1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /* deflate.h -- internal compression state
26 * Copyright (C) 1995-2016 Jean-loup Gailly
27 * For conditions of distribution and use, see copyright notice in zlib.h
28 */
29
30 /* WARNING: this file should *not* be used by applications. It is
31 part of the implementation of the compression library and is
32 subject to change. Applications should only use zlib.h.
33 */
34
35 /* @(#) $Id$ */
36
37 #ifndef DEFLATE_H
38 #define DEFLATE_H
39
40 #include "zutil.h"
41
42 /* define NO_GZIP when compiling if you want to disable gzip header and
43 trailer creation by deflate(). NO_GZIP would be used to avoid linking in
44 the crc code when it is not needed. For shared libraries, gzip encoding
45 should be left enabled. */
46 #ifndef NO_GZIP
47 # define GZIP
48 #endif
49
50 /* ===========================================================================
51 * Internal compression state.
52 */
53
54 #define LENGTH_CODES 29
55 /* number of length codes, not counting the special END_BLOCK code */
56
57 #define LITERALS 256
58 /* number of literal bytes 0..255 */
59
60 #define L_CODES (LITERALS+1+LENGTH_CODES)
61 /* number of Literal or Length codes, including the END_BLOCK code */
62
63 #define D_CODES 30
64 /* number of distance codes */
65
66 #define BL_CODES 19
67 /* number of codes used to transfer the bit lengths */
68
69 #define HEAP_SIZE (2*L_CODES+1)
70 /* maximum heap size */
71
72 #define MAX_BITS 15
73 /* All codes must not exceed MAX_BITS bits */
74
75 #define Buf_size 16
76 /* size of bit buffer in bi_buf */
77
78 #define INIT_STATE 42 /* zlib header -> BUSY_STATE */
79 #ifdef GZIP
80 # define GZIP_STATE 57 /* gzip header -> BUSY_STATE | EXTRA_STATE */
81 #endif
82 #define EXTRA_STATE 69 /* gzip extra block -> NAME_STATE */
83 #define NAME_STATE 73 /* gzip file name -> COMMENT_STATE */
84 #define COMMENT_STATE 91 /* gzip comment -> HCRC_STATE */
85 #define HCRC_STATE 103 /* gzip header CRC -> BUSY_STATE */
86 #define BUSY_STATE 113 /* deflate -> FINISH_STATE */
87 #define FINISH_STATE 666 /* stream complete */
88 /* Stream status */
89
90
91 /* Data structure describing a single value and its code string. */
92 typedef struct ct_data_s {
93 union {
94 ush freq; /* frequency count */
95 ush code; /* bit string */
96 } fc;
97 union {
98 ush dad; /* father node in Huffman tree */
99 ush len; /* length of bit string */
100 } dl;
101 } FAR ct_data;
102
103 #define Freq fc.freq
104 #define Code fc.code
105 #define Dad dl.dad
106 #define Len dl.len
107
108 typedef struct static_tree_desc_s static_tree_desc;
109
110 typedef struct tree_desc_s {
111 ct_data *dyn_tree; /* the dynamic tree */
112 int max_code; /* largest code with non zero frequency */
113 const static_tree_desc *stat_desc; /* the corresponding static tree */
114 } FAR tree_desc;
115
116 typedef ush Pos;
117 typedef Pos FAR Posf;
118 typedef unsigned IPos;
119
120 /* A Pos is an index in the character window. We use short instead of int to
121 * save space in the various tables. IPos is used only for parameter passing.
122 */
123
124 typedef struct internal_state {
125 z_streamp strm; /* pointer back to this zlib stream */
126 int status; /* as the name implies */
127 Bytef *pending_buf; /* output still pending */
128 ulg pending_buf_size; /* size of pending_buf */
129 Bytef *pending_out; /* next pending byte to output to the stream */
130 ulg pending; /* nb of bytes in the pending buffer */
131 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
132 gz_headerp gzhead; /* gzip header information to write */
133 ulg gzindex; /* where in extra, name, or comment */
134 Byte method; /* can only be DEFLATED */
135 int last_flush; /* value of flush param for previous deflate call */
136
137 /* used by deflate.c: */
138
139 uInt w_size; /* LZ77 window size (32K by default) */
140 uInt w_bits; /* log2(w_size) (8..16) */
141 uInt w_mask; /* w_size - 1 */
142
143 Bytef *window;
144 /* Sliding window. Input bytes are read into the second half of the window,
145 * and move to the first half later to keep a dictionary of at least wSize
146 * bytes. With this organization, matches are limited to a distance of
147 * wSize-MAX_MATCH bytes, but this ensures that IO is always
148 * performed with a length multiple of the block size. Also, it limits
149 * the window size to 64K, which is quite useful on MSDOS.
150 * To do: use the user input buffer as sliding window.
151 */
152
153 ulg window_size;
154 /* Actual size of window: 2*wSize, except when the user input buffer
155 * is directly used as sliding window.
156 */
157
158 Posf *prev;
159 /* Link to older string with same hash index. To limit the size of this
160 * array to 64K, this link is maintained only for the last 32K strings.
161 * An index in this array is thus a window index modulo 32K.
162 */
163
164 Posf *head; /* Heads of the hash chains or NIL. */
165
166 uInt ins_h; /* hash index of string to be inserted */
167 uInt hash_size; /* number of elements in hash table */
168 uInt hash_bits; /* log2(hash_size) */
169 uInt hash_mask; /* hash_size-1 */
170
171 uInt hash_shift;
172 /* Number of bits by which ins_h must be shifted at each input
173 * step. It must be such that after MIN_MATCH steps, the oldest
174 * byte no longer takes part in the hash key, that is:
175 * hash_shift * MIN_MATCH >= hash_bits
176 */
177
178 long block_start;
179 /* Window position at the beginning of the current output block. Gets
180 * negative when the window is moved backwards.
181 */
182
183 uInt match_length; /* length of best match */
184 IPos prev_match; /* previous match */
185 int match_available; /* set if previous match exists */
186 uInt strstart; /* start of string to insert */
187 uInt match_start; /* start of matching string */
188 uInt lookahead; /* number of valid bytes ahead in window */
189
190 uInt prev_length;
191 /* Length of the best match at previous step. Matches not greater than this
192 * are discarded. This is used in the lazy match evaluation.
193 */
194
195 uInt max_chain_length;
196 /* To speed up deflation, hash chains are never searched beyond this
197 * length. A higher limit improves compression ratio but degrades the
198 * speed.
199 */
200
201 uInt max_lazy_match;
202 /* Attempt to find a better match only when the current match is strictly
203 * smaller than this value. This mechanism is used only for compression
204 * levels >= 4.
205 */
206 # define max_insert_length max_lazy_match
207 /* Insert new strings in the hash table only if the match length is not
208 * greater than this length. This saves time but degrades compression.
209 * max_insert_length is used only for compression levels <= 3.
210 */
211
212 int level; /* compression level (1..9) */
213 int strategy; /* favor or force Huffman coding*/
214
215 uInt good_match;
216 /* Use a faster search when the previous match is longer than this */
217
218 int nice_match; /* Stop searching when current match exceeds this */
219
220 /* used by trees.c: */
221 /* Didn't use ct_data typedef below to suppress compiler warning */
222 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */
223 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
224 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */
225
226 struct tree_desc_s l_desc; /* desc. for literal tree */
227 struct tree_desc_s d_desc; /* desc. for distance tree */
228 struct tree_desc_s bl_desc; /* desc. for bit length tree */
229
230 ush bl_count[MAX_BITS+1];
231 /* number of codes at each bit length for an optimal tree */
232
233 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
234 int heap_len; /* number of elements in the heap */
235 int heap_max; /* element of largest frequency */
236 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
237 * The same heap array is used to build all trees.
238 */
239
240 uch depth[2*L_CODES+1];
241 /* Depth of each subtree used as tie breaker for trees of equal frequency
242 */
243
244 uchf *l_buf; /* buffer for literals or lengths */
245
246 uInt lit_bufsize;
247 /* Size of match buffer for literals/lengths. There are 4 reasons for
248 * limiting lit_bufsize to 64K:
249 * - frequencies can be kept in 16 bit counters
250 * - if compression is not successful for the first block, all input
251 * data is still in the window so we can still emit a stored block even
252 * when input comes from standard input. (This can also be done for
253 * all blocks if lit_bufsize is not greater than 32K.)
254 * - if compression is not successful for a file smaller than 64K, we can
255 * even emit a stored file instead of a stored block (saving 5 bytes).
256 * This is applicable only for zip (not gzip or zlib).
257 * - creating new Huffman trees less frequently may not provide fast
258 * adaptation to changes in the input data statistics. (Take for
259 * example a binary file with poorly compressible code followed by
260 * a highly compressible string table.) Smaller buffer sizes give
261 * fast adaptation but have of course the overhead of transmitting
262 * trees more frequently.
263 * - I can't count above 4
264 */
265
266 uInt last_lit; /* running index in l_buf */
267
268 ushf *d_buf;
269 /* Buffer for distances. To simplify the code, d_buf and l_buf have
270 * the same number of elements. To use different lengths, an extra flag
271 * array would be necessary.
272 */
273
274 ulg opt_len; /* bit length of current block with optimal trees */
275 ulg static_len; /* bit length of current block with static trees */
276 uInt matches; /* number of string matches in current block */
277 uInt insert; /* bytes at end of window left to insert */
278
279 #ifdef ZLIB_DEBUG
280 ulg compressed_len; /* total bit length of compressed file mod 2^32 */
281 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */
282 #endif
283
284 ush bi_buf;
285 /* Output buffer. bits are inserted starting at the bottom (least
286 * significant bits).
287 */
288 int bi_valid;
289 /* Number of valid bits in bi_buf. All bits above the last valid bit
290 * are always zero.
291 */
292
293 ulg high_water;
294 /* High water mark offset in window for initialized bytes -- bytes above
295 * this are set to zero in order to avoid memory check warnings when
296 * longest match routines access bytes past the input. This is then
297 * updated to the new high water mark.
298 */
299
300 } FAR deflate_state;
301
302 /* Output a byte on the stream.
303 * IN assertion: there is enough room in pending_buf.
304 */
305 #define put_byte(s, c) {s->pending_buf[s->pending++] = (Bytef)(c);}
306
307
308 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
309 /* Minimum amount of lookahead, except at the end of the input file.
310 * See deflate.c for comments about the MIN_MATCH+1.
311 */
312
313 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
314 /* In order to simplify the code, particularly on 16 bit machines, match
315 * distances are limited to MAX_DIST instead of WSIZE.
316 */
317
318 #define WIN_INIT MAX_MATCH
319 /* Number of bytes after end of data in window to initialize in order to avoid
320 memory checker errors from longest match routines */
321
322 /* in trees.c */
323 void ZLIB_INTERNAL _tr_init OF((deflate_state *s));
324 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
325 void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf,
326 ulg stored_len, int last));
327 void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s));
328 void ZLIB_INTERNAL _tr_align OF((deflate_state *s));
329 void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
330 ulg stored_len, int last));
331
332 #define d_code(dist) \
333 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
334 /* Mapping from a distance to a distance code. dist is the distance - 1 and
335 * must not have side effects. _dist_code[256] and _dist_code[257] are never
336 * used.
337 */
338
339 #ifndef ZLIB_DEBUG
340 /* Inline versions of _tr_tally for speed: */
341
342 #if defined(GEN_TREES_H) || !defined(STDC)
343 extern uch ZLIB_INTERNAL _length_code[];
344 extern uch ZLIB_INTERNAL _dist_code[];
345 #else
346 extern const uch ZLIB_INTERNAL _length_code[];
347 extern const uch ZLIB_INTERNAL _dist_code[];
348 #endif
349
350 # define _tr_tally_lit(s, c, flush) \
351 { uch cc = (c); \
352 s->d_buf[s->last_lit] = 0; \
353 s->l_buf[s->last_lit++] = cc; \
354 s->dyn_ltree[cc].Freq++; \
355 flush = (s->last_lit == s->lit_bufsize-1); \
356 }
357 # define _tr_tally_dist(s, distance, length, flush) \
358 { uch len = (uch)(length); \
359 ush dist = (ush)(distance); \
360 s->d_buf[s->last_lit] = dist; \
361 s->l_buf[s->last_lit++] = len; \
362 dist--; \
363 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
364 s->dyn_dtree[d_code(dist)].Freq++; \
365 flush = (s->last_lit == s->lit_bufsize-1); \
366 }
367 #else
368 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
369 # define _tr_tally_dist(s, distance, length, flush) \
370 flush = _tr_tally(s, distance, length)
371 #endif
372
373 #endif /* DEFLATE_H */