mirror of https://github.com/macssh/macssh.git
129 lines
2.8 KiB
C
129 lines
2.8 KiB
C
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/* double mpz_get_d (mpz_t src) -- Return the double approximation to SRC.
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Copyright (C) 1996, 1997, 2000 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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static int
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#if __STDC__
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mpn_zero_p (mp_ptr p, mp_size_t n)
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#else
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mpn_zero_p (p, n)
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mp_ptr p;
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mp_size_t n;
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#endif
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{
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mp_size_t i;
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for (i = 0; i < n; i++)
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{
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if (p[i] != 0)
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return 0;
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}
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return 1;
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}
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double
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#if __STDC__
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mpz_get_d (mpz_srcptr src)
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#else
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mpz_get_d (src)
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mpz_srcptr src;
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#endif
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{
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double res;
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mp_size_t size;
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int negative;
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mp_ptr qp;
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mp_limb_t hz, lz;
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int cnt;
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size = SIZ(src);
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if (size == 0)
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return 0.0;
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negative = size < 0;
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size = ABS (size);
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qp = PTR(src);
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if (size == 1)
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{
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res = qp[size - 1];
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}
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else if (size == 2)
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{
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res = MP_BASE_AS_DOUBLE * qp[size - 1] + qp[size - 2];
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}
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else
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{
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count_leading_zeros (cnt, qp[size - 1]);
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#if BITS_PER_MP_LIMB == 32
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if (cnt == 0)
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{
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hz = qp[size - 1];
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lz = qp[size - 2];
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}
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else
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{
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hz = (qp[size - 1] << cnt) | (qp[size - 2] >> BITS_PER_MP_LIMB - cnt);
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lz = (qp[size - 2] << cnt) | (qp[size - 3] >> BITS_PER_MP_LIMB - cnt);
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}
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#if _GMP_IEEE_FLOATS
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/* Take bits from less significant limbs, but only if they may affect
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the result. */
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if ((lz & 0x7ff) == 0x400)
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{
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if (cnt != 0)
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lz += ((qp[size - 3] << cnt) != 0 || ! mpn_zero_p (qp, size - 3));
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else
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lz += (! mpn_zero_p (qp, size - 2));
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}
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#endif
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res = MP_BASE_AS_DOUBLE * hz + lz;
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res = __gmp_scale2 (res, (size - 2) * BITS_PER_MP_LIMB - cnt);
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#endif
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#if BITS_PER_MP_LIMB == 64
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if (cnt == 0)
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hz = qp[size - 1];
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else
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hz = (qp[size - 1] << cnt) | (qp[size - 2] >> BITS_PER_MP_LIMB - cnt);
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#if _GMP_IEEE_FLOATS
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if ((hz & 0x7ff) == 0x400)
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{
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if (cnt != 0)
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hz += ((qp[size - 2] << cnt) != 0 || ! mpn_zero_p (qp, size - 2));
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else
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hz += (! mpn_zero_p (qp, size - 1));
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}
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#endif
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res = hz;
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res = __gmp_scale2 (res, (size - 1) * BITS_PER_MP_LIMB - cnt);
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#endif
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}
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return negative ? -res : res;
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}
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