1/* deflate.h -- internal compression state 2 * Copyright (C) 1995-1998 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: deflate.h,v 1.1.1.1 2008/10/15 03:25:54 james26_jang Exp $ */ 12 13#ifndef _DEFLATE_H 14#define _DEFLATE_H 15 16#include "zutil.h" 17 18/* =========================================================================== 19 * Internal compression state. 20 */ 21 22#define LENGTH_CODES 29 23/* number of length codes, not counting the special END_BLOCK code */ 24 25#define LITERALS 256 26/* number of literal bytes 0..255 */ 27 28#define L_CODES (LITERALS+1+LENGTH_CODES) 29/* number of Literal or Length codes, including the END_BLOCK code */ 30 31#define D_CODES 30 32/* number of distance codes */ 33 34#define BL_CODES 19 35/* number of codes used to transfer the bit lengths */ 36 37#define HEAP_SIZE (2*L_CODES+1) 38/* maximum heap size */ 39 40#define MAX_BITS 15 41/* All codes must not exceed MAX_BITS bits */ 42 43#define INIT_STATE 42 44#define BUSY_STATE 113 45#define FINISH_STATE 666 46/* Stream status */ 47 48 49/* Data structure describing a single value and its code string. */ 50typedef struct ct_data_s { 51 union { 52 ush freq; /* frequency count */ 53 ush code; /* bit string */ 54 } fc; 55 union { 56 ush dad; /* father node in Huffman tree */ 57 ush len; /* length of bit string */ 58 } dl; 59} FAR ct_data; 60 61#define Freq fc.freq 62#define Code fc.code 63#define Dad dl.dad 64#define Len dl.len 65 66typedef struct static_tree_desc_s static_tree_desc; 67 68typedef struct tree_desc_s { 69 ct_data *dyn_tree; /* the dynamic tree */ 70 int max_code; /* largest code with non zero frequency */ 71 static_tree_desc *stat_desc; /* the corresponding static tree */ 72} FAR tree_desc; 73 74typedef ush Pos; 75typedef Pos FAR Posf; 76typedef unsigned IPos; 77 78/* A Pos is an index in the character window. We use short instead of int to 79 * save space in the various tables. IPos is used only for parameter passing. 80 */ 81 82typedef struct internal_state { 83 z_streamp strm; /* pointer back to this zlib stream */ 84 int status; /* as the name implies */ 85 Bytef *pending_buf; /* output still pending */ 86 ulg pending_buf_size; /* size of pending_buf */ 87 Bytef *pending_out; /* next pending byte to output to the stream */ 88 int pending; /* nb of bytes in the pending buffer */ 89 int noheader; /* suppress zlib header and adler32 */ 90 Byte data_type; /* UNKNOWN, BINARY or ASCII */ 91 Byte method; /* STORED (for zip only) or DEFLATED */ 92 int last_flush; /* value of flush param for previous deflate call */ 93 94 /* used by deflate.c: */ 95 96 uInt w_size; /* LZ77 window size (32K by default) */ 97 uInt w_bits; /* log2(w_size) (8..16) */ 98 uInt w_mask; /* w_size - 1 */ 99 100 Bytef *window; 101 /* Sliding window. Input bytes are read into the second half of the window, 102 * and move to the first half later to keep a dictionary of at least wSize 103 * bytes. With this organization, matches are limited to a distance of 104 * wSize-MAX_MATCH bytes, but this ensures that IO is always 105 * performed with a length multiple of the block size. Also, it limits 106 * the window size to 64K, which is quite useful on MSDOS. 107 * To do: use the user input buffer as sliding window. 108 */ 109 110 ulg window_size; 111 /* Actual size of window: 2*wSize, except when the user input buffer 112 * is directly used as sliding window. 113 */ 114 115 Posf *prev; 116 /* Link to older string with same hash index. To limit the size of this 117 * array to 64K, this link is maintained only for the last 32K strings. 118 * An index in this array is thus a window index modulo 32K. 119 */ 120 121 Posf *head; /* Heads of the hash chains or NIL. */ 122 123 uInt ins_h; /* hash index of string to be inserted */ 124 uInt hash_size; /* number of elements in hash table */ 125 uInt hash_bits; /* log2(hash_size) */ 126 uInt hash_mask; /* hash_size-1 */ 127 128 uInt hash_shift; 129 /* Number of bits by which ins_h must be shifted at each input 130 * step. It must be such that after MIN_MATCH steps, the oldest 131 * byte no longer takes part in the hash key, that is: 132 * hash_shift * MIN_MATCH >= hash_bits 133 */ 134 135 long block_start; 136 /* Window position at the beginning of the current output block. Gets 137 * negative when the window is moved backwards. 138 */ 139 140 uInt match_length; /* length of best match */ 141 IPos prev_match; /* previous match */ 142 int match_available; /* set if previous match exists */ 143 uInt strstart; /* start of string to insert */ 144 uInt match_start; /* start of matching string */ 145 uInt lookahead; /* number of valid bytes ahead in window */ 146 147 uInt prev_length; 148 /* Length of the best match at previous step. Matches not greater than this 149 * are discarded. This is used in the lazy match evaluation. 150 */ 151 152 uInt max_chain_length; 153 /* To speed up deflation, hash chains are never searched beyond this 154 * length. A higher limit improves compression ratio but degrades the 155 * speed. 156 */ 157 158 uInt max_lazy_match; 159 /* Attempt to find a better match only when the current match is strictly 160 * smaller than this value. This mechanism is used only for compression 161 * levels >= 4. 162 */ 163# define max_insert_length max_lazy_match 164 /* Insert new strings in the hash table only if the match length is not 165 * greater than this length. This saves time but degrades compression. 166 * max_insert_length is used only for compression levels <= 3. 167 */ 168 169 int level; /* compression level (1..9) */ 170 int strategy; /* favor or force Huffman coding*/ 171 172 uInt good_match; 173 /* Use a faster search when the previous match is longer than this */ 174 175 int nice_match; /* Stop searching when current match exceeds this */ 176 177 /* used by trees.c: */ 178 /* Didn't use ct_data typedef below to supress compiler warning */ 179 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */ 180 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */ 181 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */ 182 183 struct tree_desc_s l_desc; /* desc. for literal tree */ 184 struct tree_desc_s d_desc; /* desc. for distance tree */ 185 struct tree_desc_s bl_desc; /* desc. for bit length tree */ 186 187 ush bl_count[MAX_BITS+1]; 188 /* number of codes at each bit length for an optimal tree */ 189 190 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */ 191 int heap_len; /* number of elements in the heap */ 192 int heap_max; /* element of largest frequency */ 193 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used. 194 * The same heap array is used to build all trees. 195 */ 196 197 uch depth[2*L_CODES+1]; 198 /* Depth of each subtree used as tie breaker for trees of equal frequency 199 */ 200 201 uchf *l_buf; /* buffer for literals or lengths */ 202 203 uInt lit_bufsize; 204 /* Size of match buffer for literals/lengths. There are 4 reasons for 205 * limiting lit_bufsize to 64K: 206 * - frequencies can be kept in 16 bit counters 207 * - if compression is not successful for the first block, all input 208 * data is still in the window so we can still emit a stored block even 209 * when input comes from standard input. (This can also be done for 210 * all blocks if lit_bufsize is not greater than 32K.) 211 * - if compression is not successful for a file smaller than 64K, we can 212 * even emit a stored file instead of a stored block (saving 5 bytes). 213 * This is applicable only for zip (not gzip or zlib). 214 * - creating new Huffman trees less frequently may not provide fast 215 * adaptation to changes in the input data statistics. (Take for 216 * example a binary file with poorly compressible code followed by 217 * a highly compressible string table.) Smaller buffer sizes give 218 * fast adaptation but have of course the overhead of transmitting 219 * trees more frequently. 220 * - I can't count above 4 221 */ 222 223 uInt last_lit; /* running index in l_buf */ 224 225 ushf *d_buf; 226 /* Buffer for distances. To simplify the code, d_buf and l_buf have 227 * the same number of elements. To use different lengths, an extra flag 228 * array would be necessary. 229 */ 230 231 ulg opt_len; /* bit length of current block with optimal trees */ 232 ulg static_len; /* bit length of current block with static trees */ 233 uInt matches; /* number of string matches in current block */ 234 int last_eob_len; /* bit length of EOB code for last block */ 235 236#ifdef DEBUG 237 ulg compressed_len; /* total bit length of compressed file mod 2^32 */ 238 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */ 239#endif 240 241 ush bi_buf; 242 /* Output buffer. bits are inserted starting at the bottom (least 243 * significant bits). 244 */ 245 int bi_valid; 246 /* Number of valid bits in bi_buf. All bits above the last valid bit 247 * are always zero. 248 */ 249 250} FAR deflate_state; 251 252/* Output a byte on the stream. 253 * IN assertion: there is enough room in pending_buf. 254 */ 255#define put_byte(s, c) {s->pending_buf[s->pending++] = (c);} 256 257 258#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) 259/* Minimum amount of lookahead, except at the end of the input file. 260 * See deflate.c for comments about the MIN_MATCH+1. 261 */ 262 263#define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD) 264/* In order to simplify the code, particularly on 16 bit machines, match 265 * distances are limited to MAX_DIST instead of WSIZE. 266 */ 267 268 /* in trees.c */ 269void _tr_init OF((deflate_state *s)); 270int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc)); 271void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len, 272 int eof)); 273void _tr_align OF((deflate_state *s)); 274void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len, 275 int eof)); 276 277#define d_code(dist) \ 278 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)]) 279/* Mapping from a distance to a distance code. dist is the distance - 1 and 280 * must not have side effects. _dist_code[256] and _dist_code[257] are never 281 * used. 282 */ 283 284#ifndef DEBUG 285/* Inline versions of _tr_tally for speed: */ 286 287#if defined(GEN_TREES_H) || !defined(STDC) 288 extern uch _length_code[]; 289 extern uch _dist_code[]; 290#else 291 extern const uch _length_code[]; 292 extern const uch _dist_code[]; 293#endif 294 295# define _tr_tally_lit(s, c, flush) \ 296 { uch cc = (c); \ 297 s->d_buf[s->last_lit] = 0; \ 298 s->l_buf[s->last_lit++] = cc; \ 299 s->dyn_ltree[cc].Freq++; \ 300 flush = (s->last_lit == s->lit_bufsize-1); \ 301 } 302# define _tr_tally_dist(s, distance, length, flush) \ 303 { uch len = (length); \ 304 ush dist = (distance); \ 305 s->d_buf[s->last_lit] = dist; \ 306 s->l_buf[s->last_lit++] = len; \ 307 dist--; \ 308 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \ 309 s->dyn_dtree[d_code(dist)].Freq++; \ 310 flush = (s->last_lit == s->lit_bufsize-1); \ 311 } 312#else 313# define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c) 314# define _tr_tally_dist(s, distance, length, flush) \ 315 flush = _tr_tally(s, distance, length) 316#endif 317 318#endif 319