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https://github.com/FFmpeg/FFmpeg.git
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avcodec: Implement masked lz decompression
Signed-off-by: Umair Khan <omerjerk@gmail.com>
This commit is contained in:
Umair Khan
Thilo Borgmann
parent
fb1f67a70b
commit
eabdabb982
173
libavcodec/mlz.c
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173
libavcodec/mlz.c
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/*
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* Copyright (c) 2016 Umair Khan <omerjerk@gmail.com>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "mlz.h"
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av_cold void ff_mlz_init_dict(void* context, MLZ *mlz) {
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mlz->dict = av_malloc_array(TABLE_SIZE, sizeof(*mlz->dict));
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mlz->flush_code = FLUSH_CODE;
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mlz->current_dic_index_max = DIC_INDEX_INIT;
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mlz->dic_code_bit = CODE_BIT_INIT;
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mlz->bump_code = (DIC_INDEX_INIT - 1);
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mlz->next_code = FIRST_CODE;
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mlz->freeze_flag = 0;
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mlz->context = context;
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}
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av_cold void ff_mlz_flush_dict(MLZ *mlz) {
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MLZDict *dict = mlz->dict;
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int i;
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for ( i = 0; i < TABLE_SIZE; i++ ) {
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dict[i].string_code = CODE_UNSET;
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dict[i].parent_code = CODE_UNSET;
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dict[i].match_len = 0;
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}
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mlz->current_dic_index_max = DIC_INDEX_INIT;
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mlz->dic_code_bit = CODE_BIT_INIT; // DicCodeBitInit;
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mlz->bump_code = mlz->current_dic_index_max - 1;
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mlz->next_code = FIRST_CODE;
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mlz->freeze_flag = 0;
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}
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static void set_new_entry_dict(MLZDict* dict, int string_code, int parent_code, int char_code) {
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dict[string_code].parent_code = parent_code;
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dict[string_code].string_code = string_code;
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dict[string_code].char_code = char_code;
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if (parent_code < FIRST_CODE) {
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dict[string_code].match_len = 2;
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} else {
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dict[string_code].match_len = (dict[parent_code].match_len) + 1;
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}
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}
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static int decode_string(MLZ* mlz, unsigned char *buff, int string_code, int *first_char_code, unsigned long bufsize) {
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MLZDict* dict = mlz->dict;
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unsigned long count, offset;
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int current_code, parent_code, tmp_code;
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count = 0;
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current_code = string_code;
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*first_char_code = CODE_UNSET;
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while (count < bufsize) {
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switch (current_code) {
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case CODE_UNSET:
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return count;
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break;
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default:
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if (current_code < FIRST_CODE) {
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*first_char_code = current_code;
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buff[0] = current_code;
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count++;
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return count;
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} else {
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offset = dict[current_code].match_len - 1;
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tmp_code = dict[current_code].char_code;
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buff[offset] = tmp_code;
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count++;
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}
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current_code = dict[current_code].parent_code;
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if ((current_code < 0) || (current_code > (DIC_INDEX_MAX - 1))) {
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av_log(mlz->context, AV_LOG_ERROR, "MLZ dic index error.\n");
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return count;
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}
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if (current_code > FIRST_CODE) {
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parent_code = dict[current_code].parent_code;
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offset = (dict[current_code].match_len) - 1;
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if (parent_code < 0 || parent_code > DIC_INDEX_MAX-1) {
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av_log(mlz->context, AV_LOG_ERROR, "MLZ dic index error.\n");
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return count;
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}
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if (( offset > (DIC_INDEX_MAX - 1))) {
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av_log(mlz->context, AV_LOG_ERROR, "MLZ dic offset error.\n");
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return count;
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}
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}
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break;
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}
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}
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return count;
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}
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static int input_code(GetBitContext* gb, int len) {
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int tmp_code = 0;
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int i;
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for (i = 0; i < len; ++i) {
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tmp_code |= get_bits1(gb) << i;
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}
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return tmp_code;
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}
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int ff_mlz_decompression(MLZ* mlz, GetBitContext* gb, int size, unsigned char *buff) {
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MLZDict *dict = mlz->dict;
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unsigned long output_chars;
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int string_code, last_string_code, char_code;
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string_code = 0;
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char_code = -1;
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last_string_code = -1;
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output_chars = 0;
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while (output_chars < size) {
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string_code = input_code(gb, mlz->dic_code_bit);
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switch (string_code) {
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case FLUSH_CODE:
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case MAX_CODE:
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ff_mlz_flush_dict(mlz);
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char_code = -1;
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last_string_code = -1;
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break;
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case FREEZE_CODE:
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mlz->freeze_flag = 1;
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break;
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default:
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if (string_code > mlz->current_dic_index_max) {
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av_log(mlz->context, AV_LOG_ERROR, "String code %d exceeds maximum value of %d.\n", string_code, mlz->current_dic_index_max);
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return output_chars;
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}
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if (string_code == (int) mlz->bump_code) {
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++mlz->dic_code_bit;
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mlz->current_dic_index_max *= 2;
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mlz->bump_code = mlz->current_dic_index_max - 1;
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} else {
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if (string_code >= mlz->next_code) {
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output_chars += decode_string(mlz, &buff[output_chars], last_string_code, &char_code, size - output_chars);
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output_chars += decode_string(mlz, &buff[output_chars], char_code, &char_code, size - output_chars);
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set_new_entry_dict(dict, mlz->next_code, last_string_code, char_code);
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mlz->next_code++;
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} else {
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output_chars += decode_string(mlz, &buff[output_chars], string_code, &char_code, size - output_chars);
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if (output_chars <= size && !mlz->freeze_flag) {
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if (last_string_code != -1) {
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set_new_entry_dict(dict, mlz->next_code, last_string_code, char_code);
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mlz->next_code++;
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}
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} else {
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break;
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}
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}
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last_string_code = string_code;
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}
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break;
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}
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}
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return output_chars;
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}
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70
libavcodec/mlz.h
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70
libavcodec/mlz.h
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@ -0,0 +1,70 @@
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/*
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* Copyright (c) 2016 Umair Khan <omerjerk@gmail.com>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef AVCODEC_MLZ_H
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#define AVCODEC_MLZ_H
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#include "get_bits.h"
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#define CODE_UNSET -1
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#define CODE_BIT_INIT 9
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#define DIC_INDEX_INIT 512 // 2^9
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#define DIC_INDEX_MAX 32768l // 2^15
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#define FLUSH_CODE 256
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#define FREEZE_CODE 257
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#define FIRST_CODE 258
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#define MAX_CODE 32767l
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#define TABLE_SIZE 35023l // TABLE_SIZE must be a prime number
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/** Dictionary structure for mlz decompression
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*/
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typedef struct MLZDict {
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int string_code;
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int parent_code;
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int char_code;
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int match_len;
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} MLZDict;
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/** MLZ data strucure
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*/
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typedef struct MLZ {
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int dic_code_bit;
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int current_dic_index_max;
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unsigned int bump_code;
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unsigned int flush_code;
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int next_code;
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int freeze_flag;
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MLZDict* dict;
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void* context;
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} MLZ;
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/** Initialize the dictionary
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*/
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void ff_mlz_init_dict(void* context, MLZ *mlz);
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/** Flush the dictionary
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*/
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void ff_mlz_flush_dict(MLZ *dict);
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/** Run mlz decompression on the next size bits and the output will be stored in buff
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*/
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int ff_mlz_decompression(MLZ* mlz, GetBitContext* gb, int size, unsigned char *buff);
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#endif /*AVCODEC_MLZ_H*/
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