Initial revision

1 files changed, 84 insertions, 0 deletions

diff --git a/mpz/sub_ui.c b/mpz/sub_ui.c
new file mode 100644
index 000000000..7dea4b6c0
--- /dev/null
+++ b/mpz/sub_ui.c
@@ -0,0 +1,84 @@
+/* mpz_sub_ui -- Subtract an unsigned one-word integer from an MP_INT.
+
+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 Library General Public License as published by
+the Free Software Foundation; either version 2 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 Library General Public
+License for more details.
+
+You should have received a copy of the GNU Library 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"
+
+void
+#if __STDC__
+mpz_sub_ui (mpz_ptr w, mpz_srcptr u, unsigned long int v)
+#else
+mpz_sub_ui (w, u, v)
+     mpz_ptr w;
+     mpz_srcptr u;
+     unsigned long int v;
+#endif
+{
+  mp_srcptr up;
+  mp_ptr wp;
+  mp_size_t usize, wsize;
+  mp_size_t abs_usize;
+
+  usize = u->_mp_size;
+  abs_usize = ABS (usize);
+
+  /* If not space for W (and possible carry), increase space.  */
+  wsize = abs_usize + 1;
+  if (w->_mp_alloc < wsize)
+    _mpz_realloc (w, wsize);
+
+  /* These must be after realloc (U may be the same as W).  */
+  up = u->_mp_d;
+  wp = w->_mp_d;
+
+  if (abs_usize == 0)
+    {
+      wp[0] = v;
+      w->_mp_size = -(v != 0);
+      return;
+    }
+
+  if (usize < 0)
+    {
+      mp_limb_t cy;
+      cy = mpn_add_1 (wp, up, abs_usize, v);
+      wp[abs_usize] = cy;
+      wsize = -(abs_usize + cy);
+    }
+  else
+    {
+      /* The signs are different.  Need exact comparison to determine
+	 which operand to subtract from which.  */
+      if (abs_usize == 1 && up[0] < v)
+	{
+	  wp[0] = v - up[0];
+	  wsize = -1;
+	}
+      else
+	{
+	  mpn_sub_1 (wp, up, abs_usize, v);
+	  /* Size can decrease with at most one limb.  */
+	  wsize = abs_usize - (wp[abs_usize - 1] == 0);
+	}
+    }
+
+  w->_mp_size = wsize;
+}