source/libs/gmp/gmp-src/mpn/generic/bdiv_dbm1c.c

   1 /* mpn_bdiv_dbm1c -- divide an mpn number by a divisor of B-1, where B is the
   2    limb base.  The dbm1c moniker means "Divisor of B Minus 1 with Carry".
   3
   4    THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.  IT IS ONLY
   5    SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.  IN FACT, IT IS ALMOST
   6    GUARANTEED THAT IT'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
   7
   8 Copyright 2008, 2009 Free Software Foundation, Inc.
   9
  10 This file is part of the GNU MP Library.
  11
  12 The GNU MP Library is free software; you can redistribute it and/or modify
  13 it under the terms of either:
  14
  15   * the GNU Lesser General Public License as published by the Free
  16     Software Foundation; either version 3 of the License, or (at your
  17     option) any later version.
  18
  19 or
  20
  21   * the GNU General Public License as published by the Free Software
  22     Foundation; either version 2 of the License, or (at your option) any
  23     later version.
  24
  25 or both in parallel, as here.
  26
  27 The GNU MP Library is distributed in the hope that it will be useful, but
  28 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  29 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  30 for more details.
  31
  32 You should have received copies of the GNU General Public License and the
  33 GNU Lesser General Public License along with the GNU MP Library.  If not,
  34 see https://www.gnu.org/licenses/.  */
  35
  36 #include "gmp.h"
  37 #include "gmp-impl.h"
  38 #include "longlong.h"
  39
  40
  41 mp_limb_t
  42 mpn_bdiv_dbm1c (mp_ptr qp, mp_srcptr ap, mp_size_t n, mp_limb_t bd, mp_limb_t h)
  43 {
  44   mp_limb_t a, p0, p1, cy;
  45   mp_size_t i;
  46
  47   for (i = 0; i < n; i++)
  48     {
  49       a = ap[i];
  50       umul_ppmm (p1, p0, a, bd << GMP_NAIL_BITS);
  51       p0 >>= GMP_NAIL_BITS;
  52       cy = h < p0;
  53       h = (h - p0) & GMP_NUMB_MASK;
  54       qp[i] = h;
  55       h = h - p1 - cy;
  56     }
  57
  58   return h;
  59 }