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/* mpz_ui_pow_ui(res, base, exp) -- Set RES to BASE**EXP.
Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include "gmp.h"
#include "gmp-impl.h"
#include "longlong.h"
void
#if __STDC__
mpz_ui_pow_ui (mpz_ptr r, unsigned long int b, unsigned long int e)
#else
mpz_ui_pow_ui (r, b, e)
mpz_ptr r;
unsigned long int b;
unsigned long int e;
#endif
{
mp_ptr rp, tp, xp;
mp_size_t rsize;
int cnt, i;
mp_limb_t blimb = b;
TMP_DECL (marker);
/* Single out cases that give result == 0 or 1. These tests are here
to simplify the general code below, not to optimize. */
if (e == 0)
{
r->_mp_d[0] = 1;
r->_mp_size = 1;
return;
}
if (blimb == 0)
{
r->_mp_size = 0;
return;
}
if (blimb < 0x100)
{
/* Estimate space requirements accurately. Using the code from the
`else' path would over-estimate space requirements wildly. */
float lb = __mp_bases[blimb].chars_per_bit_exactly;
rsize = 2 + ((mp_size_t) (e / lb) / BITS_PER_MP_LIMB);
}
else
{
/* Over-estimate space requirements somewhat. */
count_leading_zeros (cnt, blimb);
rsize = e - cnt * e / BITS_PER_MP_LIMB + 1;
}
TMP_MARK (marker);
/* The two areas are used to alternatingly hold the input and recieve the
product for mpn_mul. (This scheme is used to fulfill the requirements
of mpn_mul; that the product space may not be the same as any of the
input operands.) */
rp = (mp_ptr) TMP_ALLOC (rsize * BYTES_PER_MP_LIMB);
tp = (mp_ptr) TMP_ALLOC (rsize * BYTES_PER_MP_LIMB);
rp[0] = blimb;
rsize = 1;
count_leading_zeros (cnt, e);
for (i = BITS_PER_MP_LIMB - cnt - 2; i >= 0; i--)
{
mpn_mul_n (tp, rp, rp, rsize);
rsize = 2 * rsize;
rsize -= tp[rsize - 1] == 0;
xp = tp; tp = rp; rp = xp;
if ((e & ((mp_limb_t) 1 << i)) != 0)
{
mp_limb_t cy;
cy = mpn_mul_1 (tp, rp, rsize, blimb);
if (cy != 0)
{
tp[rsize] = cy;
rsize++;
}
xp = tp; tp = rp; rp = xp;
}
}
/* Now then we know the exact space requirements, reallocate if
necessary. */
if (r->_mp_alloc < rsize)
_mpz_realloc (r, rsize);
MPN_COPY (r->_mp_d, rp, rsize);
r->_mp_size = rsize;
TMP_FREE (marker);
}
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