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1 /* deflate.h -- internal compression state
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2 * Copyright (C) 1995-1998 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 /* ===========================================================================
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19 * Internal compression state.
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20 */
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21
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22 #define LENGTH_CODES 29
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23 /* number of length codes, not counting the special END_BLOCK code */
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24
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25 #define LITERALS 256
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26 /* number of literal bytes 0..255 */
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27
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28 #define L_CODES (LITERALS+1+LENGTH_CODES)
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29 /* number of Literal or Length codes, including the END_BLOCK code */
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30
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31 #define D_CODES 30
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32 /* number of distance codes */
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33
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34 #define BL_CODES 19
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35 /* number of codes used to transfer the bit lengths */
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36
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37 #define HEAP_SIZE (2*L_CODES+1)
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38 /* maximum heap size */
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39
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40 #define MAX_BITS 15
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41 /* All codes must not exceed MAX_BITS bits */
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42
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43 #define INIT_STATE 42
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44 #define BUSY_STATE 113
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45 #define FINISH_STATE 666
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46 /* Stream status */
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47
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48
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49 /* Data structure describing a single value and its code string. */
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50 typedef struct ct_data_s {
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51 union {
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52 ush freq; /* frequency count */
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53 ush code; /* bit string */
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54 } fc;
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55 union {
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56 ush dad; /* father node in Huffman tree */
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57 ush len; /* length of bit string */
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58 } dl;
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59 } FAR ct_data;
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60
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61 #define Freq fc.freq
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62 #define Code fc.code
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63 #define Dad dl.dad
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64 #define Len dl.len
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65
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66 typedef struct static_tree_desc_s static_tree_desc;
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67
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68 typedef struct tree_desc_s {
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69 ct_data *dyn_tree; /* the dynamic tree */
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70 int max_code; /* largest code with non zero frequency */
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71 static_tree_desc *stat_desc; /* the corresponding static tree */
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72 } FAR tree_desc;
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73
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74 typedef ush Pos;
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75 typedef Pos FAR Posf;
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76 typedef unsigned IPos;
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77
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78 /* A Pos is an index in the character window. We use short instead of int to
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79 * save space in the various tables. IPos is used only for parameter passing.
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80 */
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81
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82 typedef struct internal_state {
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83 z_streamp strm; /* pointer back to this zlib stream */
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84 int status; /* as the name implies */
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85 Bytef *pending_buf; /* output still pending */
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86 ulg pending_buf_size; /* size of pending_buf */
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87 Bytef *pending_out; /* next pending byte to output to the stream */
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88 int pending; /* nb of bytes in the pending buffer */
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89 int noheader; /* suppress zlib header and adler32 */
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90 Byte data_type; /* UNKNOWN, BINARY or ASCII */
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91 Byte method; /* STORED (for zip only) or DEFLATED */
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92 int last_flush; /* value of flush param for previous deflate call */
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93
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94 /* used by deflate.c: */
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95
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96 uInt w_size; /* LZ77 window size (32K by default) */
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97 uInt w_bits; /* log2(w_size) (8..16) */
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98 uInt w_mask; /* w_size - 1 */
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99
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100 Bytef *window;
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101 /* Sliding window. Input bytes are read into the second half of the window,
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102 * and move to the first half later to keep a dictionary of at least wSize
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103 * bytes. With this organization, matches are limited to a distance of
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104 * wSize-MAX_MATCH bytes, but this ensures that IO is always
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105 * performed with a length multiple of the block size. Also, it limits
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106 * the window size to 64K, which is quite useful on MSDOS.
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107 * To do: use the user input buffer as sliding window.
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108 */
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109
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110 ulg window_size;
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111 /* Actual size of window: 2*wSize, except when the user input buffer
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112 * is directly used as sliding window.
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113 */
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114
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115 Posf *prev;
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116 /* Link to older string with same hash index. To limit the size of this
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117 * array to 64K, this link is maintained only for the last 32K strings.
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118 * An index in this array is thus a window index modulo 32K.
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119 */
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120
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121 Posf *head; /* Heads of the hash chains or NIL. */
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122
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123 uInt ins_h; /* hash index of string to be inserted */
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124 uInt hash_size; /* number of elements in hash table */
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125 uInt hash_bits; /* log2(hash_size) */
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126 uInt hash_mask; /* hash_size-1 */
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127
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128 uInt hash_shift;
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129 /* Number of bits by which ins_h must be shifted at each input
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130 * step. It must be such that after MIN_MATCH steps, the oldest
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131 * byte no longer takes part in the hash key, that is:
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132 * hash_shift * MIN_MATCH >= hash_bits
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133 */
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134
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135 long block_start;
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136 /* Window position at the beginning of the current output block. Gets
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137 * negative when the window is moved backwards.
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138 */
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139
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140 uInt match_length; /* length of best match */
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141 IPos prev_match; /* previous match */
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142 int match_available; /* set if previous match exists */
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143 uInt strstart; /* start of string to insert */
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144 uInt match_start; /* start of matching string */
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145 uInt lookahead; /* number of valid bytes ahead in window */
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146
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147 uInt prev_length;
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148 /* Length of the best match at previous step. Matches not greater than this
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149 * are discarded. This is used in the lazy match evaluation.
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150 */
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151
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152 uInt max_chain_length;
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153 /* To speed up deflation, hash chains are never searched beyond this
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154 * length. A higher limit improves compression ratio but degrades the
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155 * speed.
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156 */
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157
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158 uInt max_lazy_match;
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159 /* Attempt to find a better match only when the current match is strictly
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160 * smaller than this value. This mechanism is used only for compression
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161 * levels >= 4.
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162 */
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163 # define max_insert_length max_lazy_match
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164 /* Insert new strings in the hash table only if the match length is not
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165 * greater than this length. This saves time but degrades compression.
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166 * max_insert_length is used only for compression levels <= 3.
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167 */
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168
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169 int level; /* compression level (1..9) */
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170 int strategy; /* favor or force Huffman coding*/
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171
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172 uInt good_match;
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173 /* Use a faster search when the previous match is longer than this */
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174
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175 int nice_match; /* Stop searching when current match exceeds this */
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176
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177 /* used by trees.c: */
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178 /* Didn't use ct_data typedef below to supress compiler warning */
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179 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */
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180 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
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181 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */
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182
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183 struct tree_desc_s l_desc; /* desc. for literal tree */
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184 struct tree_desc_s d_desc; /* desc. for distance tree */
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185 struct tree_desc_s bl_desc; /* desc. for bit length tree */
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186
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187 ush bl_count[MAX_BITS+1];
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188 /* number of codes at each bit length for an optimal tree */
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189
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190 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
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191 int heap_len; /* number of elements in the heap */
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192 int heap_max; /* element of largest frequency */
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193 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
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194 * The same heap array is used to build all trees.
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195 */
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196
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197 uch depth[2*L_CODES+1];
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198 /* Depth of each subtree used as tie breaker for trees of equal frequency
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199 */
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200
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201 uchf *l_buf; /* buffer for literals or lengths */
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202
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203 uInt lit_bufsize;
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204 /* Size of match buffer for literals/lengths. There are 4 reasons for
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205 * limiting lit_bufsize to 64K:
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206 * - frequencies can be kept in 16 bit counters
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207 * - if compression is not successful for the first block, all input
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208 * data is still in the window so we can still emit a stored block even
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209 * when input comes from standard input. (This can also be done for
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210 * all blocks if lit_bufsize is not greater than 32K.)
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211 * - if compression is not successful for a file smaller than 64K, we can
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212 * even emit a stored file instead of a stored block (saving 5 bytes).
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213 * This is applicable only for zip (not gzip or zlib).
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214 * - creating new Huffman trees less frequently may not provide fast
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215 * adaptation to changes in the input data statistics. (Take for
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216 * example a binary file with poorly compressible code followed by
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217 * a highly compressible string table.) Smaller buffer sizes give
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218 * fast adaptation but have of course the overhead of transmitting
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219 * trees more frequently.
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220 * - I can't count above 4
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221 */
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222
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223 uInt last_lit; /* running index in l_buf */
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224
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225 ushf *d_buf;
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226 /* Buffer for distances. To simplify the code, d_buf and l_buf have
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227 * the same number of elements. To use different lengths, an extra flag
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228 * array would be necessary.
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229 */
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230
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231 ulg opt_len; /* bit length of current block with optimal trees */
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232 ulg static_len; /* bit length of current block with static trees */
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233 uInt matches; /* number of string matches in current block */
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234 int last_eob_len; /* bit length of EOB code for last block */
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235
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236 #ifdef DEBUG
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237 ulg compressed_len; /* total bit length of compressed file mod 2^32 */
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238 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */
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239 #endif
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240
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241 ush bi_buf;
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242 /* Output buffer. bits are inserted starting at the bottom (least
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243 * significant bits).
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244 */
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245 int bi_valid;
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246 /* Number of valid bits in bi_buf. All bits above the last valid bit
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247 * are always zero.
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248 */
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249
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250 } FAR deflate_state;
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251
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252 /* Output a byte on the stream.
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253 * IN assertion: there is enough room in pending_buf.
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254 */
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255 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
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256
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257
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258 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
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259 /* Minimum amount of lookahead, except at the end of the input file.
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260 * See deflate.c for comments about the MIN_MATCH+1.
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261 */
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262
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263 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
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264 /* In order to simplify the code, particularly on 16 bit machines, match
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265 * distances are limited to MAX_DIST instead of WSIZE.
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266 */
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267
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268 /* in trees.c */
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269 void _tr_init OF((deflate_state *s));
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270 int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
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271 void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len,
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272 int eof));
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273 void _tr_align OF((deflate_state *s));
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274 void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
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275 int eof));
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276
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277 #define d_code(dist) \
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278 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
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279 /* Mapping from a distance to a distance code. dist is the distance - 1 and
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280 * must not have side effects. _dist_code[256] and _dist_code[257] are never
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281 * used.
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282 */
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283
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284 #ifndef DEBUG
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285 /* Inline versions of _tr_tally for speed: */
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286
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287 #if defined(GEN_TREES_H) || !defined(STDC)
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288 extern uch _length_code[];
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289 extern uch _dist_code[];
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290 #else
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291 extern const uch _length_code[];
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292 extern const uch _dist_code[];
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293 #endif
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294
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295 # define _tr_tally_lit(s, c, flush) \
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296 { uch cc = (c); \
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297 s->d_buf[s->last_lit] = 0; \
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298 s->l_buf[s->last_lit++] = cc; \
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299 s->dyn_ltree[cc].Freq++; \
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300 flush = (s->last_lit == s->lit_bufsize-1); \
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301 }
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302 # define _tr_tally_dist(s, distance, length, flush) \
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303 { uch len = (length); \
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304 ush dist = (distance); \
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305 s->d_buf[s->last_lit] = dist; \
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306 s->l_buf[s->last_lit++] = len; \
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307 dist--; \
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308 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
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309 s->dyn_dtree[d_code(dist)].Freq++; \
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310 flush = (s->last_lit == s->lit_bufsize-1); \
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311 }
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312 #else
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313 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
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314 # define _tr_tally_dist(s, distance, length, flush) \
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315 flush = _tr_tally(s, distance, length)
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316 #endif
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317
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318 #endif
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