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Annotation of OpenXM_contrib/gmp/mpz/sub.c, Revision 1.1.1.1

1.1       maekawa     1: /* mpz_sub -- Subtract two integers.
                      2:
                      3: Copyright (C) 1991, 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: #ifndef BERKELEY_MP
                     26: void
                     27: #if __STDC__
                     28: mpz_sub (mpz_ptr w, mpz_srcptr u, mpz_srcptr v)
                     29: #else
                     30: mpz_sub (w, u, v)
                     31:      mpz_ptr w;
                     32:      mpz_srcptr u;
                     33:      mpz_srcptr v;
                     34: #endif
                     35: #else /* BERKELEY_MP */
                     36: void
                     37: #if __STDC__
                     38: msub (mpz_srcptr u, mpz_srcptr v, mpz_ptr w)
                     39: #else
                     40: msub (u, v, w)
                     41:      mpz_srcptr u;
                     42:      mpz_srcptr v;
                     43:      mpz_ptr w;
                     44: #endif
                     45: #endif /* BERKELEY_MP */
                     46: {
                     47:   mp_srcptr up, vp;
                     48:   mp_ptr wp;
                     49:   mp_size_t usize, vsize, wsize;
                     50:   mp_size_t abs_usize;
                     51:   mp_size_t abs_vsize;
                     52:
                     53:   usize = u->_mp_size;
                     54:   vsize = -v->_mp_size;                /* The "-" makes the difference from mpz_add */
                     55:   abs_usize = ABS (usize);
                     56:   abs_vsize = ABS (vsize);
                     57:
                     58:   if (abs_usize < abs_vsize)
                     59:     {
                     60:       /* Swap U and V. */
                     61:       {const __mpz_struct *t = u; u = v; v = t;}
                     62:       {mp_size_t t = usize; usize = vsize; vsize = t;}
                     63:       {mp_size_t t = abs_usize; abs_usize = abs_vsize; abs_vsize = t;}
                     64:     }
                     65:
                     66:   /* True: ABS_USIZE >= ABS_VSIZE.  */
                     67:
                     68:   /* If not space for w (and possible carry), increase space.  */
                     69:   wsize = abs_usize + 1;
                     70:   if (w->_mp_alloc < wsize)
                     71:     _mpz_realloc (w, wsize);
                     72:
                     73:   /* These must be after realloc (u or v may be the same as w).  */
                     74:   up = u->_mp_d;
                     75:   vp = v->_mp_d;
                     76:   wp = w->_mp_d;
                     77:
                     78:   if ((usize ^ vsize) < 0)
                     79:     {
                     80:       /* U and V have different sign.  Need to compare them to determine
                     81:         which operand to subtract from which.  */
                     82:
                     83:       /* This test is right since ABS_USIZE >= ABS_VSIZE.  */
                     84:       if (abs_usize != abs_vsize)
                     85:        {
                     86:          mpn_sub (wp, up, abs_usize, vp, abs_vsize);
                     87:          wsize = abs_usize;
                     88:          MPN_NORMALIZE (wp, wsize);
                     89:          if (usize < 0)
                     90:            wsize = -wsize;
                     91:        }
                     92:       else if (mpn_cmp (up, vp, abs_usize) < 0)
                     93:        {
                     94:          mpn_sub_n (wp, vp, up, abs_usize);
                     95:          wsize = abs_usize;
                     96:          MPN_NORMALIZE (wp, wsize);
                     97:          if (usize >= 0)
                     98:            wsize = -wsize;
                     99:        }
                    100:       else
                    101:        {
                    102:          mpn_sub_n (wp, up, vp, abs_usize);
                    103:          wsize = abs_usize;
                    104:          MPN_NORMALIZE (wp, wsize);
                    105:          if (usize < 0)
                    106:            wsize = -wsize;
                    107:        }
                    108:     }
                    109:   else
                    110:     {
                    111:       /* U and V have same sign.  Add them.  */
                    112:       mp_limb_t cy_limb = mpn_add (wp, up, abs_usize, vp, abs_vsize);
                    113:       wp[abs_usize] = cy_limb;
                    114:       wsize = abs_usize + cy_limb;
                    115:       if (usize < 0)
                    116:        wsize = -wsize;
                    117:     }
                    118:
                    119:   w->_mp_size = wsize;
                    120: }