deflate.h revision 1.1
1 /* $NetBSD: deflate.h,v 1.1 2006/01/14 20:10:28 christos Exp $ */ 2 3 /* deflate.h -- internal compression state 4 * Copyright (C) 1995-2004 Jean-loup Gailly 5 * For conditions of distribution and use, see copyright notice in zlib.h 6 */ 7 8 /* WARNING: this file should *not* be used by applications. It is 9 part of the implementation of the compression library and is 10 subject to change. Applications should only use zlib.h. 11 */ 12 13 /* @(#) Id */ 14 15 #ifndef DEFLATE_H 16 #define DEFLATE_H 17 18 #include "zutil.h" 19 20 /* define NO_GZIP when compiling if you want to disable gzip header and 21 trailer creation by deflate(). NO_GZIP would be used to avoid linking in 22 the crc code when it is not needed. For shared libraries, gzip encoding 23 should be left enabled. */ 24 #ifndef NO_GZIP 25 # define GZIP 26 #endif 27 28 /* =========================================================================== 29 * Internal compression state. 30 */ 31 32 #define LENGTH_CODES 29 33 /* number of length codes, not counting the special END_BLOCK code */ 34 35 #define LITERALS 256 36 /* number of literal bytes 0..255 */ 37 38 #define L_CODES (LITERALS+1+LENGTH_CODES) 39 /* number of Literal or Length codes, including the END_BLOCK code */ 40 41 #define D_CODES 30 42 /* number of distance codes */ 43 44 #define BL_CODES 19 45 /* number of codes used to transfer the bit lengths */ 46 47 #define HEAP_SIZE (2*L_CODES+1) 48 /* maximum heap size */ 49 50 #define MAX_BITS 15 51 /* All codes must not exceed MAX_BITS bits */ 52 53 #define INIT_STATE 42 54 #define EXTRA_STATE 69 55 #define NAME_STATE 73 56 #define COMMENT_STATE 91 57 #define HCRC_STATE 103 58 #define BUSY_STATE 113 59 #define FINISH_STATE 666 60 /* Stream status */ 61 62 63 /* Data structure describing a single value and its code string. */ 64 typedef struct ct_data_s { 65 union { 66 ush freq; /* frequency count */ 67 ush code; /* bit string */ 68 } fc; 69 union { 70 ush dad; /* father node in Huffman tree */ 71 ush len; /* length of bit string */ 72 } dl; 73 } FAR ct_data; 74 75 #define Freq fc.freq 76 #define Code fc.code 77 #define Dad dl.dad 78 #define Len dl.len 79 80 typedef struct static_tree_desc_s static_tree_desc; 81 82 typedef struct tree_desc_s { 83 ct_data *dyn_tree; /* the dynamic tree */ 84 int max_code; /* largest code with non zero frequency */ 85 static_tree_desc *stat_desc; /* the corresponding static tree */ 86 } FAR tree_desc; 87 88 typedef ush Pos; 89 typedef Pos FAR Posf; 90 typedef unsigned IPos; 91 92 /* A Pos is an index in the character window. We use short instead of int to 93 * save space in the various tables. IPos is used only for parameter passing. 94 */ 95 96 typedef struct internal_state { 97 z_streamp strm; /* pointer back to this zlib stream */ 98 int status; /* as the name implies */ 99 Bytef *pending_buf; /* output still pending */ 100 ulg pending_buf_size; /* size of pending_buf */ 101 Bytef *pending_out; /* next pending byte to output to the stream */ 102 uInt pending; /* nb of bytes in the pending buffer */ 103 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */ 104 gz_headerp gzhead; /* gzip header information to write */ 105 uInt gzindex; /* where in extra, name, or comment */ 106 Byte method; /* STORED (for zip only) or DEFLATED */ 107 int last_flush; /* value of flush param for previous deflate call */ 108 109 /* used by deflate.c: */ 110 111 uInt w_size; /* LZ77 window size (32K by default) */ 112 uInt w_bits; /* log2(w_size) (8..16) */ 113 uInt w_mask; /* w_size - 1 */ 114 115 Bytef *window; 116 /* Sliding window. Input bytes are read into the second half of the window, 117 * and move to the first half later to keep a dictionary of at least wSize 118 * bytes. With this organization, matches are limited to a distance of 119 * wSize-MAX_MATCH bytes, but this ensures that IO is always 120 * performed with a length multiple of the block size. Also, it limits 121 * the window size to 64K, which is quite useful on MSDOS. 122 * To do: use the user input buffer as sliding window. 123 */ 124 125 ulg window_size; 126 /* Actual size of window: 2*wSize, except when the user input buffer 127 * is directly used as sliding window. 128 */ 129 130 Posf *prev; 131 /* Link to older string with same hash index. To limit the size of this 132 * array to 64K, this link is maintained only for the last 32K strings. 133 * An index in this array is thus a window index modulo 32K. 134 */ 135 136 Posf *head; /* Heads of the hash chains or NIL. */ 137 138 uInt ins_h; /* hash index of string to be inserted */ 139 uInt hash_size; /* number of elements in hash table */ 140 uInt hash_bits; /* log2(hash_size) */ 141 uInt hash_mask; /* hash_size-1 */ 142 143 uInt hash_shift; 144 /* Number of bits by which ins_h must be shifted at each input 145 * step. It must be such that after MIN_MATCH steps, the oldest 146 * byte no longer takes part in the hash key, that is: 147 * hash_shift * MIN_MATCH >= hash_bits 148 */ 149 150 long block_start; 151 /* Window position at the beginning of the current output block. Gets 152 * negative when the window is moved backwards. 153 */ 154 155 uInt match_length; /* length of best match */ 156 IPos prev_match; /* previous match */ 157 int match_available; /* set if previous match exists */ 158 uInt strstart; /* start of string to insert */ 159 uInt match_start; /* start of matching string */ 160 uInt lookahead; /* number of valid bytes ahead in window */ 161 162 uInt prev_length; 163 /* Length of the best match at previous step. Matches not greater than this 164 * are discarded. This is used in the lazy match evaluation. 165 */ 166 167 uInt max_chain_length; 168 /* To speed up deflation, hash chains are never searched beyond this 169 * length. A higher limit improves compression ratio but degrades the 170 * speed. 171 */ 172 173 uInt max_lazy_match; 174 /* Attempt to find a better match only when the current match is strictly 175 * smaller than this value. This mechanism is used only for compression 176 * levels >= 4. 177 */ 178 # define max_insert_length max_lazy_match 179 /* Insert new strings in the hash table only if the match length is not 180 * greater than this length. This saves time but degrades compression. 181 * max_insert_length is used only for compression levels <= 3. 182 */ 183 184 int level; /* compression level (1..9) */ 185 int strategy; /* favor or force Huffman coding*/ 186 187 uInt good_match; 188 /* Use a faster search when the previous match is longer than this */ 189 190 int nice_match; /* Stop searching when current match exceeds this */ 191 192 /* used by trees.c: */ 193 /* Didn't use ct_data typedef below to supress compiler warning */ 194 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */ 195 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */ 196 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */ 197 198 struct tree_desc_s l_desc; /* desc. for literal tree */ 199 struct tree_desc_s d_desc; /* desc. for distance tree */ 200 struct tree_desc_s bl_desc; /* desc. for bit length tree */ 201 202 ush bl_count[MAX_BITS+1]; 203 /* number of codes at each bit length for an optimal tree */ 204 205 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */ 206 int heap_len; /* number of elements in the heap */ 207 int heap_max; /* element of largest frequency */ 208 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used. 209 * The same heap array is used to build all trees. 210 */ 211 212 uch depth[2*L_CODES+1]; 213 /* Depth of each subtree used as tie breaker for trees of equal frequency 214 */ 215 216 uchf *l_buf; /* buffer for literals or lengths */ 217 218 uInt lit_bufsize; 219 /* Size of match buffer for literals/lengths. There are 4 reasons for 220 * limiting lit_bufsize to 64K: 221 * - frequencies can be kept in 16 bit counters 222 * - if compression is not successful for the first block, all input 223 * data is still in the window so we can still emit a stored block even 224 * when input comes from standard input. (This can also be done for 225 * all blocks if lit_bufsize is not greater than 32K.) 226 * - if compression is not successful for a file smaller than 64K, we can 227 * even emit a stored file instead of a stored block (saving 5 bytes). 228 * This is applicable only for zip (not gzip or zlib). 229 * - creating new Huffman trees less frequently may not provide fast 230 * adaptation to changes in the input data statistics. (Take for 231 * example a binary file with poorly compressible code followed by 232 * a highly compressible string table.) Smaller buffer sizes give 233 * fast adaptation but have of course the overhead of transmitting 234 * trees more frequently. 235 * - I can't count above 4 236 */ 237 238 uInt last_lit; /* running index in l_buf */ 239 240 ushf *d_buf; 241 /* Buffer for distances. To simplify the code, d_buf and l_buf have 242 * the same number of elements. To use different lengths, an extra flag 243 * array would be necessary. 244 */ 245 246 ulg opt_len; /* bit length of current block with optimal trees */ 247 ulg static_len; /* bit length of current block with static trees */ 248 uInt matches; /* number of string matches in current block */ 249 int last_eob_len; /* bit length of EOB code for last block */ 250 251 #ifdef DEBUG 252 ulg compressed_len; /* total bit length of compressed file mod 2^32 */ 253 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */ 254 #endif 255 256 ush bi_buf; 257 /* Output buffer. bits are inserted starting at the bottom (least 258 * significant bits). 259 */ 260 int bi_valid; 261 /* Number of valid bits in bi_buf. All bits above the last valid bit 262 * are always zero. 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 /* in trees.c */ 284 void _tr_init OF((deflate_state *s)); 285 int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc)); 286 void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len, 287 int eof)); 288 void _tr_align OF((deflate_state *s)); 289 void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len, 290 int eof)); 291 292 #define d_code(dist) \ 293 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)]) 294 /* Mapping from a distance to a distance code. dist is the distance - 1 and 295 * must not have side effects. _dist_code[256] and _dist_code[257] are never 296 * used. 297 */ 298 299 #ifndef DEBUG 300 /* Inline versions of _tr_tally for speed: */ 301 302 #if defined(GEN_TREES_H) || !defined(STDC) 303 extern uch _length_code[]; 304 extern uch _dist_code[]; 305 #else 306 extern const uch _length_code[]; 307 extern const uch _dist_code[]; 308 #endif 309 310 # define _tr_tally_lit(s, c, flush) \ 311 { uch cc = (c); \ 312 s->d_buf[s->last_lit] = 0; \ 313 s->l_buf[s->last_lit++] = cc; \ 314 s->dyn_ltree[cc].Freq++; \ 315 flush = (s->last_lit == s->lit_bufsize-1); \ 316 } 317 # define _tr_tally_dist(s, distance, length, flush) \ 318 { uch len = (length); \ 319 ush dist = (distance); \ 320 s->d_buf[s->last_lit] = dist; \ 321 s->l_buf[s->last_lit++] = len; \ 322 dist--; \ 323 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \ 324 s->dyn_dtree[d_code(dist)].Freq++; \ 325 flush = (s->last_lit == s->lit_bufsize-1); \ 326 } 327 #else 328 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c) 329 # define _tr_tally_dist(s, distance, length, flush) \ 330 flush = _tr_tally(s, distance, length) 331 #endif 332 333 #endif /* DEFLATE_H */ 334
Indexes created Mon Sep 29 18:09:42 GMT 2025