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deflate.h
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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 /* @(#) $Id$ */
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 
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 
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 
130  /* Actual size of window: 2*wSize, except when the user input buffer
131  * is directly used as sliding window.
132  */
133 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 */
300 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
302  ulg stored_len, int last));
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 */
uInt good_match
Definition: deflate.h:191
uInt hash_bits
Definition: deflate.h:144
ulg static_len
Definition: deflate.h:251
Bytef * window
Definition: deflate.h:119
#define BL_CODES
Definition: deflate.h:42
int heap[2 *L_CODES+1]
Definition: deflate.h:209
unsigned char Byte
Definition: zconf.h:391
GLenum GLuint GLenum GLsizei const GLchar * buf
Definition: glext.h:7751
POINT last
Definition: font.c:46
uInt max_lazy_match
Definition: deflate.h:177
uInt hash_mask
Definition: deflate.h:145
uInt match_length
Definition: deflate.h:159
void ZLIB_INTERNAL _tr_align(deflate_state *s)
Definition: trees.c:896
#define MAX_BITS
Definition: deflate.h:48
ush Pos
Definition: deflate.h:92
uInt hash_shift
Definition: deflate.h:147
uInt prev_length
Definition: deflate.h:166
Posf * prev
Definition: deflate.h:134
struct ct_data_s dyn_ltree[HEAP_SIZE]
Definition: deflate.h:198
ct_data * dyn_tree
Definition: deflate.h:87
Bytef * pending_out
Definition: deflate.h:105
unsigned long ulg
Definition: zutil.h:38
uInt match_start
Definition: deflate.h:163
ush code
Definition: deflate.h:71
uch ZLIB_INTERNAL _dist_code[]
Definition: trees.c:98
gz_headerp gzhead
Definition: deflate.h:108
Byte FAR Bytef
Definition: zconf.h:400
ulg high_water
Definition: deflate.h:269
uInt lookahead
Definition: deflate.h:164
union ct_data_s::@3913 fc
z_stream FAR * z_streamp
Definition: zlib.h:108
void ZLIB_INTERNAL _tr_init OF((deflate_state *s))
#define FAR
Definition: guiddef.h:36
int max_code
Definition: deflate.h:88
ulg window_size
Definition: deflate.h:129
z_streamp strm
Definition: deflate.h:101
struct tree_desc_s bl_desc
Definition: deflate.h:204
struct tree_desc_s d_desc
Definition: deflate.h:203
Posf * head
Definition: deflate.h:140
unsigned short ush
Definition: zutil.h:36
void ZLIB_INTERNAL _tr_init(deflate_state *s)
Definition: trees.c:379
const static_tree_desc * stat_desc
Definition: deflate.h:89
ush dad
Definition: deflate.h:74
ush freq
Definition: deflate.h:70
uchf * l_buf
Definition: deflate.h:220
Pos FAR Posf
Definition: deflate.h:93
#define HEAP_SIZE
Definition: deflate.h:45
void ZLIB_INTERNAL _tr_flush_bits(deflate_state *s)
Definition: trees.c:886
ush bl_count[MAX_BITS+1]
Definition: deflate.h:206
union ct_data_s::@3914 dl
GLint GLint GLsizei GLsizei GLsizei depth
Definition: gl.h:1546
Bytef * pending_buf
Definition: deflate.h:103
uInt lit_bufsize
Definition: deflate.h:222
ushf * d_buf
Definition: deflate.h:244
GLdouble s
Definition: gl.h:2039
void ZLIB_INTERNAL _tr_stored_block(deflate_state *s, charf *buf, ulg stored_len, int last)
Definition: trees.c:863
long block_start
Definition: deflate.h:154
int match_available
Definition: deflate.h:161
struct ct_data_s dyn_dtree[2 *D_CODES+1]
Definition: deflate.h:199
struct tree_desc_s l_desc
Definition: deflate.h:202
int ZLIB_INTERNAL _tr_tally(deflate_state *s, unsigned dist, unsigned lc)
Definition: trees.c:1014
struct ct_data_s ct_data
uInt max_chain_length
Definition: deflate.h:171
int nice_match
Definition: deflate.h:194
struct internal_state deflate_state
#define ZLIB_INTERNAL
Definition: compress.c:32
uInt last_lit
Definition: deflate.h:242
uInt strstart
Definition: deflate.h:162
ulg pending_buf_size
Definition: deflate.h:104
uch ZLIB_INTERNAL _length_code[]
Definition: trees.c:104
ush len
Definition: deflate.h:75
gz_header FAR * gz_headerp
Definition: zlib.h:131
void ZLIB_INTERNAL _tr_flush_block(deflate_state *s, charf *buf, ulg stored_len, int last)
Definition: trees.c:911
uInt matches
Definition: deflate.h:252
IPos prev_match
Definition: deflate.h:160
ush FAR ushf
Definition: zutil.h:37
int last_flush
Definition: deflate.h:111
#define D_CODES
Definition: deflate.h:39
uch FAR uchf
Definition: zutil.h:35
struct ct_data_s bl_tree[2 *BL_CODES+1]
Definition: deflate.h:200
uInt hash_size
Definition: deflate.h:143
unsigned int uInt
Definition: zconf.h:393
unsigned char uch
Definition: zutil.h:34
char FAR charf
Definition: zconf.h:402
struct tree_desc_s tree_desc
unsigned IPos
Definition: deflate.h:94
#define L_CODES
Definition: deflate.h:36