freebsd-nq/contrib/libgmp/mpz/pow_ui.c
Mark Murray aa9bc17601 Clean import of libgmp 2.0.2, with only the non-x86 bits removed.
BMakefiles and other bits will follow.

Requested by:	Andrey Chernov
Made world by:	Chuck Robey
1996-10-20 08:49:26 +00:00

130 lines
3.4 KiB
C

/* mpz_pow_ui(res, base, exp) -- Set RES to BASE**EXP.
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. */
#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 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;
rsize = 2 + ((mp_size_t) (e / lb) / BITS_PER_MP_LIMB);
}
else
{
/* Over-estimate space requirements somewhat. */
count_leading_zeros (cnt, blimb);
rsize = bsize * e - cnt * e / BITS_PER_MP_LIMB + 1;
}
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 (rsize * BYTES_PER_MP_LIMB);
tp = (mp_ptr) TMP_ALLOC (rsize * 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);
}