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/* Handle floating-point rounding mode within libc.
Copyright (C) 2012-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef _ROUNDING_MODE_H
#define _ROUNDING_MODE_H 1
#include <fenv.h>
#include <stdbool.h>
#include <stdlib.h>
/* Get the architecture-specific definition of how to determine the
rounding mode in libc. This header must also define the FE_*
macros for any standard rounding modes the architecture does not
have in <fenv.h>, to arbitrary distinct values. */
#include <get-rounding-mode.h>
/* Return true if a number should be rounded away from zero in
rounding mode MODE, false otherwise. NEGATIVE is true if the
number is negative, false otherwise. LAST_DIGIT_ODD is true if the
last digit of the truncated value (last bit for binary) is odd,
false otherwise. HALF_BIT is true if the number is at least half
way from the truncated value to the next value with the
least-significant digit in the same place, false otherwise.
MORE_BITS is true if the number is not exactly equal to the
truncated value or the half-way value, false otherwise. */
static bool
round_away (bool negative, bool last_digit_odd, bool half_bit, bool more_bits,
int mode)
{
switch (mode)
{
case FE_DOWNWARD:
return negative && (half_bit || more_bits);
case FE_TONEAREST:
return half_bit && (last_digit_odd || more_bits);
case FE_TOWARDZERO:
return false;
case FE_UPWARD:
return !negative && (half_bit || more_bits);
default:
abort ();
}
}
#endif /* rounding-mode.h */
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