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3
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1 /* deflate.c -- compress data using the deflation algorithm
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2 * Copyright (C) 1995 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 /*
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7 * ALGORITHM
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8 *
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9 * The "deflation" process depends on being able to identify portions
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10 * of the input text which are identical to earlier input (within a
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11 * sliding window trailing behind the input currently being processed).
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12 *
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13 * The most straightforward technique turns out to be the fastest for
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14 * most input files: try all possible matches and select the longest.
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15 * The key feature of this algorithm is that insertions into the string
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16 * dictionary are very simple and thus fast, and deletions are avoided
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17 * completely. Insertions are performed at each input character, whereas
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18 * string matches are performed only when the previous match ends. So it
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19 * is preferable to spend more time in matches to allow very fast string
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20 * insertions and avoid deletions. The matching algorithm for small
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21 * strings is inspired from that of Rabin & Karp. A brute force approach
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22 * is used to find longer strings when a small match has been found.
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23 * A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
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24 * (by Leonid Broukhis).
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25 * A previous version of this file used a more sophisticated algorithm
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26 * (by Fiala and Greene) which is guaranteed to run in linear amortized
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27 * time, but has a larger average cost, uses more memory and is patented.
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28 * However the F&G algorithm may be faster for some highly redundant
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29 * files if the parameter max_chain_length (described below) is too large.
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30 *
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31 * ACKNOWLEDGEMENTS
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32 *
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33 * The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
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34 * I found it in 'freeze' written by Leonid Broukhis.
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35 * Thanks to many people for bug reports and testing.
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36 *
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37 * REFERENCES
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38 *
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39 * Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
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40 * Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
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41 *
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42 * A description of the Rabin and Karp algorithm is given in the book
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43 * "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
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44 *
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45 * Fiala,E.R., and Greene,D.H.
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46 * Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
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47 *
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48 */
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49
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50 /* $Id: deflate.c,v 1.1.1.1 1997/12/06 05:41:35 darius Exp $ */
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51
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52 #include "deflate.h"
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53
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54 char copyright[] = " deflate Copyright 1995 Jean-loup Gailly ";
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55 /*
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56 If you use the zlib library in a product, an acknowledgment is welcome
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57 in the documentation of your product. If for some reason you cannot
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58 include such an acknowledgment, I would appreciate that you keep this
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59 copyright string in the executable of your product.
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60 */
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61
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62 #define NIL 0
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63 /* Tail of hash chains */
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64
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65 #ifndef TOO_FAR
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66 # define TOO_FAR 4096
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67 #endif
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68 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
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69
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70 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
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71 /* Minimum amount of lookahead, except at the end of the input file.
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72 * See deflate.c for comments about the MIN_MATCH+1.
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73 */
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74
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75 /* Values for max_lazy_match, good_match and max_chain_length, depending on
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76 * the desired pack level (0..9). The values given below have been tuned to
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77 * exclude worst case performance for pathological files. Better values may be
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78 * found for specific files.
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79 */
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80
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81 typedef struct config_s {
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82 ush good_length; /* reduce lazy search above this match length */
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83 ush max_lazy; /* do not perform lazy search above this match length */
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84 ush nice_length; /* quit search above this match length */
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85 ush max_chain;
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86 } config;
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87
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88 local config configuration_table[10] = {
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89 /* good lazy nice chain */
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90 /* 0 */ {0, 0, 0, 0}, /* store only */
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91 /* 1 */ {4, 4, 8, 4}, /* maximum speed, no lazy matches */
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92 /* 2 */ {4, 5, 16, 8},
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93 /* 3 */ {4, 6, 32, 32},
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94
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95 /* 4 */ {4, 4, 16, 16}, /* lazy matches */
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96 /* 5 */ {8, 16, 32, 32},
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97 /* 6 */ {8, 16, 128, 128},
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98 /* 7 */ {8, 32, 128, 256},
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99 /* 8 */ {32, 128, 258, 1024},
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100 /* 9 */ {32, 258, 258, 4096}}; /* maximum compression */
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101
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102 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
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103 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
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104 * meaning.
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105 */
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106
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107 #define EQUAL 0
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108 /* result of memcmp for equal strings */
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109
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110 struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
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111
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112 /* ===========================================================================
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113 * Prototypes for local functions.
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114 */
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115
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116 local void fill_window __P((deflate_state *s));
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117 local int deflate_fast __P((deflate_state *s, int flush));
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118 local int deflate_slow __P((deflate_state *s, int flush));
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119 local void lm_init __P((deflate_state *s));
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120 local int longest_match __P((deflate_state *s, IPos cur_match));
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121 local void putShortMSB __P((deflate_state *s, uInt b));
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122 local void flush_pending __P((z_stream *strm));
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123 local int read_buf __P((z_stream *strm, char *buf, unsigned size));
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124 #ifdef ASMV
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125 void match_init __P((void)); /* asm code initialization */
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126 #endif
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127
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128 #ifdef DEBUG
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129 local void check_match __P((deflate_state *s, IPos start, IPos match,
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130 int length));
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131 #endif
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132
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133
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134 /* ===========================================================================
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135 * Update a hash value with the given input byte
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136 * IN assertion: all calls to to UPDATE_HASH are made with consecutive
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137 * input characters, so that a running hash key can be computed from the
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138 * previous key instead of complete recalculation each time.
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139 */
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140 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
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141
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142 /* ===========================================================================
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143 * Insert string str in the dictionary and set match_head to the previous head
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144 * of the hash chain (the most recent string with same hash key). Return
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145 * the previous length of the hash chain.
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146 * IN assertion: all calls to to INSERT_STRING are made with consecutive
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147 * input characters and the first MIN_MATCH bytes of str are valid
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148 * (except for the last MIN_MATCH-1 bytes of the input file).
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149 */
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150 #define INSERT_STRING(s, str, match_head) \
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151 (UPDATE_HASH(s, s->ins_h, s->window[(str) + MIN_MATCH-1]), \
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152 s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \
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153 s->head[s->ins_h] = (str))
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154
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155 /* ===========================================================================
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156 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
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157 * prev[] will be initialized on the fly.
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158 */
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159 #define CLEAR_HASH(s) \
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160 s->head[s->hash_size-1] = NIL; \
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161 zmemzero((char*)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
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162
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163 /* ========================================================================= */
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164 int deflateInit (strm, level)
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165 z_stream *strm;
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166 int level;
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167 {
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168 return deflateInit2 (strm, level, DEFLATED, MAX_WBITS, DEF_MEM_LEVEL, 0);
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169 /* To do: ignore strm->next_in if we use it as window */
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170 }
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171
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172 /* ========================================================================= */
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173 int deflateInit2 (strm, level, method, windowBits, memLevel, strategy)
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174 z_stream *strm;
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175 int level;
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176 int method;
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177 int windowBits;
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178 int memLevel;
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179 int strategy;
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180 {
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181 deflate_state *s;
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182 int noheader = 0;
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183
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184 if (strm == Z_NULL) return Z_STREAM_ERROR;
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185
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186 strm->msg = Z_NULL;
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187 if (strm->zalloc == Z_NULL) strm->zalloc = zcalloc;
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188 if (strm->zfree == Z_NULL) strm->zfree = zcfree;
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189
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190 if (level == Z_DEFAULT_COMPRESSION) level = 6;
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191
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192 if (windowBits < 0) { /* undocumented feature: suppress zlib header */
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193 noheader = 1;
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194 windowBits = -windowBits;
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195 }
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196 if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != DEFLATED ||
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197 windowBits < 8 || windowBits > 15 || level < 1 || level > 9) {
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198 return Z_STREAM_ERROR;
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199 }
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200 s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
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201 if (s == Z_NULL) return Z_MEM_ERROR;
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202 strm->state = (struct internal_state *)s;
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203 s->strm = strm;
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204
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205 s->noheader = noheader;
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206 s->w_bits = windowBits;
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207 s->w_size = 1 << s->w_bits;
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208 s->w_mask = s->w_size - 1;
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209
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210 s->hash_bits = memLevel + 7;
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211 s->hash_size = 1 << s->hash_bits;
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212 s->hash_mask = s->hash_size - 1;
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213 s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
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214
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215 s->window = (Byte*) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
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216 s->prev = (Pos*) ZALLOC(strm, s->w_size, sizeof(Pos));
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217 s->head = (Pos*) ZALLOC(strm, s->hash_size, sizeof(Pos));
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218
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219 s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
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220
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221 s->pending_buf = (uch*) ZALLOC(strm, s->lit_bufsize, 2*sizeof(ush));
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222
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223 if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
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224 s->pending_buf == Z_NULL) {
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225 strm->msg = z_errmsg[1-Z_MEM_ERROR];
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226 deflateEnd (strm);
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227 return Z_MEM_ERROR;
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228 }
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229 s->d_buf = (ush*) &(s->pending_buf[s->lit_bufsize]);
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230 s->l_buf = (uch*) &(s->pending_buf[3*s->lit_bufsize]);
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231 /* We overlay pending_buf and d_buf+l_buf. This works since the average
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232 * output size for (length,distance) codes is <= 32 bits (worst case
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233 * is 15+15+13=33).
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234 */
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235
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236 s->level = level;
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237 s->strategy = strategy;
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238 s->method = (Byte)method;
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239
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240 return deflateReset(strm);
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241 }
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242
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243 /* ========================================================================= */
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244 int deflateReset (strm)
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245 z_stream *strm;
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246 {
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247 deflate_state *s;
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248
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249 if (strm == Z_NULL || strm->state == Z_NULL ||
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250 strm->zalloc == Z_NULL || strm->zfree == Z_NULL) return Z_STREAM_ERROR;
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251
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252 strm->total_in = strm->total_out = 0;
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253 strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
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254 strm->data_type = Z_UNKNOWN;
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255
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256 s = (deflate_state *)strm->state;
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257 s->pending = 0;
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258 s->pending_out = s->pending_buf;
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259
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260 s->status = s->noheader ? BUSY_STATE : INIT_STATE;
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261 s->adler = 1;
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262
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263 ct_init(s);
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264 lm_init(s);
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265
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266 return Z_OK;
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267 }
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268
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269 /* =========================================================================
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270 * Put a short the pending_out buffer. The 16-bit value is put in MSB order.
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271 * IN assertion: the stream state is correct and there is enough room in
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272 * the pending_out buffer.
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273 */
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274 local void putShortMSB (s, b)
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275 deflate_state *s;
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276 uInt b;
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277 {
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278 put_byte(s, (Byte)(b >> 8));
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279 put_byte(s, (Byte)(b & 0xff));
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280 }
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281
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282 /* =========================================================================
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283 * Flush as much pending output as possible.
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284 */
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285 local void flush_pending(strm)
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286 z_stream *strm;
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287 {
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288 unsigned len = strm->state->pending;
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289
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290 if (len > strm->avail_out) len = strm->avail_out;
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291 if (len == 0) return;
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292
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293 zmemcpy(strm->next_out, strm->state->pending_out, len);
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294 strm->next_out += len;
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295 strm->state->pending_out += len;
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296 strm->total_out += len;
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297 strm->avail_out -= len;
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298 strm->state->pending -= len;
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299 if (strm->state->pending == 0) {
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300 strm->state->pending_out = strm->state->pending_buf;
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301 }
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302 }
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303
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304 /* ========================================================================= */
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305 int deflate (strm, flush)
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306 z_stream *strm;
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307 int flush;
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308 {
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309 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
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310
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311 if (strm->next_out == Z_NULL || strm->next_in == Z_NULL) {
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312 ERR_RETURN(strm, Z_STREAM_ERROR);
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313 }
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314 if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
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315
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316 strm->state->strm = strm; /* just in case */
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317
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318 /* Write the zlib header */
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319 if (strm->state->status == INIT_STATE) {
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320
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321 uInt header = (DEFLATED + ((strm->state->w_bits-8)<<4)) << 8;
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322 uInt level_flags = (strm->state->level-1) >> 1;
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323
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324 if (level_flags > 3) level_flags = 3;
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325 header |= (level_flags << 6);
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326 header += 31 - (header % 31);
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327
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328 strm->state->status = BUSY_STATE;
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329 putShortMSB(strm->state, header);
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330 }
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331
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332 /* Flush as much pending output as possible */
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333 if (strm->state->pending != 0) {
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334 flush_pending(strm);
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335 if (strm->avail_out == 0) return Z_OK;
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336 }
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337
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338 /* User must not provide more input after the first FINISH: */
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339 if (strm->state->status == FINISH_STATE && strm->avail_in != 0) {
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340 ERR_RETURN(strm, Z_BUF_ERROR);
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341 }
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342
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343 /* Start a new block or continue the current one.
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344 */
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345 if (strm->avail_in != 0 ||
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346 (flush == Z_FINISH && strm->state->status != FINISH_STATE)) {
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347 int quit;
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348
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349 if (flush == Z_FINISH) {
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350 strm->state->status = FINISH_STATE;
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351 }
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352 if (strm->state->level <= 3) {
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353 quit = deflate_fast(strm->state, flush);
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354 } else {
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355 quit = deflate_slow(strm->state, flush);
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356 }
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357 if (flush == Z_FULL_FLUSH) {
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358 ct_stored_block(strm->state, (char*)0, 0L, 0); /* special marker */
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359 flush_pending(strm);
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360 CLEAR_HASH(strm->state); /* forget history */
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361 if (strm->avail_out == 0) return Z_OK;
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362 }
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363 if (quit) return Z_OK;
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364 }
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365 Assert(strm->avail_out > 0, "bug2");
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366
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367 if (flush != Z_FINISH) return Z_OK;
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368 if (strm->state->noheader) return Z_STREAM_END;
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369
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370 /* Write the zlib trailer (adler32) */
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371 putShortMSB(strm->state, (uInt)(strm->state->adler >> 16));
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372 putShortMSB(strm->state, (uInt)(strm->state->adler & 0xffff));
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373 flush_pending(strm);
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374 /* If avail_out is zero, the application will call deflate again
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375 * to flush the rest.
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376 */
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377 strm->state->noheader = 1; /* write the trailer only once! */
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|
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378 return strm->state->pending != 0 ? Z_OK : Z_STREAM_END;
|
|
|
379 }
|
|
|
380
|
|
|
381 /* ========================================================================= */
|
|
|
382 int deflateEnd (strm)
|
|
|
383 z_stream *strm;
|
|
|
384 {
|
|
|
385 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
|
|
|
386
|
|
|
387 TRY_FREE(strm, strm->state->window);
|
|
|
388 TRY_FREE(strm, strm->state->prev);
|
|
|
389 TRY_FREE(strm, strm->state->head);
|
|
|
390 TRY_FREE(strm, strm->state->pending_buf);
|
|
|
391
|
|
|
392 ZFREE(strm, strm->state);
|
|
|
393 strm->state = Z_NULL;
|
|
|
394
|
|
|
395 return Z_OK;
|
|
|
396 }
|
|
|
397
|
|
|
398 /* ========================================================================= */
|
|
|
399 int deflateCopy (dest, source)
|
|
|
400 z_stream *dest;
|
|
|
401 z_stream *source;
|
|
|
402 {
|
|
|
403 if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
|
|
|
404 return Z_STREAM_ERROR;
|
|
|
405 }
|
|
|
406 *dest = *source;
|
|
|
407 return Z_STREAM_ERROR; /* to be implemented */
|
|
|
408 #if 0
|
|
|
409 dest->state = (struct internal_state *)
|
|
|
410 (*dest->zalloc)(1, sizeof(deflate_state));
|
|
|
411 if (dest->state == Z_NULL) return Z_MEM_ERROR;
|
|
|
412
|
|
|
413 *(dest->state) = *(source->state);
|
|
|
414 return Z_OK;
|
|
|
415 #endif
|
|
|
416 }
|
|
|
417
|
|
|
418 /* ===========================================================================
|
|
|
419 * Read a new buffer from the current input stream, update the adler32
|
|
|
420 * and total number of bytes read.
|
|
|
421 */
|
|
|
422 local int read_buf(strm, buf, size)
|
|
|
423 z_stream *strm;
|
|
|
424 char *buf;
|
|
|
425 unsigned size;
|
|
|
426 {
|
|
|
427 unsigned len = strm->avail_in;
|
|
|
428
|
|
|
429 if (len > size) len = size;
|
|
|
430 if (len == 0) return 0;
|
|
|
431
|
|
|
432 strm->avail_in -= len;
|
|
|
433
|
|
|
434 if (!strm->state->noheader) {
|
|
|
435 strm->state->adler = adler32(strm->state->adler, strm->next_in, len);
|
|
|
436 }
|
|
|
437 zmemcpy(buf, strm->next_in, len);
|
|
|
438 strm->next_in += len;
|
|
|
439 strm->total_in += len;
|
|
|
440
|
|
|
441 return (int)len;
|
|
|
442 }
|
|
|
443
|
|
|
444 /* ===========================================================================
|
|
|
445 * Initialize the "longest match" routines for a new zlib stream
|
|
|
446 */
|
|
|
447 local void lm_init (s)
|
|
|
448 deflate_state *s;
|
|
|
449 {
|
|
|
450 register unsigned j;
|
|
|
451
|
|
|
452 s->window_size = (ulg)2L*s->w_size;
|
|
|
453
|
|
|
454 CLEAR_HASH(s);
|
|
|
455
|
|
|
456 /* Set the default configuration parameters:
|
|
|
457 */
|
|
|
458 s->max_lazy_match = configuration_table[s->level].max_lazy;
|
|
|
459 s->good_match = configuration_table[s->level].good_length;
|
|
|
460 s->nice_match = configuration_table[s->level].nice_length;
|
|
|
461 s->max_chain_length = configuration_table[s->level].max_chain;
|
|
|
462
|
|
|
463 s->strstart = 0;
|
|
|
464 s->block_start = 0L;
|
|
|
465 s->lookahead = 0;
|
|
|
466 s->match_length = MIN_MATCH-1;
|
|
|
467 s->match_available = 0;
|
|
|
468 #ifdef ASMV
|
|
|
469 match_init(); /* initialize the asm code */
|
|
|
470 #endif
|
|
|
471
|
|
|
472 s->ins_h = 0;
|
|
|
473 for (j=0; j<MIN_MATCH-1; j++) UPDATE_HASH(s, s->ins_h, s->window[j]);
|
|
|
474 /* If lookahead < MIN_MATCH, ins_h is garbage, but this is
|
|
|
475 * not important since only literal bytes will be emitted.
|
|
|
476 */
|
|
|
477 }
|
|
|
478
|
|
|
479 /* ===========================================================================
|
|
|
480 * Set match_start to the longest match starting at the given string and
|
|
|
481 * return its length. Matches shorter or equal to prev_length are discarded,
|
|
|
482 * in which case the result is equal to prev_length and match_start is
|
|
|
483 * garbage.
|
|
|
484 * IN assertions: cur_match is the head of the hash chain for the current
|
|
|
485 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
|
|
|
486 */
|
|
|
487 #ifndef ASMV
|
|
|
488 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
|
|
|
489 * match.S. The code will be functionally equivalent.
|
|
|
490 */
|
|
|
491 local INLINE int longest_match(s, cur_match)
|
|
|
492 deflate_state *s;
|
|
|
493 IPos cur_match; /* current match */
|
|
|
494 {
|
|
|
495 unsigned chain_length = s->max_chain_length;/* max hash chain length */
|
|
|
496 register Byte *scan = s->window + s->strstart; /* current string */
|
|
|
497 register Byte *match; /* matched string */
|
|
|
498 register int len; /* length of current match */
|
|
|
499 int best_len = s->prev_length; /* best match length so far */
|
|
|
500 IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
|
|
|
501 s->strstart - (IPos)MAX_DIST(s) : NIL;
|
|
|
502 /* Stop when cur_match becomes <= limit. To simplify the code,
|
|
|
503 * we prevent matches with the string of window index 0.
|
|
|
504 */
|
|
|
505 Pos *prev = s->prev;
|
|
|
506 uInt wmask = s->w_mask;
|
|
|
507
|
|
|
508 #ifdef UNALIGNED_OK
|
|
|
509 /* Compare two bytes at a time. Note: this is not always beneficial.
|
|
|
510 * Try with and without -DUNALIGNED_OK to check.
|
|
|
511 */
|
|
|
512 register Byte *strend = s->window + s->strstart + MAX_MATCH - 1;
|
|
|
513 register ush scan_start = *(ush*)scan;
|
|
|
514 register ush scan_end = *(ush*)(scan+best_len-1);
|
|
|
515 #else
|
|
|
516 register Byte *strend = s->window + s->strstart + MAX_MATCH;
|
|
|
517 register Byte scan_end1 = scan[best_len-1];
|
|
|
518 register Byte scan_end = scan[best_len];
|
|
|
519 #endif
|
|
|
520
|
|
|
521 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
|
|
|
522 * It is easy to get rid of this optimization if necessary.
|
|
|
523 */
|
|
|
524 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
|
|
|
525
|
|
|
526 /* Do not waste too much time if we already have a good match: */
|
|
|
527 if (s->prev_length >= s->good_match) {
|
|
|
528 chain_length >>= 2;
|
|
|
529 }
|
|
|
530 Assert(s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
|
|
|
531
|
|
|
532 do {
|
|
|
533 Assert(cur_match < s->strstart, "no future");
|
|
|
534 match = s->window + cur_match;
|
|
|
535
|
|
|
536 /* Skip to next match if the match length cannot increase
|
|
|
537 * or if the match length is less than 2:
|
|
|
538 */
|
|
|
539 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
|
|
|
540 /* This code assumes sizeof(unsigned short) == 2. Do not use
|
|
|
541 * UNALIGNED_OK if your compiler uses a different size.
|
|
|
542 */
|
|
|
543 if (*(ush*)(match+best_len-1) != scan_end ||
|
|
|
544 *(ush*)match != scan_start) continue;
|
|
|
545
|
|
|
546 /* It is not necessary to compare scan[2] and match[2] since they are
|
|
|
547 * always equal when the other bytes match, given that the hash keys
|
|
|
548 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
|
|
|
549 * strstart+3, +5, ... up to strstart+257. We check for insufficient
|
|
|
550 * lookahead only every 4th comparison; the 128th check will be made
|
|
|
551 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
|
|
|
552 * necessary to put more guard bytes at the end of the window, or
|
|
|
553 * to check more often for insufficient lookahead.
|
|
|
554 */
|
|
|
555 scan++, match++;
|
|
|
556 do {
|
|
|
557 } while (*(ush*)(scan+=2) == *(ush*)(match+=2) &&
|
|
|
558 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
|
|
|
559 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
|
|
|
560 *(ush*)(scan+=2) == *(ush*)(match+=2) &&
|
|
|
561 scan < strend);
|
|
|
562 /* The funny "do {}" generates better code on most compilers */
|
|
|
563
|
|
|
564 /* Here, scan <= window+strstart+257 */
|
|
|
565 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
|
|
|
566 if (*scan == *match) scan++;
|
|
|
567
|
|
|
568 len = (MAX_MATCH - 1) - (int)(strend-scan);
|
|
|
569 scan = strend - (MAX_MATCH-1);
|
|
|
570
|
|
|
571 #else /* UNALIGNED_OK */
|
|
|
572
|
|
|
573 if (match[best_len] != scan_end ||
|
|
|
574 match[best_len-1] != scan_end1 ||
|
|
|
575 *match != *scan ||
|
|
|
576 *++match != scan[1]) continue;
|
|
|
577
|
|
|
578 /* The check at best_len-1 can be removed because it will be made
|
|
|
579 * again later. (This heuristic is not always a win.)
|
|
|
580 * It is not necessary to compare scan[2] and match[2] since they
|
|
|
581 * are always equal when the other bytes match, given that
|
|
|
582 * the hash keys are equal and that HASH_BITS >= 8.
|
|
|
583 */
|
|
|
584 scan += 2, match++;
|
|
|
585
|
|
|
586 /* We check for insufficient lookahead only every 8th comparison;
|
|
|
587 * the 256th check will be made at strstart+258.
|
|
|
588 */
|
|
|
589 do {
|
|
|
590 } while (*++scan == *++match && *++scan == *++match &&
|
|
|
591 *++scan == *++match && *++scan == *++match &&
|
|
|
592 *++scan == *++match && *++scan == *++match &&
|
|
|
593 *++scan == *++match && *++scan == *++match &&
|
|
|
594 scan < strend);
|
|
|
595
|
|
|
596 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
|
|
|
597
|
|
|
598 len = MAX_MATCH - (int)(strend - scan);
|
|
|
599 scan = strend - MAX_MATCH;
|
|
|
600
|
|
|
601 #endif /* UNALIGNED_OK */
|
|
|
602
|
|
|
603 if (len > best_len) {
|
|
|
604 s->match_start = cur_match;
|
|
|
605 best_len = len;
|
|
|
606 if (len >= s->nice_match) break;
|
|
|
607 #ifdef UNALIGNED_OK
|
|
|
608 scan_end = *(ush*)(scan+best_len-1);
|
|
|
609 #else
|
|
|
610 scan_end1 = scan[best_len-1];
|
|
|
611 scan_end = scan[best_len];
|
|
|
612 #endif
|
|
|
613 }
|
|
|
614 } while ((cur_match = prev[cur_match & wmask]) > limit
|
|
|
615 && --chain_length != 0);
|
|
|
616
|
|
|
617 return best_len;
|
|
|
618 }
|
|
|
619 #endif /* ASMV */
|
|
|
620
|
|
|
621 #ifdef DEBUG
|
|
|
622 /* ===========================================================================
|
|
|
623 * Check that the match at match_start is indeed a match.
|
|
|
624 */
|
|
|
625 local void check_match(s, start, match, length)
|
|
|
626 deflate_state *s;
|
|
|
627 IPos start, match;
|
|
|
628 int length;
|
|
|
629 {
|
|
|
630 /* check that the match is indeed a match */
|
|
|
631 if (memcmp((char*)s->window + match,
|
|
|
632 (char*)s->window + start, length) != EQUAL) {
|
|
|
633 fprintf(stderr,
|
|
|
634 " start %d, match %d, length %d\n",
|
|
|
635 start, match, length);
|
|
|
636 z_error("invalid match");
|
|
|
637 }
|
|
|
638 if (verbose > 1) {
|
|
|
639 fprintf(stderr,"\\[%d,%d]", start-match, length);
|
|
|
640 do { putc(s->window[start++], stderr); } while (--length != 0);
|
|
|
641 }
|
|
|
642 }
|
|
|
643 #else
|
|
|
644 # define check_match(s, start, match, length)
|
|
|
645 #endif
|
|
|
646
|
|
|
647 /* ===========================================================================
|
|
|
648 * Fill the window when the lookahead becomes insufficient.
|
|
|
649 * Updates strstart and lookahead.
|
|
|
650 *
|
|
|
651 * IN assertion: lookahead < MIN_LOOKAHEAD
|
|
|
652 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
|
|
|
653 * At least one byte has been read, or avail_in == 0; reads are
|
|
|
654 * performed for at least two bytes (required for the zip translate_eol
|
|
|
655 * option -- not supported here).
|
|
|
656 */
|
|
|
657 local void fill_window(s)
|
|
|
658 deflate_state *s;
|
|
|
659 {
|
|
|
660 register unsigned n, m;
|
|
|
661 register Pos *p;
|
|
|
662 unsigned more; /* Amount of free space at the end of the window. */
|
|
|
663 uInt wsize = s->w_size;
|
|
|
664
|
|
|
665 do {
|
|
|
666 more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
|
|
|
667
|
|
|
668 /* Deal with !@#$% 64K limit: */
|
|
|
669 if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
|
|
|
670 more = wsize;
|
|
|
671 } else if (more == (unsigned)(-1)) {
|
|
|
672 /* Very unlikely, but possible on 16 bit machine if strstart == 0
|
|
|
673 * and lookahead == 1 (input done one byte at time)
|
|
|
674 */
|
|
|
675 more--;
|
|
|
676
|
|
|
677 /* If the window is almost full and there is insufficient lookahead,
|
|
|
678 * move the upper half to the lower one to make room in the upper half.
|
|
|
679 */
|
|
|
680 } else if (s->strstart >= wsize+MAX_DIST(s)) {
|
|
|
681
|
|
|
682 /* By the IN assertion, the window is not empty so we can't confuse
|
|
|
683 * more == 0 with more == 64K on a 16 bit machine.
|
|
|
684 */
|
|
|
685 zmemcpy((char*)s->window, (char*)s->window+wsize,
|
|
|
686 (unsigned)wsize);
|
|
|
687 s->match_start -= wsize;
|
|
|
688 s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
|
|
|
689
|
|
|
690 s->block_start -= (long) wsize;
|
|
|
691
|
|
|
692 /* Slide the hash table (could be avoided with 32 bit values
|
|
|
693 at the expense of memory usage):
|
|
|
694 */
|
|
|
695 n = s->hash_size;
|
|
|
696 p = &s->head[n-1];
|
|
|
697 do {
|
|
|
698 m = *p;
|
|
|
699 *p-- = (Pos)(m >= wsize ? m-wsize : NIL);
|
|
|
700 } while (--n);
|
|
|
701
|
|
|
702 n = wsize;
|
|
|
703 p = &s->prev[n-1];
|
|
|
704 do {
|
|
|
705 m = *p;
|
|
|
706 *p-- = (Pos)(m >= wsize ? m-wsize : NIL);
|
|
|
707 /* If n is not on any hash chain, prev[n] is garbage but
|
|
|
708 * its value will never be used.
|
|
|
709 */
|
|
|
710 } while (--n);
|
|
|
711
|
|
|
712 more += wsize;
|
|
|
713 }
|
|
|
714 if (s->strm->avail_in == 0) return;
|
|
|
715
|
|
|
716 /* If there was no sliding:
|
|
|
717 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
|
|
|
718 * more == window_size - lookahead - strstart
|
|
|
719 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
|
|
|
720 * => more >= window_size - 2*WSIZE + 2
|
|
|
721 * In the BIG_MEM or MMAP case (not yet supported),
|
|
|
722 * window_size == input_size + MIN_LOOKAHEAD &&
|
|
|
723 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
|
|
|
724 * Otherwise, window_size == 2*WSIZE so more >= 2.
|
|
|
725 * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
|
|
|
726 */
|
|
|
727 Assert(more >= 2, "more < 2");
|
|
|
728
|
|
|
729 n = read_buf(s->strm, (char*)s->window + s->strstart + s->lookahead,
|
|
|
730 more);
|
|
|
731 s->lookahead += n;
|
|
|
732
|
|
|
733 } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
|
|
|
734 }
|
|
|
735
|
|
|
736 /* ===========================================================================
|
|
|
737 * Flush the current block, with given end-of-file flag.
|
|
|
738 * IN assertion: strstart is set to the end of the current match.
|
|
|
739 */
|
|
|
740 #define FLUSH_BLOCK_ONLY(s, eof) { \
|
|
|
741 ct_flush_block(s, (s->block_start >= 0L ? \
|
|
|
742 (char*)&s->window[(unsigned)s->block_start] : \
|
|
|
743 (char*)Z_NULL), (long)s->strstart - s->block_start, (eof)); \
|
|
|
744 s->block_start = s->strstart; \
|
|
|
745 flush_pending(s->strm); \
|
|
|
746 }
|
|
|
747
|
|
|
748 /* Same but force premature exit if necessary. */
|
|
|
749 #define FLUSH_BLOCK(s, eof) { \
|
|
|
750 FLUSH_BLOCK_ONLY(s, eof); \
|
|
|
751 if (s->strm->avail_out == 0) return 1; \
|
|
|
752 }
|
|
|
753
|
|
|
754 /* ===========================================================================
|
|
|
755 * Compress as much as possible from the input stream, return true if
|
|
|
756 * processing was terminated prematurely (no more input or output space).
|
|
|
757 * This function does not perform lazy evaluationof matches and inserts
|
|
|
758 * new strings in the dictionary only for unmatched strings or for short
|
|
|
759 * matches. It is used only for the fast compression options.
|
|
|
760 */
|
|
|
761 local int deflate_fast(s, flush)
|
|
|
762 deflate_state *s;
|
|
|
763 int flush;
|
|
|
764 {
|
|
|
765 IPos hash_head; /* head of the hash chain */
|
|
|
766 int bflush; /* set if current block must be flushed */
|
|
|
767
|
|
|
768 s->prev_length = MIN_MATCH-1;
|
|
|
769
|
|
|
770 for (;;) {
|
|
|
771 /* Make sure that we always have enough lookahead, except
|
|
|
772 * at the end of the input file. We need MAX_MATCH bytes
|
|
|
773 * for the next match, plus MIN_MATCH bytes to insert the
|
|
|
774 * string following the next match.
|
|
|
775 */
|
|
|
776 if (s->lookahead < MIN_LOOKAHEAD) {
|
|
|
777 fill_window(s);
|
|
|
778 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) return 1;
|
|
|
779
|
|
|
780 if (s->lookahead == 0) break; /* flush the current block */
|
|
|
781 }
|
|
|
782
|
|
|
783 /* Insert the string window[strstart .. strstart+2] in the
|
|
|
784 * dictionary, and set hash_head to the head of the hash chain:
|
|
|
785 */
|
|
|
786 INSERT_STRING(s, s->strstart, hash_head);
|
|
|
787
|
|
|
788 /* Find the longest match, discarding those <= prev_length.
|
|
|
789 * At this point we have always match_length < MIN_MATCH
|
|
|
790 */
|
|
|
791 if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
|
|
|
792 /* To simplify the code, we prevent matches with the string
|
|
|
793 * of window index 0 (in particular we have to avoid a match
|
|
|
794 * of the string with itself at the start of the input file).
|
|
|
795 */
|
|
|
796 if (s->strategy != Z_HUFFMAN_ONLY) {
|
|
|
797 s->match_length = longest_match (s, hash_head);
|
|
|
798 }
|
|
|
799 /* longest_match() sets match_start */
|
|
|
800
|
|
|
801 if (s->match_length > s->lookahead) s->match_length = s->lookahead;
|
|
|
802 }
|
|
|
803 if (s->match_length >= MIN_MATCH) {
|
|
|
804 check_match(s, s->strstart, s->match_start, s->match_length);
|
|
|
805
|
|
|
806 bflush = ct_tally(s, s->strstart - s->match_start,
|
|
|
807 s->match_length - MIN_MATCH);
|
|
|
808
|
|
|
809 s->lookahead -= s->match_length;
|
|
|
810
|
|
|
811 /* Insert new strings in the hash table only if the match length
|
|
|
812 * is not too large. This saves time but degrades compression.
|
|
|
813 */
|
|
|
814 if (s->match_length <= s->max_insert_length) {
|
|
|
815 s->match_length--; /* string at strstart already in hash table */
|
|
|
816 do {
|
|
|
817 s->strstart++;
|
|
|
818 INSERT_STRING(s, s->strstart, hash_head);
|
|
|
819 /* strstart never exceeds WSIZE-MAX_MATCH, so there are
|
|
|
820 * always MIN_MATCH bytes ahead. If lookahead < MIN_MATCH
|
|
|
821 * these bytes are garbage, but it does not matter since
|
|
|
822 * the next lookahead bytes will be emitted as literals.
|
|
|
823 */
|
|
|
824 } while (--s->match_length != 0);
|
|
|
825 s->strstart++;
|
|
|
826 } else {
|
|
|
827 s->strstart += s->match_length;
|
|
|
828 s->match_length = 0;
|
|
|
829 s->ins_h = s->window[s->strstart];
|
|
|
830 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
|
|
|
831 #if MIN_MATCH != 3
|
|
|
832 Call UPDATE_HASH() MIN_MATCH-3 more times
|
|
|
833 #endif
|
|
|
834 }
|
|
|
835 } else {
|
|
|
836 /* No match, output a literal byte */
|
|
|
837 Tracevv((stderr,"%c", s->window[s->strstart]));
|
|
|
838 bflush = ct_tally (s, 0, s->window[s->strstart]);
|
|
|
839 s->lookahead--;
|
|
|
840 s->strstart++;
|
|
|
841 }
|
|
|
842 if (bflush) FLUSH_BLOCK(s, 0);
|
|
|
843 }
|
|
|
844 FLUSH_BLOCK(s, flush == Z_FINISH);
|
|
|
845 return 0; /* normal exit */
|
|
|
846 }
|
|
|
847
|
|
|
848 /* ===========================================================================
|
|
|
849 * Same as above, but achieves better compression. We use a lazy
|
|
|
850 * evaluation for matches: a match is finally adopted only if there is
|
|
|
851 * no better match at the next window position.
|
|
|
852 */
|
|
|
853 local int deflate_slow(s, flush)
|
|
|
854 deflate_state *s;
|
|
|
855 int flush;
|
|
|
856 {
|
|
|
857 IPos hash_head; /* head of hash chain */
|
|
|
858 int bflush; /* set if current block must be flushed */
|
|
|
859
|
|
|
860 /* Process the input block. */
|
|
|
861 for (;;) {
|
|
|
862 /* Make sure that we always have enough lookahead, except
|
|
|
863 * at the end of the input file. We need MAX_MATCH bytes
|
|
|
864 * for the next match, plus MIN_MATCH bytes to insert the
|
|
|
865 * string following the next match.
|
|
|
866 */
|
|
|
867 if (s->lookahead < MIN_LOOKAHEAD) {
|
|
|
868 fill_window(s);
|
|
|
869 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) return 1;
|
|
|
870
|
|
|
871 if (s->lookahead == 0) break; /* flush the current block */
|
|
|
872 }
|
|
|
873
|
|
|
874 /* Insert the string window[strstart .. strstart+2] in the
|
|
|
875 * dictionary, and set hash_head to the head of the hash chain:
|
|
|
876 */
|
|
|
877 INSERT_STRING(s, s->strstart, hash_head);
|
|
|
878
|
|
|
879 /* Find the longest match, discarding those <= prev_length.
|
|
|
880 */
|
|
|
881 s->prev_length = s->match_length, s->prev_match = s->match_start;
|
|
|
882 s->match_length = MIN_MATCH-1;
|
|
|
883
|
|
|
884 if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
|
|
|
885 s->strstart - hash_head <= MAX_DIST(s)) {
|
|
|
886 /* To simplify the code, we prevent matches with the string
|
|
|
887 * of window index 0 (in particular we have to avoid a match
|
|
|
888 * of the string with itself at the start of the input file).
|
|
|
889 */
|
|
|
890 if (s->strategy != Z_HUFFMAN_ONLY) {
|
|
|
891 s->match_length = longest_match (s, hash_head);
|
|
|
892 }
|
|
|
893 /* longest_match() sets match_start */
|
|
|
894 if (s->match_length > s->lookahead) s->match_length = s->lookahead;
|
|
|
895
|
|
|
896 if (s->match_length <= 5 && (s->strategy == Z_FILTERED ||
|
|
|
897 (s->match_length == MIN_MATCH &&
|
|
|
898 s->strstart - s->match_start > TOO_FAR))) {
|
|
|
899
|
|
|
900 /* If prev_match is also MIN_MATCH, match_start is garbage
|
|
|
901 * but we will ignore the current match anyway.
|
|
|
902 */
|
|
|
903 s->match_length = MIN_MATCH-1;
|
|
|
904 }
|
|
|
905 }
|
|
|
906 /* If there was a match at the previous step and the current
|
|
|
907 * match is not better, output the previous match:
|
|
|
908 */
|
|
|
909 if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
|
|
|
910
|
|
|
911 check_match(s, s->strstart-1, s->prev_match, s->prev_length);
|
|
|
912
|
|
|
913 bflush = ct_tally(s, s->strstart -1 - s->prev_match,
|
|
|
914 s->prev_length - MIN_MATCH);
|
|
|
915
|
|
|
916 /* Insert in hash table all strings up to the end of the match.
|
|
|
917 * strstart-1 and strstart are already inserted.
|
|
|
918 */
|
|
|
919 s->lookahead -= s->prev_length-1;
|
|
|
920 s->prev_length -= 2;
|
|
|
921 do {
|
|
|
922 s->strstart++;
|
|
|
923 INSERT_STRING(s, s->strstart, hash_head);
|
|
|
924 /* strstart never exceeds WSIZE-MAX_MATCH, so there are
|
|
|
925 * always MIN_MATCH bytes ahead. If lookahead < MIN_MATCH
|
|
|
926 * these bytes are garbage, but it does not matter since the
|
|
|
927 * next lookahead bytes will always be emitted as literals.
|
|
|
928 */
|
|
|
929 } while (--s->prev_length != 0);
|
|
|
930 s->match_available = 0;
|
|
|
931 s->match_length = MIN_MATCH-1;
|
|
|
932 s->strstart++;
|
|
|
933
|
|
|
934 if (bflush) FLUSH_BLOCK(s, 0);
|
|
|
935
|
|
|
936 } else if (s->match_available) {
|
|
|
937 /* If there was no match at the previous position, output a
|
|
|
938 * single literal. If there was a match but the current match
|
|
|
939 * is longer, truncate the previous match to a single literal.
|
|
|
940 */
|
|
|
941 Tracevv((stderr,"%c", s->window[s->strstart-1]));
|
|
|
942 if (ct_tally (s, 0, s->window[s->strstart-1])) {
|
|
|
943 FLUSH_BLOCK_ONLY(s, 0);
|
|
|
944 }
|
|
|
945 s->strstart++;
|
|
|
946 s->lookahead--;
|
|
|
947 if (s->strm->avail_out == 0) return 1;
|
|
|
948 } else {
|
|
|
949 /* There is no previous match to compare with, wait for
|
|
|
950 * the next step to decide.
|
|
|
951 */
|
|
|
952 s->match_available = 1;
|
|
|
953 s->strstart++;
|
|
|
954 s->lookahead--;
|
|
|
955 }
|
|
|
956 }
|
|
|
957 if (s->match_available) {
|
|
|
958 ct_tally (s, 0, s->window[s->strstart-1]);
|
|
|
959 s->match_available = 0;
|
|
|
960 }
|
|
|
961 FLUSH_BLOCK(s, flush == Z_FINISH);
|
|
|
962 return 0;
|
|
|
963 }
|
