+++ /dev/null
-/* mpz_powm_ui(res,base,exp,mod) -- Set RES to (base**exp) mod MOD.
-
-Copyright (C) 1991, 1992 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 General Public License as published by
-the Free Software Foundation; either version 2, 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 General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with the GNU MP Library; see the file COPYING. If not, write to
-the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
-
-#include "gmp.h"
-#include "gmp-impl.h"
-#include "longlong.h"
-
-void
-#ifdef __STDC__
-mpz_powm_ui (MP_INT *res, const MP_INT *base, unsigned long int exp,
- const MP_INT *mod)
-#else
-mpz_powm_ui (res, base, exp, mod)
- MP_INT *res;
- const MP_INT *base;
- unsigned long int exp;
- const MP_INT *mod;
-#endif
-{
- mp_ptr rp, mp, bp;
- mp_size msize, bsize, rsize;
- mp_size size;
- int mod_shift_cnt;
- int negative_result;
- mp_limb *free_me = NULL;
- size_t free_me_size;
-
- msize = ABS (mod->size);
- size = 2 * msize;
-
- rp = res->d;
-
- /* Normalize MOD (i.e. make its most significant bit set) as required by
- mpn_div. 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) alloca (msize * BYTES_PER_MP_LIMB);
- count_leading_zeros (mod_shift_cnt, mod->d[msize - 1]);
- if (mod_shift_cnt != 0)
- (void) mpn_lshift (mp, mod->d, msize, mod_shift_cnt);
- else
- MPN_COPY (mp, mod->d, msize);
-
- bsize = ABS (base->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) alloca ((bsize + 1) * BYTES_PER_MP_LIMB);
- MPN_COPY (bp, base->d, bsize);
- /* We don't care about the quotient, store it above the remainder,
- at BP + MSIZE. */
- mpn_div (bp + msize, bp, bsize, mp, msize);
- bsize = msize;
- while (bsize > 0 && bp[bsize - 1] == 0)
- bsize--;
- }
- else
- {
- bp = base->d;
- bsize = ABS (base->size);
- }
-
- if (res->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->alloc;
- }
- else
- (*_mp_free_func) (rp, res->alloc * BYTES_PER_MP_LIMB);
-
- rp = (mp_ptr) (*_mp_allocate_func) (size * BYTES_PER_MP_LIMB);
- res->alloc = size;
- res->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) alloca (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) alloca (msize * BYTES_PER_MP_LIMB);
- MPN_COPY (mp, rp, msize);
- }
- }
-
- if (exp == 0)
- {
- rp[0] = 1;
- res->size = 1;
- return;
- }
-
- MPN_COPY (rp, bp, bsize);
- rsize = bsize;
-
- {
- mp_size xsize;
- mp_ptr dummyp = (mp_ptr) alloca ((msize + 1) * BYTES_PER_MP_LIMB);
- mp_ptr xp = (mp_ptr) alloca (2 * (msize + 1) * BYTES_PER_MP_LIMB);
- int c;
- mp_limb e;
- mp_limb carry_limb;
-
- negative_result = (exp & 1) && base->size < 0;
-
- e = exp;
- count_leading_zeros (c, e);
- e <<= (c + 1); /* shift the exp bits to the left, loose 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_div. With 50% probability
- the result after this loop will be in the area originally pointed
- by RP (==RES->D), and with 50% probability in the area originally
- pointed to by XP. */
-
- while (c != 0)
- {
- mp_ptr tp;
- mp_size tsize;
-
- xsize = mpn_mul (xp, rp, rsize, rp, rsize);
- mpn_div (dummyp, xp, xsize, mp, msize);
-
- /* Remove any leading zero words from the result. */
- if (xsize > msize)
- xsize = msize;
- while (xsize > 0 && xp[xsize - 1] == 0)
- xsize--;
-
- tp = rp; rp = xp; xp = tp;
- tsize = rsize; rsize = xsize; xsize = tsize;
-
- if ((mp_limb_signed) e < 0)
- {
- if (rsize > bsize)
- xsize = mpn_mul (xp, rp, rsize, bp, bsize);
- else
- xsize = mpn_mul (xp, bp, bsize, rp, rsize);
- mpn_div (dummyp, xp, xsize, mp, msize);
-
- /* Remove any leading zero words from the result. */
- if (xsize > msize)
- xsize = msize;
- while (xsize > 0 && xp[xsize - 1] == 0)
- xsize--;
-
- tp = rp; rp = xp; xp = tp;
- tsize = rsize; rsize = xsize; xsize = tsize;
- }
- 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->D (where it already
- might be, see above). */
-
- carry_limb = mpn_lshift (res->d, rp, rsize, mod_shift_cnt);
- rp = res->d;
- if (carry_limb != 0)
- {
- rp[rsize] = carry_limb;
- rsize++;
- }
- mpn_div (dummyp, rp, rsize, mp, msize);
- /* Remove any leading zero words from the result. */
- if (rsize > msize)
- rsize = msize;
- while (rsize > 0 && rp[rsize - 1] == 0)
- rsize--;
- rsize = mpn_rshift (rp, rp, rsize, mod_shift_cnt);
- }
-
- res->size = negative_result >= 0 ? rsize : -rsize;
-
- if (free_me != NULL)
- (*_mp_free_func) (free_me, free_me_size * BYTES_PER_MP_LIMB);
-
- alloca (0);
-}
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