[FFmpeg-cvslog] avcodec: Implement masked lz decompression
Umair Khan
git at videolan.org
Mon Aug 22 16:30:28 EEST 2016
ffmpeg | branch: master | Umair Khan <omerjerk at gmail.com> | Fri Aug 12 18:07:15 2016 +0530| [eabdabb9822ed028cd8aeed94ded784b6364ba78] | committer: Thilo Borgmann
avcodec: Implement masked lz decompression
Signed-off-by: Umair Khan <omerjerk at gmail.com>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=eabdabb9822ed028cd8aeed94ded784b6364ba78
---
libavcodec/mlz.c | 173 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
libavcodec/mlz.h | 70 ++++++++++++++++++++++
2 files changed, 243 insertions(+)
diff --git a/libavcodec/mlz.c b/libavcodec/mlz.c
new file mode 100644
index 0000000..04b684d
--- /dev/null
+++ b/libavcodec/mlz.c
@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) 2016 Umair Khan <omerjerk at 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;
+}
diff --git a/libavcodec/mlz.h b/libavcodec/mlz.h
new file mode 100644
index 0000000..158715e
--- /dev/null
+++ b/libavcodec/mlz.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2016 Umair Khan <omerjerk at 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*/
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