1 /* deflate.h -- internal compression state
2 * Copyright (C) 1995-2012 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 Buf_size 16
52 /* size of bit buffer in bi_buf */
53
54 #define INIT_STATE 42
55 #define EXTRA_STATE 69
56 #define NAME_STATE 73
57 #define COMMENT_STATE 91
58 #define HCRC_STATE 103
59 #define BUSY_STATE 113
60 #define FINISH_STATE 666
61 /* Stream status */
62
63
64 /* Data structure describing a single value and its code string. */
65 typedef struct ct_data_s {
66 union {
67 ush freq; /* frequency count */
68 ush code; /* bit string */
69 } fc;
70 union {
71 ush dad; /* father node in Huffman tree */
72 ush len; /* length of bit string */
73 } dl;
74 } FAR ct_data;
75
76 #define Freq fc.freq
77 #define Code fc.code
78 #define Dad dl.dad
79 #define Len dl.len
80
81 typedef struct static_tree_desc_s static_tree_desc;
82
83 typedef struct tree_desc_s {
84 ct_data *dyn_tree; /* the dynamic tree */
85 int max_code; /* largest code with non zero frequency */
86 static_tree_desc *stat_desc; /* the corresponding static tree */
87 } FAR tree_desc;
88
89 typedef ush Pos;
90 typedef Pos FAR Posf;
91 typedef unsigned IPos;
92
93 /* A Pos is an index in the character window. We use short instead of int to
94 * save space in the various tables. IPos is used only for parameter passing.
95 */
96
97 typedef struct internal_state {
98 z_streamp strm; /* pointer back to this zlib stream */
99 int status; /* as the name implies */
100 Bytef *pending_buf; /* output still pending */
101 ulg pending_buf_size; /* size of pending_buf */
102 Bytef *pending_out; /* next pending byte to output to the stream */
103 uInt pending; /* nb of bytes in the pending buffer */
104 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
105 gz_headerp gzhead; /* gzip header information to write */
106 uInt gzindex; /* where in extra, name, or comment */
107 Byte method; /* can only be DEFLATED */
108 int last_flush; /* value of flush param for previous deflate call */
109
110 /* used by deflate.c: */
111
112 uInt w_size; /* LZ77 window size (32K by default) */
113 uInt w_bits; /* log2(w_size) (8..16) */
114 uInt w_mask; /* w_size - 1 */
115
116 Bytef *window;
117 /* Sliding window. Input bytes are read into the second half of the window,
118 * and move to the first half later to keep a dictionary of at least wSize
119 * bytes. With this organization, matches are limited to a distance of
120 * wSize-MAX_MATCH bytes, but this ensures that IO is always
121 * performed with a length multiple of the block size. Also, it limits
122 * the window size to 64K, which is quite useful on MSDOS.
123 * To do: use the user input buffer as sliding window.
124 */
125
126 ulg window_size;
127 /* Actual size of window: 2*wSize, except when the user input buffer
128 * is directly used as sliding window.
129 */
130
131 Posf *prev;
132 /* Link to older string with same hash index. To limit the size of this
133 * array to 64K, this link is maintained only for the last 32K strings.
134 * An index in this array is thus a window index modulo 32K.
135 */
136
137 Posf *head; /* Heads of the hash chains or NIL. */
138
139 uInt ins_h; /* hash index of string to be inserted */
140 uInt hash_size; /* number of elements in hash table */
141 uInt hash_bits; /* log2(hash_size) */
142 uInt hash_mask; /* hash_size-1 */
143
144 uInt hash_shift;
145 /* Number of bits by which ins_h must be shifted at each input
146 * step. It must be such that after MIN_MATCH steps, the oldest
147 * byte no longer takes part in the hash key, that is:
148 * hash_shift * MIN_MATCH >= hash_bits
149 */
150
151 long block_start;
152 /* Window position at the beginning of the current output block. Gets
153 * negative when the window is moved backwards.
154 */
155
156 uInt match_length; /* length of best match */
157 IPos prev_match; /* previous match */
158 int match_available; /* set if previous match exists */
159 uInt strstart; /* start of string to insert */
160 uInt match_start; /* start of matching string */
161 uInt lookahead; /* number of valid bytes ahead in window */
162
163 uInt prev_length;
164 /* Length of the best match at previous step. Matches not greater than this
165 * are discarded. This is used in the lazy match evaluation.
166 */
167
168 uInt max_chain_length;
169 /* To speed up deflation, hash chains are never searched beyond this
170 * length. A higher limit improves compression ratio but degrades the
171 * speed.
172 */
173
174 uInt max_lazy_match;
175 /* Attempt to find a better match only when the current match is strictly
176 * smaller than this value. This mechanism is used only for compression
177 * levels >= 4.
178 */
179 # define max_insert_length max_lazy_match
180 /* Insert new strings in the hash table only if the match length is not
181 * greater than this length. This saves time but degrades compression.
182 * max_insert_length is used only for compression levels <= 3.
183 */
184
185 int level; /* compression level (1..9) */
186 int strategy; /* favor or force Huffman coding*/
187
188 uInt good_match;
189 /* Use a faster search when the previous match is longer than this */
190
191 int nice_match; /* Stop searching when current match exceeds this */
192
193 /* used by trees.c: */
194 /* Didn't use ct_data typedef below to suppress compiler warning */
195 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */
196 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
197 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */
198
199 struct tree_desc_s l_desc; /* desc. for literal tree */
200 struct tree_desc_s d_desc; /* desc. for distance tree */
201 struct tree_desc_s bl_desc; /* desc. for bit length tree */
202
203 ush bl_count[MAX_BITS+1];
204 /* number of codes at each bit length for an optimal tree */
205
206 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
207 int heap_len; /* number of elements in the heap */
208 int heap_max; /* element of largest frequency */
209 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
210 * The same heap array is used to build all trees.
211 */
212
213 uch depth[2*L_CODES+1];
214 /* Depth of each subtree used as tie breaker for trees of equal frequency
215 */
216
217 uchf *l_buf; /* buffer for literals or lengths */
218
219 uInt lit_bufsize;
220 /* Size of match buffer for literals/lengths. There are 4 reasons for
221 * limiting lit_bufsize to 64K:
222 * - frequencies can be kept in 16 bit counters
223 * - if compression is not successful for the first block, all input
224 * data is still in the window so we can still emit a stored block even
225 * when input comes from standard input. (This can also be done for
226 * all blocks if lit_bufsize is not greater than 32K.)
227 * - if compression is not successful for a file smaller than 64K, we can
228 * even emit a stored file instead of a stored block (saving 5 bytes).
229 * This is applicable only for zip (not gzip or zlib).
230 * - creating new Huffman trees less frequently may not provide fast
231 * adaptation to changes in the input data statistics. (Take for
232 * example a binary file with poorly compressible code followed by
233 * a highly compressible string table.) Smaller buffer sizes give
234 * fast adaptation but have of course the overhead of transmitting
235 * trees more frequently.
236 * - I can't count above 4
237 */
238
239 uInt last_lit; /* running index in l_buf */
240
241 ushf *d_buf;
242 /* Buffer for distances. To simplify the code, d_buf and l_buf have
243 * the same number of elements. To use different lengths, an extra flag
244 * array would be necessary.
245 */
246
247 ulg opt_len; /* bit length of current block with optimal trees */
248 ulg static_len; /* bit length of current block with static trees */
249 uInt matches; /* number of string matches in current block */
250 uInt insert; /* bytes at end of window left to insert */
251
252 #ifdef DEBUG
253 ulg compressed_len; /* total bit length of compressed file mod 2^32 */
254 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */
255 #endif
256
257 ush bi_buf;
258 /* Output buffer. bits are inserted starting at the bottom (least
259 * significant bits).
260 */
261 int bi_valid;
262 /* Number of valid bits in bi_buf. All bits above the last valid bit
263 * are always zero.
264 */
265
266 ulg high_water;
267 /* High water mark offset in window for initialized bytes -- bytes above
268 * this are set to zero in order to avoid memory check warnings when
269 * longest match routines access bytes past the input. This is then
270 * updated to the new high water mark.
271 */
272
273 } FAR deflate_state;
274
275 /* Output a byte on the stream.
276 * IN assertion: there is enough room in pending_buf.
277 */
278 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
279
280
281 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
282 /* Minimum amount of lookahead, except at the end of the input file.
283 * See deflate.c for comments about the MIN_MATCH+1.
284 */
285
286 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
287 /* In order to simplify the code, particularly on 16 bit machines, match
288 * distances are limited to MAX_DIST instead of WSIZE.
289 */
290
291 #define WIN_INIT MAX_MATCH
292 /* Number of bytes after end of data in window to initialize in order to avoid
293 memory checker errors from longest match routines */
294
295 /* in trees.c */
296 void ZLIB_INTERNAL _tr_init OF((deflate_state *s));
297 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
298 void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf,
299 ulg stored_len, int last));
300 void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s));
301 void ZLIB_INTERNAL _tr_align OF((deflate_state *s));
302 void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
303 ulg stored_len, int last));
304
305 #define d_code(dist) \
306 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
307 /* Mapping from a distance to a distance code. dist is the distance - 1 and
308 * must not have side effects. _dist_code[256] and _dist_code[257] are never
309 * used.
310 */
311
312 #ifndef DEBUG
313 /* Inline versions of _tr_tally for speed: */
314
315 #if defined(GEN_TREES_H) || !defined(STDC)
316 extern uch ZLIB_INTERNAL _length_code[];
317 extern uch ZLIB_INTERNAL _dist_code[];
318 #else
319 extern const uch ZLIB_INTERNAL _length_code[];
320 extern const uch ZLIB_INTERNAL _dist_code[];
321 #endif
322
323 # define _tr_tally_lit(s, c, flush) \
324 { uch cc = (c); \
325 s->d_buf[s->last_lit] = 0; \
326 s->l_buf[s->last_lit++] = cc; \
327 s->dyn_ltree[cc].Freq++; \
328 flush = (s->last_lit == s->lit_bufsize-1); \
329 }
330 # define _tr_tally_dist(s, distance, length, flush) \
331 { uch len = (length); \
332 ush dist = (distance); \
333 s->d_buf[s->last_lit] = dist; \
334 s->l_buf[s->last_lit++] = len; \
335 dist--; \
336 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
337 s->dyn_dtree[d_code(dist)].Freq++; \
338 flush = (s->last_lit == s->lit_bufsize-1); \
339 }
340 #else
341 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
342 # define _tr_tally_dist(s, distance, length, flush) \
343 flush = _tr_tally(s, distance, length)
344 #endif
345
346 #endif /* DEFLATE_H */