1/*
2 * This file is part of FFmpeg.
3 *
4 * FFmpeg is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2.1 of the License, or (at your option) any later version.
8 *
9 * FFmpeg is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12 * Lesser General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with FFmpeg; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17 */
18
19#ifndef AVCODEC_FLOAT2HALF_H
20#define AVCODEC_FLOAT2HALF_H
21
22#include <stdint.h>
23
24static void float2half_tables(uint16_t *basetable, uint8_t *shifttable)
25{
26    for (int i = 0; i < 256; i++) {
27        int e = i - 127;
28
29        if (e < -24) { // Very small numbers map to zero
30            basetable[i|0x000]  = 0x0000;
31            basetable[i|0x100]  = 0x8000;
32            shifttable[i|0x000] = 24;
33            shifttable[i|0x100] = 24;
34        } else if (e < -14) { // Small numbers map to denorms
35            basetable[i|0x000] = (0x0400>>(-e-14));
36            basetable[i|0x100] = (0x0400>>(-e-14)) | 0x8000;
37            shifttable[i|0x000] = -e-1;
38            shifttable[i|0x100] = -e-1;
39        } else if (e <= 15) { // Normal numbers just lose precision
40            basetable[i|0x000] = ((e + 15) << 10);
41            basetable[i|0x100] = ((e + 15) << 10) | 0x8000;
42            shifttable[i|0x000] = 13;
43            shifttable[i|0x100] = 13;
44        } else if (e < 128) { // Large numbers map to Infinity
45            basetable[i|0x000]  = 0x7C00;
46            basetable[i|0x100]  = 0xFC00;
47            shifttable[i|0x000] = 24;
48            shifttable[i|0x100] = 24;
49        } else { // Infinity and NaN's stay Infinity and NaN's
50            basetable[i|0x000]  = 0x7C00;
51            basetable[i|0x100]  = 0xFC00;
52            shifttable[i|0x000] = 13;
53            shifttable[i|0x100] = 13;
54        }
55    }
56}
57
58static uint16_t float2half(uint32_t f, uint16_t *basetable, uint8_t *shifttable)
59{
60    uint16_t h;
61
62    h = basetable[(f >> 23) & 0x1ff] + ((f & 0x007fffff) >> shifttable[(f >> 23) & 0x1ff]);
63
64    return h;
65}
66
67#endif /* AVCODEC_FLOAT2HALF_H */
68