### view libtommath/bn_mp_rand.c @ 1549:5212630893ab

only clean libtom when using bundled libraries
author Matt Johnston Mon, 26 Feb 2018 23:13:54 +0800 8bba51a55704 f52919ffd3b1
line wrap: on
line source
```#include <tommath_private.h>
#ifdef BN_MP_RAND_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
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, [email protected], http://libtom.org
*/

#if MP_GEN_RANDOM_MAX == 0xffffffff
#define MP_GEN_RANDOM_SHIFT  32
#elif MP_GEN_RANDOM_MAX == 32767
/* SHRT_MAX */
#define MP_GEN_RANDOM_SHIFT  15
#elif MP_GEN_RANDOM_MAX == 2147483647
/* INT_MAX */
#define MP_GEN_RANDOM_SHIFT  31
#elif !defined(MP_GEN_RANDOM_SHIFT)
#error Thou shalt define their own valid MP_GEN_RANDOM_SHIFT
#endif

/* makes a pseudo-random int of a given size */
static mp_digit s_gen_random(void)
{
mp_digit d = 0, msk = 0;
do {
d <<= MP_GEN_RANDOM_SHIFT;
d |= ((mp_digit) MP_GEN_RANDOM());
msk <<= MP_GEN_RANDOM_SHIFT;
return d;
}

int
mp_rand (mp_int * a, int digits)
{
int     res;
mp_digit d;

mp_zero (a);
if (digits <= 0) {
return MP_OKAY;
}

/* first place a random non-zero digit */
do {
d = s_gen_random();
} while (d == 0);

if ((res = mp_add_d (a, d, a)) != MP_OKAY) {
return res;
}

while (--digits > 0) {
if ((res = mp_lshd (a, 1)) != MP_OKAY) {
return res;
}

if ((res = mp_add_d (a, s_gen_random(), a)) != MP_OKAY) {
return res;
}
}

return MP_OKAY;
}
#endif

/* ref:         \$Format:%D\$ */
/* git commit:  \$Format:%H\$ */
/* commit time: \$Format:%ai\$ */
```