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---
deflate.h (12159B)
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1 /* deflate.h -- internal compression state
2 * Copyright (C) 1995-2004 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 1925 2005-10-06 19:32:02Z baford $ */
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 INIT_STATE 42
52 #define EXTRA_STATE 69
53 #define NAME_STATE 73
54 #define COMMENT_STATE 91
55 #define HCRC_STATE 103
56 #define BUSY_STATE 113
57 #define FINISH_STATE 666
58 /* Stream status */
59
60
61 /* Data structure describing a single value and its code string. */
62 typedef struct ct_data_s {
63 union {
64 ush freq; /* frequency count */
65 ush code; /* bit string */
66 } fc;
67 union {
68 ush dad; /* father node in Huffman tree */
69 ush len; /* length of bit string */
70 } dl;
71 } FAR ct_data;
72
73 #define Freq fc.freq
74 #define Code fc.code
75 #define Dad dl.dad
76 #define Len dl.len
77
78 typedef struct static_tree_desc_s static_tree_desc;
79
80 typedef struct tree_desc_s {
81 ct_data *dyn_tree; /* the dynamic tree */
82 int max_code; /* largest code with non zero frequency */
83 static_tree_desc *stat_desc; /* the corresponding static tree */
84 } FAR tree_desc;
85
86 typedef ush Pos;
87 typedef Pos FAR Posf;
88 typedef unsigned IPos;
89
90 /* A Pos is an index in the character window. We use short instead of int to
91 * save space in the various tables. IPos is used only for parameter passing.
92 */
93
94 typedef struct internal_state {
95 z_streamp strm; /* pointer back to this zlib stream */
96 int status; /* as the name implies */
97 Bytef *pending_buf; /* output still pending */
98 ulg pending_buf_size; /* size of pending_buf */
99 Bytef *pending_out; /* next pending byte to output to the stream */
100 uInt pending; /* nb of bytes in the pending buffer */
101 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
102 gz_headerp gzhead; /* gzip header information to write */
103 uInt gzindex; /* where in extra, name, or comment */
104 Byte method; /* STORED (for zip only) or DEFLATED */
105 int last_flush; /* value of flush param for previous deflate call */
106
107 /* used by deflate.c: */
108
109 uInt w_size; /* LZ77 window size (32K by default) */
110 uInt w_bits; /* log2(w_size) (8..16) */
111 uInt w_mask; /* w_size - 1 */
112
113 Bytef *window;
114 /* Sliding window. Input bytes are read into the second half of the window,
115 * and move to the first half later to keep a dictionary of at least wSize
116 * bytes. With this organization, matches are limited to a distance of
117 * wSize-MAX_MATCH bytes, but this ensures that IO is always
118 * performed with a length multiple of the block size. Also, it limits
119 * the window size to 64K, which is quite useful on MSDOS.
120 * To do: use the user input buffer as sliding window.
121 */
122
123 ulg window_size;
124 /* Actual size of window: 2*wSize, except when the user input buffer
125 * is directly used as sliding window.
126 */
127
128 Posf *prev;
129 /* Link to older string with same hash index. To limit the size of this
130 * array to 64K, this link is maintained only for the last 32K strings.
131 * An index in this array is thus a window index modulo 32K.
132 */
133
134 Posf *head; /* Heads of the hash chains or NIL. */
135
136 uInt ins_h; /* hash index of string to be inserted */
137 uInt hash_size; /* number of elements in hash table */
138 uInt hash_bits; /* log2(hash_size) */
139 uInt hash_mask; /* hash_size-1 */
140
141 uInt hash_shift;
142 /* Number of bits by which ins_h must be shifted at each input
143 * step. It must be such that after MIN_MATCH steps, the oldest
144 * byte no longer takes part in the hash key, that is:
145 * hash_shift * MIN_MATCH >= hash_bits
146 */
147
148 long block_start;
149 /* Window position at the beginning of the current output block. Gets
150 * negative when the window is moved backwards.
151 */
152
153 uInt match_length; /* length of best match */
154 IPos prev_match; /* previous match */
155 int match_available; /* set if previous match exists */
156 uInt strstart; /* start of string to insert */
157 uInt match_start; /* start of matching string */
158 uInt lookahead; /* number of valid bytes ahead in window */
159
160 uInt prev_length;
161 /* Length of the best match at previous step. Matches not greater than this
162 * are discarded. This is used in the lazy match evaluation.
163 */
164
165 uInt max_chain_length;
166 /* To speed up deflation, hash chains are never searched beyond this
167 * length. A higher limit improves compression ratio but degrades the
168 * speed.
169 */
170
171 uInt max_lazy_match;
172 /* Attempt to find a better match only when the current match is strictly
173 * smaller than this value. This mechanism is used only for compression
174 * levels >= 4.
175 */
176 # define max_insert_length max_lazy_match
177 /* Insert new strings in the hash table only if the match length is not
178 * greater than this length. This saves time but degrades compression.
179 * max_insert_length is used only for compression levels <= 3.
180 */
181
182 int level; /* compression level (1..9) */
183 int strategy; /* favor or force Huffman coding*/
184
185 uInt good_match;
186 /* Use a faster search when the previous match is longer than this */
187
188 int nice_match; /* Stop searching when current match exceeds this */
189
190 /* used by trees.c: */
191 /* Didn't use ct_data typedef below to supress compiler warning */
192 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */
193 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
194 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */
195
196 struct tree_desc_s l_desc; /* desc. for literal tree */
197 struct tree_desc_s d_desc; /* desc. for distance tree */
198 struct tree_desc_s bl_desc; /* desc. for bit length tree */
199
200 ush bl_count[MAX_BITS+1];
201 /* number of codes at each bit length for an optimal tree */
202
203 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
204 int heap_len; /* number of elements in the heap */
205 int heap_max; /* element of largest frequency */
206 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
207 * The same heap array is used to build all trees.
208 */
209
210 uch depth[2*L_CODES+1];
211 /* Depth of each subtree used as tie breaker for trees of equal frequency
212 */
213
214 uchf *l_buf; /* buffer for literals or lengths */
215
216 uInt lit_bufsize;
217 /* Size of match buffer for literals/lengths. There are 4 reasons for
218 * limiting lit_bufsize to 64K:
219 * - frequencies can be kept in 16 bit counters
220 * - if compression is not successful for the first block, all input
221 * data is still in the window so we can still emit a stored block even
222 * when input comes from standard input. (This can also be done for
223 * all blocks if lit_bufsize is not greater than 32K.)
224 * - if compression is not successful for a file smaller than 64K, we can
225 * even emit a stored file instead of a stored block (saving 5 bytes).
226 * This is applicable only for zip (not gzip or zlib).
227 * - creating new Huffman trees less frequently may not provide fast
228 * adaptation to changes in the input data statistics. (Take for
229 * example a binary file with poorly compressible code followed by
230 * a highly compressible string table.) Smaller buffer sizes give
231 * fast adaptation but have of course the overhead of transmitting
232 * trees more frequently.
233 * - I can't count above 4
234 */
235
236 uInt last_lit; /* running index in l_buf */
237
238 ushf *d_buf;
239 /* Buffer for distances. To simplify the code, d_buf and l_buf have
240 * the same number of elements. To use different lengths, an extra flag
241 * array would be necessary.
242 */
243
244 ulg opt_len; /* bit length of current block with optimal trees */
245 ulg static_len; /* bit length of current block with static trees */
246 uInt matches; /* number of string matches in current block */
247 int last_eob_len; /* bit length of EOB code for last block */
248
249 #ifdef DEBUG
250 ulg compressed_len; /* total bit length of compressed file mod 2^32 */
251 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */
252 #endif
253
254 ush bi_buf;
255 /* Output buffer. bits are inserted starting at the bottom (least
256 * significant bits).
257 */
258 int bi_valid;
259 /* Number of valid bits in bi_buf. All bits above the last valid bit
260 * are always zero.
261 */
262
263 } FAR deflate_state;
264
265 /* Output a byte on the stream.
266 * IN assertion: there is enough room in pending_buf.
267 */
268 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
269
270
271 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
272 /* Minimum amount of lookahead, except at the end of the input file.
273 * See deflate.c for comments about the MIN_MATCH+1.
274 */
275
276 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
277 /* In order to simplify the code, particularly on 16 bit machines, match
278 * distances are limited to MAX_DIST instead of WSIZE.
279 */
280
281 /* in trees.c */
282 void _tr_init OF((deflate_state *s));
283 int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
284 void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len,
285 int eof));
286 void _tr_align OF((deflate_state *s));
287 void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
288 int eof));
289
290 #define d_code(dist) \
291 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
292 /* Mapping from a distance to a distance code. dist is the distance - 1 and
293 * must not have side effects. _dist_code[256] and _dist_code[257] are never
294 * used.
295 */
296
297 #ifndef DEBUG
298 /* Inline versions of _tr_tally for speed: */
299
300 #if defined(GEN_TREES_H) || !defined(STDC)
301 extern uch _length_code[];
302 extern uch _dist_code[];
303 #else
304 extern const uch _length_code[];
305 extern const uch _dist_code[];
306 #endif
307
308 # define _tr_tally_lit(s, c, flush) \
309 { uch cc = (c); \
310 s->d_buf[s->last_lit] = 0; \
311 s->l_buf[s->last_lit++] = cc; \
312 s->dyn_ltree[cc].Freq++; \
313 flush = (s->last_lit == s->lit_bufsize-1); \
314 }
315 # define _tr_tally_dist(s, distance, length, flush) \
316 { uch len = (length); \
317 ush dist = (distance); \
318 s->d_buf[s->last_lit] = dist; \
319 s->l_buf[s->last_lit++] = len; \
320 dist--; \
321 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
322 s->dyn_dtree[d_code(dist)].Freq++; \
323 flush = (s->last_lit == s->lit_bufsize-1); \
324 }
325 #else
326 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
327 # define _tr_tally_dist(s, distance, length, flush) \
328 flush = _tr_tally(s, distance, length)
329 #endif
330
331 #endif /* DEFLATE_H */