46 lines
1.1 KiB
C
46 lines
1.1 KiB
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.
|
|
*
|
|
* Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
|
|
*/
|
|
#include <tommath.h>
|
|
|
|
/* determines if mp_reduce_2k can be used */
|
|
int mp_reduce_is_2k(mp_int *a)
|
|
{
|
|
int ix, iy, iz, iw;
|
|
|
|
if (a->used == 0) {
|
|
return 0;
|
|
} else if (a->used == 1) {
|
|
return 1;
|
|
} else if (a->used > 1) {
|
|
iy = mp_count_bits(a);
|
|
iz = 1;
|
|
iw = 1;
|
|
|
|
/* Test every bit from the second digit up, must be 1 */
|
|
for (ix = DIGIT_BIT; ix < iy; ix++) {
|
|
if ((a->dp[iw] & iz) == 0) {
|
|
return 0;
|
|
}
|
|
iz <<= 1;
|
|
if (iz > (int)MP_MASK) {
|
|
++iw;
|
|
iz = 1;
|
|
}
|
|
}
|
|
}
|
|
return 1;
|
|
}
|
|
|