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Annotation of OpenXM_contrib/gmp/mpz/mul_2exp.c, Revision 1.1

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
        !             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: 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: }