text: #include <tommath.h>
  #ifdef BN_MP_DIV_2D_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis
   *
   * LibTomMath is a library that provides multiple-precision
   * integer arithmetic as well as number theoretic functionality.
   *
   * The library was designed directly after the MPI library by
   * Michael Fromberger but has been written from scratch with
   * additional optimizations in place.
   *
   * The library is free for all purposes without any express
   * guarantee it works.
   *
   * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com
   */
  
  /* shift right by a certain bit count (store quotient in c, optional remainder in d) */
  int mp_div_2d (mp_int * a, int b, mp_int * c, mp_int * d)
  {
    mp_digit D, r, rr;
    int     x, res;
    mp_int  t;
  
  
    /* if the shift count is <= 0 then we do no work */
    if (b <= 0) {
      res = mp_copy (a, c);
      if (d != NULL) {
        mp_zero (d);
      }
      return res;
    }
  
    if ((res = mp_init (&t)) != MP_OKAY) {
      return res;
    }
  
    /* get the remainder */
    if (d != NULL) {
      if ((res = mp_mod_2d (a, b, &t)) != MP_OKAY) {
        mp_clear (&t);
        return res;
      }
    }
  
    /* copy */
    if ((res = mp_copy (a, c)) != MP_OKAY) {
      mp_clear (&t);
      return res;
    }
  
    /* shift by as many digits in the bit count */
    if (b >= (int)DIGIT_BIT) {
      mp_rshd (c, b / DIGIT_BIT);
    }
  
    /* shift any bit count < DIGIT_BIT */
    D = (mp_digit) (b % DIGIT_BIT);
    if (D != 0) {
      register mp_digit *tmpc, mask, shift;
  
      /* mask */
      mask = (((mp_digit)1) << D) - 1;
  
      /* shift for lsb */
      shift = DIGIT_BIT - D;
  
      /* alias */
      tmpc = c->dp + (c->used - 1);
  
      /* carry */
      r = 0;
      for (x = c->used - 1; x >= 0; x--) {
        /* get the lower  bits of this word in a temp */
        rr = *tmpc & mask;
  
        /* shift the current word and mix in the carry bits from the previous word */
        *tmpc = (*tmpc >> D) | (r << shift);
        --tmpc;
  
        /* set the carry to the carry bits of the current word found above */
        r = rr;
      }
    }
    mp_clamp (c);
    if (d != NULL) {
      mp_exch (&t, d);
    }
    mp_clear (&t);
    return MP_OKAY;
  }
  #endif
  
  /* $Source$ */
  /* $Revision: 24838 $ */
  /* $Date: 2007-01-23 23:16:57 -0600 (Tue, 23 Jan 2007) $ */
  