1 /* deflate.h -- internal compression state 2 * Copyright (C) 1995-2018 Jean-loup Gailly 3 * For conditions of distribution and use, see copyright notice in zlib.h 4 */ 5 6 /* WARNING: this file should *not* be used by applications. It is 7 part of the implementation of the compression library and is 8 subject to change. Applications should only use zlib.h. 9 */ 10 11 #ifndef DEFLATE_H 12 #define DEFLATE_H 13 14 #include "zutil.h" 15 16 /* define NO_GZIP when compiling if you want to disable gzip header and 17 trailer creation by deflate(). NO_GZIP would be used to avoid linking in 18 the crc code when it is not needed. For shared libraries, gzip encoding 19 should be left enabled. */ 20 #ifndef NO_GZIP 21 # define GZIP 22 #endif 23 24 /* =========================================================================== 25 * Internal compression state. 26 */ 27 28 #define LENGTH_CODES 29 29 /* number of length codes, not counting the special END_BLOCK code */ 30 31 #define LITERALS 256 32 /* number of literal bytes 0..255 */ 33 34 #define L_CODES (LITERALS+1+LENGTH_CODES) 35 /* number of Literal or Length codes, including the END_BLOCK code */ 36 37 #define D_CODES 30 38 /* number of distance codes */ 39 40 #define BL_CODES 19 41 /* number of codes used to transfer the bit lengths */ 42 43 #define HEAP_SIZE (2*L_CODES+1) 44 /* maximum heap size */ 45 46 #define MAX_BITS 15 47 /* All codes must not exceed MAX_BITS bits */ 48 49 #define Buf_size 16 50 /* size of bit buffer in bi_buf */ 51 52 #define INIT_STATE 42 /* zlib header -> BUSY_STATE */ 53 #ifdef GZIP 54 # define GZIP_STATE 57 /* gzip header -> BUSY_STATE | EXTRA_STATE */ 55 #endif 56 #define EXTRA_STATE 69 /* gzip extra block -> NAME_STATE */ 57 #define NAME_STATE 73 /* gzip file name -> COMMENT_STATE */ 58 #define COMMENT_STATE 91 /* gzip comment -> HCRC_STATE */ 59 #define HCRC_STATE 103 /* gzip header CRC -> BUSY_STATE */ 60 #define BUSY_STATE 113 /* deflate -> FINISH_STATE */ 61 #define FINISH_STATE 666 /* stream complete */ 62 /* Stream status */ 63 64 65 /* Data structure describing a single value and its code string. */ 66 typedef struct ct_data_s { 67 union { 68 ush freq; /* frequency count */ 69 ush code; /* bit string */ 70 } fc; 71 union { 72 ush dad; /* father node in Huffman tree */ 73 ush len; /* length of bit string */ 74 } dl; 75 } FAR ct_data; 76 77 #define Freq fc.freq 78 #define Code fc.code 79 #define Dad dl.dad 80 #define Len dl.len 81 82 typedef struct static_tree_desc_s static_tree_desc; 83 84 typedef struct tree_desc_s { 85 ct_data *dyn_tree; /* the dynamic tree */ 86 int max_code; /* largest code with non zero frequency */ 87 const static_tree_desc *stat_desc; /* the corresponding static tree */ 88 } FAR tree_desc; 89 90 typedef ush Pos; 91 typedef Pos FAR Posf; 92 typedef unsigned IPos; 93 94 /* A Pos is an index in the character window. We use short instead of int to 95 * save space in the various tables. IPos is used only for parameter passing. 96 */ 97 98 typedef struct internal_state { 99 z_streamp strm; /* pointer back to this zlib stream */ 100 int status; /* as the name implies */ 101 Bytef *pending_buf; /* output still pending */ 102 ulg pending_buf_size; /* size of pending_buf */ 103 Bytef *pending_out; /* next pending byte to output to the stream */ 104 ulg pending; /* nb of bytes in the pending buffer */ 105 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */ 106 gz_headerp gzhead; /* gzip header information to write */ 107 ulg gzindex; /* where in extra, name, or comment */ 108 Byte method; /* can only be DEFLATED */ 109 int last_flush; /* value of flush param for previous deflate call */ 110 111 /* used by deflate.c: */ 112 113 uInt w_size; /* LZ77 window size (32K by default) */ 114 uInt w_bits; /* log2(w_size) (8..16) */ 115 uInt w_mask; /* w_size - 1 */ 116 117 Bytef *window; 118 /* Sliding window. Input bytes are read into the second half of the window, 119 * and move to the first half later to keep a dictionary of at least wSize 120 * bytes. With this organization, matches are limited to a distance of 121 * wSize-MAX_MATCH bytes, but this ensures that IO is always 122 * performed with a length multiple of the block size. Also, it limits 123 * the window size to 64K, which is quite useful on MSDOS. 124 * To do: use the user input buffer as sliding window. 125 */ 126 127 ulg window_size; 128 /* Actual size of window: 2*wSize, except when the user input buffer 129 * is directly used as sliding window. 130 */ 131 132 Posf *prev; 133 /* Link to older string with same hash index. To limit the size of this 134 * array to 64K, this link is maintained only for the last 32K strings. 135 * An index in this array is thus a window index modulo 32K. 136 */ 137 138 Posf *head; /* Heads of the hash chains or NIL. */ 139 140 uInt ins_h; /* hash index of string to be inserted */ 141 uInt hash_size; /* number of elements in hash table */ 142 uInt hash_bits; /* log2(hash_size) */ 143 uInt hash_mask; /* hash_size-1 */ 144 145 uInt hash_shift; 146 /* Number of bits by which ins_h must be shifted at each input 147 * step. It must be such that after MIN_MATCH steps, the oldest 148 * byte no longer takes part in the hash key, that is: 149 * hash_shift * MIN_MATCH >= hash_bits 150 */ 151 152 long block_start; 153 /* Window position at the beginning of the current output block. Gets 154 * negative when the window is moved backwards. 155 */ 156 157 uInt match_length; /* length of best match */ 158 IPos prev_match; /* previous match */ 159 int match_available; /* set if previous match exists */ 160 uInt strstart; /* start of string to insert */ 161 uInt match_start; /* start of matching string */ 162 uInt lookahead; /* number of valid bytes ahead in window */ 163 164 uInt prev_length; 165 /* Length of the best match at previous step. Matches not greater than this 166 * are discarded. This is used in the lazy match evaluation. 167 */ 168 169 uInt max_chain_length; 170 /* To speed up deflation, hash chains are never searched beyond this 171 * length. A higher limit improves compression ratio but degrades the 172 * speed. 173 */ 174 175 uInt max_lazy_match; 176 /* Attempt to find a better match only when the current match is strictly 177 * smaller than this value. This mechanism is used only for compression 178 * levels >= 4. 179 */ 180 # define max_insert_length max_lazy_match 181 /* Insert new strings in the hash table only if the match length is not 182 * greater than this length. This saves time but degrades compression. 183 * max_insert_length is used only for compression levels <= 3. 184 */ 185 186 int level; /* compression level (1..9) */ 187 int strategy; /* favor or force Huffman coding*/ 188 189 uInt good_match; 190 /* Use a faster search when the previous match is longer than this */ 191 192 int nice_match; /* Stop searching when current match exceeds this */ 193 194 /* used by trees.c: */ 195 /* Didn't use ct_data typedef below to suppress compiler warning */ 196 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */ 197 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */ 198 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */ 199 200 struct tree_desc_s l_desc; /* desc. for literal tree */ 201 struct tree_desc_s d_desc; /* desc. for distance tree */ 202 struct tree_desc_s bl_desc; /* desc. for bit length tree */ 203 204 ush bl_count[MAX_BITS+1]; 205 /* number of codes at each bit length for an optimal tree */ 206 207 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */ 208 int heap_len; /* number of elements in the heap */ 209 int heap_max; /* element of largest frequency */ 210 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used. 211 * The same heap array is used to build all trees. 212 */ 213 214 uch depth[2*L_CODES+1]; 215 /* Depth of each subtree used as tie breaker for trees of equal frequency 216 */ 217 218 uchf *sym_buf; /* buffer for distances and literals/lengths */ 219 220 uInt lit_bufsize; 221 /* Size of match buffer for literals/lengths. There are 4 reasons for 222 * limiting lit_bufsize to 64K: 223 * - frequencies can be kept in 16 bit counters 224 * - if compression is not successful for the first block, all input 225 * data is still in the window so we can still emit a stored block even 226 * when input comes from standard input. (This can also be done for 227 * all blocks if lit_bufsize is not greater than 32K.) 228 * - if compression is not successful for a file smaller than 64K, we can 229 * even emit a stored file instead of a stored block (saving 5 bytes). 230 * This is applicable only for zip (not gzip or zlib). 231 * - creating new Huffman trees less frequently may not provide fast 232 * adaptation to changes in the input data statistics. (Take for 233 * example a binary file with poorly compressible code followed by 234 * a highly compressible string table.) Smaller buffer sizes give 235 * fast adaptation but have of course the overhead of transmitting 236 * trees more frequently. 237 * - I can't count above 4 238 */ 239 240 uInt sym_next; /* running index in sym_buf */ 241 uInt sym_end; /* symbol table full when sym_next reaches this */ 242 243 ulg opt_len; /* bit length of current block with optimal trees */ 244 ulg static_len; /* bit length of current block with static trees */ 245 uInt matches; /* number of string matches in current block */ 246 uInt insert; /* bytes at end of window left to insert */ 247 248 #ifdef ZLIB_DEBUG 249 ulg compressed_len; /* total bit length of compressed file mod 2^32 */ 250 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */ 251 #endif 252 253 ush bi_buf; 254 /* Output buffer. bits are inserted starting at the bottom (least 255 * significant bits). 256 */ 257 int bi_valid; 258 /* Number of valid bits in bi_buf. All bits above the last valid bit 259 * are always zero. 260 */ 261 262 ulg high_water; 263 /* High water mark offset in window for initialized bytes -- bytes above 264 * this are set to zero in order to avoid memory check warnings when 265 * longest match routines access bytes past the input. This is then 266 * updated to the new high water mark. 267 */ 268 269 } FAR deflate_state; 270 271 /* Output a byte on the stream. 272 * IN assertion: there is enough room in pending_buf. 273 */ 274 #define put_byte(s, c) {s->pending_buf[s->pending++] = (Bytef)(c);} 275 276 277 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) 278 /* Minimum amount of lookahead, except at the end of the input file. 279 * See deflate.c for comments about the MIN_MATCH+1. 280 */ 281 282 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD) 283 /* In order to simplify the code, particularly on 16 bit machines, match 284 * distances are limited to MAX_DIST instead of WSIZE. 285 */ 286 287 #define WIN_INIT MAX_MATCH 288 /* Number of bytes after end of data in window to initialize in order to avoid 289 memory checker errors from longest match routines */ 290 291 /* in trees.c */ 292 void ZLIB_INTERNAL _tr_init OF((deflate_state *s)); 293 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc)); 294 void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf, 295 ulg stored_len, int last)); 296 void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s)); 297 void ZLIB_INTERNAL _tr_align OF((deflate_state *s)); 298 void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf, 299 ulg stored_len, int last)); 300 301 #define d_code(dist) \ 302 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)]) 303 /* Mapping from a distance to a distance code. dist is the distance - 1 and 304 * must not have side effects. _dist_code[256] and _dist_code[257] are never 305 * used. 306 */ 307 308 #ifndef ZLIB_DEBUG 309 /* Inline versions of _tr_tally for speed: */ 310 311 #if defined(GEN_TREES_H) || !defined(STDC) 312 extern uch ZLIB_INTERNAL _length_code[]; 313 extern uch ZLIB_INTERNAL _dist_code[]; 314 #else 315 extern const uch ZLIB_INTERNAL _length_code[]; 316 extern const uch ZLIB_INTERNAL _dist_code[]; 317 #endif 318 319 # define _tr_tally_lit(s, c, flush) \ 320 { uch cc = (c); \ 321 s->sym_buf[s->sym_next++] = 0; \ 322 s->sym_buf[s->sym_next++] = 0; \ 323 s->sym_buf[s->sym_next++] = cc; \ 324 s->dyn_ltree[cc].Freq++; \ 325 flush = (s->sym_next == s->sym_end); \ 326 } 327 # define _tr_tally_dist(s, distance, length, flush) \ 328 { uch len = (uch)(length); \ 329 ush dist = (ush)(distance); \ 330 s->sym_buf[s->sym_next++] = dist; \ 331 s->sym_buf[s->sym_next++] = dist >> 8; \ 332 s->sym_buf[s->sym_next++] = len; \ 333 dist--; \ 334 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \ 335 s->dyn_dtree[d_code(dist)].Freq++; \ 336 flush = (s->sym_next == s->sym_end); \ 337 } 338 #else 339 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c) 340 # define _tr_tally_dist(s, distance, length, flush) \ 341 flush = _tr_tally(s, distance, length) 342 #endif 343 344 #endif /* DEFLATE_H */ 345