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