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_HALF2FLOAT_H
20#define AVCODEC_HALF2FLOAT_H
21
22#include <stdint.h>
23
24static uint32_t convertmantissa(uint32_t i)
25{
26    int32_t m = i << 13; // Zero pad mantissa bits
27    int32_t e = 0; // Zero exponent
28
29    while (!(m & 0x00800000)) { // While not normalized
30        e -= 0x00800000; // Decrement exponent (1<<23)
31        m <<= 1; // Shift mantissa
32    }
33
34    m &= ~0x00800000; // Clear leading 1 bit
35    e +=  0x38800000; // Adjust bias ((127-14)<<23)
36
37    return m | e; // Return combined number
38}
39
40static void half2float_table(uint32_t *mantissatable, uint32_t *exponenttable,
41                             uint16_t *offsettable)
42{
43    mantissatable[0] = 0;
44    for (int i = 1; i < 1024; i++)
45        mantissatable[i] = convertmantissa(i);
46    for (int i = 1024; i < 2048; i++)
47        mantissatable[i] = 0x38000000UL + ((i - 1024) << 13UL);
48
49    exponenttable[0] = 0;
50    for (int i = 1; i < 31; i++)
51        exponenttable[i] = i << 23;
52    for (int i = 33; i < 63; i++)
53        exponenttable[i] = 0x80000000UL + ((i - 32) << 23UL);
54    exponenttable[31]= 0x47800000UL;
55    exponenttable[32]= 0x80000000UL;
56    exponenttable[63]= 0xC7800000UL;
57
58    offsettable[0] = 0;
59    for (int i = 1; i < 64; i++)
60        offsettable[i] = 1024;
61    offsettable[32] = 0;
62}
63
64static uint32_t half2float(uint16_t h, uint32_t *mantissatable, uint32_t *exponenttable,
65                           uint16_t *offsettable)
66{
67    uint32_t f;
68
69    f = mantissatable[offsettable[h >> 10] + (h & 0x3ff)] + exponenttable[h >> 10];
70
71    return f;
72}
73
74#endif /* AVCODEC_HALF2FLOAT_H */
75