1  /* Handle floating-point rounding mode within libc.
       2     Copyright (C) 2012-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #ifndef _ROUNDING_MODE_H
      20  #define _ROUNDING_MODE_H	1
      21  
      22  #include <fenv.h>
      23  #include <stdbool.h>
      24  #include <stdlib.h>
      25  
      26  /* Get the architecture-specific definition of how to determine the
      27     rounding mode in libc.  This header must also define the FE_*
      28     macros for any standard rounding modes the architecture does not
      29     have in <fenv.h>, to arbitrary distinct values.  */
      30  #include <get-rounding-mode.h>
      31  
      32  /* Return true if a number should be rounded away from zero in
      33     rounding mode MODE, false otherwise.  NEGATIVE is true if the
      34     number is negative, false otherwise.  LAST_DIGIT_ODD is true if the
      35     last digit of the truncated value (last bit for binary) is odd,
      36     false otherwise.  HALF_BIT is true if the number is at least half
      37     way from the truncated value to the next value with the
      38     least-significant digit in the same place, false otherwise.
      39     MORE_BITS is true if the number is not exactly equal to the
      40     truncated value or the half-way value, false otherwise.  */
      41  
      42  static bool
      43  round_away (bool negative, bool last_digit_odd, bool half_bit, bool more_bits,
      44  	    int mode)
      45  {
      46    switch (mode)
      47      {
      48      case FE_DOWNWARD:
      49        return negative && (half_bit || more_bits);
      50  
      51      case FE_TONEAREST:
      52        return half_bit && (last_digit_odd || more_bits);
      53  
      54      case FE_TOWARDZERO:
      55        return false;
      56  
      57      case FE_UPWARD:
      58        return !negative && (half_bit || more_bits);
      59  
      60      default:
      61        abort ();
      62      }
      63  }
      64  
      65  #endif /* rounding-mode.h */