github.com/aergoio/aergo@v1.3.1/libtool/src/gmp-6.1.2/mpn/generic/sec_div.c (about)

     1  /* mpn_sec_div_qr, mpn_sec_div_r -- Compute Q = floor(U / V), U = U mod V.
     2     Side-channel silent under the assumption that the used instructions are
     3     side-channel silent.
     4  
     5     Contributed to the GNU project by Torbjörn Granlund.
     6  
     7  Copyright 2011-2014 Free Software Foundation, Inc.
     8  
     9  This file is part of the GNU MP Library.
    10  
    11  The GNU MP Library is free software; you can redistribute it and/or modify
    12  it under the terms of either:
    13  
    14    * the GNU Lesser General Public License as published by the Free
    15      Software Foundation; either version 3 of the License, or (at your
    16      option) any later version.
    17  
    18  or
    19  
    20    * the GNU General Public License as published by the Free Software
    21      Foundation; either version 2 of the License, or (at your option) any
    22      later version.
    23  
    24  or both in parallel, as here.
    25  
    26  The GNU MP Library is distributed in the hope that it will be useful, but
    27  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    28  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    29  for more details.
    30  
    31  You should have received copies of the GNU General Public License and the
    32  GNU Lesser General Public License along with the GNU MP Library.  If not,
    33  see https://www.gnu.org/licenses/.  */
    34  
    35  #include "gmp.h"
    36  #include "gmp-impl.h"
    37  #include "longlong.h"
    38  
    39  #if OPERATION_sec_div_qr
    40  #define FNAME mpn_sec_div_qr
    41  #define FNAME_itch mpn_sec_div_qr_itch
    42  #define Q(q) q,
    43  #define RETTYPE mp_limb_t
    44  #endif
    45  #if OPERATION_sec_div_r
    46  #define FNAME mpn_sec_div_r
    47  #define FNAME_itch mpn_sec_div_r_itch
    48  #define Q(q)
    49  #define RETTYPE void
    50  #endif
    51  
    52  mp_size_t
    53  FNAME_itch (mp_size_t nn, mp_size_t dn)
    54  {
    55  #if OPERATION_sec_div_qr
    56  /* Needs (nn + dn + 1) + mpn_sec_pi1_div_qr's needs of (2nn' - dn + 1) for a
    57     total of 3nn + 4 limbs at tp.  Note that mpn_sec_pi1_div_qr's nn is one
    58     greater than ours, therefore +4 and not just +2.  */
    59    return 3 * nn + 4;
    60  #endif
    61  #if OPERATION_sec_div_r
    62  /* Needs (nn + dn + 1) + mpn_sec_pi1_div_r's needs of (dn + 1) for a total of
    63     nn + 2dn + 2 limbs at tp.  */
    64    return nn + 2 * dn + 2;
    65  #endif
    66  }
    67  
    68  RETTYPE
    69  FNAME (Q(mp_ptr qp)
    70         mp_ptr np, mp_size_t nn,
    71         mp_srcptr dp, mp_size_t dn,
    72         mp_ptr tp)
    73  {
    74    mp_limb_t d1, d0;
    75    unsigned int cnt;
    76    gmp_pi1_t dinv;
    77    mp_limb_t inv32;
    78  
    79    ASSERT (dn >= 1);
    80    ASSERT (nn >= dn);
    81    ASSERT (dp[dn - 1] != 0);
    82  
    83    d1 = dp[dn - 1];
    84    count_leading_zeros (cnt, d1);
    85  
    86    if (cnt != 0)
    87      {
    88        mp_limb_t qh, cy;
    89        mp_ptr np2, dp2;
    90        dp2 = tp;					/* dn limbs */
    91        mpn_lshift (dp2, dp, dn, cnt);
    92  
    93        np2 = tp + dn;				/* (nn + 1) limbs */
    94        cy = mpn_lshift (np2, np, nn, cnt);
    95        np2[nn++] = cy;
    96  
    97        d0 = dp2[dn - 1];
    98        d0 += (~d0 != 0);
    99        invert_limb (inv32, d0);
   100  
   101        /* We add nn + dn to tp here, not nn + 1 + dn, as expected.  This is
   102  	 since nn here will have been incremented.  */
   103  #if OPERATION_sec_div_qr
   104        qh = mpn_sec_pi1_div_qr (np2 + dn, np2, nn, dp2, dn, inv32, tp + nn + dn);
   105        ASSERT (qh == 0);		/* FIXME: this indicates inefficiency! */
   106        MPN_COPY (qp, np2 + dn, nn - dn - 1);
   107        qh = np2[nn - 1];
   108  #else
   109        mpn_sec_pi1_div_r (np2, nn, dp2, dn, inv32, tp + nn + dn);
   110  #endif
   111  
   112        mpn_rshift (np, np2, dn, cnt);
   113  
   114  #if OPERATION_sec_div_qr
   115        return qh;
   116  #endif
   117      }
   118    else
   119      {
   120        /* FIXME: Consider copying np => np2 here, adding a 0-limb at the top.
   121  	 That would simplify the underlying pi1 function, since then it could
   122  	 assume nn > dn.  */
   123        d0 = dp[dn - 1];
   124        d0 += (~d0 != 0);
   125        invert_limb (inv32, d0);
   126  
   127  #if OPERATION_sec_div_qr
   128        return mpn_sec_pi1_div_qr (qp, np, nn, dp, dn, inv32, tp);
   129  #else
   130        mpn_sec_pi1_div_r (np, nn, dp, dn, inv32, tp);
   131  #endif
   132      }
   133  }