deflate.h (14041B)
1 /* deflate.h -- internal compression state 2 * Copyright (C) 1995-2024 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 /* @(#) $Id$ */ 12 13 #ifndef DEFLATE_H 14 #define DEFLATE_H 15 16 #include "zutil.h" 17 18 /* define NO_GZIP when compiling if you want to disable gzip header and 19 trailer creation by deflate(). NO_GZIP would be used to avoid linking in 20 the crc code when it is not needed. For shared libraries, gzip encoding 21 should be left enabled. */ 22 #ifndef NO_GZIP 23 # define GZIP 24 #endif 25 26 /* define LIT_MEM to slightly increase the speed of deflate (order 1% to 2%) at 27 the cost of a larger memory footprint */ 28 /* #define LIT_MEM */ 29 30 /* =========================================================================== 31 * Internal compression state. 32 */ 33 34 #define LENGTH_CODES 29 35 /* number of length codes, not counting the special END_BLOCK code */ 36 37 #define LITERALS 256 38 /* number of literal bytes 0..255 */ 39 40 #define L_CODES (LITERALS+1+LENGTH_CODES) 41 /* number of Literal or Length codes, including the END_BLOCK code */ 42 43 #define D_CODES 30 44 /* number of distance codes */ 45 46 #define BL_CODES 19 47 /* number of codes used to transfer the bit lengths */ 48 49 #define HEAP_SIZE (2*L_CODES+1) 50 /* maximum heap size */ 51 52 #define MAX_BITS 15 53 /* All codes must not exceed MAX_BITS bits */ 54 55 #define Buf_size 16 56 /* size of bit buffer in bi_buf */ 57 58 #define INIT_STATE 42 /* zlib header -> BUSY_STATE */ 59 #ifdef GZIP 60 # define GZIP_STATE 57 /* gzip header -> BUSY_STATE | EXTRA_STATE */ 61 #endif 62 #define EXTRA_STATE 69 /* gzip extra block -> NAME_STATE */ 63 #define NAME_STATE 73 /* gzip file name -> COMMENT_STATE */ 64 #define COMMENT_STATE 91 /* gzip comment -> HCRC_STATE */ 65 #define HCRC_STATE 103 /* gzip header CRC -> BUSY_STATE */ 66 #define BUSY_STATE 113 /* deflate -> FINISH_STATE */ 67 #define FINISH_STATE 666 /* stream complete */ 68 /* Stream status */ 69 70 71 /* Data structure describing a single value and its code string. */ 72 typedef struct ct_data_s { 73 union { 74 ush freq; /* frequency count */ 75 ush code; /* bit string */ 76 } fc; 77 union { 78 ush dad; /* father node in Huffman tree */ 79 ush len; /* length of bit string */ 80 } dl; 81 } FAR ct_data; 82 83 #define Freq fc.freq 84 #define Code fc.code 85 #define Dad dl.dad 86 #define Len dl.len 87 88 typedef struct static_tree_desc_s static_tree_desc; 89 90 typedef struct tree_desc_s { 91 ct_data *dyn_tree; /* the dynamic tree */ 92 int max_code; /* largest code with non zero frequency */ 93 const static_tree_desc *stat_desc; /* the corresponding static tree */ 94 } FAR tree_desc; 95 96 typedef ush Pos; 97 typedef Pos FAR Posf; 98 typedef unsigned IPos; 99 100 /* A Pos is an index in the character window. We use short instead of int to 101 * save space in the various tables. IPos is used only for parameter passing. 102 */ 103 104 typedef struct internal_state { 105 z_streamp strm; /* pointer back to this zlib stream */ 106 int status; /* as the name implies */ 107 Bytef *pending_buf; /* output still pending */ 108 ulg pending_buf_size; /* size of pending_buf */ 109 Bytef *pending_out; /* next pending byte to output to the stream */ 110 ulg pending; /* nb of bytes in the pending buffer */ 111 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */ 112 gz_headerp gzhead; /* gzip header information to write */ 113 ulg gzindex; /* where in extra, name, or comment */ 114 Byte method; /* can only be DEFLATED */ 115 int last_flush; /* value of flush param for previous deflate call */ 116 117 /* used by deflate.c: */ 118 119 uInt w_size; /* LZ77 window size (32K by default) */ 120 uInt w_bits; /* log2(w_size) (8..16) */ 121 uInt w_mask; /* w_size - 1 */ 122 123 Bytef *window; 124 /* Sliding window. Input bytes are read into the second half of the window, 125 * and move to the first half later to keep a dictionary of at least wSize 126 * bytes. With this organization, matches are limited to a distance of 127 * wSize-MAX_MATCH bytes, but this ensures that IO is always 128 * performed with a length multiple of the block size. Also, it limits 129 * the window size to 64K, which is quite useful on MSDOS. 130 * To do: use the user input buffer as sliding window. 131 */ 132 133 ulg window_size; 134 /* Actual size of window: 2*wSize, except when the user input buffer 135 * is directly used as sliding window. 136 */ 137 138 Posf *prev; 139 /* Link to older string with same hash index. To limit the size of this 140 * array to 64K, this link is maintained only for the last 32K strings. 141 * An index in this array is thus a window index modulo 32K. 142 */ 143 144 Posf *head; /* Heads of the hash chains or NIL. */ 145 146 uInt ins_h; /* hash index of string to be inserted */ 147 uInt hash_size; /* number of elements in hash table */ 148 uInt hash_bits; /* log2(hash_size) */ 149 uInt hash_mask; /* hash_size-1 */ 150 151 uInt hash_shift; 152 /* Number of bits by which ins_h must be shifted at each input 153 * step. It must be such that after MIN_MATCH steps, the oldest 154 * byte no longer takes part in the hash key, that is: 155 * hash_shift * MIN_MATCH >= hash_bits 156 */ 157 158 long block_start; 159 /* Window position at the beginning of the current output block. Gets 160 * negative when the window is moved backwards. 161 */ 162 163 uInt match_length; /* length of best match */ 164 IPos prev_match; /* previous match */ 165 int match_available; /* set if previous match exists */ 166 uInt strstart; /* start of string to insert */ 167 uInt match_start; /* start of matching string */ 168 uInt lookahead; /* number of valid bytes ahead in window */ 169 170 uInt prev_length; 171 /* Length of the best match at previous step. Matches not greater than this 172 * are discarded. This is used in the lazy match evaluation. 173 */ 174 175 uInt max_chain_length; 176 /* To speed up deflation, hash chains are never searched beyond this 177 * length. A higher limit improves compression ratio but degrades the 178 * speed. 179 */ 180 181 uInt max_lazy_match; 182 /* Attempt to find a better match only when the current match is strictly 183 * smaller than this value. This mechanism is used only for compression 184 * levels >= 4. 185 */ 186 # define max_insert_length max_lazy_match 187 /* Insert new strings in the hash table only if the match length is not 188 * greater than this length. This saves time but degrades compression. 189 * max_insert_length is used only for compression levels <= 3. 190 */ 191 192 int level; /* compression level (1..9) */ 193 int strategy; /* favor or force Huffman coding*/ 194 195 uInt good_match; 196 /* Use a faster search when the previous match is longer than this */ 197 198 int nice_match; /* Stop searching when current match exceeds this */ 199 200 /* used by trees.c: */ 201 /* Didn't use ct_data typedef below to suppress compiler warning */ 202 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */ 203 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */ 204 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */ 205 206 struct tree_desc_s l_desc; /* desc. for literal tree */ 207 struct tree_desc_s d_desc; /* desc. for distance tree */ 208 struct tree_desc_s bl_desc; /* desc. for bit length tree */ 209 210 ush bl_count[MAX_BITS+1]; 211 /* number of codes at each bit length for an optimal tree */ 212 213 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */ 214 int heap_len; /* number of elements in the heap */ 215 int heap_max; /* element of largest frequency */ 216 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used. 217 * The same heap array is used to build all trees. 218 */ 219 220 uch depth[2*L_CODES+1]; 221 /* Depth of each subtree used as tie breaker for trees of equal frequency 222 */ 223 224 #ifdef LIT_MEM 225 # define LIT_BUFS 5 226 ushf *d_buf; /* buffer for distances */ 227 uchf *l_buf; /* buffer for literals/lengths */ 228 #else 229 # define LIT_BUFS 4 230 uchf *sym_buf; /* buffer for distances and literals/lengths */ 231 #endif 232 233 uInt lit_bufsize; 234 /* Size of match buffer for literals/lengths. There are 4 reasons for 235 * limiting lit_bufsize to 64K: 236 * - frequencies can be kept in 16 bit counters 237 * - if compression is not successful for the first block, all input 238 * data is still in the window so we can still emit a stored block even 239 * when input comes from standard input. (This can also be done for 240 * all blocks if lit_bufsize is not greater than 32K.) 241 * - if compression is not successful for a file smaller than 64K, we can 242 * even emit a stored file instead of a stored block (saving 5 bytes). 243 * This is applicable only for zip (not gzip or zlib). 244 * - creating new Huffman trees less frequently may not provide fast 245 * adaptation to changes in the input data statistics. (Take for 246 * example a binary file with poorly compressible code followed by 247 * a highly compressible string table.) Smaller buffer sizes give 248 * fast adaptation but have of course the overhead of transmitting 249 * trees more frequently. 250 * - I can't count above 4 251 */ 252 253 uInt sym_next; /* running index in symbol buffer */ 254 uInt sym_end; /* symbol table full when sym_next reaches this */ 255 256 ulg opt_len; /* bit length of current block with optimal trees */ 257 ulg static_len; /* bit length of current block with static trees */ 258 uInt matches; /* number of string matches in current block */ 259 uInt insert; /* bytes at end of window left to insert */ 260 261 #ifdef ZLIB_DEBUG 262 ulg compressed_len; /* total bit length of compressed file mod 2^32 */ 263 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */ 264 #endif 265 266 ush bi_buf; 267 /* Output buffer. bits are inserted starting at the bottom (least 268 * significant bits). 269 */ 270 int bi_valid; 271 /* Number of valid bits in bi_buf. All bits above the last valid bit 272 * are always zero. 273 */ 274 275 ulg high_water; 276 /* High water mark offset in window for initialized bytes -- bytes above 277 * this are set to zero in order to avoid memory check warnings when 278 * longest match routines access bytes past the input. This is then 279 * updated to the new high water mark. 280 */ 281 282 } FAR deflate_state; 283 284 /* Output a byte on the stream. 285 * IN assertion: there is enough room in pending_buf. 286 */ 287 #define put_byte(s, c) {s->pending_buf[s->pending++] = (Bytef)(c);} 288 289 290 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) 291 /* Minimum amount of lookahead, except at the end of the input file. 292 * See deflate.c for comments about the MIN_MATCH+1. 293 */ 294 295 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD) 296 /* In order to simplify the code, particularly on 16 bit machines, match 297 * distances are limited to MAX_DIST instead of WSIZE. 298 */ 299 300 #define WIN_INIT MAX_MATCH 301 /* Number of bytes after end of data in window to initialize in order to avoid 302 memory checker errors from longest match routines */ 303 304 /* in trees.c */ 305 void ZLIB_INTERNAL _tr_init(deflate_state *s); 306 int ZLIB_INTERNAL _tr_tally(deflate_state *s, unsigned dist, unsigned lc); 307 void ZLIB_INTERNAL _tr_flush_block(deflate_state *s, charf *buf, 308 ulg stored_len, int last); 309 void ZLIB_INTERNAL _tr_flush_bits(deflate_state *s); 310 void ZLIB_INTERNAL _tr_align(deflate_state *s); 311 void ZLIB_INTERNAL _tr_stored_block(deflate_state *s, charf *buf, 312 ulg stored_len, int last); 313 314 #define d_code(dist) \ 315 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)]) 316 /* Mapping from a distance to a distance code. dist is the distance - 1 and 317 * must not have side effects. _dist_code[256] and _dist_code[257] are never 318 * used. 319 */ 320 321 #ifndef ZLIB_DEBUG 322 /* Inline versions of _tr_tally for speed: */ 323 324 #if defined(GEN_TREES_H) || !defined(STDC) 325 extern uch ZLIB_INTERNAL _length_code[]; 326 extern uch ZLIB_INTERNAL _dist_code[]; 327 #else 328 extern const uch ZLIB_INTERNAL _length_code[]; 329 extern const uch ZLIB_INTERNAL _dist_code[]; 330 #endif 331 332 #ifdef LIT_MEM 333 # define _tr_tally_lit(s, c, flush) \ 334 { uch cc = (c); \ 335 s->d_buf[s->sym_next] = 0; \ 336 s->l_buf[s->sym_next++] = cc; \ 337 s->dyn_ltree[cc].Freq++; \ 338 flush = (s->sym_next == s->sym_end); \ 339 } 340 # define _tr_tally_dist(s, distance, length, flush) \ 341 { uch len = (uch)(length); \ 342 ush dist = (ush)(distance); \ 343 s->d_buf[s->sym_next] = dist; \ 344 s->l_buf[s->sym_next++] = len; \ 345 dist--; \ 346 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \ 347 s->dyn_dtree[d_code(dist)].Freq++; \ 348 flush = (s->sym_next == s->sym_end); \ 349 } 350 #else 351 # define _tr_tally_lit(s, c, flush) \ 352 { uch cc = (c); \ 353 s->sym_buf[s->sym_next++] = 0; \ 354 s->sym_buf[s->sym_next++] = 0; \ 355 s->sym_buf[s->sym_next++] = cc; \ 356 s->dyn_ltree[cc].Freq++; \ 357 flush = (s->sym_next == s->sym_end); \ 358 } 359 # define _tr_tally_dist(s, distance, length, flush) \ 360 { uch len = (uch)(length); \ 361 ush dist = (ush)(distance); \ 362 s->sym_buf[s->sym_next++] = (uch)dist; \ 363 s->sym_buf[s->sym_next++] = (uch)(dist >> 8); \ 364 s->sym_buf[s->sym_next++] = len; \ 365 dist--; \ 366 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \ 367 s->dyn_dtree[d_code(dist)].Freq++; \ 368 flush = (s->sym_next == s->sym_end); \ 369 } 370 #endif 371 #else 372 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c) 373 # define _tr_tally_dist(s, distance, length, flush) \ 374 flush = _tr_tally(s, distance, length) 375 #endif 376 377 #endif /* DEFLATE_H */