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102 lines
2.8 KiB
C
102 lines
2.8 KiB
C
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/* mpfr_cmp_si_2exp -- compare a floating-point number with a signed
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machine integer multiplied by a power of 2
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Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
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Contributed by the Arenaire and Cacao projects, INRIA.
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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 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 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 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 MPFR Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#define MPFR_NEED_LONGLONG_H
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#include "mpfr-impl.h"
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/* returns a positive value if b > i*2^f,
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a negative value if b < i*2^f,
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zero if b = i*2^f.
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b must not be NaN.
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*/
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int
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mpfr_cmp_si_2exp (mpfr_srcptr b, long int i, mp_exp_t f)
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{
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int si;
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si = i < 0 ? -1 : 1; /* sign of i */
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if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (b)))
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{
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if (MPFR_IS_INF(b))
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return MPFR_INT_SIGN(b);
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else if (MPFR_IS_ZERO(b))
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return i != 0 ? -si : 0;
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/* NAN */
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MPFR_SET_ERANGE ();
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return 0;
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}
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else if (MPFR_SIGN(b) != si || i == 0)
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return MPFR_INT_SIGN (b);
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else /* b and i are of same sign si */
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{
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mp_exp_t e;
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unsigned long ai;
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int k;
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mp_size_t bn;
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mp_limb_t c, *bp;
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ai = SAFE_ABS(unsigned long, i);
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/* ai must be representable in a mp_limb_t */
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MPFR_ASSERTN(ai == (mp_limb_t) ai);
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e = MPFR_GET_EXP (b); /* 2^(e-1) <= b < 2^e */
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if (e <= f)
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return -si;
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if (f < MPFR_EMAX_MAX - BITS_PER_MP_LIMB &&
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e > f + BITS_PER_MP_LIMB)
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return si;
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/* now f < e <= f + BITS_PER_MP_LIMB */
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c = (mp_limb_t) ai;
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count_leading_zeros(k, c);
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if ((int) (e - f) > BITS_PER_MP_LIMB - k)
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return si;
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if ((int) (e - f) < BITS_PER_MP_LIMB - k)
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return -si;
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/* now b and i*2^f have the same exponent */
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c <<= k;
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bn = (MPFR_PREC(b) - 1) / BITS_PER_MP_LIMB;
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bp = MPFR_MANT(b);
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if (bp[bn] > c)
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return si;
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if (bp[bn] < c)
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return -si;
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/* most significant limbs agree, check remaining limbs from b */
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while (bn > 0)
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if (bp[--bn])
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return si;
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return 0;
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}
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}
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#undef mpfr_cmp_si
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int
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mpfr_cmp_si (mpfr_srcptr b, long int i)
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{
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return mpfr_cmp_si_2exp (b, i, 0);
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}
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