size)
+#else
+mpn_sub_n (res_ptr, s1_ptr, s2_ptr, size)
+     register mp_ptr res_ptr;
+     register mp_srcptr s1_ptr;
+     register mp_srcptr s2_ptr;
+     mp_size_t size;
+#endif
+{
+  register mp_limb_t x, y, cy;
+  register mp_size_t j;
+
+  /* The loop counter and index J goes from -SIZE to -1.  This way
+     the loop becomes faster.  */
+  j = -size;
+
+  /* Offset the base pointers to compensate for the negative indices.  */
+  s1_ptr -= j;
+  s2_ptr -= j;
+  res_ptr -= j;
+
+  cy = 0;
+  do
+    {
+      y = s2_ptr[j];
+      x = s1_ptr[j];
+      y += cy;			/* add previous carry to subtrahend */
+      cy = (y < cy);		/* get out carry from that addition */
+      y = x - y;		/* main subtract */
+      cy = (y > x) + cy;	/* get out carry from the subtract, combine */
+      res_ptr[j] = y;
+    }
+  while (++j != 0);
+
+  return cy;
+}