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annotate libs/zlib/deflate.h @ 43:73813c1176de

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author John Tsiombikas <nuclear@member.fsf.org>
date Fri, 14 Aug 2015 04:33:42 +0300
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nuclear@26 1 /* deflate.h -- internal compression state
nuclear@26 2 * Copyright (C) 1995-2004 Jean-loup Gailly
nuclear@26 3 * For conditions of distribution and use, see copyright notice in zlib.h
nuclear@26 4 */
nuclear@26 5
nuclear@26 6 /* WARNING: this file should *not* be used by applications. It is
nuclear@26 7 part of the implementation of the compression library and is
nuclear@26 8 subject to change. Applications should only use zlib.h.
nuclear@26 9 */
nuclear@26 10
nuclear@26 11 /* @(#) $Id$ */
nuclear@26 12
nuclear@26 13 #ifndef DEFLATE_H
nuclear@26 14 #define DEFLATE_H
nuclear@26 15
nuclear@26 16 #include "zutil.h"
nuclear@26 17
nuclear@26 18 /* define NO_GZIP when compiling if you want to disable gzip header and
nuclear@26 19 trailer creation by deflate(). NO_GZIP would be used to avoid linking in
nuclear@26 20 the crc code when it is not needed. For shared libraries, gzip encoding
nuclear@26 21 should be left enabled. */
nuclear@26 22 #ifndef NO_GZIP
nuclear@26 23 # define GZIP
nuclear@26 24 #endif
nuclear@26 25
nuclear@26 26 /* ===========================================================================
nuclear@26 27 * Internal compression state.
nuclear@26 28 */
nuclear@26 29
nuclear@26 30 #define LENGTH_CODES 29
nuclear@26 31 /* number of length codes, not counting the special END_BLOCK code */
nuclear@26 32
nuclear@26 33 #define LITERALS 256
nuclear@26 34 /* number of literal bytes 0..255 */
nuclear@26 35
nuclear@26 36 #define L_CODES (LITERALS+1+LENGTH_CODES)
nuclear@26 37 /* number of Literal or Length codes, including the END_BLOCK code */
nuclear@26 38
nuclear@26 39 #define D_CODES 30
nuclear@26 40 /* number of distance codes */
nuclear@26 41
nuclear@26 42 #define BL_CODES 19
nuclear@26 43 /* number of codes used to transfer the bit lengths */
nuclear@26 44
nuclear@26 45 #define HEAP_SIZE (2*L_CODES+1)
nuclear@26 46 /* maximum heap size */
nuclear@26 47
nuclear@26 48 #define MAX_BITS 15
nuclear@26 49 /* All codes must not exceed MAX_BITS bits */
nuclear@26 50
nuclear@26 51 #define INIT_STATE 42
nuclear@26 52 #define EXTRA_STATE 69
nuclear@26 53 #define NAME_STATE 73
nuclear@26 54 #define COMMENT_STATE 91
nuclear@26 55 #define HCRC_STATE 103
nuclear@26 56 #define BUSY_STATE 113
nuclear@26 57 #define FINISH_STATE 666
nuclear@26 58 /* Stream status */
nuclear@26 59
nuclear@26 60
nuclear@26 61 /* Data structure describing a single value and its code string. */
nuclear@26 62 typedef struct ct_data_s {
nuclear@26 63 union {
nuclear@26 64 ush freq; /* frequency count */
nuclear@26 65 ush code; /* bit string */
nuclear@26 66 } fc;
nuclear@26 67 union {
nuclear@26 68 ush dad; /* father node in Huffman tree */
nuclear@26 69 ush len; /* length of bit string */
nuclear@26 70 } dl;
nuclear@26 71 } FAR ct_data;
nuclear@26 72
nuclear@26 73 #define Freq fc.freq
nuclear@26 74 #define Code fc.code
nuclear@26 75 #define Dad dl.dad
nuclear@26 76 #define Len dl.len
nuclear@26 77
nuclear@26 78 typedef struct static_tree_desc_s static_tree_desc;
nuclear@26 79
nuclear@26 80 typedef struct tree_desc_s {
nuclear@26 81 ct_data *dyn_tree; /* the dynamic tree */
nuclear@26 82 int max_code; /* largest code with non zero frequency */
nuclear@26 83 static_tree_desc *stat_desc; /* the corresponding static tree */
nuclear@26 84 } FAR tree_desc;
nuclear@26 85
nuclear@26 86 typedef ush Pos;
nuclear@26 87 typedef Pos FAR Posf;
nuclear@26 88 typedef unsigned IPos;
nuclear@26 89
nuclear@26 90 /* A Pos is an index in the character window. We use short instead of int to
nuclear@26 91 * save space in the various tables. IPos is used only for parameter passing.
nuclear@26 92 */
nuclear@26 93
nuclear@26 94 typedef struct internal_state {
nuclear@26 95 z_streamp strm; /* pointer back to this zlib stream */
nuclear@26 96 int status; /* as the name implies */
nuclear@26 97 Bytef *pending_buf; /* output still pending */
nuclear@26 98 ulg pending_buf_size; /* size of pending_buf */
nuclear@26 99 Bytef *pending_out; /* next pending byte to output to the stream */
nuclear@26 100 uInt pending; /* nb of bytes in the pending buffer */
nuclear@26 101 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
nuclear@26 102 gz_headerp gzhead; /* gzip header information to write */
nuclear@26 103 uInt gzindex; /* where in extra, name, or comment */
nuclear@26 104 Byte method; /* STORED (for zip only) or DEFLATED */
nuclear@26 105 int last_flush; /* value of flush param for previous deflate call */
nuclear@26 106
nuclear@26 107 /* used by deflate.c: */
nuclear@26 108
nuclear@26 109 uInt w_size; /* LZ77 window size (32K by default) */
nuclear@26 110 uInt w_bits; /* log2(w_size) (8..16) */
nuclear@26 111 uInt w_mask; /* w_size - 1 */
nuclear@26 112
nuclear@26 113 Bytef *window;
nuclear@26 114 /* Sliding window. Input bytes are read into the second half of the window,
nuclear@26 115 * and move to the first half later to keep a dictionary of at least wSize
nuclear@26 116 * bytes. With this organization, matches are limited to a distance of
nuclear@26 117 * wSize-MAX_MATCH bytes, but this ensures that IO is always
nuclear@26 118 * performed with a length multiple of the block size. Also, it limits
nuclear@26 119 * the window size to 64K, which is quite useful on MSDOS.
nuclear@26 120 * To do: use the user input buffer as sliding window.
nuclear@26 121 */
nuclear@26 122
nuclear@26 123 ulg window_size;
nuclear@26 124 /* Actual size of window: 2*wSize, except when the user input buffer
nuclear@26 125 * is directly used as sliding window.
nuclear@26 126 */
nuclear@26 127
nuclear@26 128 Posf *prev;
nuclear@26 129 /* Link to older string with same hash index. To limit the size of this
nuclear@26 130 * array to 64K, this link is maintained only for the last 32K strings.
nuclear@26 131 * An index in this array is thus a window index modulo 32K.
nuclear@26 132 */
nuclear@26 133
nuclear@26 134 Posf *head; /* Heads of the hash chains or NIL. */
nuclear@26 135
nuclear@26 136 uInt ins_h; /* hash index of string to be inserted */
nuclear@26 137 uInt hash_size; /* number of elements in hash table */
nuclear@26 138 uInt hash_bits; /* log2(hash_size) */
nuclear@26 139 uInt hash_mask; /* hash_size-1 */
nuclear@26 140
nuclear@26 141 uInt hash_shift;
nuclear@26 142 /* Number of bits by which ins_h must be shifted at each input
nuclear@26 143 * step. It must be such that after MIN_MATCH steps, the oldest
nuclear@26 144 * byte no longer takes part in the hash key, that is:
nuclear@26 145 * hash_shift * MIN_MATCH >= hash_bits
nuclear@26 146 */
nuclear@26 147
nuclear@26 148 long block_start;
nuclear@26 149 /* Window position at the beginning of the current output block. Gets
nuclear@26 150 * negative when the window is moved backwards.
nuclear@26 151 */
nuclear@26 152
nuclear@26 153 uInt match_length; /* length of best match */
nuclear@26 154 IPos prev_match; /* previous match */
nuclear@26 155 int match_available; /* set if previous match exists */
nuclear@26 156 uInt strstart; /* start of string to insert */
nuclear@26 157 uInt match_start; /* start of matching string */
nuclear@26 158 uInt lookahead; /* number of valid bytes ahead in window */
nuclear@26 159
nuclear@26 160 uInt prev_length;
nuclear@26 161 /* Length of the best match at previous step. Matches not greater than this
nuclear@26 162 * are discarded. This is used in the lazy match evaluation.
nuclear@26 163 */
nuclear@26 164
nuclear@26 165 uInt max_chain_length;
nuclear@26 166 /* To speed up deflation, hash chains are never searched beyond this
nuclear@26 167 * length. A higher limit improves compression ratio but degrades the
nuclear@26 168 * speed.
nuclear@26 169 */
nuclear@26 170
nuclear@26 171 uInt max_lazy_match;
nuclear@26 172 /* Attempt to find a better match only when the current match is strictly
nuclear@26 173 * smaller than this value. This mechanism is used only for compression
nuclear@26 174 * levels >= 4.
nuclear@26 175 */
nuclear@26 176 # define max_insert_length max_lazy_match
nuclear@26 177 /* Insert new strings in the hash table only if the match length is not
nuclear@26 178 * greater than this length. This saves time but degrades compression.
nuclear@26 179 * max_insert_length is used only for compression levels <= 3.
nuclear@26 180 */
nuclear@26 181
nuclear@26 182 int level; /* compression level (1..9) */
nuclear@26 183 int strategy; /* favor or force Huffman coding*/
nuclear@26 184
nuclear@26 185 uInt good_match;
nuclear@26 186 /* Use a faster search when the previous match is longer than this */
nuclear@26 187
nuclear@26 188 int nice_match; /* Stop searching when current match exceeds this */
nuclear@26 189
nuclear@26 190 /* used by trees.c: */
nuclear@26 191 /* Didn't use ct_data typedef below to supress compiler warning */
nuclear@26 192 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */
nuclear@26 193 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
nuclear@26 194 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */
nuclear@26 195
nuclear@26 196 struct tree_desc_s l_desc; /* desc. for literal tree */
nuclear@26 197 struct tree_desc_s d_desc; /* desc. for distance tree */
nuclear@26 198 struct tree_desc_s bl_desc; /* desc. for bit length tree */
nuclear@26 199
nuclear@26 200 ush bl_count[MAX_BITS+1];
nuclear@26 201 /* number of codes at each bit length for an optimal tree */
nuclear@26 202
nuclear@26 203 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
nuclear@26 204 int heap_len; /* number of elements in the heap */
nuclear@26 205 int heap_max; /* element of largest frequency */
nuclear@26 206 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
nuclear@26 207 * The same heap array is used to build all trees.
nuclear@26 208 */
nuclear@26 209
nuclear@26 210 uch depth[2*L_CODES+1];
nuclear@26 211 /* Depth of each subtree used as tie breaker for trees of equal frequency
nuclear@26 212 */
nuclear@26 213
nuclear@26 214 uchf *l_buf; /* buffer for literals or lengths */
nuclear@26 215
nuclear@26 216 uInt lit_bufsize;
nuclear@26 217 /* Size of match buffer for literals/lengths. There are 4 reasons for
nuclear@26 218 * limiting lit_bufsize to 64K:
nuclear@26 219 * - frequencies can be kept in 16 bit counters
nuclear@26 220 * - if compression is not successful for the first block, all input
nuclear@26 221 * data is still in the window so we can still emit a stored block even
nuclear@26 222 * when input comes from standard input. (This can also be done for
nuclear@26 223 * all blocks if lit_bufsize is not greater than 32K.)
nuclear@26 224 * - if compression is not successful for a file smaller than 64K, we can
nuclear@26 225 * even emit a stored file instead of a stored block (saving 5 bytes).
nuclear@26 226 * This is applicable only for zip (not gzip or zlib).
nuclear@26 227 * - creating new Huffman trees less frequently may not provide fast
nuclear@26 228 * adaptation to changes in the input data statistics. (Take for
nuclear@26 229 * example a binary file with poorly compressible code followed by
nuclear@26 230 * a highly compressible string table.) Smaller buffer sizes give
nuclear@26 231 * fast adaptation but have of course the overhead of transmitting
nuclear@26 232 * trees more frequently.
nuclear@26 233 * - I can't count above 4
nuclear@26 234 */
nuclear@26 235
nuclear@26 236 uInt last_lit; /* running index in l_buf */
nuclear@26 237
nuclear@26 238 ushf *d_buf;
nuclear@26 239 /* Buffer for distances. To simplify the code, d_buf and l_buf have
nuclear@26 240 * the same number of elements. To use different lengths, an extra flag
nuclear@26 241 * array would be necessary.
nuclear@26 242 */
nuclear@26 243
nuclear@26 244 ulg opt_len; /* bit length of current block with optimal trees */
nuclear@26 245 ulg static_len; /* bit length of current block with static trees */
nuclear@26 246 uInt matches; /* number of string matches in current block */
nuclear@26 247 int last_eob_len; /* bit length of EOB code for last block */
nuclear@26 248
nuclear@26 249 #ifdef DEBUG
nuclear@26 250 ulg compressed_len; /* total bit length of compressed file mod 2^32 */
nuclear@26 251 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */
nuclear@26 252 #endif
nuclear@26 253
nuclear@26 254 ush bi_buf;
nuclear@26 255 /* Output buffer. bits are inserted starting at the bottom (least
nuclear@26 256 * significant bits).
nuclear@26 257 */
nuclear@26 258 int bi_valid;
nuclear@26 259 /* Number of valid bits in bi_buf. All bits above the last valid bit
nuclear@26 260 * are always zero.
nuclear@26 261 */
nuclear@26 262
nuclear@26 263 } FAR deflate_state;
nuclear@26 264
nuclear@26 265 /* Output a byte on the stream.
nuclear@26 266 * IN assertion: there is enough room in pending_buf.
nuclear@26 267 */
nuclear@26 268 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
nuclear@26 269
nuclear@26 270
nuclear@26 271 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
nuclear@26 272 /* Minimum amount of lookahead, except at the end of the input file.
nuclear@26 273 * See deflate.c for comments about the MIN_MATCH+1.
nuclear@26 274 */
nuclear@26 275
nuclear@26 276 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
nuclear@26 277 /* In order to simplify the code, particularly on 16 bit machines, match
nuclear@26 278 * distances are limited to MAX_DIST instead of WSIZE.
nuclear@26 279 */
nuclear@26 280
nuclear@26 281 /* in trees.c */
nuclear@26 282 void _tr_init OF((deflate_state *s));
nuclear@26 283 int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
nuclear@26 284 void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len,
nuclear@26 285 int eof));
nuclear@26 286 void _tr_align OF((deflate_state *s));
nuclear@26 287 void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
nuclear@26 288 int eof));
nuclear@26 289
nuclear@26 290 #define d_code(dist) \
nuclear@26 291 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
nuclear@26 292 /* Mapping from a distance to a distance code. dist is the distance - 1 and
nuclear@26 293 * must not have side effects. _dist_code[256] and _dist_code[257] are never
nuclear@26 294 * used.
nuclear@26 295 */
nuclear@26 296
nuclear@26 297 #ifndef DEBUG
nuclear@26 298 /* Inline versions of _tr_tally for speed: */
nuclear@26 299
nuclear@26 300 #if defined(GEN_TREES_H) || !defined(STDC)
nuclear@26 301 extern uch _length_code[];
nuclear@26 302 extern uch _dist_code[];
nuclear@26 303 #else
nuclear@26 304 extern const uch _length_code[];
nuclear@26 305 extern const uch _dist_code[];
nuclear@26 306 #endif
nuclear@26 307
nuclear@26 308 # define _tr_tally_lit(s, c, flush) \
nuclear@26 309 { uch cc = (c); \
nuclear@26 310 s->d_buf[s->last_lit] = 0; \
nuclear@26 311 s->l_buf[s->last_lit++] = cc; \
nuclear@26 312 s->dyn_ltree[cc].Freq++; \
nuclear@26 313 flush = (s->last_lit == s->lit_bufsize-1); \
nuclear@26 314 }
nuclear@26 315 # define _tr_tally_dist(s, distance, length, flush) \
nuclear@26 316 { uch len = (length); \
nuclear@26 317 ush dist = (distance); \
nuclear@26 318 s->d_buf[s->last_lit] = dist; \
nuclear@26 319 s->l_buf[s->last_lit++] = len; \
nuclear@26 320 dist--; \
nuclear@26 321 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
nuclear@26 322 s->dyn_dtree[d_code(dist)].Freq++; \
nuclear@26 323 flush = (s->last_lit == s->lit_bufsize-1); \
nuclear@26 324 }
nuclear@26 325 #else
nuclear@26 326 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
nuclear@26 327 # define _tr_tally_dist(s, distance, length, flush) \
nuclear@26 328 flush = _tr_tally(s, distance, length)
nuclear@26 329 #endif
nuclear@26 330
nuclear@26 331 #endif /* DEFLATE_H */