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1 /* deflate.h -- internal compression state |
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2 * Copyright (C) 1995-2004 Jean-loup Gailly |
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3 * For conditions of distribution and use, see copyright notice in zlib.h |
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4 */ |
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5 |
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6 /* WARNING: this file should *not* be used by applications. It is |
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7 part of the implementation of the compression library and is |
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8 subject to change. Applications should only use zlib.h. |
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9 */ |
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10 |
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11 /* @(#) $Id$ */ |
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12 |
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13 #ifndef DEFLATE_H |
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14 #define DEFLATE_H |
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15 |
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16 #include "zutil.h" |
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17 |
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18 /* define NO_GZIP when compiling if you want to disable gzip header and |
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19 trailer creation by deflate(). NO_GZIP would be used to avoid linking in |
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20 the crc code when it is not needed. For shared libraries, gzip encoding |
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21 should be left enabled. */ |
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22 #ifndef NO_GZIP |
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23 # define GZIP |
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24 #endif |
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25 |
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26 /* =========================================================================== |
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27 * Internal compression state. |
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28 */ |
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29 |
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30 #define LENGTH_CODES 29 |
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31 /* number of length codes, not counting the special END_BLOCK code */ |
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32 |
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33 #define LITERALS 256 |
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34 /* number of literal bytes 0..255 */ |
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35 |
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36 #define L_CODES (LITERALS+1+LENGTH_CODES) |
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37 /* number of Literal or Length codes, including the END_BLOCK code */ |
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38 |
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39 #define D_CODES 30 |
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40 /* number of distance codes */ |
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41 |
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42 #define BL_CODES 19 |
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43 /* number of codes used to transfer the bit lengths */ |
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44 |
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45 #define HEAP_SIZE (2*L_CODES+1) |
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46 /* maximum heap size */ |
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47 |
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48 #define MAX_BITS 15 |
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49 /* All codes must not exceed MAX_BITS bits */ |
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50 |
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51 #define INIT_STATE 42 |
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52 #define EXTRA_STATE 69 |
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53 #define NAME_STATE 73 |
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54 #define COMMENT_STATE 91 |
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55 #define HCRC_STATE 103 |
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56 #define BUSY_STATE 113 |
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57 #define FINISH_STATE 666 |
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58 /* Stream status */ |
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59 |
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60 |
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61 /* Data structure describing a single value and its code string. */ |
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62 typedef struct ct_data_s { |
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63 union { |
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64 ush freq; /* frequency count */ |
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65 ush code; /* bit string */ |
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66 } fc; |
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67 union { |
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68 ush dad; /* father node in Huffman tree */ |
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69 ush len; /* length of bit string */ |
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70 } dl; |
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71 } FAR ct_data; |
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72 |
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73 #define Freq fc.freq |
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74 #define Code fc.code |
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75 #define Dad dl.dad |
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76 #define Len dl.len |
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77 |
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78 typedef struct static_tree_desc_s static_tree_desc; |
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79 |
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80 typedef struct tree_desc_s { |
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81 ct_data *dyn_tree; /* the dynamic tree */ |
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82 int max_code; /* largest code with non zero frequency */ |
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83 static_tree_desc *stat_desc; /* the corresponding static tree */ |
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84 } FAR tree_desc; |
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85 |
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86 typedef ush Pos; |
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87 typedef Pos FAR Posf; |
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88 typedef unsigned IPos; |
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89 |
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90 /* A Pos is an index in the character window. We use short instead of int to |
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91 * save space in the various tables. IPos is used only for parameter passing. |
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92 */ |
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93 |
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94 typedef struct internal_state { |
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95 z_streamp strm; /* pointer back to this zlib stream */ |
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96 int status; /* as the name implies */ |
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97 Bytef *pending_buf; /* output still pending */ |
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98 ulg pending_buf_size; /* size of pending_buf */ |
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99 Bytef *pending_out; /* next pending byte to output to the stream */ |
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100 uInt pending; /* nb of bytes in the pending buffer */ |
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101 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */ |
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102 gz_headerp gzhead; /* gzip header information to write */ |
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103 uInt gzindex; /* where in extra, name, or comment */ |
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104 Byte method; /* STORED (for zip only) or DEFLATED */ |
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105 int last_flush; /* value of flush param for previous deflate call */ |
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106 |
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107 /* used by deflate.c: */ |
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108 |
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109 uInt w_size; /* LZ77 window size (32K by default) */ |
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110 uInt w_bits; /* log2(w_size) (8..16) */ |
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111 uInt w_mask; /* w_size - 1 */ |
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112 |
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113 Bytef *window; |
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114 /* Sliding window. Input bytes are read into the second half of the window, |
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115 * and move to the first half later to keep a dictionary of at least wSize |
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116 * bytes. With this organization, matches are limited to a distance of |
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117 * wSize-MAX_MATCH bytes, but this ensures that IO is always |
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118 * performed with a length multiple of the block size. Also, it limits |
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119 * the window size to 64K, which is quite useful on MSDOS. |
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120 * To do: use the user input buffer as sliding window. |
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121 */ |
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122 |
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123 ulg window_size; |
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124 /* Actual size of window: 2*wSize, except when the user input buffer |
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125 * is directly used as sliding window. |
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126 */ |
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127 |
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128 Posf *prev; |
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129 /* Link to older string with same hash index. To limit the size of this |
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130 * array to 64K, this link is maintained only for the last 32K strings. |
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131 * An index in this array is thus a window index modulo 32K. |
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132 */ |
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133 |
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134 Posf *head; /* Heads of the hash chains or NIL. */ |
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135 |
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136 uInt ins_h; /* hash index of string to be inserted */ |
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137 uInt hash_size; /* number of elements in hash table */ |
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138 uInt hash_bits; /* log2(hash_size) */ |
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139 uInt hash_mask; /* hash_size-1 */ |
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140 |
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141 uInt hash_shift; |
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142 /* Number of bits by which ins_h must be shifted at each input |
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143 * step. It must be such that after MIN_MATCH steps, the oldest |
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144 * byte no longer takes part in the hash key, that is: |
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145 * hash_shift * MIN_MATCH >= hash_bits |
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146 */ |
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147 |
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148 long block_start; |
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149 /* Window position at the beginning of the current output block. Gets |
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150 * negative when the window is moved backwards. |
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151 */ |
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152 |
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153 uInt match_length; /* length of best match */ |
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154 IPos prev_match; /* previous match */ |
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155 int match_available; /* set if previous match exists */ |
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156 uInt strstart; /* start of string to insert */ |
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157 uInt match_start; /* start of matching string */ |
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158 uInt lookahead; /* number of valid bytes ahead in window */ |
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159 |
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160 uInt prev_length; |
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161 /* Length of the best match at previous step. Matches not greater than this |
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162 * are discarded. This is used in the lazy match evaluation. |
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163 */ |
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164 |
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165 uInt max_chain_length; |
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166 /* To speed up deflation, hash chains are never searched beyond this |
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167 * length. A higher limit improves compression ratio but degrades the |
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168 * speed. |
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169 */ |
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170 |
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171 uInt max_lazy_match; |
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172 /* Attempt to find a better match only when the current match is strictly |
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173 * smaller than this value. This mechanism is used only for compression |
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174 * levels >= 4. |
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175 */ |
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176 # define max_insert_length max_lazy_match |
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177 /* Insert new strings in the hash table only if the match length is not |
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178 * greater than this length. This saves time but degrades compression. |
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179 * max_insert_length is used only for compression levels <= 3. |
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180 */ |
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181 |
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182 int level; /* compression level (1..9) */ |
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183 int strategy; /* favor or force Huffman coding*/ |
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184 |
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185 uInt good_match; |
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186 /* Use a faster search when the previous match is longer than this */ |
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187 |
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188 int nice_match; /* Stop searching when current match exceeds this */ |
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189 |
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190 /* used by trees.c: */ |
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191 /* Didn't use ct_data typedef below to supress compiler warning */ |
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192 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */ |
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193 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */ |
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194 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */ |
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195 |
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196 struct tree_desc_s l_desc; /* desc. for literal tree */ |
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197 struct tree_desc_s d_desc; /* desc. for distance tree */ |
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198 struct tree_desc_s bl_desc; /* desc. for bit length tree */ |
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199 |
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200 ush bl_count[MAX_BITS+1]; |
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201 /* number of codes at each bit length for an optimal tree */ |
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202 |
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203 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */ |
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204 int heap_len; /* number of elements in the heap */ |
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205 int heap_max; /* element of largest frequency */ |
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206 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used. |
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207 * The same heap array is used to build all trees. |
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208 */ |
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209 |
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210 uch depth[2*L_CODES+1]; |
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211 /* Depth of each subtree used as tie breaker for trees of equal frequency |
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212 */ |
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213 |
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214 uchf *l_buf; /* buffer for literals or lengths */ |
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215 |
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216 uInt lit_bufsize; |
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217 /* Size of match buffer for literals/lengths. There are 4 reasons for |
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218 * limiting lit_bufsize to 64K: |
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219 * - frequencies can be kept in 16 bit counters |
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220 * - if compression is not successful for the first block, all input |
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221 * data is still in the window so we can still emit a stored block even |
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222 * when input comes from standard input. (This can also be done for |
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223 * all blocks if lit_bufsize is not greater than 32K.) |
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224 * - if compression is not successful for a file smaller than 64K, we can |
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225 * even emit a stored file instead of a stored block (saving 5 bytes). |
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226 * This is applicable only for zip (not gzip or zlib). |
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227 * - creating new Huffman trees less frequently may not provide fast |
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228 * adaptation to changes in the input data statistics. (Take for |
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229 * example a binary file with poorly compressible code followed by |
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230 * a highly compressible string table.) Smaller buffer sizes give |
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231 * fast adaptation but have of course the overhead of transmitting |
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232 * trees more frequently. |
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233 * - I can't count above 4 |
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234 */ |
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235 |
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236 uInt last_lit; /* running index in l_buf */ |
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237 |
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238 ushf *d_buf; |
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239 /* Buffer for distances. To simplify the code, d_buf and l_buf have |
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240 * the same number of elements. To use different lengths, an extra flag |
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241 * array would be necessary. |
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242 */ |
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243 |
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244 ulg opt_len; /* bit length of current block with optimal trees */ |
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245 ulg static_len; /* bit length of current block with static trees */ |
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246 uInt matches; /* number of string matches in current block */ |
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247 int last_eob_len; /* bit length of EOB code for last block */ |
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248 |
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249 #ifdef DEBUG |
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250 ulg compressed_len; /* total bit length of compressed file mod 2^32 */ |
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251 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */ |
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252 #endif |
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253 |
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254 ush bi_buf; |
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255 /* Output buffer. bits are inserted starting at the bottom (least |
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256 * significant bits). |
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257 */ |
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258 int bi_valid; |
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259 /* Number of valid bits in bi_buf. All bits above the last valid bit |
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260 * are always zero. |
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261 */ |
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262 |
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263 } FAR deflate_state; |
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264 |
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265 /* Output a byte on the stream. |
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266 * IN assertion: there is enough room in pending_buf. |
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267 */ |
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268 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);} |
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269 |
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270 |
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271 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) |
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272 /* Minimum amount of lookahead, except at the end of the input file. |
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273 * See deflate.c for comments about the MIN_MATCH+1. |
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274 */ |
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275 |
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276 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD) |
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277 /* In order to simplify the code, particularly on 16 bit machines, match |
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278 * distances are limited to MAX_DIST instead of WSIZE. |
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279 */ |
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280 |
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281 /* in trees.c */ |
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282 void _tr_init OF((deflate_state *s)); |
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283 int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc)); |
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284 void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len, |
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285 int eof)); |
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286 void _tr_align OF((deflate_state *s)); |
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287 void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len, |
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288 int eof)); |
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289 |
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290 #define d_code(dist) \ |
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291 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)]) |
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292 /* Mapping from a distance to a distance code. dist is the distance - 1 and |
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293 * must not have side effects. _dist_code[256] and _dist_code[257] are never |
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294 * used. |
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295 */ |
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296 |
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297 #ifndef DEBUG |
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298 /* Inline versions of _tr_tally for speed: */ |
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299 |
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300 #if defined(GEN_TREES_H) || !defined(STDC) |
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301 extern uch _length_code[]; |
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302 extern uch _dist_code[]; |
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303 #else |
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304 extern const uch _length_code[]; |
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305 extern const uch _dist_code[]; |
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306 #endif |
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307 |
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308 # define _tr_tally_lit(s, c, flush) \ |
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309 { uch cc = (c); \ |
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310 s->d_buf[s->last_lit] = 0; \ |
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311 s->l_buf[s->last_lit++] = cc; \ |
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312 s->dyn_ltree[cc].Freq++; \ |
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313 flush = (s->last_lit == s->lit_bufsize-1); \ |
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314 } |
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315 # define _tr_tally_dist(s, distance, length, flush) \ |
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316 { uch len = (length); \ |
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317 ush dist = (distance); \ |
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318 s->d_buf[s->last_lit] = dist; \ |
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319 s->l_buf[s->last_lit++] = len; \ |
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320 dist--; \ |
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321 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \ |
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322 s->dyn_dtree[d_code(dist)].Freq++; \ |
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323 flush = (s->last_lit == s->lit_bufsize-1); \ |
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324 } |
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325 #else |
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326 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c) |
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327 # define _tr_tally_dist(s, distance, length, flush) \ |
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328 flush = _tr_tally(s, distance, length) |
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329 #endif |
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330 |
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331 #endif /* DEFLATE_H */ |