--- /dev/null
+/* mpz_powm(res,base,exp,mod) -- Set RES to (base**exp) mod MOD.
+
+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"
+
+#ifndef BERKELEY_MP
+void
+#if __STDC__
+mpz_powm (mpz_ptr res, mpz_srcptr base, mpz_srcptr exp, mpz_srcptr mod)
+#else
+mpz_powm (res, base, exp, mod)
+ mpz_ptr res;
+ mpz_srcptr base;
+ mpz_srcptr exp;
+ mpz_srcptr mod;
+#endif
+#else /* BERKELEY_MP */
+void
+#if __STDC__
+pow (mpz_srcptr base, mpz_srcptr exp, mpz_srcptr mod, mpz_ptr res)
+#else
+pow (base, exp, mod, res)
+ mpz_srcptr base;
+ mpz_srcptr exp;
+ mpz_srcptr mod;
+ mpz_ptr res;
+#endif
+#endif /* BERKELEY_MP */
+{
+ mp_ptr rp, ep, mp, bp;
+ mp_size_t esize, 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);
+
+ esize = ABS (exp->_mp_size);
+ msize = ABS (mod->_mp_size);
+ size = 2 * msize;
+
+ rp = res->_mp_d;
+ ep = exp->_mp_d;
+
+ if (msize == 0)
+ msize = 1 / msize; /* provoke a signal */
+
+ if (esize == 0)
+ {
+ /* Exponent is zero, result is 1 mod MOD, i.e., 1 or 0
+ depending on if MOD equals 1. */
+ rp[0] = 1;
+ res->_mp_size = (msize == 1 && (mod->_mp_d)[0] == 1) ? 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 == ep || 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 == ep)
+ {
+ /* RES and EXP are identical. Allocate temp. space for EXP. */
+ ep = (mp_ptr) TMP_ALLOC (esize * BYTES_PER_MP_LIMB);
+ MPN_COPY (ep, rp, esize);
+ }
+ 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_size_t i;
+ 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 = (ep[0] & 1) && base->_mp_size < 0;
+
+ i = esize - 1;
+ e = ep[i];
+ 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. */
+
+ for (;;)
+ {
+ while (c != 0)
+ {
+ mp_ptr tp;
+ mp_size_t xsize;
+
+ mpn_mul_n (xp, rp, rp, rsize);
+ xsize = 2 * rsize;
+ 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;
+ if (xsize > msize)
+ {
+ mpn_divmod (xp + msize, xp, xsize, mp, msize);
+ xsize = msize;
+ }
+
+ tp = rp; rp = xp; xp = tp;
+ rsize = xsize;
+ }
+ e <<= 1;
+ c--;
+ }
+
+ i--;
+ if (i < 0)
+ break;
+ e = ep[i];
+ c = BITS_PER_MP_LIMB;
+ }
+
+ /* 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);
+}
projects / ghc-hetmet.git / blobdiff