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66 lines
2.2 KiB
C
66 lines
2.2 KiB
C
/* Handle floating-point rounding mode within libc.
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Copyright (C) 2012-2019 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _ROUNDING_MODE_H
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#define _ROUNDING_MODE_H 1
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#include <fenv.h>
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#include <stdbool.h>
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#include <stdlib.h>
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/* Get the architecture-specific definition of how to determine the
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rounding mode in libc. This header must also define the FE_*
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macros for any standard rounding modes the architecture does not
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have in <fenv.h>, to arbitrary distinct values. */
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#include <get-rounding-mode.h>
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/* Return true if a number should be rounded away from zero in
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rounding mode MODE, false otherwise. NEGATIVE is true if the
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number is negative, false otherwise. LAST_DIGIT_ODD is true if the
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last digit of the truncated value (last bit for binary) is odd,
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false otherwise. HALF_BIT is true if the number is at least half
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way from the truncated value to the next value with the
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least-significant digit in the same place, false otherwise.
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MORE_BITS is true if the number is not exactly equal to the
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truncated value or the half-way value, false otherwise. */
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static bool
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round_away (bool negative, bool last_digit_odd, bool half_bit, bool more_bits,
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int mode)
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{
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switch (mode)
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{
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case FE_DOWNWARD:
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return negative && (half_bit || more_bits);
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case FE_TONEAREST:
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return half_bit && (last_digit_odd || more_bits);
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case FE_TOWARDZERO:
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return false;
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case FE_UPWARD:
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return !negative && (half_bit || more_bits);
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default:
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abort ();
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}
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}
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#endif /* rounding-mode.h */
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