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/*
Copyright (C) 2016 Pascal Molin
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "nmod.h"
#include "dlog.h"
ulong
dlog_power(const dlog_power_t t, ulong b)
{
int k;
ulong x, pk[30]; /* 3^30*2+1, 2^30*3+1 are primes */
pk[0] = 1;
for (k = 1; k < t->e; k++)
pk[k] = pk[k-1] * t->p;
x = 0;
for(k = 0; k < t->e; k++)
{
ulong bk, xk;
bk = nmod_pow_ui(b, pk[t->e-1-k], t->mod);
xk = dlog_precomp(t->pre, bk);
b = nmod_mul(b, nmod_pow_ui(t->apk[k], xk, t->mod), t->mod);
x += xk * pk[k]; /* cannot overflow */
}
return x;
}