56 lines
1.3 KiB
C
56 lines
1.3 KiB
C
#include "tommath_private.h"
|
|
#ifdef BN_MP_GET_BIT_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.
|
|
*/
|
|
|
|
/* Checks the bit at position b and returns MP_YES
|
|
if the bit is 1, MP_NO if it is 0 and MP_VAL
|
|
in case of error */
|
|
int mp_get_bit(const mp_int *a, int b)
|
|
{
|
|
int limb;
|
|
mp_digit bit, isset;
|
|
|
|
if (b < 0) {
|
|
return MP_VAL;
|
|
}
|
|
|
|
limb = b / DIGIT_BIT;
|
|
|
|
/*
|
|
* Zero is a special value with the member "used" set to zero.
|
|
* Needs to be tested before the check for the upper boundary
|
|
* otherwise (limb >= a->used) would be true for a = 0
|
|
*/
|
|
|
|
if (mp_iszero(a)) {
|
|
return MP_NO;
|
|
}
|
|
|
|
if (limb >= a->used) {
|
|
return MP_VAL;
|
|
}
|
|
|
|
bit = (mp_digit)(1) << (b % DIGIT_BIT);
|
|
|
|
isset = a->dp[limb] & bit;
|
|
return (isset != 0) ? MP_YES : MP_NO;
|
|
}
|
|
|
|
#endif
|
|
|
|
/* ref: $Format:%D$ */
|
|
/* git commit: $Format:%H$ */
|
|
/* commit time: $Format:%ai$ */
|