github.com/aergoio/aergo@v1.3.1/libtool/src/gmp-6.1.2/mpz/tdiv_q_2exp.c (about)

     1  /* mpz_tdiv_q_2exp -- Divide an integer by 2**CNT.  Round the quotient
     2     towards -infinity.
     3  
     4  Copyright 1991, 1993, 1994, 1996, 2001, 2002, 2012 Free Software Foundation,
     5  Inc.
     6  
     7  This file is part of the GNU MP Library.
     8  
     9  The GNU MP Library is free software; you can redistribute it and/or modify
    10  it under the terms of either:
    11  
    12    * the GNU Lesser General Public License as published by the Free
    13      Software Foundation; either version 3 of the License, or (at your
    14      option) any later version.
    15  
    16  or
    17  
    18    * the GNU General Public License as published by the Free Software
    19      Foundation; either version 2 of the License, or (at your option) any
    20      later version.
    21  
    22  or both in parallel, as here.
    23  
    24  The GNU MP Library is distributed in the hope that it will be useful, but
    25  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    26  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    27  for more details.
    28  
    29  You should have received copies of the GNU General Public License and the
    30  GNU Lesser General Public License along with the GNU MP Library.  If not,
    31  see https://www.gnu.org/licenses/.  */
    32  
    33  #include "gmp.h"
    34  #include "gmp-impl.h"
    35  
    36  void
    37  mpz_tdiv_q_2exp (mpz_ptr r, mpz_srcptr u, mp_bitcnt_t cnt)
    38  {
    39    mp_size_t un, rn;
    40    mp_size_t limb_cnt;
    41    mp_ptr rp;
    42    mp_srcptr up;
    43  
    44    un = SIZ(u);
    45    limb_cnt = cnt / GMP_NUMB_BITS;
    46    rn = ABS (un) - limb_cnt;
    47  
    48    if (rn <= 0)
    49      rn = 0;
    50    else
    51      {
    52        rp = MPZ_REALLOC (r, rn);
    53        up = PTR(u) + limb_cnt;
    54  
    55        cnt %= GMP_NUMB_BITS;
    56        if (cnt != 0)
    57  	{
    58  	  mpn_rshift (rp, up, rn, cnt);
    59  	  rn -= rp[rn - 1] == 0;
    60  	}
    61        else
    62  	{
    63  	  MPN_COPY_INCR (rp, up, rn);
    64  	}
    65      }
    66  
    67    SIZ(r) = un >= 0 ? rn : -rn;
    68  }