Watt-32 tcp/ip  2.2 dev-rel.10
zdeflate.h
1 /* deflate.h -- internal compression state
2  * Copyright (C) 1995-2002 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 BUSY_STATE 113
53 #define FINISH_STATE 666
54 /* Stream status */
55 
56 
57 /* Data structure describing a single value and its code string. */
58 typedef struct ct_data_s {
59  union {
60  ush freq; /* frequency count */
61  ush code; /* bit string */
62  } fc;
63  union {
64  ush dad; /* father node in Huffman tree */
65  ush len; /* length of bit string */
66  } dl;
67 } FAR ct_data;
68 
69 #define Freq fc.freq
70 #define Code fc.code
71 #define Dad dl.dad
72 #define Len dl.len
73 
75 
76 typedef struct tree_desc_s {
77  ct_data *dyn_tree; /* the dynamic tree */
78  int max_code; /* largest code with non zero frequency */
79  static_tree_desc *stat_desc; /* the corresponding static tree */
80 } FAR tree_desc;
81 
82 typedef ush Pos;
83 typedef Pos FAR Posf;
84 typedef unsigned IPos;
85 
86 /* A Pos is an index in the character window. We use short instead of int to
87  * save space in the various tables. IPos is used only for parameter passing.
88  */
89 
90 typedef struct internal_state {
91  z_streamp strm; /* pointer back to this zlib stream */
92  int status; /* as the name implies */
93  Bytef *pending_buf; /* output still pending */
94  ulg pending_buf_size; /* size of pending_buf */
95  Bytef *pending_out; /* next pending byte to output to the stream */
96  int pending; /* nb of bytes in the pending buffer */
97  int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
98  Byte data_type; /* UNKNOWN, BINARY or ASCII */
99  Byte method; /* STORED (for zip only) or DEFLATED */
100  int last_flush; /* value of flush param for previous deflate call */
101 
102  /* used by deflate.c: */
103 
104  uInt w_size; /* LZ77 window size (32K by default) */
105  uInt w_bits; /* log2(w_size) (8..16) */
106  uInt w_mask; /* w_size - 1 */
107 
108  Bytef *window;
109  /* Sliding window. Input bytes are read into the second half of the window,
110  * and move to the first half later to keep a dictionary of at least wSize
111  * bytes. With this organization, matches are limited to a distance of
112  * wSize-MAX_MATCH bytes, but this ensures that IO is always
113  * performed with a length multiple of the block size. Also, it limits
114  * the window size to 64K, which is quite useful on MSDOS.
115  * To do: use the user input buffer as sliding window.
116  */
117 
118  ulg window_size;
119  /* Actual size of window: 2*wSize, except when the user input buffer
120  * is directly used as sliding window.
121  */
122 
123  Posf *prev;
124  /* Link to older string with same hash index. To limit the size of this
125  * array to 64K, this link is maintained only for the last 32K strings.
126  * An index in this array is thus a window index modulo 32K.
127  */
128 
129  Posf *head; /* Heads of the hash chains or NIL. */
130 
131  uInt ins_h; /* hash index of string to be inserted */
132  uInt hash_size; /* number of elements in hash table */
133  uInt hash_bits; /* log2(hash_size) */
134  uInt hash_mask; /* hash_size-1 */
135 
136  uInt hash_shift;
137  /* Number of bits by which ins_h must be shifted at each input
138  * step. It must be such that after MIN_MATCH steps, the oldest
139  * byte no longer takes part in the hash key, that is:
140  * hash_shift * MIN_MATCH >= hash_bits
141  */
142 
143  long block_start;
144  /* Window position at the beginning of the current output block. Gets
145  * negative when the window is moved backwards.
146  */
147 
148  uInt match_length; /* length of best match */
149  IPos prev_match; /* previous match */
150  int match_available; /* set if previous match exists */
151  uInt strstart; /* start of string to insert */
152  uInt match_start; /* start of matching string */
153  uInt lookahead; /* number of valid bytes ahead in window */
154 
155  uInt prev_length;
156  /* Length of the best match at previous step. Matches not greater than this
157  * are discarded. This is used in the lazy match evaluation.
158  */
159 
160  uInt max_chain_length;
161  /* To speed up deflation, hash chains are never searched beyond this
162  * length. A higher limit improves compression ratio but degrades the
163  * speed.
164  */
165 
166  uInt max_lazy_match;
167  /* Attempt to find a better match only when the current match is strictly
168  * smaller than this value. This mechanism is used only for compression
169  * levels >= 4.
170  */
171 # define max_insert_length max_lazy_match
172  /* Insert new strings in the hash table only if the match length is not
173  * greater than this length. This saves time but degrades compression.
174  * max_insert_length is used only for compression levels <= 3.
175  */
176 
177  int level; /* compression level (1..9) */
178  int strategy; /* favor or force Huffman coding*/
179 
180  uInt good_match;
181  /* Use a faster search when the previous match is longer than this */
182 
183  int nice_match; /* Stop searching when current match exceeds this */
184 
185  /* used by trees.c: */
186  /* Didn't use ct_data typedef below to supress compiler warning */
187  struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */
188  struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
189  struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */
190 
191  struct tree_desc_s l_desc; /* desc. for literal tree */
192  struct tree_desc_s d_desc; /* desc. for distance tree */
193  struct tree_desc_s bl_desc; /* desc. for bit length tree */
194 
195  ush bl_count[MAX_BITS+1];
196  /* number of codes at each bit length for an optimal tree */
197 
198  int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
199  int heap_len; /* number of elements in the heap */
200  int heap_max; /* element of largest frequency */
201  /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
202  * The same heap array is used to build all trees.
203  */
204 
205  uch depth[2*L_CODES+1];
206  /* Depth of each subtree used as tie breaker for trees of equal frequency
207  */
208 
209  uchf *l_buf; /* buffer for literals or lengths */
210 
211  uInt lit_bufsize;
212  /* Size of match buffer for literals/lengths. There are 4 reasons for
213  * limiting lit_bufsize to 64K:
214  * - frequencies can be kept in 16 bit counters
215  * - if compression is not successful for the first block, all input
216  * data is still in the window so we can still emit a stored block even
217  * when input comes from standard input. (This can also be done for
218  * all blocks if lit_bufsize is not greater than 32K.)
219  * - if compression is not successful for a file smaller than 64K, we can
220  * even emit a stored file instead of a stored block (saving 5 bytes).
221  * This is applicable only for zip (not gzip or zlib).
222  * - creating new Huffman trees less frequently may not provide fast
223  * adaptation to changes in the input data statistics. (Take for
224  * example a binary file with poorly compressible code followed by
225  * a highly compressible string table.) Smaller buffer sizes give
226  * fast adaptation but have of course the overhead of transmitting
227  * trees more frequently.
228  * - I can't count above 4
229  */
230 
231  uInt last_lit; /* running index in l_buf */
232 
233  ushf *d_buf;
234  /* Buffer for distances. To simplify the code, d_buf and l_buf have
235  * the same number of elements. To use different lengths, an extra flag
236  * array would be necessary.
237  */
238 
239  ulg opt_len; /* bit length of current block with optimal trees */
240  ulg static_len; /* bit length of current block with static trees */
241  uInt matches; /* number of string matches in current block */
242  int last_eob_len; /* bit length of EOB code for last block */
243 
244 #ifdef DEBUG
245  ulg compressed_len; /* total bit length of compressed file mod 2^32 */
246  ulg bits_sent; /* bit length of compressed data sent mod 2^32 */
247 #endif
248 
249  ush bi_buf;
250  /* Output buffer. bits are inserted starting at the bottom (least
251  * significant bits).
252  */
253  int bi_valid;
254  /* Number of valid bits in bi_buf. All bits above the last valid bit
255  * are always zero.
256  */
257 
258 } FAR deflate_state;
259 
260 /* Output a byte on the stream.
261  * IN assertion: there is enough room in pending_buf.
262  */
263 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
264 
265 
266 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
267 /* Minimum amount of lookahead, except at the end of the input file.
268  * See deflate.c for comments about the MIN_MATCH+1.
269  */
270 
271 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
272 /* In order to simplify the code, particularly on 16 bit machines, match
273  * distances are limited to MAX_DIST instead of WSIZE.
274  */
275 
276  /* in trees.c */
277 void _tr_init OF((deflate_state *s));
278 int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
279 void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len,
280  int eof));
281 void _tr_align OF((deflate_state *s));
282 void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
283  int eof));
284 
285 #define d_code(dist) \
286  ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
287 /* Mapping from a distance to a distance code. dist is the distance - 1 and
288  * must not have side effects. _dist_code[256] and _dist_code[257] are never
289  * used.
290  */
291 
292 #ifndef DEBUG
293 /* Inline versions of _tr_tally for speed: */
294 
295 #if defined(GEN_TREES_H) || !defined(STDC)
296  extern uch _length_code[];
297  extern uch _dist_code[];
298 #else
299  extern const uch _length_code[];
300  extern const uch _dist_code[];
301 #endif
302 
303 # define _tr_tally_lit(s, c, flush) \
304  { uch cc = (c); \
305  s->d_buf[s->last_lit] = 0; \
306  s->l_buf[s->last_lit++] = cc; \
307  s->dyn_ltree[cc].Freq++; \
308  flush = (s->last_lit == s->lit_bufsize-1); \
309  }
310 # define _tr_tally_dist(s, distance, length, flush) \
311  { uch len = (length); \
312  ush dist = (distance); \
313  s->d_buf[s->last_lit] = dist; \
314  s->l_buf[s->last_lit++] = len; \
315  dist--; \
316  s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
317  s->dyn_dtree[d_code(dist)].Freq++; \
318  flush = (s->last_lit == s->lit_bufsize-1); \
319  }
320 #else
321 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
322 # define _tr_tally_dist(s, distance, length, flush) \
323  flush = _tr_tally(s, distance, length)
324 #endif
325 
326 #endif /* DEFLATE_H */
Definition: zinftree.h:24