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: deflate.h,v 1.1.1.1 2000-10-28 01:10:33 ghudson Exp $ */ |
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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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