1 /* deflate.h -- internal compression state 2 * Copyright (C) 1995-2010 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 INIT_STATE 42 52 #define EXTRA_STATE 69 53 #define NAME_STATE 73 54 #define COMMENT_STATE 91 55 #define HCRC_STATE 103 56 #define BUSY_STATE 113 57 #define FINISH_STATE 666 58 /* Stream status */ 59 60 61 /* Data structure describing a single value and its code string. */ 62 typedef struct ct_data_s { 63 union { 64 ush freq; /* frequency count */ 65 ush code; /* bit string */ 66 } fc; 67 union { 68 ush dad; /* father node in Huffman tree */ 69 ush len; /* length of bit string */ 70 } dl; 71 } FAR ct_data; 72 73 #define Freq fc.freq 74 #define Code fc.code 75 #define Dad dl.dad 76 #define Len dl.len 77 78 typedef struct static_tree_desc_s static_tree_desc; 79 80 typedef struct tree_desc_s { 81 ct_data *dyn_tree; /* the dynamic tree */ 82 int max_code; /* largest code with non zero frequency */ 83 static_tree_desc *stat_desc; /* the corresponding static tree */ 84 } FAR tree_desc; 85 86 typedef ush Pos; 87 typedef Pos FAR Posf; 88 typedef unsigned IPos; 89 90 /* A Pos is an index in the character window. We use short instead of int to 91 * save space in the various tables. IPos is used only for parameter passing. 92 */ 93 94 #define Z_COOKIE_HASH_SIZE 256 95 #define Z_COOKIE_HASH_MASK (Z_COOKIE_HASH_SIZE-1) 96 97 typedef struct internal_state { 98 z_streamp strm; /* pointer back to this zlib stream */ 99 int status; /* as the name implies */ 100 Bytef *pending_buf; /* output still pending */ 101 ulg pending_buf_size; /* size of pending_buf */ 102 Bytef *pending_out; /* next pending byte to output to the stream */ 103 uInt pending; /* nb of bytes in the pending buffer */ 104 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */ 105 gz_headerp gzhead; /* gzip header information to write */ 106 uInt gzindex; /* where in extra, name, or comment */ 107 Byte method; /* STORED (for zip only) or DEFLATED */ 108 int last_flush; /* value of flush param for previous deflate call */ 109 110 /* used by deflate.c: */ 111 112 uInt w_size; /* LZ77 window size (32K by default) */ 113 uInt w_bits; /* log2(w_size) (8..16) */ 114 uInt w_mask; /* w_size - 1 */ 115 116 Bytef *window; 117 /* Sliding window. Input bytes are read into the second half of the window, 118 * and move to the first half later to keep a dictionary of at least wSize 119 * bytes. With this organization, matches are limited to a distance of 120 * wSize-MAX_MATCH bytes, but this ensures that IO is always 121 * performed with a length multiple of the block size. Also, it limits 122 * the window size to 64K, which is quite useful on MSDOS. 123 * To do: use the user input buffer as sliding window. 124 */ 125 126 ulg window_size; 127 /* Actual size of window: 2*wSize, except when the user input buffer 128 * is directly used as sliding window. 129 */ 130 131 Posf *prev; 132 /* Link to older string with same hash index. To limit the size of this 133 * array to 64K, this link is maintained only for the last 32K strings. 134 * An index in this array is thus a window index modulo 32K. 135 */ 136 137 Posf *head; /* Heads of the hash chains or NIL. */ 138 139 uInt ins_h; /* hash index of string to be inserted */ 140 uInt hash_size; /* number of elements in hash table */ 141 uInt hash_bits; /* log2(hash_size) */ 142 uInt hash_mask; /* hash_size-1 */ 143 144 uInt hash_shift; 145 Bytef *class_bitmap; /* bitmap of class for each byte in window */ 146 IPos cookie_locations[Z_COOKIE_HASH_SIZE]; 147 /* Number of bits by which ins_h must be shifted at each input 148 * step. It must be such that after MIN_MATCH steps, the oldest 149 * byte no longer takes part in the hash key, that is: 150 * hash_shift * MIN_MATCH >= hash_bits 151 */ 152 153 long block_start; 154 /* Window position at the beginning of the current output block. Gets 155 * negative when the window is moved backwards. 156 */ 157 158 uInt match_length; /* length of best match */ 159 IPos prev_match; /* previous match */ 160 int match_available; /* set if previous match exists */ 161 uInt strstart; /* start of string to insert */ 162 uInt match_start; /* start of matching string */ 163 uInt lookahead; /* number of valid bytes ahead in window */ 164 165 uInt prev_length; 166 /* Length of the best match at previous step. Matches not greater than this 167 * are discarded. This is used in the lazy match evaluation. 168 */ 169 170 uInt max_chain_length; 171 /* To speed up deflation, hash chains are never searched beyond this 172 * length. A higher limit improves compression ratio but degrades the 173 * speed. 174 */ 175 176 uInt max_lazy_match; 177 /* Attempt to find a better match only when the current match is strictly 178 * smaller than this value. This mechanism is used only for compression 179 * levels >= 4. 180 */ 181 # define max_insert_length max_lazy_match 182 /* Insert new strings in the hash table only if the match length is not 183 * greater than this length. This saves time but degrades compression. 184 * max_insert_length is used only for compression levels <= 3. 185 */ 186 187 int level; /* compression level (1..9) */ 188 int strategy; /* favor or force Huffman coding*/ 189 190 uInt good_match; 191 /* Use a faster search when the previous match is longer than this */ 192 193 int nice_match; /* Stop searching when current match exceeds this */ 194 195 /* used by trees.c: */ 196 /* Didn't use ct_data typedef below to supress compiler warning */ 197 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */ 198 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */ 199 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */ 200 201 struct tree_desc_s l_desc; /* desc. for literal tree */ 202 struct tree_desc_s d_desc; /* desc. for distance tree */ 203 struct tree_desc_s bl_desc; /* desc. for bit length tree */ 204 205 ush bl_count[MAX_BITS+1]; 206 /* number of codes at each bit length for an optimal tree */ 207 208 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */ 209 int heap_len; /* number of elements in the heap */ 210 int heap_max; /* element of largest frequency */ 211 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used. 212 * The same heap array is used to build all trees. 213 */ 214 215 uch depth[2*L_CODES+1]; 216 /* Depth of each subtree used as tie breaker for trees of equal frequency 217 */ 218 219 uchf *l_buf; /* buffer for literals or lengths */ 220 221 uInt lit_bufsize; 222 /* Size of match buffer for literals/lengths. There are 4 reasons for 223 * limiting lit_bufsize to 64K: 224 * - frequencies can be kept in 16 bit counters 225 * - if compression is not successful for the first block, all input 226 * data is still in the window so we can still emit a stored block even 227 * when input comes from standard input. (This can also be done for 228 * all blocks if lit_bufsize is not greater than 32K.) 229 * - if compression is not successful for a file smaller than 64K, we can 230 * even emit a stored file instead of a stored block (saving 5 bytes). 231 * This is applicable only for zip (not gzip or zlib). 232 * - creating new Huffman trees less frequently may not provide fast 233 * adaptation to changes in the input data statistics. (Take for 234 * example a binary file with poorly compressible code followed by 235 * a highly compressible string table.) Smaller buffer sizes give 236 * fast adaptation but have of course the overhead of transmitting 237 * trees more frequently. 238 * - I can't count above 4 239 */ 240 241 uInt last_lit; /* running index in l_buf */ 242 243 ushf *d_buf; 244 /* Buffer for distances. To simplify the code, d_buf and l_buf have 245 * the same number of elements. To use different lengths, an extra flag 246 * array would be necessary. 247 */ 248 249 ulg opt_len; /* bit length of current block with optimal trees */ 250 ulg static_len; /* bit length of current block with static trees */ 251 uInt matches; /* number of string matches in current block */ 252 int last_eob_len; /* bit length of EOB code for last block */ 253 254 #ifdef DEBUG 255 ulg compressed_len; /* total bit length of compressed file mod 2^32 */ 256 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */ 257 #endif 258 259 ush bi_buf; 260 /* Output buffer. bits are inserted starting at the bottom (least 261 * significant bits). 262 */ 263 int bi_valid; 264 /* Number of valid bits in bi_buf. All bits above the last valid bit 265 * are always zero. 266 */ 267 268 ulg high_water; 269 /* High water mark offset in window for initialized bytes -- bytes above 270 * this are set to zero in order to avoid memory check warnings when 271 * longest match routines access bytes past the input. This is then 272 * updated to the new high water mark. 273 */ 274 275 } FAR deflate_state; 276 277 /* Output a byte on the stream. 278 * IN assertion: there is enough room in pending_buf. 279 */ 280 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);} 281 282 283 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) 284 /* Minimum amount of lookahead, except at the end of the input file. 285 * See deflate.c for comments about the MIN_MATCH+1. 286 */ 287 288 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD) 289 /* In order to simplify the code, particularly on 16 bit machines, match 290 * distances are limited to MAX_DIST instead of WSIZE. 291 */ 292 293 #define WIN_INIT MAX_MATCH 294 /* Number of bytes after end of data in window to initialize in order to avoid 295 memory checker errors from longest match routines */ 296 297 /* in trees.c */ 298 void ZLIB_INTERNAL _tr_init OF((deflate_state *s)); 299 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc)); 300 void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf, 301 ulg stored_len, int last)); 302 void ZLIB_INTERNAL _tr_align OF((deflate_state *s)); 303 void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf, 304 ulg stored_len, int last)); 305 306 #define d_code(dist) \ 307 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)]) 308 /* Mapping from a distance to a distance code. dist is the distance - 1 and 309 * must not have side effects. _dist_code[256] and _dist_code[257] are never 310 * used. 311 */ 312 313 #ifndef DEBUG 314 /* Inline versions of _tr_tally for speed: */ 315 316 #if defined(GEN_TREES_H) || !defined(STDC) 317 extern uch ZLIB_INTERNAL _length_code[]; 318 extern uch ZLIB_INTERNAL _dist_code[]; 319 #else 320 extern const uch ZLIB_INTERNAL _length_code[]; 321 extern const uch ZLIB_INTERNAL _dist_code[]; 322 #endif 323 324 # define _tr_tally_lit(s, c, flush) \ 325 { uch cc = (c); \ 326 s->d_buf[s->last_lit] = 0; \ 327 s->l_buf[s->last_lit++] = cc; \ 328 s->dyn_ltree[cc].Freq++; \ 329 flush = (s->last_lit == s->lit_bufsize-1); \ 330 } 331 # define _tr_tally_dist(s, distance, length, flush) \ 332 { uch len = (length); \ 333 ush dist = (distance); \ 334 s->d_buf[s->last_lit] = dist; \ 335 s->l_buf[s->last_lit++] = len; \ 336 dist--; \ 337 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \ 338 s->dyn_dtree[d_code(dist)].Freq++; \ 339 flush = (s->last_lit == s->lit_bufsize-1); \ 340 } 341 #else 342 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c) 343 # define _tr_tally_dist(s, distance, length, flush) \ 344 flush = _tr_tally(s, distance, length) 345 #endif 346 347 #endif /* DEFLATE_H */ 348