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