Annotation of OpenXM/src/kan96xx/gmp-2.0.2-ssh-2/mpz/com.c, Revision 1.1
1.1 ! takayama 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: }
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