[project @ 1996-01-08 20:28:12 by partain]

[ghc-hetmet.git] / ghc / runtime / gmp / mpz_sub_ui.c

diff --git a/ghc/runtime/gmp/mpz_sub_ui.c b/ghc/runtime/gmp/mpz_sub_ui.c
new file mode 100644 (file)
index 0000000..cd9a04b
--- /dev/null
+++ b/ghc/runtime/gmp/mpz_sub_ui.c
@@ -0,0 +1,84 @@
+/* mpz_sub_ui -- Subtract an unsigned one-word integer from an MP_INT.
+
+Copyright (C) 1991 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 General Public License as published by
+the Free Software Foundation; either version 2, 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with the GNU MP Library; see the file COPYING.  If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+
+void
+#ifdef __STDC__
+mpz_sub_ui (MP_INT *dif, const MP_INT *min, mp_limb sub)
+#else
+mpz_sub_ui (dif, min, sub)
+     MP_INT *dif;
+     const MP_INT *min;
+     mp_limb sub;
+#endif
+{
+  mp_srcptr minp;
+  mp_ptr difp;
+  mp_size minsize, difsize;
+  mp_size abs_minsize;
+
+  minsize = min->size;
+  abs_minsize = ABS (minsize);
+
+  /* If not space for SUM (and possible carry), increase space.  */
+  difsize = abs_minsize + 1;
+  if (dif->alloc < difsize)
+    _mpz_realloc (dif, difsize);
+
+  /* These must be after realloc (ADD1 may be the same as SUM).  */
+  minp = min->d;
+  difp = dif->d;
+
+  if (sub == 0)
+    {
+      MPN_COPY (difp, minp, abs_minsize);
+      dif->size = minsize;
+      return;
+    }
+  if (abs_minsize == 0)
+    {
+      difp[0] = sub;
+      dif->size = -1;
+      return;
+    }
+
+  if (minsize < 0)
+    {
+      difsize = mpn_add (difp, minp, abs_minsize, &sub, 1);
+      if (difsize != 0)
+       difp[abs_minsize] = 1;
+      difsize = -(difsize + abs_minsize);
+    }
+  else
+    {
+      /* The signs are different.  Need exact comparision to determine
+        which operand to subtract from which.  */
+      if (abs_minsize == 1 && minp[0] < sub)
+       difsize = -(abs_minsize
+                   + mpn_sub (difp, &sub, 1, minp, 1));
+      else
+       difsize = (abs_minsize
+                  + mpn_sub (difp, minp, abs_minsize, &sub, 1));
+    }
+
+  dif->size = difsize;
+}