Return to fdiv_r_2exp.c CVS log

Up to [local] / OpenXM_contrib / gmp / mpz

Annotation of OpenXM_contrib/gmp/mpz/fdiv_r_2exp.c, Revision 1.1.1.2

1.1       maekawa     1: /* mpz_fdiv_r_2exp -- Divide a integer by 2**CNT and produce a remainder.
                      2:
1.1.1.2 ! maekawa     3: Copyright (C) 1991, 1993, 1994, 1995, 1998, 1999 Free Software Foundation,
        !             4: Inc.
1.1       maekawa     5:
                      6: This file is part of the GNU MP Library.
                      7:
                      8: The GNU MP Library is free software; you can redistribute it and/or modify
1.1.1.2 ! maekawa     9: it under the terms of the GNU Lesser General Public License as published by
        !            10: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1       maekawa    11: option) any later version.
                     12:
                     13: The GNU MP Library is distributed in the hope that it will be useful, but
                     14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
1.1.1.2 ! maekawa    15: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
1.1       maekawa    16: License for more details.
                     17:
1.1.1.2 ! maekawa    18: You should have received a copy of the GNU Lesser General Public License
1.1       maekawa    19: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     21: MA 02111-1307, USA. */
                     22:
                     23: #include "gmp.h"
                     24: #include "gmp-impl.h"
                     25:
                     26: void
                     27: #if __STDC__
                     28: mpz_fdiv_r_2exp (mpz_ptr res, mpz_srcptr in, unsigned long int cnt)
                     29: #else
                     30: mpz_fdiv_r_2exp (res, in, cnt)
                     31:      mpz_ptr res;
                     32:      mpz_srcptr in;
                     33:      unsigned long int cnt;
                     34: #endif
                     35: {
                     36:   mp_size_t in_size = ABS (in->_mp_size);
                     37:   mp_size_t res_size;
                     38:   mp_size_t limb_cnt = cnt / BITS_PER_MP_LIMB;
                     39:   mp_srcptr in_ptr = in->_mp_d;
                     40:
                     41:   if (in_size > limb_cnt)
                     42:     {
                     43:       /* The input operand is (probably) greater than 2**CNT.  */
                     44:       mp_limb_t x;
                     45:
                     46:       x = in_ptr[limb_cnt] & (((mp_limb_t) 1 << cnt % BITS_PER_MP_LIMB) - 1);
                     47:       if (x != 0)
                     48:        {
                     49:          res_size = limb_cnt + 1;
                     50:          if (res->_mp_alloc < res_size)
                     51:            _mpz_realloc (res, res_size);
                     52:
                     53:          res->_mp_d[limb_cnt] = x;
                     54:        }
                     55:       else
                     56:        {
                     57:          res_size = limb_cnt;
                     58:          MPN_NORMALIZE (in_ptr, res_size);
                     59:
                     60:          if (res->_mp_alloc < res_size)
                     61:            _mpz_realloc (res, res_size);
                     62:
                     63:          limb_cnt = res_size;
                     64:        }
                     65:     }
                     66:   else
                     67:     {
                     68:       /* The input operand is smaller than 2**CNT.  We perform a no-op,
1.1.1.2 ! maekawa    69:         apart from that we might need to copy IN to RES, and may need
        !            70:         to round the result.  */
1.1       maekawa    71:       res_size = in_size;
                     72:       if (res->_mp_alloc < res_size)
                     73:        _mpz_realloc (res, res_size);
                     74:
                     75:       limb_cnt = res_size;
                     76:     }
                     77:
                     78:   if (res != in)
                     79:     MPN_COPY (res->_mp_d, in->_mp_d, limb_cnt);
1.1.1.2 ! maekawa    80:   in_size = in->_mp_size;
1.1       maekawa    81:   res->_mp_size = res_size;
1.1.1.2 ! maekawa    82:   if (in_size < 0 && res_size != 0)
1.1       maekawa    83:     {
                     84:       /* Result should be 2^CNT - RES */
                     85:       mpz_t tmp;
1.1.1.2 ! maekawa    86:       MPZ_TMP_INIT (tmp, cnt/BITS_PER_MP_LIMB + 2);
1.1       maekawa    87:       mpz_set_ui (tmp, 1L);
                     88:       mpz_mul_2exp (tmp, tmp, cnt);
                     89:       mpz_sub (res, tmp, res);
                     90:     }
                     91: }
1.1.1.2 ! maekawa    92:
        !            93: /* This is an alternative ending of the above function using just low-level
        !            94:    functions.  Tested, but perhaps excessive?  */
        !            95: #if 0
        !            96:   if (in->_mp_size < 0 && res_size != 0)
        !            97:     {
        !            98:       /* Result should be 2^CNT - RES */
        !            99:
        !           100:       mp_ptr rp;
        !           101:
        !           102:       limb_cnt = cnt / BITS_PER_MP_LIMB;
        !           103:
        !           104:       if (res->_mp_alloc <= limb_cnt)
        !           105:        _mpz_realloc (res, limb_cnt + 1);
        !           106:       rp = PTR(res);
        !           107:       if (res_size > limb_cnt)
        !           108:        {
        !           109:          mpn_nz_neg (rp, rp, res_size);
        !           110:          rp[limb_cnt] &= ~(~(mp_limb_t) 0 << cnt % BITS_PER_MP_LIMB);
        !           111:          MPN_NORMALIZE_NOT_ZERO (rp, res_size);
        !           112:        }
        !           113:       else
        !           114:        {
        !           115:          mp_size_t i;
        !           116:          mpn_nz_neg (rp, rp, res_size);
        !           117:          for (i = res_size; i < limb_cnt; i++)
        !           118:            rp[i] = ~ (mp_limb_t) 0;
        !           119:          res_size = limb_cnt;
        !           120:          if (cnt % BITS_PER_MP_LIMB != 0)
        !           121:            {
        !           122:              rp[res_size] = ((mp_limb_t) 1 << (cnt % BITS_PER_MP_LIMB)) - 1;
        !           123:              res_size++;
        !           124:            }
        !           125:          else
        !           126:            MPN_NORMALIZE_NOT_ZERO (rp, res_size);
        !           127:        }
        !           128:     }
        !           129:   SIZ(res) = res_size;
        !           130: }
        !           131:
        !           132: static void
        !           133: mpn_nz_neg (rp, sp, n)
        !           134:      mp_ptr rp, sp;
        !           135:      mp_size_t n;
        !           136: {
        !           137:   mp_size_t i;
        !           138:   mp_limb_t x;
        !           139:
        !           140:   x = sp[0];
        !           141:   rp[0] = -x;
        !           142:   for (i = 1; x == 0; i++)
        !           143:     {
        !           144:       x = sp[i];
        !           145:       rp[i] = -x;
        !           146:     }
        !           147:
        !           148:   for (; i < n; i++)
        !           149:     {
        !           150:       rp[i] = ~sp[i];
        !           151:     }
        !           152: }
        !           153: #endif