+++ /dev/null
-/* mpz_powm_ui(res,base,exp,mod) -- Set RES to (base**exp) mod MOD.
-
-Copyright (C) 1991, 1993, 1994, 1996, 1997, 2000 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 Lesser General Public License as published by
-the Free Software Foundation; either version 2.1 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 Lesser General Public
-License for more details.
-
-You should have received a copy of the GNU Lesser 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 <stdio.h> /* for NULL */
-#include "gmp.h"
-#include "gmp-impl.h"
-#include "longlong.h"
-
-void
-#if __STDC__
-mpz_powm_ui (mpz_ptr res, mpz_srcptr base, unsigned long int exp, mpz_srcptr mod)
-#else
-mpz_powm_ui (res, base, exp, mod)
- mpz_ptr res;
- mpz_srcptr base;
- unsigned long int exp;
- mpz_srcptr mod;
-#endif
-{
- mp_ptr rp, mp, bp;
- mp_size_t msize, bsize, rsize;
- mp_size_t size;
- int mod_shift_cnt;
- int negative_result;
- mp_limb_t *free_me = NULL;
- size_t free_me_size;
- TMP_DECL (marker);
-
- msize = ABS (mod->_mp_size);
- size = 2 * msize;
-
- rp = res->_mp_d;
-
- if (msize == 0)
- DIVIDE_BY_ZERO;
-
- if (exp == 0)
- {
- /* Exponent is zero, result is 1 mod MOD, i.e., 1 or 0
- depending on if MOD equals 1. */
- res->_mp_size = (msize == 1 && (mod->_mp_d)[0] == 1) ? 0 : 1;
- rp[0] = 1;
- return;
- }
-
- TMP_MARK (marker);
-
- /* Normalize MOD (i.e. make its most significant bit set) as required by
- mpn_divmod. This will make the intermediate values in the calculation
- slightly larger, but the correct result is obtained after a final
- reduction using the original MOD value. */
-
- mp = (mp_ptr) TMP_ALLOC (msize * BYTES_PER_MP_LIMB);
- count_leading_zeros (mod_shift_cnt, mod->_mp_d[msize - 1]);
- if (mod_shift_cnt != 0)
- mpn_lshift (mp, mod->_mp_d, msize, mod_shift_cnt);
- else
- MPN_COPY (mp, mod->_mp_d, msize);
-
- bsize = ABS (base->_mp_size);
- if (bsize > msize)
- {
- /* The base is larger than the module. Reduce it. */
-
- /* Allocate (BSIZE + 1) with space for remainder and quotient.
- (The quotient is (bsize - msize + 1) limbs.) */
- bp = (mp_ptr) TMP_ALLOC ((bsize + 1) * BYTES_PER_MP_LIMB);
- MPN_COPY (bp, base->_mp_d, bsize);
- /* We don't care about the quotient, store it above the remainder,
- at BP + MSIZE. */
- mpn_divmod (bp + msize, bp, bsize, mp, msize);
- bsize = msize;
- /* Canonicalize the base, since we are going to multiply with it
- quite a few times. */
- MPN_NORMALIZE (bp, bsize);
- }
- else
- bp = base->_mp_d;
-
- if (bsize == 0)
- {
- res->_mp_size = 0;
- TMP_FREE (marker);
- return;
- }
-
- if (res->_mp_alloc < size)
- {
- /* We have to allocate more space for RES. If any of the input
- parameters are identical to RES, defer deallocation of the old
- space. */
-
- if (rp == mp || rp == bp)
- {
- free_me = rp;
- free_me_size = res->_mp_alloc;
- }
- else
- (*_mp_free_func) (rp, res->_mp_alloc * BYTES_PER_MP_LIMB);
-
- rp = (mp_ptr) (*_mp_allocate_func) (size * BYTES_PER_MP_LIMB);
- res->_mp_alloc = size;
- res->_mp_d = rp;
- }
- else
- {
- /* Make BASE, EXP and MOD not overlap with RES. */
- if (rp == bp)
- {
- /* RES and BASE are identical. Allocate temp. space for BASE. */
- bp = (mp_ptr) TMP_ALLOC (bsize * BYTES_PER_MP_LIMB);
- MPN_COPY (bp, rp, bsize);
- }
- if (rp == mp)
- {
- /* RES and MOD are identical. Allocate temporary space for MOD. */
- mp = (mp_ptr) TMP_ALLOC (msize * BYTES_PER_MP_LIMB);
- MPN_COPY (mp, rp, msize);
- }
- }
-
- MPN_COPY (rp, bp, bsize);
- rsize = bsize;
-
- {
- mp_ptr xp = (mp_ptr) TMP_ALLOC (2 * (msize + 1) * BYTES_PER_MP_LIMB);
- int c;
- mp_limb_t e;
- mp_limb_t carry_limb;
-
- negative_result = (exp & 1) && base->_mp_size < 0;
-
- e = exp;
- count_leading_zeros (c, e);
- e = (e << c) << 1; /* shift the exp bits to the left, lose msb */
- c = BITS_PER_MP_LIMB - 1 - c;
-
- /* Main loop.
-
- Make the result be pointed to alternately by XP and RP. This
- helps us avoid block copying, which would otherwise be necessary
- with the overlap restrictions of mpn_divmod. With 50% probability
- the result after this loop will be in the area originally pointed
- by RP (==RES->_mp_d), and with 50% probability in the area originally
- pointed to by XP. */
-
- while (c != 0)
- {
- mp_ptr tp;
- mp_size_t xsize;
-
- mpn_mul_n (xp, rp, rp, rsize);
- xsize = 2 * rsize;
- xsize -= xp[xsize - 1] == 0;
- if (xsize > msize)
- {
- mpn_divmod (xp + msize, xp, xsize, mp, msize);
- xsize = msize;
- }
-
- tp = rp; rp = xp; xp = tp;
- rsize = xsize;
-
- if ((mp_limb_signed_t) e < 0)
- {
- mpn_mul (xp, rp, rsize, bp, bsize);
- xsize = rsize + bsize;
- xsize -= xp[xsize - 1] == 0;
- if (xsize > msize)
- {
- mpn_divmod (xp + msize, xp, xsize, mp, msize);
- xsize = msize;
- }
-
- tp = rp; rp = xp; xp = tp;
- rsize = xsize;
- }
- e <<= 1;
- c--;
- }
-
- /* We shifted MOD, the modulo reduction argument, left MOD_SHIFT_CNT
- steps. Adjust the result by reducing it with the original MOD.
-
- Also make sure the result is put in RES->_mp_d (where it already
- might be, see above). */
-
- if (mod_shift_cnt != 0)
- {
- carry_limb = mpn_lshift (res->_mp_d, rp, rsize, mod_shift_cnt);
- rp = res->_mp_d;
- if (carry_limb != 0)
- {
- rp[rsize] = carry_limb;
- rsize++;
- }
- }
- else
- {
- MPN_COPY (res->_mp_d, rp, rsize);
- rp = res->_mp_d;
- }
-
- if (rsize >= msize)
- {
- mpn_divmod (rp + msize, rp, rsize, mp, msize);
- rsize = msize;
- }
-
- /* Remove any leading zero words from the result. */
- if (mod_shift_cnt != 0)
- mpn_rshift (rp, rp, rsize, mod_shift_cnt);
- MPN_NORMALIZE (rp, rsize);
- }
-
- if (negative_result && rsize != 0)
- {
- if (mod_shift_cnt != 0)
- mpn_rshift (mp, mp, msize, mod_shift_cnt);
- mpn_sub (rp, mp, msize, rp, rsize);
- rsize = msize;
- MPN_NORMALIZE (rp, rsize);
- }
- res->_mp_size = rsize;
-
- if (free_me != NULL)
- (*_mp_free_func) (free_me, free_me_size * BYTES_PER_MP_LIMB);
- TMP_FREE (marker);
-}
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