1 /* mpz_pow_ui(res, base, exp) -- Set RES to BASE**EXP.
3 Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
5 This file is part of the GNU MP Library.
7 The GNU MP Library is free software; you can redistribute it and/or modify
8 it under the terms of the GNU Library General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or (at your
10 option) any later version.
12 The GNU MP Library is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
15 License for more details.
17 You should have received a copy of the GNU Library General Public License
18 along with the GNU MP Library; see the file COPYING.LIB. If not, write to
19 the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
20 MA 02111-1307, USA. */
32 mpz_pow_ui (mpz_ptr r, mpz_srcptr b, unsigned long int e)
39 #else /* BERKELEY_MP */
42 rpow (const MINT *b, signed short int e, MINT *r)
49 #endif /* BERKELEY_MP */
51 mp_ptr rp, bp, tp, xp;
52 mp_size_t rsize, bsize;
57 bsize = ABS (b->_mp_size);
59 /* Single out cases that give result == 0 or 1. These tests are here
60 to simplify the general code below, not to optimize. */
79 blimb = bp[bsize - 1];
80 if (bsize == 1 && blimb < 0x100)
82 /* Estimate space requirements accurately. Using the code from the
83 `else' path would over-estimate space requirements wildly. */
84 float lb = __mp_bases[blimb].chars_per_bit_exactly;
85 rsize = 2 + ((mp_size_t) (e / lb) / BITS_PER_MP_LIMB);
89 /* Over-estimate space requirements somewhat. */
90 count_leading_zeros (cnt, blimb);
91 rsize = bsize * e - cnt * e / BITS_PER_MP_LIMB + 1;
96 /* The two areas are used to alternatingly hold the input and recieve the
97 product for mpn_mul. (This scheme is used to fulfill the requirements
98 of mpn_mul; that the product space may not be the same as any of the
100 rp = (mp_ptr) TMP_ALLOC (rsize * BYTES_PER_MP_LIMB);
101 tp = (mp_ptr) TMP_ALLOC (rsize * BYTES_PER_MP_LIMB);
103 MPN_COPY (rp, bp, bsize);
105 count_leading_zeros (cnt, e);
107 for (i = BITS_PER_MP_LIMB - cnt - 2; i >= 0; i--)
109 mpn_mul_n (tp, rp, rp, rsize);
111 rsize -= tp[rsize - 1] == 0;
112 xp = tp; tp = rp; rp = xp;
114 if ((e & ((mp_limb_t) 1 << i)) != 0)
116 rsize = rsize + bsize - (mpn_mul (tp, rp, rsize, bp, bsize) == 0);
117 xp = tp; tp = rp; rp = xp;
121 /* Now then we know the exact space requirements, reallocate if
123 if (r->_mp_alloc < rsize)
124 _mpz_realloc (r, rsize);
126 MPN_COPY (r->_mp_d, rp, rsize);
127 r->_mp_size = (e & 1) == 0 || b->_mp_size >= 0 ? rsize : -rsize;