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

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

diff --git a/ghc/runtime/gmp/mpz_com.c b/ghc/runtime/gmp/mpz_com.c
new file mode 100644 (file)
index 0000000..3c0d3b1
--- /dev/null
+++ b/ghc/runtime/gmp/mpz_com.c
@@ -0,0 +1,96 @@
+/* mpz_com(MP_INT *dst, MP_INT *src) -- Assign the bit-complemented value of
+   SRC to DST.
+
+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_com (MP_INT *dst, const MP_INT *src)
+#else
+mpz_com (dst, src)
+     MP_INT *dst;
+     const MP_INT *src;
+#endif
+{
+  mp_size size = src->size;
+  mp_srcptr src_ptr;
+  mp_ptr dst_ptr;
+
+  if (size >= 0)
+    {
+      /* As with infinite precision: one's complement, two's complement.
+        But this can be simplified using the identity -x = ~x + 1.
+        So we're going to compute (~~x) + 1 = x + 1!  */
+
+      if (dst->alloc < size + 1)
+       _mpz_realloc (dst, size + 1);
+
+      src_ptr = src->d;
+      dst_ptr = dst->d;
+
+      if (size == 0)
+       {
+         /* Special case, as mpn_add wants the first arg's size >= the
+            second arg's size.  */
+         dst_ptr[0] = 1;
+         dst->size = -1;
+         return;
+       }
+
+      {
+       mp_limb one = 1;
+       int cy;
+
+       cy = mpn_add (dst_ptr, src_ptr, size, &one, 1);
+       if (cy)
+         {
+           dst_ptr[size] = cy;
+           size++;
+         }
+      }
+
+      /* Store a negative size, to indicate ones-extension.  */
+      dst->size = -size;
+    }
+  else
+    {
+      /* As with infinite precision: two's complement, then one's complement.
+        But that can be simplified using the identity -x = ~(x - 1).
+        So we're going to compute ~~(x - 1) = x - 1!  */
+      size = -size;
+
+      if (dst->alloc < size)
+       _mpz_realloc (dst, size);
+
+      src_ptr = src->d;
+      dst_ptr = dst->d;
+
+      {
+       mp_limb one = 1;
+
+       size += mpn_sub (dst_ptr, src_ptr, size, &one, 1);
+      }
+
+      /* Store a positive size, to indicate zero-extension.  */
+      dst->size = size;
+    }
+}