versadac  1
versadac - Scalable Recorder Firmware
deflate.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 /* ===========================================================================
19  * Internal compression state.
20  */
21 
22 #define LENGTH_CODES 29
23 /* number of length codes, not counting the special END_BLOCK code */
24 
25 #define LITERALS 256
26 /* number of literal bytes 0..255 */
27 
28 #define L_CODES (LITERALS+1+LENGTH_CODES)
29 /* number of Literal or Length codes, including the END_BLOCK code */
30 
31 #define D_CODES 30
32 /* number of distance codes */
33 
34 #define BL_CODES 19
35 /* number of codes used to transfer the bit lengths */
36 
37 #define HEAP_SIZE (2*L_CODES+1)
38 /* maximum heap size */
39 
40 #define MAX_BITS 15
41 /* All codes must not exceed MAX_BITS bits */
42 
43 #define INIT_STATE 42
44 #define BUSY_STATE 113
45 #define FINISH_STATE 666
46 /* Stream status */
47 
48 
49 /* Data structure describing a single value and its code string. */
50 typedef struct ct_data_s {
51  union {
52  ush freq; /* frequency count */
53  ush code; /* bit string */
54  } fc;
55  union {
56  ush dad; /* father node in Huffman tree */
57  ush len; /* length of bit string */
58  } dl;
59 } FAR ct_data;
60 
61 #define Freq fc.freq
62 #define Code fc.code
63 #define Dad dl.dad
64 #define Len dl.len
65 
67 
68 typedef struct tree_desc_s {
69  ct_data *dyn_tree; /* the dynamic tree */
70  int max_code; /* largest code with non zero frequency */
71  static_tree_desc *stat_desc; /* the corresponding static tree */
72 } FAR tree_desc;
73 
74 typedef ush Pos;
75 typedef Pos FAR Posf;
76 typedef unsigned IPos;
77 
78 /* A Pos is an index in the character window. We use short instead of int to
79  * save space in the various tables. IPos is used only for parameter passing.
80  */
81 
82 typedef struct internal_state {
83  z_streamp strm; /* pointer back to this zlib stream */
84  int status; /* as the name implies */
85  Bytef *pending_buf; /* output still pending */
86  ulg pending_buf_size; /* size of pending_buf */
87  Bytef *pending_out; /* next pending byte to output to the stream */
88  int pending; /* nb of bytes in the pending buffer */
89  int noheader; /* suppress zlib header and adler32 */
90  Byte data_type; /* UNKNOWN, BINARY or ASCII */
91  Byte method; /* STORED (for zip only) or DEFLATED */
92  int last_flush; /* value of flush param for previous deflate call */
93 
94  /* used by deflate.c: */
95 
96  uInt w_size; /* LZ77 window size (32K by default) */
97  uInt w_bits; /* log2(w_size) (8..16) */
98  uInt w_mask; /* w_size - 1 */
99 
100  Bytef *window;
101  /* Sliding window. Input bytes are read into the second half of the window,
102  * and move to the first half later to keep a dictionary of at least wSize
103  * bytes. With this organization, matches are limited to a distance of
104  * wSize-MAX_MATCH bytes, but this ensures that IO is always
105  * performed with a length multiple of the block size. Also, it limits
106  * the window size to 64K, which is quite useful on MSDOS.
107  * To do: use the user input buffer as sliding window.
108  */
109 
110  ulg window_size;
111  /* Actual size of window: 2*wSize, except when the user input buffer
112  * is directly used as sliding window.
113  */
114 
115  Posf *prev;
116  /* Link to older string with same hash index. To limit the size of this
117  * array to 64K, this link is maintained only for the last 32K strings.
118  * An index in this array is thus a window index modulo 32K.
119  */
120 
121  Posf *head; /* Heads of the hash chains or NIL. */
122 
123  uInt ins_h; /* hash index of string to be inserted */
124  uInt hash_size; /* number of elements in hash table */
125  uInt hash_bits; /* log2(hash_size) */
126  uInt hash_mask; /* hash_size-1 */
127 
128  uInt hash_shift;
129  /* Number of bits by which ins_h must be shifted at each input
130  * step. It must be such that after MIN_MATCH steps, the oldest
131  * byte no longer takes part in the hash key, that is:
132  * hash_shift * MIN_MATCH >= hash_bits
133  */
134 
135  long block_start;
136  /* Window position at the beginning of the current output block. Gets
137  * negative when the window is moved backwards.
138  */
139 
140  uInt match_length; /* length of best match */
141  IPos prev_match; /* previous match */
142  int match_available; /* set if previous match exists */
143  uInt strstart; /* start of string to insert */
144  uInt match_start; /* start of matching string */
145  uInt lookahead; /* number of valid bytes ahead in window */
146 
147  uInt prev_length;
148  /* Length of the best match at previous step. Matches not greater than this
149  * are discarded. This is used in the lazy match evaluation.
150  */
151 
152  uInt max_chain_length;
153  /* To speed up deflation, hash chains are never searched beyond this
154  * length. A higher limit improves compression ratio but degrades the
155  * speed.
156  */
157 
158  uInt max_lazy_match;
159  /* Attempt to find a better match only when the current match is strictly
160  * smaller than this value. This mechanism is used only for compression
161  * levels >= 4.
162  */
163 # define max_insert_length max_lazy_match
164  /* Insert new strings in the hash table only if the match length is not
165  * greater than this length. This saves time but degrades compression.
166  * max_insert_length is used only for compression levels <= 3.
167  */
168 
169  int level; /* compression level (1..9) */
170  int strategy; /* favor or force Huffman coding*/
171 
172  uInt good_match;
173  /* Use a faster search when the previous match is longer than this */
174 
175  int nice_match; /* Stop searching when current match exceeds this */
176 
177  /* used by trees.c: */
178  /* Didn't use ct_data typedef below to supress compiler warning */
179  struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */
180  struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
181  struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */
182 
183  struct tree_desc_s l_desc; /* desc. for literal tree */
184  struct tree_desc_s d_desc; /* desc. for distance tree */
185  struct tree_desc_s bl_desc; /* desc. for bit length tree */
186 
187  ush bl_count[MAX_BITS+1];
188  /* number of codes at each bit length for an optimal tree */
189 
190  int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
191  int heap_len; /* number of elements in the heap */
192  int heap_max; /* element of largest frequency */
193  /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
194  * The same heap array is used to build all trees.
195  */
196 
197  uch depth[2*L_CODES+1];
198  /* Depth of each subtree used as tie breaker for trees of equal frequency
199  */
200 
201  uchf *l_buf; /* buffer for literals or lengths */
202 
203  uInt lit_bufsize;
204  /* Size of match buffer for literals/lengths. There are 4 reasons for
205  * limiting lit_bufsize to 64K:
206  * - frequencies can be kept in 16 bit counters
207  * - if compression is not successful for the first block, all input
208  * data is still in the window so we can still emit a stored block even
209  * when input comes from standard input. (This can also be done for
210  * all blocks if lit_bufsize is not greater than 32K.)
211  * - if compression is not successful for a file smaller than 64K, we can
212  * even emit a stored file instead of a stored block (saving 5 bytes).
213  * This is applicable only for zip (not gzip or zlib).
214  * - creating new Huffman trees less frequently may not provide fast
215  * adaptation to changes in the input data statistics. (Take for
216  * example a binary file with poorly compressible code followed by
217  * a highly compressible string table.) Smaller buffer sizes give
218  * fast adaptation but have of course the overhead of transmitting
219  * trees more frequently.
220  * - I can't count above 4
221  */
222 
223  uInt last_lit; /* running index in l_buf */
224 
225  ushf *d_buf;
226  /* Buffer for distances. To simplify the code, d_buf and l_buf have
227  * the same number of elements. To use different lengths, an extra flag
228  * array would be necessary.
229  */
230 
231  ulg opt_len; /* bit length of current block with optimal trees */
232  ulg static_len; /* bit length of current block with static trees */
233  uInt matches; /* number of string matches in current block */
234  int last_eob_len; /* bit length of EOB code for last block */
235 
236 #ifdef DEBUG
237  ulg compressed_len; /* total bit length of compressed file mod 2^32 */
238  ulg bits_sent; /* bit length of compressed data sent mod 2^32 */
239 #endif
240 
241  ush bi_buf;
242  /* Output buffer. bits are inserted starting at the bottom (least
243  * significant bits).
244  */
245  int bi_valid;
246  /* Number of valid bits in bi_buf. All bits above the last valid bit
247  * are always zero.
248  */
249 
250 } FAR deflate_state;
251 
252 /* Output a byte on the stream.
253  * IN assertion: there is enough room in pending_buf.
254  */
255 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
256 
257 
258 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
259 /* Minimum amount of lookahead, except at the end of the input file.
260  * See deflate.c for comments about the MIN_MATCH+1.
261  */
262 
263 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
264 /* In order to simplify the code, particularly on 16 bit machines, match
265  * distances are limited to MAX_DIST instead of WSIZE.
266  */
267 
268  /* in trees.c */
269 void _zlib_tr_init OF((deflate_state *s));
270 int _zlib_tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
271 void _zlib_tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len,
272  int eof));
273 void _zlib_tr_align OF((deflate_state *s));
274 void _zlib_tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
275  int eof));
276 
277 #define d_code(dist) \
278  ((dist) < 256 ? _zlib_dist_code[dist] : _zlib_dist_code[256+((dist)>>7)])
279 /* Mapping from a distance to a distance code. dist is the distance - 1 and
280  * must not have side effects. _zlib_dist_code[256] and _zlib_dist_code[257] are never
281  * used.
282  */
283 
284 #ifndef DEBUG
285 /* Inline versions of _zlib_tr_tally for speed: */
286 
287 #if defined(GEN_TREES_H) || !defined(STDC)
288  extern uch _zlib_length_code[];
289  extern uch _zlib_dist_code[];
290 #else
291  extern const uch _zlib_length_code[];
292  extern const uch _zlib_dist_code[];
293 #endif
294 
295 # define _tr_tally_lit(s, c, flush) \
296  { uch cc = (c); \
297  s->d_buf[s->last_lit] = 0; \
298  s->l_buf[s->last_lit++] = cc; \
299  s->dyn_ltree[cc].Freq++; \
300  flush = (s->last_lit == s->lit_bufsize-1); \
301  }
302 # define _tr_tally_dist(s, distance, length, flush) \
303  { uch len = (length); \
304  ush dist = (distance); \
305  s->d_buf[s->last_lit] = dist; \
306  s->l_buf[s->last_lit++] = len; \
307  dist--; \
308  s->dyn_ltree[_zlib_length_code[len]+LITERALS+1].Freq++; \
309  s->dyn_dtree[d_code(dist)].Freq++; \
310  flush = (s->last_lit == s->lit_bufsize-1); \
311  }
312 #else
313 # define _tr_tally_lit(s, c, flush) flush = _zlib_tr_tally(s, 0, c)
314 # define _tr_tally_dist(s, distance, length, flush) \
315  flush = _zlib_tr_tally(s, distance, length)
316 #endif
317 
318 #endif
Definition: zlib_deflate.c:148
Definition: deflate.h:68
Definition: deflate.h:82
Definition: deflate.h:50