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Annotation of OpenXM_contrib/gmp/mpz/fdiv_r_2exp.c, Revision 1.1

1.1     ! maekawa     1: /* mpz_fdiv_r_2exp -- Divide a integer by 2**CNT and produce a remainder.
        !             2:
        !             3: Copyright (C) 1991, 1993, 1994, 1995 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_fdiv_r_2exp (mpz_ptr res, mpz_srcptr in, unsigned long int cnt)
        !            28: #else
        !            29: mpz_fdiv_r_2exp (res, in, cnt)
        !            30:      mpz_ptr res;
        !            31:      mpz_srcptr in;
        !            32:      unsigned long int cnt;
        !            33: #endif
        !            34: {
        !            35:   mp_size_t in_size = ABS (in->_mp_size);
        !            36:   mp_size_t res_size;
        !            37:   mp_size_t limb_cnt = cnt / BITS_PER_MP_LIMB;
        !            38:   mp_srcptr in_ptr = in->_mp_d;
        !            39:
        !            40:   if (in_size > limb_cnt)
        !            41:     {
        !            42:       /* The input operand is (probably) greater than 2**CNT.  */
        !            43:       mp_limb_t x;
        !            44:
        !            45:       x = in_ptr[limb_cnt] & (((mp_limb_t) 1 << cnt % BITS_PER_MP_LIMB) - 1);
        !            46:       if (x != 0)
        !            47:        {
        !            48:          res_size = limb_cnt + 1;
        !            49:          if (res->_mp_alloc < res_size)
        !            50:            _mpz_realloc (res, res_size);
        !            51:
        !            52:          res->_mp_d[limb_cnt] = x;
        !            53:        }
        !            54:       else
        !            55:        {
        !            56:          res_size = limb_cnt;
        !            57:          MPN_NORMALIZE (in_ptr, res_size);
        !            58:
        !            59:          if (res->_mp_alloc < res_size)
        !            60:            _mpz_realloc (res, res_size);
        !            61:
        !            62:          limb_cnt = res_size;
        !            63:        }
        !            64:     }
        !            65:   else
        !            66:     {
        !            67:       /* The input operand is smaller than 2**CNT.  We perform a no-op,
        !            68:         apart from that we might need to copy IN to RES.  */
        !            69:       res_size = in_size;
        !            70:       if (res->_mp_alloc < res_size)
        !            71:        _mpz_realloc (res, res_size);
        !            72:
        !            73:       limb_cnt = res_size;
        !            74:     }
        !            75:
        !            76:   if (res != in)
        !            77:     MPN_COPY (res->_mp_d, in->_mp_d, limb_cnt);
        !            78:   res->_mp_size = res_size;
        !            79:   if (in->_mp_size < 0 && res_size != 0)
        !            80:     {
        !            81:       /* Result should be 2^CNT - RES */
        !            82:       mpz_t tmp;
        !            83:       MPZ_TMP_INIT (tmp, limb_cnt + 1);
        !            84:       mpz_set_ui (tmp, 1L);
        !            85:       mpz_mul_2exp (tmp, tmp, cnt);
        !            86:       mpz_sub (res, tmp, res);
        !            87:     }
        !            88: }