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/* Extract the payload of a NaN 'double'.
Copyright 2024-2026 Free Software Foundation, Inc.
This file 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 3 of the
License, or (at your option) any later version.
This file 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 this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible. */
#include <config.h>
/* Specification. */
#include <math.h>
#include <float.h>
#include <stdint.h>
#include <string.h>
double
getpayload (const double *value)
{
if (isnand (*value))
{
#if DBL_MANT_DIG == 53
union { uint64_t i; double f; } x;
# if 0
x.f = *value;
# else
/* On 32-bit x86 processors, as well as on x86_64 processors with
CC="gcc -mfpmath=387", the evaluation of *value above is done
through an 'fldl' instruction, which converts a signalling NaN to
a quiet NaN. See
<https://lists.gnu.org/archive/html/bug-gnulib/2023-10/msg00060.html>
for details. Use memcpy to avoid this. */
memcpy (&x.f, value, sizeof (double));
# endif
int64_t payload = x.i & (((uint64_t) 1 << (DBL_MANT_DIG - 2)) - 1);
return payload;
#else
# error "Please port gnulib getpayload.c to your platform!"
#endif
}
else
return -1.0;
}
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