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Ulrich Müller
c7eb52fe14
https://github.com/espeak-ng/espeak-ng/issues/1072 Signed-off-by: Ulrich Müller <ulm@gentoo.org>
75 lines
2.0 KiB
C
75 lines
2.0 KiB
C
/*
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* Copyright (C) 2022 Ulrich Müller <ulm@gentoo.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program 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 General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see: <http://www.gnu.org/licenses/>.
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*
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*
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* Alternatively, at your option, you can distribute this file under
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* the terms of the 2-clause BSD license.
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*/
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#include <math.h>
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#include <stdint.h>
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#include "ieee80.h"
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#ifndef INFINITY
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# define INFINITY 0.
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#endif
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#ifndef NAN
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# define NAN 0.
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#endif
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/*
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* Convert an IEEE 754 80-bit extended precision floating-point number
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* to a double. Input is expected as 10 bytes in big-endian order.
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*
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* Implemented according to the format described in:
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* https://en.wikipedia.org/wiki/Extended_precision
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* https://en.wikipedia.org/wiki/IEEE_754
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*/
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double
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ieee_extended_to_double(const unsigned char *bytes)
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{
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int sign, exp, i;
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uint64_t mant;
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double ret;
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sign = (bytes[0] & 0x80) != 0;
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exp = (bytes[0] & 0x7f) << 8 | bytes[1];
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/* Unfortunately, there is no 64-bit variant of ntohl(), and we
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cannot use be64toh() either, because it is nonstandard */
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mant = 0;
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for (i = 2; i < 10; i++)
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mant = (mant << 8) | bytes[i];
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switch (exp) {
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case 0: /* zero or denormalized number */
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ret = (mant == 0) ? 0. : ldexp(mant, - (16382 + 63));
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break;
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case 0x7fff: /* infinity or not a number */
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/* Convert infinity to INFINITY, and anything else
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(signalling NaN, quiet NaN, indefinite) to NAN */
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ret = ((mant & 0x7fffffffffffffff) == 0) ? INFINITY : NAN;
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break;
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default:
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ret = ldexp(mant, exp - (16383 + 63));
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}
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if (sign) ret = -ret;
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return ret;
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}
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