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/*
Copyright (C) 2009 William Hart
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 "ulong_extras.h"
int
n_remove(ulong * n, ulong p)
{
int exp, i;
ulong powp[6];
ulong quot, rem;
if (p == 2)
{
exp = flint_ctz(*n);
if (exp)
(*n) >>= exp;
return exp;
}
powp[0] = p;
for (i = 0; ; i++)
{
if ((*n) < powp[i])
break;
quot = (*n) / powp[i];
rem = (*n) - quot * powp[i];
if (rem != UWORD(0))
break;
powp[i + 1] = powp[i] * powp[i];
(*n) = quot;
}
exp = (1 << i) - 1;
while (i > 0)
{
i--;
if ((*n) < powp[i])
continue;
quot = (*n) / powp[i];
rem = (*n) - quot * powp[i];
if (rem == UWORD(0))
{
exp += (UWORD(1) << i);
(*n) = quot;
}
}
return exp;
}
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