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Annotation of OpenXM_contrib/gmp/mpz/com.c, Revision 1.1.1.3

1.1       maekawa     1: /* mpz_com(mpz_ptr dst, mpz_ptr src) -- Assign the bit-complemented value of
                      2:    SRC to DST.
                      3:
1.1.1.3 ! ohara       4: Copyright 1991, 1993, 1994, 1996, 2001 Free Software Foundation, Inc.
1.1       maekawa     5:
                      6: This file is part of the GNU MP Library.
                      7:
                      8: The GNU MP Library is free software; you can redistribute it and/or modify
1.1.1.2   maekawa     9: it under the terms of the GNU Lesser General Public License as published by
                     10: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1       maekawa    11: option) any later version.
                     12:
                     13: The GNU MP Library is distributed in the hope that it will be useful, but
                     14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
1.1.1.2   maekawa    15: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
1.1       maekawa    16: License for more details.
                     17:
1.1.1.2   maekawa    18: You should have received a copy of the GNU Lesser General Public License
1.1       maekawa    19: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     21: MA 02111-1307, USA. */
                     22:
                     23: #include "gmp.h"
                     24: #include "gmp-impl.h"
                     25:
                     26: void
                     27: mpz_com (mpz_ptr dst, mpz_srcptr src)
                     28: {
                     29:   mp_size_t size = src->_mp_size;
                     30:   mp_srcptr src_ptr;
                     31:   mp_ptr dst_ptr;
                     32:
                     33:   if (size >= 0)
                     34:     {
                     35:       /* As with infinite precision: one's complement, two's complement.
                     36:         But this can be simplified using the identity -x = ~x + 1.
                     37:         So we're going to compute (~~x) + 1 = x + 1!  */
                     38:
                     39:       if (dst->_mp_alloc < size + 1)
                     40:        _mpz_realloc (dst, size + 1);
                     41:
                     42:       src_ptr = src->_mp_d;
                     43:       dst_ptr = dst->_mp_d;
                     44:
                     45:       if (size == 0)
                     46:        {
                     47:          /* Special case, as mpn_add wants the first arg's size >= the
                     48:             second arg's size.  */
                     49:          dst_ptr[0] = 1;
                     50:          dst->_mp_size = -1;
                     51:          return;
                     52:        }
                     53:
                     54:       {
                     55:        mp_limb_t cy;
                     56:
                     57:        cy = mpn_add_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
                     58:        if (cy)
                     59:          {
                     60:            dst_ptr[size] = cy;
                     61:            size++;
                     62:          }
                     63:       }
                     64:
                     65:       /* Store a negative size, to indicate ones-extension.  */
                     66:       dst->_mp_size = -size;
                     67:     }
                     68:   else
                     69:     {
                     70:       /* As with infinite precision: two's complement, then one's complement.
                     71:         But that can be simplified using the identity -x = ~(x - 1).
                     72:         So we're going to compute ~~(x - 1) = x - 1!  */
                     73:       size = -size;
                     74:
                     75:       if (dst->_mp_alloc < size)
                     76:        _mpz_realloc (dst, size);
                     77:
                     78:       src_ptr = src->_mp_d;
                     79:       dst_ptr = dst->_mp_d;
                     80:
                     81:       mpn_sub_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
                     82:       size -= dst_ptr[size - 1] == 0;
                     83:
                     84:       /* Store a positive size, to indicate zero-extension.  */
                     85:       dst->_mp_size = size;
                     86:     }
                     87: }