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Annotation of OpenXM_contrib/gmp/mpz/mul_2exp.c, Revision 1.1.1.2

1.1       maekawa     1: /* mpz_mul_2exp -- Multiply a bignum by 2**CNT
                      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
1.1.1.2 ! maekawa     8: it under the terms of the GNU Lesser General Public License as published by
        !             9: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1       maekawa    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
1.1.1.2 ! maekawa    14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
1.1       maekawa    15: License for more details.
                     16:
1.1.1.2 ! maekawa    17: You should have received a copy of the GNU Lesser General Public License
1.1       maekawa    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: void
                     26: #if __STDC__
                     27: mpz_mul_2exp (mpz_ptr w, mpz_srcptr u, unsigned long int cnt)
                     28: #else
                     29: mpz_mul_2exp (w, u, cnt)
                     30:      mpz_ptr w;
                     31:      mpz_srcptr u;
                     32:      unsigned long int cnt;
                     33: #endif
                     34: {
                     35:   mp_size_t usize = u->_mp_size;
                     36:   mp_size_t abs_usize = ABS (usize);
                     37:   mp_size_t wsize;
                     38:   mp_size_t limb_cnt;
                     39:   mp_ptr wp;
                     40:   mp_limb_t wlimb;
                     41:
                     42:   if (usize == 0)
                     43:     {
                     44:       w->_mp_size = 0;
                     45:       return;
                     46:     }
                     47:
                     48:   limb_cnt = cnt / BITS_PER_MP_LIMB;
                     49:   wsize = abs_usize + limb_cnt + 1;
                     50:   if (w->_mp_alloc < wsize)
                     51:     _mpz_realloc (w, wsize);
                     52:
                     53:   wp = w->_mp_d;
                     54:   wsize = abs_usize + limb_cnt;
                     55:
                     56:   cnt %= BITS_PER_MP_LIMB;
                     57:   if (cnt != 0)
                     58:     {
                     59:       wlimb = mpn_lshift (wp + limb_cnt, u->_mp_d, abs_usize, cnt);
                     60:       if (wlimb != 0)
                     61:        {
                     62:          wp[wsize] = wlimb;
                     63:          wsize++;
                     64:        }
                     65:     }
                     66:   else
                     67:     {
                     68:       MPN_COPY_DECR (wp + limb_cnt, u->_mp_d, abs_usize);
                     69:     }
                     70:
                     71:   /* Zero all whole limbs at low end.  Do it here and not before calling
                     72:      mpn_lshift, not to lose for U == W.  */
                     73:   MPN_ZERO (wp, limb_cnt);
                     74:
                     75:   w->_mp_size = usize >= 0 ? wsize : -wsize;
                     76: }