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Annotation of OpenXM/src/kan96xx/gmp-2.0.2-ssh-2/mpn/generic/sub_n.c, Revision 1.1

1.1     ! takayama    1: /* mpn_sub_n -- Subtract two limb vectors of equal, non-zero length.
        !             2:
        !             3: Copyright (C) 1992, 1993, 1994, 1996 Free Software Foundation, Inc.
        !             4:
        !             5: This file is part of the GNU MP Library.
        !             6:
        !             7: The GNU MP Library is free software; you can redistribute it and/or modify
        !             8: it under the terms of the GNU Library General Public License as published by
        !             9: the Free Software Foundation; either version 2 of the License, or (at your
        !            10: option) any later version.
        !            11:
        !            12: The GNU MP Library is distributed in the hope that it will be useful, but
        !            13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
        !            15: License for more details.
        !            16:
        !            17: You should have received a copy of the GNU Library General Public License
        !            18: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
        !            19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            20: MA 02111-1307, USA. */
        !            21:
        !            22: #include "gmp.h"
        !            23: #include "gmp-impl.h"
        !            24:
        !            25: mp_limb_t
        !            26: #if __STDC__
        !            27: mpn_sub_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr, mp_size_t size)
        !            28: #else
        !            29: mpn_sub_n (res_ptr, s1_ptr, s2_ptr, size)
        !            30:      register mp_ptr res_ptr;
        !            31:      register mp_srcptr s1_ptr;
        !            32:      register mp_srcptr s2_ptr;
        !            33:      mp_size_t size;
        !            34: #endif
        !            35: {
        !            36:   register mp_limb_t x, y, cy;
        !            37:   register mp_size_t j;
        !            38:
        !            39:   /* The loop counter and index J goes from -SIZE to -1.  This way
        !            40:      the loop becomes faster.  */
        !            41:   j = -size;
        !            42:
        !            43:   /* Offset the base pointers to compensate for the negative indices.  */
        !            44:   s1_ptr -= j;
        !            45:   s2_ptr -= j;
        !            46:   res_ptr -= j;
        !            47:
        !            48:   cy = 0;
        !            49:   do
        !            50:     {
        !            51:       y = s2_ptr[j];
        !            52:       x = s1_ptr[j];
        !            53:       y += cy;                 /* add previous carry to subtrahend */
        !            54:       cy = (y < cy);           /* get out carry from that addition */
        !            55:       y = x - y;               /* main subtract */
        !            56:       cy = (y > x) + cy;       /* get out carry from the subtract, combine */
        !            57:       res_ptr[j] = y;
        !            58:     }
        !            59:   while (++j != 0);
        !            60:
        !            61:   return cy;
        !            62: }