toxcore/nacl/curvecp/randommod.c
2013-07-02 09:53:34 -04:00

15 lines
325 B
C

#include "randombytes.h"
/* XXX: current implementation is limited to n<2^55 */
long long randommod(long long n)
{
long long result = 0;
long long j;
unsigned char r[32];
if (n <= 1) return 0;
randombytes(r,32);
for (j = 0;j < 32;++j) result = (result * 256 + (unsigned long long) r[j]) % n;
return result;
}