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55 lines
1.7 KiB
C
55 lines
1.7 KiB
C
/* Extract the payload of a NaN 'float'.
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Copyright 2024-2026 Free Software Foundation, Inc.
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This file 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
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published by the Free Software Foundation, either version 3 of the
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License, or (at your option) any later version.
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This file 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
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GNU Lesser General Public 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 this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Bruno Haible. */
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#include <config.h>
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/* Specification. */
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#include <math.h>
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#include <float.h>
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#include <stdint.h>
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#include <string.h>
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float
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getpayloadf (const float *value)
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{
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if (isnanf (*value))
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{
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#if FLT_MANT_DIG == 24
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union { uint32_t i; float f; } x;
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# if 0
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x.f = *value;
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# else
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/* On 32-bit x86 processors, as well as on x86_64 processors with
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CC="gcc -mfpmath=387", the evaluation of *value above is done
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through an 'flds' instruction, which converts a signalling NaN to
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a quiet NaN. See
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<https://lists.gnu.org/archive/html/bug-gnulib/2023-10/msg00060.html>
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for details. Use memcpy to avoid this. */
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memcpy (&x.f, value, sizeof (float));
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# endif
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int32_t payload = x.i & (((uint32_t) 1 << (FLT_MANT_DIG - 2)) - 1);
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return payload;
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#else
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# error "Please port gnulib getpayloadf.c to your platform!"
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#endif
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}
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else
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return -1.0f;
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}
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