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deflate.h
Go to the documentation of this file.
1 /* deflate.h -- internal compression state
2 * Copyright (C) 1995-2010 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 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 ulg high_water;
264 /* High water mark offset in window for initialized bytes -- bytes above
265 * this are set to zero in order to avoid memory check warnings when
266 * longest match routines access bytes past the input. This is then
267 * updated to the new high water mark.
268 */
269
270 } FAR deflate_state;
271
272 /* Output a byte on the stream.
273 * IN assertion: there is enough room in pending_buf.
274 */
275 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
276
277
278 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
279 /* Minimum amount of lookahead, except at the end of the input file.
280 * See deflate.c for comments about the MIN_MATCH+1.
281 */
282
283 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
284 /* In order to simplify the code, particularly on 16 bit machines, match
285 * distances are limited to MAX_DIST instead of WSIZE.
286 */
287
288 #define WIN_INIT MAX_MATCH
289 /* Number of bytes after end of data in window to initialize in order to avoid
290 memory checker errors from longest match routines */
291
292 /* in trees.c */
293 void ZLIB_INTERNAL _tr_init OF((deflate_state *s));
294 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
295 void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf,
296 ulg stored_len, int last));
297 void ZLIB_INTERNAL _tr_align OF((deflate_state *s));
298 void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
299 ulg stored_len, int last));
300
301 #define d_code(dist) \
302 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
303 /* Mapping from a distance to a distance code. dist is the distance - 1 and
304 * must not have side effects. _dist_code[256] and _dist_code[257] are never
305 * used.
306 */
307
308 #ifndef DEBUG
309 /* Inline versions of _tr_tally for speed: */
310
311 #if defined(GEN_TREES_H) || !defined(STDC)
312 extern uch ZLIB_INTERNAL _length_code[];
313 extern uch ZLIB_INTERNAL _dist_code[];
314 #else
315 extern const uch ZLIB_INTERNAL _length_code[];
316 extern const uch ZLIB_INTERNAL _dist_code[];
317 #endif
318
319 # define _tr_tally_lit(s, c, flush) \
320 { uch cc = (c); \
321 s->d_buf[s->last_lit] = 0; \
322 s->l_buf[s->last_lit++] = cc; \
323 s->dyn_ltree[cc].Freq++; \
324 flush = (s->last_lit == s->lit_bufsize-1); \
325 }
326 # define _tr_tally_dist(s, distance, length, flush) \
327 { uch len = (length); \
328 ush dist = (distance); \
329 s->d_buf[s->last_lit] = dist; \
330 s->l_buf[s->last_lit++] = len; \
331 dist--; \
332 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
333 s->dyn_dtree[d_code(dist)].Freq++; \
334 flush = (s->last_lit == s->lit_bufsize-1); \
335 }
336 #else
337 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
338 # define _tr_tally_dist(s, distance, length, flush) \
339 flush = _tr_tally(s, distance, length)
340 #endif
341
342 #endif /* DEFLATE_H */
internal_state::good_match
uInt good_match
Definition: deflate.h:185
internal_state::hash_bits
uInt hash_bits
Definition: deflate.h:138
internal_state::static_len
ulg static_len
Definition: deflate.h:245
static_tree_desc_s
Definition: deflate.c:155
internal_state::heap_len
int heap_len
Definition: deflate.h:204
internal_state::heap_max
int heap_max
Definition: deflate.h:205
internal_state::w_mask
uInt w_mask
Definition: deflate.h:111
ushf
ush FAR ushf
Definition: zutil.h:40
internal_state::window
Bytef * window
Definition: deflate.h:113
BL_CODES
#define BL_CODES
Definition: deflate.h:42
Byte
unsigned char Byte
Definition: zconf.h:333
internal_state::max_lazy_match
uInt max_lazy_match
Definition: deflate.h:171
internal_state::hash_mask
uInt hash_mask
Definition: deflate.h:139
internal_state::match_length
uInt match_length
Definition: deflate.h:153
_tr_align
void ZLIB_INTERNAL _tr_align(deflate_state *s)
Definition: trees.c:896
MAX_BITS
#define MAX_BITS
Definition: deflate.h:48
Pos
ush Pos
Definition: deflate.h:86
internal_state::hash_shift
uInt hash_shift
Definition: deflate.h:141
internal_state::status
int status
Definition: deflate.h:96
internal_state::strategy
int strategy
Definition: deflate.h:183
internal_state::prev_length
uInt prev_length
Definition: deflate.h:160
internal_state::prev
Posf * prev
Definition: deflate.h:128
ZLIB_INTERNAL
#define ZLIB_INTERNAL
Definition: compress.c:8
tree_desc_s::dyn_tree
ct_data * dyn_tree
Definition: deflate.h:81
tree_desc_s::stat_desc
static_tree_desc * stat_desc
Definition: deflate.h:83
internal_state::pending_out
Bytef * pending_out
Definition: deflate.h:99
internal_state::match_start
uInt match_start
Definition: deflate.h:157
gz_headerp
gz_header FAR * gz_headerp
Definition: zlib.h:129
ct_data_s::code
ush code
Definition: deflate.h:65
_dist_code
uch ZLIB_INTERNAL _dist_code[]
Definition: trees.c:103
internal_state::gzhead
gz_headerp gzhead
Definition: deflate.h:102
Bytef
Byte FAR Bytef
Definition: zconf.h:342
internal_state::high_water
ulg high_water
Definition: deflate.h:263
internal_state::lookahead
uInt lookahead
Definition: deflate.h:158
OF
void ZLIB_INTERNAL _tr_init OF((deflate_state *s))
tree_desc_s::max_code
int max_code
Definition: deflate.h:82
internal_state::window_size
ulg window_size
Definition: deflate.h:123
internal_state::level
int level
Definition: deflate.h:182
internal_state::last_eob_len
int last_eob_len
Definition: deflate.h:247
internal_state::strm
z_streamp strm
Definition: deflate.h:95
internal_state::opt_len
ulg opt_len
Definition: deflate.h:244
internal_state::head
Posf * head
Definition: deflate.h:134
_tr_init
void ZLIB_INTERNAL _tr_init(deflate_state *s)
Definition: trees.c:386
ct_data_s::fc
union ct_data_s::@14 fc
ct_data_s::dad
ush dad
Definition: deflate.h:68
ush
unsigned short ush
Definition: zutil.h:39
ct_data_s::freq
ush freq
Definition: deflate.h:64
FAR
#define FAR
Definition: jmorecfg.h:215
internal_state::w_size
uInt w_size
Definition: deflate.h:109
internal_state::l_buf
uchf * l_buf
Definition: deflate.h:214
tree_desc_s
Definition: deflate.h:80
Posf
Pos FAR Posf
Definition: deflate.h:87
HEAP_SIZE
#define HEAP_SIZE
Definition: deflate.h:45
internal_state::wrap
int wrap
Definition: deflate.h:101
internal_state::pending_buf
Bytef * pending_buf
Definition: deflate.h:97
internal_state::bi_buf
ush bi_buf
Definition: deflate.h:254
internal_state::lit_bufsize
uInt lit_bufsize
Definition: deflate.h:216
internal_state::d_buf
ushf * d_buf
Definition: deflate.h:238
_tr_stored_block
void ZLIB_INTERNAL _tr_stored_block(deflate_state *s, charf *buf, ulg stored_len, int last)
Definition: trees.c:871
internal_state::block_start
long block_start
Definition: deflate.h:148
internal_state::match_available
int match_available
Definition: deflate.h:155
internal_state::gzindex
uInt gzindex
Definition: deflate.h:103
_tr_tally
int ZLIB_INTERNAL _tr_tally(deflate_state *s, unsigned dist, unsigned lc)
Definition: trees.c:1026
ct_data
struct ct_data_s ct_data
internal_state::max_chain_length
uInt max_chain_length
Definition: deflate.h:165
internal_state::nice_match
int nice_match
Definition: deflate.h:188
deflate_state
struct internal_state deflate_state
internal_state
Definition: deflate.h:94
internal_state::last_lit
uInt last_lit
Definition: deflate.h:236
uch
unsigned char uch
Definition: zutil.h:37
internal_state::w_bits
uInt w_bits
Definition: deflate.h:110
internal_state::pending
uInt pending
Definition: deflate.h:100
ulg
unsigned long ulg
Definition: zutil.h:41
internal_state::strstart
uInt strstart
Definition: deflate.h:156
internal_state::pending_buf_size
ulg pending_buf_size
Definition: deflate.h:98
_length_code
uch ZLIB_INTERNAL _length_code[]
Definition: trees.c:109
ct_data_s::len
ush len
Definition: deflate.h:69
ct_data_s
Definition: deflate.h:62
_tr_flush_block
void ZLIB_INTERNAL _tr_flush_block(deflate_state *s, charf *buf, ulg stored_len, int last)
Definition: trees.c:925
internal_state::matches
uInt matches
Definition: deflate.h:246
zutil.h
z_streamp
z_stream FAR * z_streamp
Definition: zlib.h:106
internal_state::prev_match
IPos prev_match
Definition: deflate.h:154
internal_state::last_flush
int last_flush
Definition: deflate.h:105
ct_data_s::dl
union ct_data_s::@15 dl
D_CODES
#define D_CODES
Definition: deflate.h:39
internal_state::bi_valid
int bi_valid
Definition: deflate.h:258
uchf
uch FAR uchf
Definition: zutil.h:38
internal_state::hash_size
uInt hash_size
Definition: deflate.h:137
internal_state::ins_h
uInt ins_h
Definition: deflate.h:136
internal_state::method
Byte method
Definition: deflate.h:104
uInt
unsigned int uInt
Definition: zconf.h:335
charf
char FAR charf
Definition: zconf.h:344
tree_desc
struct tree_desc_s tree_desc
IPos
unsigned IPos
Definition: deflate.h:88
L_CODES
#define L_CODES
Definition: deflate.h:36