1  /* mpfr_cmp_si_2exp -- compare a floating-point number with a signed
       2  machine integer multiplied by a power of 2
       3  
       4  Copyright 1999, 2001-2023 Free Software Foundation, Inc.
       5  Contributed by the AriC and Caramba projects, INRIA.
       6  
       7  This file is part of the GNU MPFR Library.
       8  
       9  The GNU MPFR Library is free software; you can redistribute it and/or modify
      10  it under the terms of the GNU Lesser General Public License as published by
      11  the Free Software Foundation; either version 3 of the License, or (at your
      12  option) any later version.
      13  
      14  The GNU MPFR Library is distributed in the hope that it will be useful, but
      15  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      16  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
      17  License for more details.
      18  
      19  You should have received a copy of the GNU Lesser General Public License
      20  along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
      21  https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
      22  51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
      23  
      24  #define MPFR_NEED_LONGLONG_H
      25  #include "mpfr-impl.h"
      26  
      27  /* returns a positive value if b > i*2^f,
      28             a negative value if b < i*2^f,
      29             zero if b = i*2^f.
      30     b must not be NaN.
      31  */
      32  
      33  int
      34  mpfr_cmp_si_2exp (mpfr_srcptr b, long int i, mpfr_exp_t f)
      35  {
      36    int si;
      37  
      38    si = i < 0 ? -1 : 1; /* sign of i */
      39    if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (b)))
      40      {
      41        if (MPFR_IS_INF(b))
      42          return MPFR_INT_SIGN(b);
      43        else if (MPFR_IS_ZERO(b))
      44          return i != 0 ? -si : 0;
      45        /* NAN */
      46        MPFR_SET_ERANGEFLAG ();
      47        return 0;
      48      }
      49    else if (MPFR_SIGN(b) != si || i == 0)
      50      return MPFR_INT_SIGN (b);
      51    else /* b and i are of same sign si */
      52  #ifdef MPFR_LONG_WITHIN_LIMB
      53      {
      54        mpfr_exp_t e;
      55        unsigned long ai;
      56        int k;
      57        mp_size_t bn;
      58        mp_limb_t c, *bp;
      59  
      60        ai = SAFE_ABS(unsigned long, i);
      61  
      62        /* ai must be representable in a mp_limb_t */
      63        MPFR_ASSERTN(ai == (mp_limb_t) ai);
      64  
      65        e = MPFR_GET_EXP (b); /* 2^(e-1) <= b < 2^e */
      66        if (e <= f)
      67          return -si;
      68        if (f < MPFR_EMAX_MAX - GMP_NUMB_BITS &&
      69            e > f + GMP_NUMB_BITS)
      70          return si;
      71  
      72        /* now f < e <= f + GMP_NUMB_BITS */
      73        c = (mp_limb_t) ai;
      74        count_leading_zeros(k, c);
      75        if ((int) (e - f) > GMP_NUMB_BITS - k)
      76          return si;
      77        if ((int) (e - f) < GMP_NUMB_BITS - k)
      78          return -si;
      79  
      80        /* now b and i*2^f have the same exponent */
      81        c <<= k;
      82        bn = (MPFR_PREC(b) - 1) / GMP_NUMB_BITS;
      83        bp = MPFR_MANT(b);
      84        if (bp[bn] > c)
      85          return si;
      86        if (bp[bn] < c)
      87          return -si;
      88  
      89        /* most significant limbs agree, check remaining limbs from b */
      90        while (bn > 0)
      91          if (bp[--bn])
      92            return si;
      93        return 0;
      94      }
      95  #else
      96    {
      97        mpfr_t uu;
      98        int ret;
      99        MPFR_SAVE_EXPO_DECL (expo);
     100  
     101        mpfr_init2 (uu, sizeof (unsigned long) * CHAR_BIT);
     102        /* Warning: i*2^f might be outside the current exponent range! */
     103        MPFR_SAVE_EXPO_MARK (expo);
     104        mpfr_set_si_2exp (uu, i, f, MPFR_RNDZ);
     105        MPFR_SAVE_EXPO_FREE (expo);
     106        ret = mpfr_cmp (b, uu);
     107        mpfr_clear (uu);
     108        return ret;
     109    }
     110  #endif /* MPFR_LONG_WITHIN_LIMB */
     111  }
     112  
     113  #undef mpfr_cmp_si
     114  int
     115  mpfr_cmp_si (mpfr_srcptr b, long int i)
     116  {
     117    return mpfr_cmp_si_2exp (b, i, 0);
     118  }