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/*
* This file is part of FFmpeg.
*
* FFmpeg 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.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVUTIL_FLOAT2HALF_H
#define AVUTIL_FLOAT2HALF_H
#include <stdint.h>
typedef struct Float2HalfTables {
uint16_t basetable[512];
uint8_t shifttable[512];
} Float2HalfTables;
static void init_float2half_tables(Float2HalfTables *t)
{
for (int i = 0; i < 256; i++) {
int e = i - 127;
if (e < -24) { // Very small numbers map to zero
t->basetable[i|0x000] = 0x0000;
t->basetable[i|0x100] = 0x8000;
t->shifttable[i|0x000] = 24;
t->shifttable[i|0x100] = 24;
} else if (e < -14) { // Small numbers map to denorms
t->basetable[i|0x000] = (0x0400>>(-e-14));
t->basetable[i|0x100] = (0x0400>>(-e-14)) | 0x8000;
t->shifttable[i|0x000] = -e-1;
t->shifttable[i|0x100] = -e-1;
} else if (e <= 15) { // Normal numbers just lose precision
t->basetable[i|0x000] = ((e + 15) << 10);
t->basetable[i|0x100] = ((e + 15) << 10) | 0x8000;
t->shifttable[i|0x000] = 13;
t->shifttable[i|0x100] = 13;
} else if (e < 128) { // Large numbers map to Infinity
t->basetable[i|0x000] = 0x7C00;
t->basetable[i|0x100] = 0xFC00;
t->shifttable[i|0x000] = 24;
t->shifttable[i|0x100] = 24;
} else { // Infinity and NaN's stay Infinity and NaN's
t->basetable[i|0x000] = 0x7C00;
t->basetable[i|0x100] = 0xFC00;
t->shifttable[i|0x000] = 13;
t->shifttable[i|0x100] = 13;
}
}
}
static uint16_t float2half(uint32_t f, const Float2HalfTables *t)
{
uint16_t h;
h = t->basetable[(f >> 23) & 0x1ff] + ((f & 0x007fffff) >> t->shifttable[(f >> 23) & 0x1ff]);
return h;
}
#endif /* AVUTIL_FLOAT2HALF_H */
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