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-rw-r--r--gnu/lib/libgmp/mpz_com.c96
1 files changed, 96 insertions, 0 deletions
diff --git a/gnu/lib/libgmp/mpz_com.c b/gnu/lib/libgmp/mpz_com.c
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+++ b/gnu/lib/libgmp/mpz_com.c
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+/* 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;
+ }
+}
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