1/*
2 * MJPEG decoder VLC code
3 * Copyright (c) 2000, 2001 Fabrice Bellard
4 * Copyright (c) 2003 Alex Beregszaszi
5 * Copyright (c) 2003-2004 Michael Niedermayer
6 *
7 * This file is part of FFmpeg.
8 *
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24#include <stdint.h>
25#include "libavutil/avassert.h"
26#include "mjpegdec.h"
27#include "vlc.h"
28
29static int build_huffman_codes(uint8_t *huff_size, const uint8_t *bits_table)
30{
31    int nb_codes = 0;
32    for (int i = 1, j = 0; i <= 16; i++) {
33        nb_codes += bits_table[i];
34        av_assert1(nb_codes <= 256);
35        for (; j < nb_codes; j++)
36            huff_size[j] = i;
37    }
38    return nb_codes;
39}
40
41int ff_mjpeg_build_vlc(VLC *vlc, const uint8_t *bits_table,
42                       const uint8_t *val_table, int is_ac, void *logctx)
43{
44    uint8_t huff_size[256];
45    uint16_t huff_sym[256];
46    int nb_codes = build_huffman_codes(huff_size, bits_table);
47
48    for (int i = 0; i < nb_codes; i++) {
49        huff_sym[i] = val_table[i] + 16 * is_ac;
50
51        if (is_ac && !val_table[i])
52            huff_sym[i] = 16 * 256;
53    }
54
55    return ff_init_vlc_from_lengths(vlc, 9, nb_codes, huff_size, 1,
56                                    huff_sym, 2, 2, 0, 0, logctx);
57}
58