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Annotation of OpenXM_contrib/gmp/mpz/com.c, Revision 1.1

1.1     ! maekawa     1: /* mpz_com(mpz_ptr dst, mpz_ptr src) -- Assign the bit-complemented value of
        !             2:    SRC to DST.
        !             3:
        !             4: Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
        !             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
        !             9: it under the terms of the GNU Library General Public License as published by
        !            10: the Free Software Foundation; either version 2 of the License, or (at your
        !            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
        !            15: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
        !            16: License for more details.
        !            17:
        !            18: You should have received a copy of the GNU Library General Public License
        !            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: #if __STDC__
        !            28: mpz_com (mpz_ptr dst, mpz_srcptr src)
        !            29: #else
        !            30: mpz_com (dst, src)
        !            31:      mpz_ptr dst;
        !            32:      mpz_srcptr src;
        !            33: #endif
        !            34: {
        !            35:   mp_size_t size = src->_mp_size;
        !            36:   mp_srcptr src_ptr;
        !            37:   mp_ptr dst_ptr;
        !            38:
        !            39:   if (size >= 0)
        !            40:     {
        !            41:       /* As with infinite precision: one's complement, two's complement.
        !            42:         But this can be simplified using the identity -x = ~x + 1.
        !            43:         So we're going to compute (~~x) + 1 = x + 1!  */
        !            44:
        !            45:       if (dst->_mp_alloc < size + 1)
        !            46:        _mpz_realloc (dst, size + 1);
        !            47:
        !            48:       src_ptr = src->_mp_d;
        !            49:       dst_ptr = dst->_mp_d;
        !            50:
        !            51:       if (size == 0)
        !            52:        {
        !            53:          /* Special case, as mpn_add wants the first arg's size >= the
        !            54:             second arg's size.  */
        !            55:          dst_ptr[0] = 1;
        !            56:          dst->_mp_size = -1;
        !            57:          return;
        !            58:        }
        !            59:
        !            60:       {
        !            61:        mp_limb_t cy;
        !            62:
        !            63:        cy = mpn_add_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
        !            64:        if (cy)
        !            65:          {
        !            66:            dst_ptr[size] = cy;
        !            67:            size++;
        !            68:          }
        !            69:       }
        !            70:
        !            71:       /* Store a negative size, to indicate ones-extension.  */
        !            72:       dst->_mp_size = -size;
        !            73:     }
        !            74:   else
        !            75:     {
        !            76:       /* As with infinite precision: two's complement, then one's complement.
        !            77:         But that can be simplified using the identity -x = ~(x - 1).
        !            78:         So we're going to compute ~~(x - 1) = x - 1!  */
        !            79:       size = -size;
        !            80:
        !            81:       if (dst->_mp_alloc < size)
        !            82:        _mpz_realloc (dst, size);
        !            83:
        !            84:       src_ptr = src->_mp_d;
        !            85:       dst_ptr = dst->_mp_d;
        !            86:
        !            87:       mpn_sub_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
        !            88:       size -= dst_ptr[size - 1] == 0;
        !            89:
        !            90:       /* Store a positive size, to indicate zero-extension.  */
        !            91:       dst->_mp_size = size;
        !            92:     }
        !            93: }