LCOV - code coverage report
Current view: top level - source4/heimdal/lib/hcrypto/libtommath - bn_mp_reduce.c (source / functions) Hit Total Coverage
Test: coverage report for abartlet/fix-coverage dd10fb34 Lines: 0 29 0.0 %
Date: 2021-09-23 10:06:22 Functions: 0 1 0.0 %

          Line data    Source code
       1             : #include <tommath.h>
       2             : #ifdef BN_MP_REDUCE_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             : /* reduces x mod m, assumes 0 < x < m**2, mu is
      19             :  * precomputed via mp_reduce_setup.
      20             :  * From HAC pp.604 Algorithm 14.42
      21             :  */
      22           0 : int mp_reduce (mp_int * x, mp_int * m, mp_int * mu)
      23             : {
      24             :   mp_int  q;
      25           0 :   int     res, um = m->used;
      26             : 
      27             :   /* q = x */
      28           0 :   if ((res = mp_init_copy (&q, x)) != MP_OKAY) {
      29           0 :     return res;
      30             :   }
      31             : 
      32             :   /* q1 = x / b**(k-1)  */
      33           0 :   mp_rshd (&q, um - 1);
      34             : 
      35             :   /* according to HAC this optimization is ok */
      36           0 :   if (((unsigned long) um) > (((mp_digit)1) << (DIGIT_BIT - 1))) {
      37           0 :     if ((res = mp_mul (&q, mu, &q)) != MP_OKAY) {
      38           0 :       goto CLEANUP;
      39             :     }
      40             :   } else {
      41             : #ifdef BN_S_MP_MUL_HIGH_DIGS_C
      42           0 :     if ((res = s_mp_mul_high_digs (&q, mu, &q, um)) != MP_OKAY) {
      43           0 :       goto CLEANUP;
      44             :     }
      45             : #elif defined(BN_FAST_S_MP_MUL_HIGH_DIGS_C)
      46             :     if ((res = fast_s_mp_mul_high_digs (&q, mu, &q, um)) != MP_OKAY) {
      47             :       goto CLEANUP;
      48             :     }
      49             : #else
      50             :     {
      51             :       res = MP_VAL;
      52             :       goto CLEANUP;
      53             :     }
      54             : #endif
      55             :   }
      56             : 
      57             :   /* q3 = q2 / b**(k+1) */
      58           0 :   mp_rshd (&q, um + 1);
      59             : 
      60             :   /* x = x mod b**(k+1), quick (no division) */
      61           0 :   if ((res = mp_mod_2d (x, DIGIT_BIT * (um + 1), x)) != MP_OKAY) {
      62           0 :     goto CLEANUP;
      63             :   }
      64             : 
      65             :   /* q = q * m mod b**(k+1), quick (no division) */
      66           0 :   if ((res = s_mp_mul_digs (&q, m, &q, um + 1)) != MP_OKAY) {
      67           0 :     goto CLEANUP;
      68             :   }
      69             : 
      70             :   /* x = x - q */
      71           0 :   if ((res = mp_sub (x, &q, x)) != MP_OKAY) {
      72           0 :     goto CLEANUP;
      73             :   }
      74             : 
      75             :   /* If x < 0, add b**(k+1) to it */
      76           0 :   if (mp_cmp_d (x, 0) == MP_LT) {
      77           0 :     mp_set (&q, 1);
      78           0 :     if ((res = mp_lshd (&q, um + 1)) != MP_OKAY)
      79           0 :       goto CLEANUP;
      80           0 :     if ((res = mp_add (x, &q, x)) != MP_OKAY)
      81           0 :       goto CLEANUP;
      82             :   }
      83             : 
      84             :   /* Back off if it's too big */
      85           0 :   while (mp_cmp (x, m) != MP_LT) {
      86           0 :     if ((res = s_mp_sub (x, m, x)) != MP_OKAY) {
      87           0 :       goto CLEANUP;
      88             :     }
      89             :   }
      90             : 
      91           0 : CLEANUP:
      92           0 :   mp_clear (&q);
      93             : 
      94           0 :   return res;
      95             : }
      96             : #endif
      97             : 
      98             : /* $Source: /cvs/libtom/libtommath/bn_mp_reduce.c,v $ */
      99             : /* $Revision: 1.4 $ */
     100             : /* $Date: 2006/12/28 01:25:13 $ */

Generated by: LCOV version 1.13