summaryrefslogtreecommitdiff
path: root/libavcodec/mlz.c
blob: ebce796ba52beb40a6a2af7a76ac72eda51a5bb0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
/*
 * Copyright (c) 2016 Umair Khan <omerjerk@gmail.com>
 *
 * 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
 */

#include "mlz.h"

av_cold void ff_mlz_init_dict(void* context, MLZ *mlz) {
    mlz->dict = av_mallocz_array(TABLE_SIZE, sizeof(*mlz->dict));

    mlz->flush_code            = FLUSH_CODE;
    mlz->current_dic_index_max = DIC_INDEX_INIT;
    mlz->dic_code_bit          = CODE_BIT_INIT;
    mlz->bump_code             = (DIC_INDEX_INIT - 1);
    mlz->next_code             = FIRST_CODE;
    mlz->freeze_flag           = 0;
    mlz->context               = context;
}

av_cold void ff_mlz_flush_dict(MLZ *mlz) {
    MLZDict *dict = mlz->dict;
    int i;
    for ( i = 0; i < TABLE_SIZE; i++ ) {
        dict[i].string_code = CODE_UNSET;
        dict[i].parent_code = CODE_UNSET;
        dict[i].match_len = 0;
    }
    mlz->current_dic_index_max = DIC_INDEX_INIT;
    mlz->dic_code_bit          = CODE_BIT_INIT;  // DicCodeBitInit;
    mlz->bump_code             = mlz->current_dic_index_max - 1;
    mlz->next_code             = FIRST_CODE;
    mlz->freeze_flag           = 0;
}

static void set_new_entry_dict(MLZDict* dict, int string_code, int parent_code, int char_code) {
    dict[string_code].parent_code = parent_code;
    dict[string_code].string_code = string_code;
    dict[string_code].char_code   = char_code;
    if (parent_code < FIRST_CODE) {
        dict[string_code].match_len = 2;
    } else {
        dict[string_code].match_len = (dict[parent_code].match_len) + 1;
    }
}

static int decode_string(MLZ* mlz, unsigned char *buff, int string_code, int *first_char_code, unsigned long bufsize) {
    MLZDict* dict = mlz->dict;
    unsigned long count, offset;
    int current_code, parent_code, tmp_code;

    count            = 0;
    current_code     = string_code;
    *first_char_code = CODE_UNSET;

    while (count < bufsize) {
        switch (current_code) {
        case CODE_UNSET:
            return count;
            break;
        default:
            if (current_code < FIRST_CODE) {
                *first_char_code = current_code;
                buff[0] = current_code;
                count++;
                return count;
            } else {
                offset  = dict[current_code].match_len - 1;
                tmp_code = dict[current_code].char_code;
                if (offset >= bufsize) {
                    av_log(mlz->context, AV_LOG_ERROR, "MLZ offset error.\n");
                    return count;
                }
                buff[offset] = tmp_code;
                count++;
            }
            current_code = dict[current_code].parent_code;
            if ((current_code < 0) || (current_code > (DIC_INDEX_MAX - 1))) {
                av_log(mlz->context, AV_LOG_ERROR, "MLZ dic index error.\n");
                return count;
            }
            if (current_code > FIRST_CODE) {
                parent_code = dict[current_code].parent_code;
                offset = (dict[current_code].match_len) - 1;
                if (parent_code < 0 || parent_code > DIC_INDEX_MAX-1) {
                    av_log(mlz->context, AV_LOG_ERROR, "MLZ dic index error.\n");
                    return count;
                }
                if (( offset > (DIC_INDEX_MAX - 1))) {
                    av_log(mlz->context, AV_LOG_ERROR, "MLZ dic offset error.\n");
                    return count;
                }
            }
            break;
        }
    }
    return count;
}

static int input_code(GetBitContext* gb, int len) {
    int tmp_code = 0;
    int i;
    for (i = 0; i < len; ++i) {
        tmp_code |= get_bits1(gb) << i;
    }
    return tmp_code;
}

int ff_mlz_decompression(MLZ* mlz, GetBitContext* gb, int size, unsigned char *buff) {
    MLZDict *dict = mlz->dict;
    unsigned long output_chars;
    int string_code, last_string_code, char_code;

    string_code = 0;
    char_code   = -1;
    last_string_code = -1;
    output_chars = 0;

    while (output_chars < size) {
        string_code = input_code(gb, mlz->dic_code_bit);
        switch (string_code) {
            case FLUSH_CODE:
            case MAX_CODE:
                ff_mlz_flush_dict(mlz);
                char_code = -1;
                last_string_code = -1;
                break;
            case FREEZE_CODE:
                mlz->freeze_flag = 1;
                break;
            default:
                if (string_code > mlz->current_dic_index_max) {
                    av_log(mlz->context, AV_LOG_ERROR, "String code %d exceeds maximum value of %d.\n", string_code, mlz->current_dic_index_max);
                    return output_chars;
                }
                if (string_code == (int) mlz->bump_code) {
                    ++mlz->dic_code_bit;
                    mlz->current_dic_index_max *= 2;
                    mlz->bump_code = mlz->current_dic_index_max - 1;
                } else {
                    if (string_code >= mlz->next_code) {
                        int ret = decode_string(mlz, &buff[output_chars], last_string_code, &char_code, size - output_chars);
                        if (ret < 0 || ret > size - output_chars) {
                            av_log(mlz->context, AV_LOG_ERROR, "output chars overflow\n");
                            return output_chars;
                        }
                        output_chars += ret;
                        ret = decode_string(mlz, &buff[output_chars], char_code, &char_code, size - output_chars);
                        if (ret < 0 || ret > size - output_chars) {
                            av_log(mlz->context, AV_LOG_ERROR, "output chars overflow\n");
                            return output_chars;
                        }
                        output_chars += ret;
                        set_new_entry_dict(dict, mlz->next_code, last_string_code, char_code);
                        if (mlz->next_code >= TABLE_SIZE - 1) {
                            av_log(mlz->context, AV_LOG_ERROR, "Too many MLZ codes\n");
                            return output_chars;
                        }
                        mlz->next_code++;
                    } else {
                        int ret = decode_string(mlz, &buff[output_chars], string_code, &char_code, size - output_chars);
                        if (ret < 0 || ret > size - output_chars) {
                            av_log(mlz->context, AV_LOG_ERROR, "output chars overflow\n");
                            return output_chars;
                        }
                        output_chars += ret;
                        if (output_chars <= size && !mlz->freeze_flag) {
                            if (last_string_code != -1) {
                                set_new_entry_dict(dict, mlz->next_code, last_string_code, char_code);
                                if (mlz->next_code >= TABLE_SIZE - 1) {
                                    av_log(mlz->context, AV_LOG_ERROR, "Too many MLZ codes\n");
                                    return output_chars;
                                }
                                mlz->next_code++;
                            }
                        } else {
                            break;
                        }
                    }
                    last_string_code = string_code;
                }
                break;
        }
    }
    return output_chars;
}