RTEMS: cpukit/zlib/deflate.h Source File

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