1 | /**************************************************************************
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2 | *
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3 | * text.h -- Header file for compression related stuff
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4 | * Copyright (C) 1994 Neil Sharman
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5 | *
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6 | * This program is free software; you can redistribute it and/or modify
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7 | * it under the terms of the GNU General Public License as published by
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8 | * the Free Software Foundation; either version 2 of the License, or
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9 | * (at your option) any later version.
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10 | *
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11 | * This program is distributed in the hope that it will be useful,
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12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 | * GNU General Public License for more details.
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15 | *
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16 | * You should have received a copy of the GNU General Public License
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17 | * along with this program; if not, write to the Free Software
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18 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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19 | *
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20 | * $Id: text.h 439 1999-08-10 21:23:37Z sjboddie $
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21 | *
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22 | **************************************************************************/
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23 |
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24 |
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25 |
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26 | #ifndef H_TEXT
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27 | #define H_TEXT
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28 |
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29 | #include "huffman.h"
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30 |
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31 |
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32 |
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33 |
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34 |
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35 | /*****************************************************************************
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36 | *
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37 | * There are several different methods of compressing the text of the
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38 | * database. The following defines list the different methods of text
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39 | * compression
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40 | *
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41 | */
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42 |
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43 |
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44 | /* The dictionary contains all the fragments that occur in the collection
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45 | i.e. escapes are not possible */
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46 | #define MG_COMPLETE_DICTIONARY 0
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47 |
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48 |
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49 | /* Certain words have been deleted from the dictionary. The words deleted
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50 | have been used to create the frequency huffman codes of the characters.
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51 | This dictionary has an escape code and may be used to compress novel
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52 | words. This dictionary may fail if there is a novel character. */
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53 | #define MG_PARTIAL_DICTIONARY 1
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54 |
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55 |
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56 | /* This dictionary has an escape so that novel words and non-words can be
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57 | coded. The method for coding the novel words and non-words is determined
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58 | by a dictionary parameter. */
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59 | #define MG_SEED_DICTIONARY 2
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60 |
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61 |
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62 |
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63 |
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64 |
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65 |
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66 |
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67 |
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68 |
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69 | /*****************************************************************************
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70 | *
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71 | * With a seed dictionary there are several methods for coding the novel
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72 | * words and non-words the following defined values specify the different
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73 | * methods of coding.
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74 | *
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75 | */
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76 |
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77 |
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78 | /* Code novel words and non-words character by character using huffman codes.
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79 | The huffman codes for the word and non-word lengths and characters are
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80 | generated from the distribution of lengths and characters in the
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81 | dictionary. */
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82 | #define MG_NOVEL_HUFFMAN_CHARS 0
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83 |
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84 |
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85 | /* This method codes novel words using binary codes. The novel words are stored
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86 | in a auxillary dictionary which is built by pass two. */
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87 | #define MG_NOVEL_BINARY 1
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88 |
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89 |
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90 | /* This method codes novel words using delta codes. The novel words are stored
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91 | in a auxillary dictionary which is built by pass two. */
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92 | #define MG_NOVEL_DELTA 2
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93 |
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94 |
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95 | /* This method codes novel words using hybrid version of delta. The novel
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96 | words are stored in a auxillary dictionary which is built by pass two. */
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97 | #define MG_NOVEL_HYBRID 3
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98 |
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99 |
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100 | /* This method codes novel words using hybrid version of delta and a MTF
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101 | operation. The novel words are stored in a auxillary dictionary which
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102 | is built by pass two. */
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103 | #define MG_NOVEL_HYBRID_MTF 4
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104 |
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105 |
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106 |
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107 |
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108 |
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109 |
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110 | /* This specified an amount of extra space allocated in the
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111 | compression_dict_header for adding new parameters. As new
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112 | parameters are added this should be decreased. */
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113 | #define TEXT_PARAMS 15
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114 |
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115 |
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116 |
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117 | typedef struct compression_dict_header
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118 | {
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119 | u_long dict_type;
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120 | u_long novel_method;
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121 | u_long params[TEXT_PARAMS];
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122 | u_long num_words[2];
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123 | u_long num_word_chars[2];
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124 | u_long lookback;
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125 | }
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126 | compression_dict_header;
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127 |
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128 |
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129 | typedef struct comp_frags_header
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130 | {
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131 | huff_data hd;
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132 | u_long uncompressed_size;
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133 | u_long huff_words_size[MAX_HUFFCODE_LEN + 1];
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134 | }
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135 | comp_frags_header;
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136 |
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137 |
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138 |
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139 | typedef struct compressed_text_header
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140 | {
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141 | u_long num_of_docs;
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142 | u_long num_of_words; /* number of words in collection */
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143 | double num_of_bytes; /* [RJM 07/97: 4G limit] */
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144 | double ratio;
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145 | u_long length_of_longest_doc; /* (characters) */
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146 | u_long dummy; /* added to make the structure the same on different architectures */
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147 | }
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148 | compressed_text_header;
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149 |
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150 |
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151 | typedef struct compression_stats_header
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152 | {
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153 | u_long num_docs;
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154 | u_long dummy; /* added to make the structure the same on different architectures */
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155 | double num_bytes; /* [RJM 07/97: 4G limit] */
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156 | }
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157 | compression_stats_header;
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158 |
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159 |
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160 | typedef struct frags_stats_header
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161 | {
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162 | u_long num_frags;
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163 | u_long mem_for_frags;
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164 | }
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165 | frags_stats_header;
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166 |
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167 |
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168 | typedef struct aux_frags_header
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169 | {
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170 | u_long num_frags;
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171 | u_long mem_for_frags;
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172 | }
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173 | aux_frags_header;
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174 |
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175 |
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176 | #endif
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