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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 int ff_mlz_init_dict(void *context, MLZ *mlz) |
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{ |
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mlz->dict = av_mallocz(TABLE_SIZE * sizeof(*mlz->dict)); |
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if (!mlz->dict) |
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return AVERROR(ENOMEM); |
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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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return 0; |
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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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if (offset >= bufsize) { |
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av_log(mlz->context, AV_LOG_ERROR, "MLZ offset error.\n"); |
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return count; |
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} |
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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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int ret = decode_string(mlz, &buff[output_chars], last_string_code, &char_code, size - output_chars); |
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if (ret < 0 || ret > size - output_chars) { |
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av_log(mlz->context, AV_LOG_ERROR, "output chars overflow\n"); |
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return output_chars; |
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} |
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output_chars += ret; |
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ret = decode_string(mlz, &buff[output_chars], char_code, &char_code, size - output_chars); |
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if (ret < 0 || ret > size - output_chars) { |
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av_log(mlz->context, AV_LOG_ERROR, "output chars overflow\n"); |
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return output_chars; |
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} |
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output_chars += ret; |
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set_new_entry_dict(dict, mlz->next_code, last_string_code, char_code); |
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if (mlz->next_code >= TABLE_SIZE - 1) { |
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av_log(mlz->context, AV_LOG_ERROR, "Too many MLZ codes\n"); |
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return output_chars; |
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} |
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mlz->next_code++; |
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} else { |
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int ret = decode_string(mlz, &buff[output_chars], string_code, &char_code, size - output_chars); |
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if (ret < 0 || ret > size - output_chars) { |
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av_log(mlz->context, AV_LOG_ERROR, "output chars overflow\n"); |
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return output_chars; |
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} |
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output_chars += ret; |
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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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if (mlz->next_code >= TABLE_SIZE - 1) { |
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av_log(mlz->context, AV_LOG_ERROR, "Too many MLZ codes\n"); |
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return output_chars; |
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} |
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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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