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annotate libs/zlib/deflate.h @ 13:ea928c313344

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