1 /* deflate.h -- internal compression state
2 * Copyright (C) 1995-2016 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 1.1.1.2 2002/03/11 21:53:23 tromey Exp $ */
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 /* zlib header -> BUSY_STATE */
55 #ifdef GZIP
56 # define GZIP_STATE 57 /* gzip header -> BUSY_STATE | EXTRA_STATE */
57 #endif
58 #define EXTRA_STATE 69 /* gzip extra block -> NAME_STATE */
59 #define NAME_STATE 73 /* gzip file name -> COMMENT_STATE */
60 #define COMMENT_STATE 91 /* gzip comment -> HCRC_STATE */
61 #define HCRC_STATE 103 /* gzip header CRC -> BUSY_STATE */
62 #define BUSY_STATE 113 /* deflate -> FINISH_STATE */
63 #define FINISH_STATE 666 /* stream complete */
64 /* Stream status */
65
66
67 /* Data structure describing a single value and its code string. */
68 typedef struct ct_data_s {
69 union {
70 ush freq; /* frequency count */
71 ush code; /* bit string */
72 } fc;
73 union {
74 ush dad; /* father node in Huffman tree */
75 ush len; /* length of bit string */
76 } dl;
77 } FAR ct_data;
78
79 #define Freq fc.freq
80 #define Code fc.code
81 #define Dad dl.dad
82 #define Len dl.len
83
84 typedef struct static_tree_desc_s static_tree_desc;
85
86 typedef struct tree_desc_s {
87 ct_data *dyn_tree; /* the dynamic tree */
88 int max_code; /* largest code with non zero frequency */
89 const static_tree_desc *stat_desc; /* the corresponding static tree */
90 } FAR tree_desc;
91
92 typedef ush Pos;
93 typedef Pos FAR Posf;
94 typedef unsigned IPos;
95
96 /* A Pos is an index in the character window. We use short instead of int to
97 * save space in the various tables. IPos is used only for parameter passing.
98 */
99
100 typedef struct internal_state {
101 z_streamp strm; /* pointer back to this zlib stream */
102 int status; /* as the name implies */
103 Bytef *pending_buf; /* output still pending */
104 ulg pending_buf_size; /* size of pending_buf */
105 Bytef *pending_out; /* next pending byte to output to the stream */
106 ulg pending; /* nb of bytes in the pending buffer */
107 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
108 gz_headerp gzhead; /* gzip header information to write */
109 ulg gzindex; /* where in extra, name, or comment */
110 Byte method; /* can only be DEFLATED */
111 int last_flush; /* value of flush param for previous deflate call */
112
113 /* used by deflate.c: */
114
115 uInt w_size; /* LZ77 window size (32K by default) */
116 uInt w_bits; /* log2(w_size) (8..16) */
117 uInt w_mask; /* w_size - 1 */
118
119 Bytef *window;
120 /* Sliding window. Input bytes are read into the second half of the window,
121 * and move to the first half later to keep a dictionary of at least wSize
122 * bytes. With this organization, matches are limited to a distance of
123 * wSize-MAX_MATCH bytes, but this ensures that IO is always
124 * performed with a length multiple of the block size. Also, it limits
125 * the window size to 64K, which is quite useful on MSDOS.
126 * To do: use the user input buffer as sliding window.
127 */
128
129 ulg window_size;
130 /* Actual size of window: 2*wSize, except when the user input buffer
131 * is directly used as sliding window.
132 */
133
134 Posf *prev;
135 /* Link to older string with same hash index. To limit the size of this
136 * array to 64K, this link is maintained only for the last 32K strings.
137 * An index in this array is thus a window index modulo 32K.
138 */
139
140 Posf *head; /* Heads of the hash chains or NIL. */
141
142 uInt ins_h; /* hash index of string to be inserted */
143 uInt hash_size; /* number of elements in hash table */
144 uInt hash_bits; /* log2(hash_size) */
145 uInt hash_mask; /* hash_size-1 */
146
147 uInt hash_shift;
148 /* Number of bits by which ins_h must be shifted at each input
149 * step. It must be such that after MIN_MATCH steps, the oldest
150 * byte no longer takes part in the hash key, that is:
151 * hash_shift * MIN_MATCH >= hash_bits
152 */
153
154 long block_start;
155 /* Window position at the beginning of the current output block. Gets
156 * negative when the window is moved backwards.
157 */
158
159 uInt match_length; /* length of best match */
160 IPos prev_match; /* previous match */
161 int match_available; /* set if previous match exists */
162 uInt strstart; /* start of string to insert */
163 uInt match_start; /* start of matching string */
164 uInt lookahead; /* number of valid bytes ahead in window */
165
166 uInt prev_length;
167 /* Length of the best match at previous step. Matches not greater than this
168 * are discarded. This is used in the lazy match evaluation.
169 */
170
171 uInt max_chain_length;
172 /* To speed up deflation, hash chains are never searched beyond this
173 * length. A higher limit improves compression ratio but degrades the
174 * speed.
175 */
176
177 uInt max_lazy_match;
178 /* Attempt to find a better match only when the current match is strictly
179 * smaller than this value. This mechanism is used only for compression
180 * levels >= 4.
181 */
182 # define max_insert_length max_lazy_match
183 /* Insert new strings in the hash table only if the match length is not
184 * greater than this length. This saves time but degrades compression.
185 * max_insert_length is used only for compression levels <= 3.
186 */
187
188 int level; /* compression level (1..9) */
189 int strategy; /* favor or force Huffman coding*/
190
191 uInt good_match;
192 /* Use a faster search when the previous match is longer than this */
193
194 int nice_match; /* Stop searching when current match exceeds this */
195
196 /* used by trees.c: */
197 /* Didn't use ct_data typedef below to suppress compiler warning */
198 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */
199 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
200 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */
201
202 struct tree_desc_s l_desc; /* desc. for literal tree */
203 struct tree_desc_s d_desc; /* desc. for distance tree */
204 struct tree_desc_s bl_desc; /* desc. for bit length tree */
205
206 ush bl_count[MAX_BITS+1];
207 /* number of codes at each bit length for an optimal tree */
208
209 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
210 int heap_len; /* number of elements in the heap */
211 int heap_max; /* element of largest frequency */
212 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
213 * The same heap array is used to build all trees.
214 */
215
216 uch depth[2*L_CODES+1];
217 /* Depth of each subtree used as tie breaker for trees of equal frequency
218 */
219
220 uchf *l_buf; /* buffer for literals or lengths */
221
222 uInt lit_bufsize;
223 /* Size of match buffer for literals/lengths. There are 4 reasons for
224 * limiting lit_bufsize to 64K:
225 * - frequencies can be kept in 16 bit counters
226 * - if compression is not successful for the first block, all input
227 * data is still in the window so we can still emit a stored block even
228 * when input comes from standard input. (This can also be done for
229 * all blocks if lit_bufsize is not greater than 32K.)
230 * - if compression is not successful for a file smaller than 64K, we can
231 * even emit a stored file instead of a stored block (saving 5 bytes).
232 * This is applicable only for zip (not gzip or zlib).
233 * - creating new Huffman trees less frequently may not provide fast
234 * adaptation to changes in the input data statistics. (Take for
235 * example a binary file with poorly compressible code followed by
236 * a highly compressible string table.) Smaller buffer sizes give
237 * fast adaptation but have of course the overhead of transmitting
238 * trees more frequently.
239 * - I can't count above 4
240 */
241
242 uInt last_lit; /* running index in l_buf */
243
244 ushf *d_buf;
245 /* Buffer for distances. To simplify the code, d_buf and l_buf have
246 * the same number of elements. To use different lengths, an extra flag
247 * array would be necessary.
248 */
249
250 ulg opt_len; /* bit length of current block with optimal trees */
251 ulg static_len; /* bit length of current block with static trees */
252 uInt matches; /* number of string matches in current block */
253 uInt insert; /* bytes at end of window left to insert */
254
255 #ifdef ZLIB_DEBUG
256 ulg compressed_len; /* total bit length of compressed file mod 2^32 */
257 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */
258 #endif
259
260 ush bi_buf;
261 /* Output buffer. bits are inserted starting at the bottom (least
262 * significant bits).
263 */
264 int bi_valid;
265 /* Number of valid bits in bi_buf. All bits above the last valid bit
266 * are always zero.
267 */
268
269 ulg high_water;
270 /* High water mark offset in window for initialized bytes -- bytes above
271 * this are set to zero in order to avoid memory check warnings when
272 * longest match routines access bytes past the input. This is then
273 * updated to the new high water mark.
274 */
275
276 } FAR deflate_state;
277
278 /* Output a byte on the stream.
279 * IN assertion: there is enough room in pending_buf.
280 */
281 #define put_byte(s, c) {s->pending_buf[s->pending++] = (Bytef)(c);}
282
283
284 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
285 /* Minimum amount of lookahead, except at the end of the input file.
286 * See deflate.c for comments about the MIN_MATCH+1.
287 */
288
289 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
290 /* In order to simplify the code, particularly on 16 bit machines, match
291 * distances are limited to MAX_DIST instead of WSIZE.
292 */
293
294 #define WIN_INIT MAX_MATCH
295 /* Number of bytes after end of data in window to initialize in order to avoid
296 memory checker errors from longest match routines */
297
298 /* in trees.c */
299 void ZLIB_INTERNAL _tr_init OF((deflate_state *s));
300 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
301 void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf,
302 ulg stored_len, int last));
303 void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s));
304 void ZLIB_INTERNAL _tr_align OF((deflate_state *s));
305 void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
306 ulg stored_len, int last));
307
308 #define d_code(dist) \
309 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
310 /* Mapping from a distance to a distance code. dist is the distance - 1 and
311 * must not have side effects. _dist_code[256] and _dist_code[257] are never
312 * used.
313 */
314
315 #ifndef ZLIB_DEBUG
316 /* Inline versions of _tr_tally for speed: */
317
318 #if defined(GEN_TREES_H) || !defined(STDC)
319 extern uch ZLIB_INTERNAL _length_code[];
320 extern uch ZLIB_INTERNAL _dist_code[];
321 #else
322 extern const uch ZLIB_INTERNAL _length_code[];
323 extern const uch ZLIB_INTERNAL _dist_code[];
324 #endif
325
326 # define _tr_tally_lit(s, c, flush) \
327 { uch cc = (c); \
328 s->d_buf[s->last_lit] = 0; \
329 s->l_buf[s->last_lit++] = cc; \
330 s->dyn_ltree[cc].Freq++; \
331 flush = (s->last_lit == s->lit_bufsize-1); \
332 }
333 # define _tr_tally_dist(s, distance, length, flush) \
334 { uch len = (uch)(length); \
335 ush dist = (ush)(distance); \
336 s->d_buf[s->last_lit] = dist; \
337 s->l_buf[s->last_lit++] = len; \
338 dist--; \
339 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
340 s->dyn_dtree[d_code(dist)].Freq++; \
341 flush = (s->last_lit == s->lit_bufsize-1); \
342 }
343 #else
344 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
345 # define _tr_tally_dist(s, distance, length, flush) \
346 flush = _tr_tally(s, distance, length)
347 #endif
348
349 #endif /* DEFLATE_H */