libtommath/bn_mp_get_long.c
2019-05-20 05:36:24 +02:00

30 lines
770 B
C

#include "tommath_private.h"
#ifdef BN_MP_GET_LONG_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* get the lower unsigned long of an mp_int, platform dependent */
unsigned long mp_get_long(const mp_int *a)
{
int i;
unsigned long res;
if (MP_IS_ZERO(a)) {
return 0;
}
/* get number of digits of the lsb we have to read */
i = MP_MIN(a->used, (((int)MP_SIZEOF_BITS(unsigned long) + MP_DIGIT_BIT - 1) / MP_DIGIT_BIT)) - 1;
/* get most significant digit of result */
res = (unsigned long)a->dp[i];
#if (ULONG_MAX != 0xFFFFFFFFuL) || (MP_DIGIT_BIT < 32)
while (--i >= 0) {
res = (res << MP_DIGIT_BIT) | (unsigned long)a->dp[i];
}
#endif
return res;
}
#endif