/* mpz_pow_ui(res, base, exp) -- Set RES to BASE**EXP. Copyright (C) 1991, 1993, 1994, 1996, 1997 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. */ #ifdef BERKELEY_MP #include "mp.h" #endif #include "gmp.h" #include "gmp-impl.h" #include "longlong.h" #ifndef BERKELEY_MP void #if __STDC__ mpz_pow_ui (mpz_ptr r, mpz_srcptr b, unsigned long int e) #else mpz_pow_ui (r, b, e) mpz_ptr r; mpz_srcptr b; unsigned long int e; #endif #else /* BERKELEY_MP */ void #if __STDC__ rpow (const MINT *b, signed short int e, MINT *r) #else rpow (b, e, r) const MINT *b; signed short int e; MINT *r; #endif #endif /* BERKELEY_MP */ { mp_ptr rp, bp, tp, xp; mp_size_t ralloc, rsize, bsize; int cnt, i; mp_limb_t blimb; TMP_DECL (marker); bsize = ABS (b->_mp_size); /* 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 (bsize == 0 #ifdef BERKELEY_MP || e < 0 #endif ) { r->_mp_size = 0; return; } bp = b->_mp_d; blimb = bp[bsize - 1]; if (bsize == 1 && 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; ralloc = 3 + ((mp_size_t) (e / lb) / BITS_PER_MP_LIMB); } else { /* Over-estimate space requirements somewhat. */ count_leading_zeros (cnt, blimb); ralloc = bsize * e - cnt * e / BITS_PER_MP_LIMB + 2; } 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 (ralloc * BYTES_PER_MP_LIMB); tp = (mp_ptr) TMP_ALLOC (ralloc * BYTES_PER_MP_LIMB); MPN_COPY (rp, bp, bsize); rsize = bsize; 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) { rsize = rsize + bsize - (mpn_mul (tp, rp, rsize, bp, bsize) == 0); 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 = (e & 1) == 0 || b->_mp_size >= 0 ? rsize : -rsize; TMP_FREE (marker); }