c62d2810 |
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: deflate.h,v 1.2 2002/03/13 17:45:56 xodnizel Exp $ */ |
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 | |
66 | typedef struct static_tree_desc_s static_tree_desc; |
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 _tr_init OF((deflate_state *s)); |
270 | int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc)); |
271 | void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len, |
272 | int eof)); |
273 | void _tr_align OF((deflate_state *s)); |
274 | void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len, |
275 | int eof)); |
276 | |
277 | #define d_code(dist) \ |
278 | ((dist) < 256 ? _dist_code[dist] : _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. _dist_code[256] and _dist_code[257] are never |
281 | * used. |
282 | */ |
283 | |
284 | #ifndef DEBUG |
285 | /* Inline versions of _tr_tally for speed: */ |
286 | |
287 | #if defined(GEN_TREES_H) || !defined(STDC) |
288 | extern uch _length_code[]; |
289 | extern uch _dist_code[]; |
290 | #else |
291 | extern const uch _length_code[]; |
292 | extern const uch _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[_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 = _tr_tally(s, 0, c) |
314 | # define _tr_tally_dist(s, distance, length, flush) \ |
315 | flush = _tr_tally(s, distance, length) |
316 | #endif |
317 | |
318 | #endif |