File: randommod.c

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/*
taken from nacl-20110221, from curvecp/randommod.c
- reformated using clang-format
*/
#include "randombytes.h"
#include "randommod.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;
}