1 /* deflate.h -- internal compression state 2 * Copyright (C) 1995-2016 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 /* =========================================================================== 27 * Internal compression state. 28 */ 29 30 #define LENGTH_CODES 29 31 /* number of length codes, not counting the special END_BLOCK code */ 32 33 #define LITERALS 256 34 /* number of literal bytes 0..255 */ 35 36 #define L_CODES (LITERALS+1+LENGTH_CODES) 37 /* number of Literal or Length codes, including the END_BLOCK code */ 38 39 #define D_CODES 30 40 /* number of distance codes */ 41 42 #define BL_CODES 19 43 /* number of codes used to transfer the bit lengths */ 44 45 #define HEAP_SIZE (2*L_CODES+1) 46 /* maximum heap size */ 47 48 #define MAX_BITS 15 49 /* All codes must not exceed MAX_BITS bits */ 50 51 #define Buf_size 16 52 /* size of bit buffer in bi_buf */ 53 54 #define INIT_STATE 42 /* zlib header -> BUSY_STATE */ 55 #ifdef GZIP 56 # define GZIP_STATE 57 /* gzip header -> BUSY_STATE | EXTRA_STATE */ 57 #endif 58 #define EXTRA_STATE 69 /* gzip extra block -> NAME_STATE */ 59 #define NAME_STATE 73 /* gzip file name -> COMMENT_STATE */ 60 #define COMMENT_STATE 91 /* gzip comment -> HCRC_STATE */ 61 #define HCRC_STATE 103 /* gzip header CRC -> BUSY_STATE */ 62 #define BUSY_STATE 113 /* deflate -> FINISH_STATE */ 63 #define FINISH_STATE 666 /* stream complete */ 64 /* Stream status */ 65 66 67 /* Data structure describing a single value and its code string. */ 68 typedef struct ct_data_s { 69 union { 70 ush freq; /* frequency count */ 71 ush code; /* bit string */ 72 } fc; 73 union { 74 ush dad; /* father node in Huffman tree */ 75 ush len; /* length of bit string */ 76 } dl; 77 } FAR ct_data; 78 79 #define Freq fc.freq 80 #define Code fc.code 81 #define Dad dl.dad 82 #define Len dl.len 83 84 typedef struct static_tree_desc_s static_tree_desc; 85 86 typedef struct tree_desc_s { 87 ct_data *dyn_tree; /* the dynamic tree */ 88 int max_code; /* largest code with non zero frequency */ 89 const static_tree_desc *stat_desc; /* the corresponding static tree */ 90 } FAR tree_desc; 91 92 typedef ush Pos; 93 typedef Pos FAR Posf; 94 typedef unsigned IPos; 95 96 /* A Pos is an index in the character window. We use short instead of int to 97 * save space in the various tables. IPos is used only for parameter passing. 98 */ 99 100 typedef struct internal_state { 101 z_streamp strm; /* pointer back to this zlib stream */ 102 int status; /* as the name implies */ 103 Bytef *pending_buf; /* output still pending */ 104 ulg pending_buf_size; /* size of pending_buf */ 105 Bytef *pending_out; /* next pending byte to output to the stream */ 106 ulg pending; /* nb of bytes in the pending buffer */ 107 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */ 108 gz_headerp gzhead; /* gzip header information to write */ 109 ulg gzindex; /* where in extra, name, or comment */ 110 Byte method; /* can only be DEFLATED */ 111 int last_flush; /* value of flush param for previous deflate call */ 112 113 /* used by deflate.c: */ 114 115 uInt w_size; /* LZ77 window size (32K by default) */ 116 uInt w_bits; /* log2(w_size) (8..16) */ 117 uInt w_mask; /* w_size - 1 */ 118 119 Bytef *window; 120 /* Sliding window. Input bytes are read into the second half of the window, 121 * and move to the first half later to keep a dictionary of at least wSize 122 * bytes. With this organization, matches are limited to a distance of 123 * wSize-MAX_MATCH bytes, but this ensures that IO is always 124 * performed with a length multiple of the block size. Also, it limits 125 * the window size to 64K, which is quite useful on MSDOS. 126 * To do: use the user input buffer as sliding window. 127 */ 128 129 ulg window_size; 130 /* Actual size of window: 2*wSize, except when the user input buffer 131 * is directly used as sliding window. 132 */ 133 134 Posf *prev; 135 /* Link to older string with same hash index. To limit the size of this 136 * array to 64K, this link is maintained only for the last 32K strings. 137 * An index in this array is thus a window index modulo 32K. 138 */ 139 140 Posf *head; /* Heads of the hash chains or NIL. */ 141 142 uInt ins_h; /* hash index of string to be inserted */ 143 uInt hash_size; /* number of elements in hash table */ 144 uInt hash_bits; /* log2(hash_size) */ 145 uInt hash_mask; /* hash_size-1 */ 146 147 uInt hash_shift; 148 /* Number of bits by which ins_h must be shifted at each input 149 * step. It must be such that after MIN_MATCH steps, the oldest 150 * byte no longer takes part in the hash key, that is: 151 * hash_shift * MIN_MATCH >= hash_bits 152 */ 153 154 long block_start; 155 /* Window position at the beginning of the current output block. Gets 156 * negative when the window is moved backwards. 157 */ 158 159 uInt match_length; /* length of best match */ 160 IPos prev_match; /* previous match */ 161 int match_available; /* set if previous match exists */ 162 uInt strstart; /* start of string to insert */ 163 uInt match_start; /* start of matching string */ 164 uInt lookahead; /* number of valid bytes ahead in window */ 165 166 uInt prev_length; 167 /* Length of the best match at previous step. Matches not greater than this 168 * are discarded. This is used in the lazy match evaluation. 169 */ 170 171 uInt max_chain_length; 172 /* To speed up deflation, hash chains are never searched beyond this 173 * length. A higher limit improves compression ratio but degrades the 174 * speed. 175 */ 176 177 uInt max_lazy_match; 178 /* Attempt to find a better match only when the current match is strictly 179 * smaller than this value. This mechanism is used only for compression 180 * levels >= 4. 181 */ 182 # define max_insert_length max_lazy_match 183 /* Insert new strings in the hash table only if the match length is not 184 * greater than this length. This saves time but degrades compression. 185 * max_insert_length is used only for compression levels <= 3. 186 */ 187 188 int level; /* compression level (1..9) */ 189 int strategy; /* favor or force Huffman coding*/ 190 191 uInt good_match; 192 /* Use a faster search when the previous match is longer than this */ 193 194 int nice_match; /* Stop searching when current match exceeds this */ 195 196 /* used by trees.c: */ 197 /* Didn't use ct_data typedef below to suppress compiler warning */ 198 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */ 199 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */ 200 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */ 201 202 struct tree_desc_s l_desc; /* desc. for literal tree */ 203 struct tree_desc_s d_desc; /* desc. for distance tree */ 204 struct tree_desc_s bl_desc; /* desc. for bit length tree */ 205 206 ush bl_count[MAX_BITS+1]; 207 /* number of codes at each bit length for an optimal tree */ 208 209 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */ 210 int heap_len; /* number of elements in the heap */ 211 int heap_max; /* element of largest frequency */ 212 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used. 213 * The same heap array is used to build all trees. 214 */ 215 216 uch depth[2*L_CODES+1]; 217 /* Depth of each subtree used as tie breaker for trees of equal frequency 218 */ 219 220 uchf *l_buf; /* buffer for literals or lengths */ 221 222 uInt lit_bufsize; 223 /* Size of match buffer for literals/lengths. There are 4 reasons for 224 * limiting lit_bufsize to 64K: 225 * - frequencies can be kept in 16 bit counters 226 * - if compression is not successful for the first block, all input 227 * data is still in the window so we can still emit a stored block even 228 * when input comes from standard input. (This can also be done for 229 * all blocks if lit_bufsize is not greater than 32K.) 230 * - if compression is not successful for a file smaller than 64K, we can 231 * even emit a stored file instead of a stored block (saving 5 bytes). 232 * This is applicable only for zip (not gzip or zlib). 233 * - creating new Huffman trees less frequently may not provide fast 234 * adaptation to changes in the input data statistics. (Take for 235 * example a binary file with poorly compressible code followed by 236 * a highly compressible string table.) Smaller buffer sizes give 237 * fast adaptation but have of course the overhead of transmitting 238 * trees more frequently. 239 * - I can't count above 4 240 */ 241 242 uInt last_lit; /* running index in l_buf */ 243 244 ushf *d_buf; 245 /* Buffer for distances. To simplify the code, d_buf and l_buf have 246 * the same number of elements. To use different lengths, an extra flag 247 * array would be necessary. 248 */ 249 250 ulg opt_len; /* bit length of current block with optimal trees */ 251 ulg static_len; /* bit length of current block with static trees */ 252 uInt matches; /* number of string matches in current block */ 253 uInt insert; /* bytes at end of window left to insert */ 254 255 #ifdef ZLIB_DEBUG 256 ulg compressed_len; /* total bit length of compressed file mod 2^32 */ 257 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */ 258 #endif 259 260 ush bi_buf; 261 /* Output buffer. bits are inserted starting at the bottom (least 262 * significant bits). 263 */ 264 int bi_valid; 265 /* Number of valid bits in bi_buf. All bits above the last valid bit 266 * are always zero. 267 */ 268 269 ulg high_water; 270 /* High water mark offset in window for initialized bytes -- bytes above 271 * this are set to zero in order to avoid memory check warnings when 272 * longest match routines access bytes past the input. This is then 273 * updated to the new high water mark. 274 */ 275 276 } FAR deflate_state; 277 278 /* Output a byte on the stream. 279 * IN assertion: there is enough room in pending_buf. 280 */ 281 #define put_byte(s, c) {s->pending_buf[s->pending++] = (Bytef)(c);} 282 283 284 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) 285 /* Minimum amount of lookahead, except at the end of the input file. 286 * See deflate.c for comments about the MIN_MATCH+1. 287 */ 288 289 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD) 290 /* In order to simplify the code, particularly on 16 bit machines, match 291 * distances are limited to MAX_DIST instead of WSIZE. 292 */ 293 294 #define WIN_INIT MAX_MATCH 295 /* Number of bytes after end of data in window to initialize in order to avoid 296 memory checker errors from longest match routines */ 297 298 /* in trees.c */ 299 void ZLIB_INTERNAL _tr_init OF((deflate_state *s)); 300 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc)); 301 void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf, 302 ulg stored_len, int last)); 303 void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s)); 304 void ZLIB_INTERNAL _tr_align OF((deflate_state *s)); 305 void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf, 306 ulg stored_len, int last)); 307 308 #define d_code(dist) \ 309 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)]) 310 /* Mapping from a distance to a distance code. dist is the distance - 1 and 311 * must not have side effects. _dist_code[256] and _dist_code[257] are never 312 * used. 313 */ 314 315 #ifndef ZLIB_DEBUG 316 /* Inline versions of _tr_tally for speed: */ 317 318 #if defined(GEN_TREES_H) || !defined(STDC) 319 extern uch ZLIB_INTERNAL _length_code[]; 320 extern uch ZLIB_INTERNAL _dist_code[]; 321 #else 322 extern const uch ZLIB_INTERNAL _length_code[]; 323 extern const uch ZLIB_INTERNAL _dist_code[]; 324 #endif 325 326 # define _tr_tally_lit(s, c, flush) \ 327 { uch cc = (c); \ 328 s->d_buf[s->last_lit] = 0; \ 329 s->l_buf[s->last_lit++] = cc; \ 330 s->dyn_ltree[cc].Freq++; \ 331 flush = (s->last_lit == s->lit_bufsize-1); \ 332 } 333 # define _tr_tally_dist(s, distance, length, flush) \ 334 { uch len = (uch)(length); \ 335 ush dist = (ush)(distance); \ 336 s->d_buf[s->last_lit] = dist; \ 337 s->l_buf[s->last_lit++] = len; \ 338 dist--; \ 339 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \ 340 s->dyn_dtree[d_code(dist)].Freq++; \ 341 flush = (s->last_lit == s->lit_bufsize-1); \ 342 } 343 #else 344 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c) 345 # define _tr_tally_dist(s, distance, length, flush) \ 346 flush = _tr_tally(s, distance, length) 347 #endif 348 349 #endif /* DEFLATE_H */ 350