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avcodec: Implement masked lz decompression

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Signed-off-by: Umair Khan <omerjerk@gmail.com>
This commit is contained in:
Umair Khan 2016-08-12 17:49:15 +05:30 committed by Thilo Borgmann
parent fb1f67a70b
commit eabdabb982
2 changed files with 243 additions and 0 deletions
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173
libavcodec/mlz.c Normal file
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/*
* 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_malloc_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;
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) {
output_chars += decode_string(mlz, &buff[output_chars], last_string_code, &char_code, size - output_chars);
output_chars += decode_string(mlz, &buff[output_chars], char_code, &char_code, size - output_chars);
set_new_entry_dict(dict, mlz->next_code, last_string_code, char_code);
mlz->next_code++;
} else {
output_chars += decode_string(mlz, &buff[output_chars], string_code, &char_code, size - output_chars);
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);
mlz->next_code++;
}
} else {
break;
}
}
last_string_code = string_code;
}
break;
}
}
return output_chars;
}

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libavcodec/mlz.h Normal file
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/*
* 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
*/
#ifndef AVCODEC_MLZ_H
#define AVCODEC_MLZ_H
#include "get_bits.h"
#define CODE_UNSET -1
#define CODE_BIT_INIT 9
#define DIC_INDEX_INIT 512 // 2^9
#define DIC_INDEX_MAX 32768l // 2^15
#define FLUSH_CODE 256
#define FREEZE_CODE 257
#define FIRST_CODE 258
#define MAX_CODE 32767l
#define TABLE_SIZE 35023l // TABLE_SIZE must be a prime number
/** Dictionary structure for mlz decompression
*/
typedef struct MLZDict {
int string_code;
int parent_code;
int char_code;
int match_len;
} MLZDict;
/** MLZ data strucure
*/
typedef struct MLZ {
int dic_code_bit;
int current_dic_index_max;
unsigned int bump_code;
unsigned int flush_code;
int next_code;
int freeze_flag;
MLZDict* dict;
void* context;
} MLZ;
/** Initialize the dictionary
*/
void ff_mlz_init_dict(void* context, MLZ *mlz);
/** Flush the dictionary
*/
void ff_mlz_flush_dict(MLZ *dict);
/** Run mlz decompression on the next size bits and the output will be stored in buff
*/
int ff_mlz_decompression(MLZ* mlz, GetBitContext* gb, int size, unsigned char *buff);
#endif /*AVCODEC_MLZ_H*/