deflate.h revision 146081
1/* deflate.h -- internal compression state 2 * Copyright (C) 1995-2002 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 BUSY_STATE 113 53#define FINISH_STATE 666 54/* Stream status */ 55 56 57/* Data structure describing a single value and its code string. */ 58typedef struct ct_data_s { 59 union { 60 ush freq; /* frequency count */ 61 ush code; /* bit string */ 62 } fc; 63 union { 64 ush dad; /* father node in Huffman tree */ 65 ush len; /* length of bit string */ 66 } dl; 67} FAR ct_data; 68 69#define Freq fc.freq 70#define Code fc.code 71#define Dad dl.dad 72#define Len dl.len 73 74typedef struct static_tree_desc_s static_tree_desc; 75 76typedef struct tree_desc_s { 77 ct_data *dyn_tree; /* the dynamic tree */ 78 int max_code; /* largest code with non zero frequency */ 79 static_tree_desc *stat_desc; /* the corresponding static tree */ 80} FAR tree_desc; 81 82typedef ush Pos; 83typedef Pos FAR Posf; 84typedef unsigned IPos; 85 86/* A Pos is an index in the character window. We use short instead of int to 87 * save space in the various tables. IPos is used only for parameter passing. 88 */ 89 90typedef struct internal_state { 91 z_streamp strm; /* pointer back to this zlib stream */ 92 int status; /* as the name implies */ 93 Bytef *pending_buf; /* output still pending */ 94 ulg pending_buf_size; /* size of pending_buf */ 95 Bytef *pending_out; /* next pending byte to output to the stream */ 96 int pending; /* nb of bytes in the pending buffer */ 97 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */ 98 Byte method; /* STORED (for zip only) or DEFLATED */ 99 int last_flush; /* value of flush param for previous deflate call */ 100 101 /* used by deflate.c: */ 102 103 uInt w_size; /* LZ77 window size (32K by default) */ 104 uInt w_bits; /* log2(w_size) (8..16) */ 105 uInt w_mask; /* w_size - 1 */ 106 107 Bytef *window; 108 /* Sliding window. Input bytes are read into the second half of the window, 109 * and move to the first half later to keep a dictionary of at least wSize 110 * bytes. With this organization, matches are limited to a distance of 111 * wSize-MAX_MATCH bytes, but this ensures that IO is always 112 * performed with a length multiple of the block size. Also, it limits 113 * the window size to 64K, which is quite useful on MSDOS. 114 * To do: use the user input buffer as sliding window. 115 */ 116 117 ulg window_size; 118 /* Actual size of window: 2*wSize, except when the user input buffer 119 * is directly used as sliding window. 120 */ 121 122 Posf *prev; 123 /* Link to older string with same hash index. To limit the size of this 124 * array to 64K, this link is maintained only for the last 32K strings. 125 * An index in this array is thus a window index modulo 32K. 126 */ 127 128 Posf *head; /* Heads of the hash chains or NIL. */ 129 130 uInt ins_h; /* hash index of string to be inserted */ 131 uInt hash_size; /* number of elements in hash table */ 132 uInt hash_bits; /* log2(hash_size) */ 133 uInt hash_mask; /* hash_size-1 */ 134 135 uInt hash_shift; 136 /* Number of bits by which ins_h must be shifted at each input 137 * step. It must be such that after MIN_MATCH steps, the oldest 138 * byte no longer takes part in the hash key, that is: 139 * hash_shift * MIN_MATCH >= hash_bits 140 */ 141 142 long block_start; 143 /* Window position at the beginning of the current output block. Gets 144 * negative when the window is moved backwards. 145 */ 146 147 uInt match_length; /* length of best match */ 148 IPos prev_match; /* previous match */ 149 int match_available; /* set if previous match exists */ 150 uInt strstart; /* start of string to insert */ 151 uInt match_start; /* start of matching string */ 152 uInt lookahead; /* number of valid bytes ahead in window */ 153 154 uInt prev_length; 155 /* Length of the best match at previous step. Matches not greater than this 156 * are discarded. This is used in the lazy match evaluation. 157 */ 158 159 uInt max_chain_length; 160 /* To speed up deflation, hash chains are never searched beyond this 161 * length. A higher limit improves compression ratio but degrades the 162 * speed. 163 */ 164 165 uInt max_lazy_match; 166 /* Attempt to find a better match only when the current match is strictly 167 * smaller than this value. This mechanism is used only for compression 168 * levels >= 4. 169 */ 170# define max_insert_length max_lazy_match 171 /* Insert new strings in the hash table only if the match length is not 172 * greater than this length. This saves time but degrades compression. 173 * max_insert_length is used only for compression levels <= 3. 174 */ 175 176 int level; /* compression level (1..9) */ 177 int strategy; /* favor or force Huffman coding*/ 178 179 uInt good_match; 180 /* Use a faster search when the previous match is longer than this */ 181 182 int nice_match; /* Stop searching when current match exceeds this */ 183 184 /* used by trees.c: */ 185 /* Didn't use ct_data typedef below to supress compiler warning */ 186 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */ 187 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */ 188 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */ 189 190 struct tree_desc_s l_desc; /* desc. for literal tree */ 191 struct tree_desc_s d_desc; /* desc. for distance tree */ 192 struct tree_desc_s bl_desc; /* desc. for bit length tree */ 193 194 ush bl_count[MAX_BITS+1]; 195 /* number of codes at each bit length for an optimal tree */ 196 197 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */ 198 int heap_len; /* number of elements in the heap */ 199 int heap_max; /* element of largest frequency */ 200 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used. 201 * The same heap array is used to build all trees. 202 */ 203 204 uch depth[2*L_CODES+1]; 205 /* Depth of each subtree used as tie breaker for trees of equal frequency 206 */ 207 208 uchf *l_buf; /* buffer for literals or lengths */ 209 210 uInt lit_bufsize; 211 /* Size of match buffer for literals/lengths. There are 4 reasons for 212 * limiting lit_bufsize to 64K: 213 * - frequencies can be kept in 16 bit counters 214 * - if compression is not successful for the first block, all input 215 * data is still in the window so we can still emit a stored block even 216 * when input comes from standard input. (This can also be done for 217 * all blocks if lit_bufsize is not greater than 32K.) 218 * - if compression is not successful for a file smaller than 64K, we can 219 * even emit a stored file instead of a stored block (saving 5 bytes). 220 * This is applicable only for zip (not gzip or zlib). 221 * - creating new Huffman trees less frequently may not provide fast 222 * adaptation to changes in the input data statistics. (Take for 223 * example a binary file with poorly compressible code followed by 224 * a highly compressible string table.) Smaller buffer sizes give 225 * fast adaptation but have of course the overhead of transmitting 226 * trees more frequently. 227 * - I can't count above 4 228 */ 229 230 uInt last_lit; /* running index in l_buf */ 231 232 ushf *d_buf; 233 /* Buffer for distances. To simplify the code, d_buf and l_buf have 234 * the same number of elements. To use different lengths, an extra flag 235 * array would be necessary. 236 */ 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} FAR deflate_state; 258 259/* Output a byte on the stream. 260 * IN assertion: there is enough room in pending_buf. 261 */ 262#define put_byte(s, c) {s->pending_buf[s->pending++] = (c);} 263 264 265#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) 266/* Minimum amount of lookahead, except at the end of the input file. 267 * See deflate.c for comments about the MIN_MATCH+1. 268 */ 269 270#define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD) 271/* In order to simplify the code, particularly on 16 bit machines, match 272 * distances are limited to MAX_DIST instead of WSIZE. 273 */ 274 275 /* in trees.c */ 276void _tr_init OF((deflate_state *s)); 277int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc)); 278void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len, 279 int eof)); 280void _tr_align OF((deflate_state *s)); 281void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len, 282 int eof)); 283 284#define d_code(dist) \ 285 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)]) 286/* Mapping from a distance to a distance code. dist is the distance - 1 and 287 * must not have side effects. _dist_code[256] and _dist_code[257] are never 288 * used. 289 */ 290 291#ifndef DEBUG 292/* Inline versions of _tr_tally for speed: */ 293 294#if defined(GEN_TREES_H) || !defined(STDC) 295 extern uch _length_code[]; 296 extern uch _dist_code[]; 297#else 298 extern const uch _length_code[]; 299 extern const uch _dist_code[]; 300#endif 301 302# define _tr_tally_lit(s, c, flush) \ 303 { uch cc = (c); \ 304 s->d_buf[s->last_lit] = 0; \ 305 s->l_buf[s->last_lit++] = cc; \ 306 s->dyn_ltree[cc].Freq++; \ 307 flush = (s->last_lit == s->lit_bufsize-1); \ 308 } 309# define _tr_tally_dist(s, distance, length, flush) \ 310 { uch len = (length); \ 311 ush dist = (distance); \ 312 s->d_buf[s->last_lit] = dist; \ 313 s->l_buf[s->last_lit++] = len; \ 314 dist--; \ 315 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \ 316 s->dyn_dtree[d_code(dist)].Freq++; \ 317 flush = (s->last_lit == s->lit_bufsize-1); \ 318 } 319#else 320# define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c) 321# define _tr_tally_dist(s, distance, length, flush) \ 322 flush = _tr_tally(s, distance, length) 323#endif 324 325#endif /* DEFLATE_H */ 326