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       1                 :            : /* mpi-bit.c  -  MPI bit level fucntions
       2                 :            :  * Copyright (C) 1998, 1999 Free Software Foundation, Inc.
       3                 :            :  *
       4                 :            :  * This file is part of GnuPG.
       5                 :            :  *
       6                 :            :  * GnuPG is free software; you can redistribute it and/or modify
       7                 :            :  * it under the terms of the GNU General Public License as published by
       8                 :            :  * the Free Software Foundation; either version 2 of the License, or
       9                 :            :  * (at your option) any later version.
      10                 :            :  *
      11                 :            :  * GnuPG is distributed in the hope that it will be useful,
      12                 :            :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      13                 :            :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14                 :            :  * GNU General Public License for more details.
      15                 :            :  *
      16                 :            :  * You should have received a copy of the GNU General Public License
      17                 :            :  * along with this program; if not, write to the Free Software
      18                 :            :  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
      19                 :            :  */
      20                 :            : 
      21                 :            : #include "mpi-internal.h"
      22                 :            : #include "longlong.h"
      23                 :            : 
      24                 :            : #define A_LIMB_1 ((mpi_limb_t) 1)
      25                 :            : 
      26                 :            : /****************
      27                 :            :  * Sometimes we have MSL (most significant limbs) which are 0;
      28                 :            :  * this is for some reasons not good, so this function removes them.
      29                 :            :  */
      30                 :          3 : void mpi_normalize(MPI a)
      31                 :            : {
      32                 :          3 :         for (; a->nlimbs && !a->d[a->nlimbs - 1]; a->nlimbs--)
      33                 :            :                 ;
      34                 :          3 : }
      35                 :            : 
      36                 :            : /****************
      37                 :            :  * Return the number of bits in A.
      38                 :            :  */
      39                 :          0 : unsigned mpi_get_nbits(MPI a)
      40                 :            : {
      41                 :            :         unsigned n;
      42                 :            : 
      43                 :            :         mpi_normalize(a);
      44                 :            : 
      45                 :          0 :         if (a->nlimbs) {
      46                 :          0 :                 mpi_limb_t alimb = a->d[a->nlimbs - 1];
      47                 :          0 :                 if (alimb)
      48                 :          0 :                         n = count_leading_zeros(alimb);
      49                 :            :                 else
      50                 :            :                         n = BITS_PER_MPI_LIMB;
      51                 :          0 :                 n = BITS_PER_MPI_LIMB - n + (a->nlimbs - 1) * BITS_PER_MPI_LIMB;
      52                 :            :         } else
      53                 :            :                 n = 0;
      54                 :          0 :         return n;
      55                 :            : }
      56                 :            : EXPORT_SYMBOL_GPL(mpi_get_nbits);