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