LCOV - code coverage report
Current view: top level - source4/heimdal/lib/hcrypto/libtommath - bn_mp_div_d.c (source / functions) Hit Total Coverage
Test: coverage report for abartlet/fix-coverage dd10fb34 Lines: 0 44 0.0 %
Date: 2021-09-23 10:06:22 Functions: 0 2 0.0 %

          Line data    Source code
       1             : #include <tommath.h>
       2             : #ifdef BN_MP_DIV_D_C
       3             : /* LibTomMath, multiple-precision integer library -- Tom St Denis
       4             :  *
       5             :  * LibTomMath is a library that provides multiple-precision
       6             :  * integer arithmetic as well as number theoretic functionality.
       7             :  *
       8             :  * The library was designed directly after the MPI library by
       9             :  * Michael Fromberger but has been written from scratch with
      10             :  * additional optimizations in place.
      11             :  *
      12             :  * The library is free for all purposes without any express
      13             :  * guarantee it works.
      14             :  *
      15             :  * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
      16             :  */
      17             : 
      18           0 : static int s_is_power_of_two(mp_digit b, int *p)
      19             : {
      20             :    int x;
      21             : 
      22             :    /* fast return if no power of two */
      23           0 :    if ((b==0) || (b & (b-1))) {
      24           0 :       return 0;
      25             :    }
      26             : 
      27           0 :    for (x = 0; x < DIGIT_BIT; x++) {
      28           0 :       if (b == (((mp_digit)1)<<x)) {
      29           0 :          *p = x;
      30           0 :          return 1;
      31             :       }
      32             :    }
      33           0 :    return 0;
      34             : }
      35             : 
      36             : /* single digit division (based on routine from MPI) */
      37           0 : int mp_div_d (mp_int * a, mp_digit b, mp_int * c, mp_digit * d)
      38             : {
      39             :   mp_int  q;
      40             :   mp_word w;
      41             :   mp_digit t;
      42             :   int     res, ix;
      43             : 
      44             :   /* cannot divide by zero */
      45           0 :   if (b == 0) {
      46           0 :      return MP_VAL;
      47             :   }
      48             : 
      49             :   /* quick outs */
      50           0 :   if (b == 1 || mp_iszero(a) == 1) {
      51           0 :      if (d != NULL) {
      52           0 :         *d = 0;
      53             :      }
      54           0 :      if (c != NULL) {
      55           0 :         return mp_copy(a, c);
      56             :      }
      57           0 :      return MP_OKAY;
      58             :   }
      59             : 
      60             :   /* power of two ? */
      61           0 :   if (s_is_power_of_two(b, &ix) == 1) {
      62           0 :      if (d != NULL) {
      63           0 :         *d = a->dp[0] & ((((mp_digit)1)<<ix) - 1);
      64             :      }
      65           0 :      if (c != NULL) {
      66           0 :         return mp_div_2d(a, ix, c, NULL);
      67             :      }
      68           0 :      return MP_OKAY;
      69             :   }
      70             : 
      71             : #ifdef BN_MP_DIV_3_C
      72             :   /* three? */
      73           0 :   if (b == 3) {
      74           0 :      return mp_div_3(a, c, d);
      75             :   }
      76             : #endif
      77             : 
      78             :   /* no easy answer [c'est la vie].  Just division */
      79           0 :   if ((res = mp_init_size(&q, a->used)) != MP_OKAY) {
      80           0 :      return res;
      81             :   }
      82             : 
      83           0 :   q.used = a->used;
      84           0 :   q.sign = a->sign;
      85           0 :   w = 0;
      86           0 :   for (ix = a->used - 1; ix >= 0; ix--) {
      87           0 :      w = (w << ((mp_word)DIGIT_BIT)) | ((mp_word)a->dp[ix]);
      88             : 
      89           0 :      if (w >= b) {
      90           0 :         t = (mp_digit)(w / b);
      91           0 :         w -= ((mp_word)t) * ((mp_word)b);
      92             :       } else {
      93           0 :         t = 0;
      94             :       }
      95           0 :       q.dp[ix] = (mp_digit)t;
      96             :   }
      97             : 
      98           0 :   if (d != NULL) {
      99           0 :      *d = (mp_digit)w;
     100             :   }
     101             : 
     102           0 :   if (c != NULL) {
     103           0 :      mp_clamp(&q);
     104           0 :      mp_exch(&q, c);
     105             :   }
     106           0 :   mp_clear(&q);
     107             : 
     108           0 :   return res;
     109             : }
     110             : 
     111             : #endif
     112             : 
     113             : /* $Source: /cvs/libtom/libtommath/bn_mp_div_d.c,v $ */
     114             : /* $Revision: 1.5 $ */
     115             : /* $Date: 2007/01/09 04:44:32 $ */

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