mirror of https://github.com/macssh/macssh.git
65 lines
1.8 KiB
C
65 lines
1.8 KiB
C
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/* mpfr_add_one_ulp, mpfr_sub_one_ulp -- add/subtract one unit in last place
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Copyright (C) 1999 PolKA project, Inria Lorraine and Loria
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This file is part of the MPFR Library.
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The MPFR Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Library General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at your
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option) any later version.
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The MPFR 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 Library General Public
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License for more details.
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You should have received a copy of the GNU Library General Public License
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along with the MPFR 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 "mpfr.h"
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/* sets x to x+sign(x)*2^(EXP(x)-PREC(x)) */
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int
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#if __STDC__
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mpfr_add_one_ulp(mpfr_ptr x)
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#else
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mpfr_add_one_ulp(x)
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mpfr_ptr x;
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#endif
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{
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int xn, sh; mp_limb_t *xp;
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xn = 1 + (PREC(x)-1)/BITS_PER_MP_LIMB;
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sh = xn*BITS_PER_MP_LIMB - PREC(x);
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xp = MANT(x);
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if (mpn_add_1(xp, xp, xn, (mp_limb_t)1<<sh)) {
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EXP(x)++;
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mpn_rshift(xp, xp, xn, 1);
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xp[xn-1] += (mp_limb_t)1<<(BITS_PER_MP_LIMB-1);
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}
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return 0;
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}
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/* sets x to x-sign(x)*ulp(x) */
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int mpfr_sub_one_ulp(mpfr_ptr x)
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{
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int xn, sh; mp_limb_t *xp;
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xn = 1 + (PREC(x)-1)/BITS_PER_MP_LIMB;
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sh = xn*BITS_PER_MP_LIMB-PREC(x);
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xp = MANT(x);
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mpn_sub_1(xp, xp, xn, (mp_limb_t)1<<sh);
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if (xp[xn-1] >> (BITS_PER_MP_LIMB-1) == 0) {
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/* was an exact power of two: not normalized any more */
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EXP(x)--;
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mpn_lshift(xp, xp, xn, 1);
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*xp |= ((mp_limb_t)1 << sh);
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}
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return 0;
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}
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