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comparison src/zlib/deflate.h @ 10:1040ca591f2e

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First entry of Paradise Server 2.9 patch 10 Beta
author darius
date Sat, 06 Dec 1997 04:37:18 +0000
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9:331055a97a9d 10:1040ca591f2e
1 /* deflate.h -- internal compression state
2 * Copyright (C) 1995 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 1.1.1.1 1997/12/06 04:37:16 darius Exp $ */
12
13 #include "zutil.h"
14
15 /* ===========================================================================
16 * Internal compression state.
17 */
18
19 /* Data type */
20 #define BINARY 0
21 #define ASCII 1
22 #define UNKNOWN 2
23
24 #define LENGTH_CODES 29
25 /* number of length codes, not counting the special END_BLOCK code */
26
27 #define LITERALS 256
28 /* number of literal bytes 0..255 */
29
30 #define L_CODES (LITERALS+1+LENGTH_CODES)
31 /* number of Literal or Length codes, including the END_BLOCK code */
32
33 #define D_CODES 30
34 /* number of distance codes */
35
36 #define BL_CODES 19
37 /* number of codes used to transfer the bit lengths */
38
39 #define HEAP_SIZE (2*L_CODES+1)
40 /* maximum heap size */
41
42 #define MAX_BITS 15
43 /* All codes must not exceed MAX_BITS bits */
44
45 #define INIT_STATE 42
46 #define BUSY_STATE 113
47 #define FINISH_STATE 666
48 /* Stream status */
49
50
51 /* Data structure describing a single value and its code string. */
52 typedef struct ct_data_s {
53 union {
54 ush freq; /* frequency count */
55 ush code; /* bit string */
56 } fc;
57 union {
58 ush dad; /* father node in Huffman tree */
59 ush len; /* length of bit string */
60 } dl;
61 } ct_data;
62
63 #define Freq fc.freq
64 #define Code fc.code
65 #define Dad dl.dad
66 #define Len dl.len
67
68 typedef struct static_tree_desc_s static_tree_desc;
69
70 typedef struct tree_desc_s {
71 ct_data *dyn_tree; /* the dynamic tree */
72 int max_code; /* largest code with non zero frequency */
73 static_tree_desc *stat_desc; /* the corresponding static tree */
74 } tree_desc;
75
76 typedef ush Pos;
77 typedef unsigned IPos;
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_stream *strm; /* pointer back to this zlib stream */
84 int status; /* as the name implies */
85 Byte *pending_buf; /* output still pending */
86 Byte *pending_out; /* next pending byte to output to the stream */
87 int pending; /* nb of bytes in the pending buffer */
88 uLong adler; /* adler32 of uncompressed data */
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
93 /* used by deflate.c: */
94
95 uInt w_size; /* LZ77 window size (32K by default) */
96 uInt w_bits; /* log2(w_size) (8..16) */
97 uInt w_mask; /* w_size - 1 */
98
99 Byte *window;
100 /* Sliding window. Input bytes are read into the second half of the window,
101 * and move to the first half later to keep a dictionary of at least wSize
102 * bytes. With this organization, matches are limited to a distance of
103 * wSize-MAX_MATCH bytes, but this ensures that IO is always
104 * performed with a length multiple of the block size. Also, it limits
105 * the window size to 64K, which is quite useful on MSDOS.
106 * To do: use the user input buffer as sliding window.
107 */
108
109 ulg window_size;
110 /* Actual size of window: 2*wSize, except when the user input buffer
111 * is directly used as sliding window.
112 */
113
114 Pos *prev;
115 /* Link to older string with same hash index. To limit the size of this
116 * array to 64K, this link is maintained only for the last 32K strings.
117 * An index in this array is thus a window index modulo 32K.
118 */
119
120 Pos *head; /* Heads of the hash chains or NIL. */
121
122 uInt ins_h; /* hash index of string to be inserted */
123 uInt hash_size; /* number of elements in hash table */
124 uInt hash_bits; /* log2(hash_size) */
125 uInt hash_mask; /* hash_size-1 */
126
127 uInt hash_shift;
128 /* Number of bits by which ins_h must be shifted at each input
129 * step. It must be such that after MIN_MATCH steps, the oldest
130 * byte no longer takes part in the hash key, that is:
131 * hash_shift * MIN_MATCH >= hash_bits
132 */
133
134 long block_start;
135 /* Window position at the beginning of the current output block. Gets
136 * negative when the window is moved backwards.
137 */
138
139 uInt match_length; /* length of best match */
140 IPos prev_match; /* previous match */
141 int match_available; /* set if previous match exists */
142 uInt strstart; /* start of string to insert */
143 uInt match_start; /* start of matching string */
144 uInt lookahead; /* number of valid bytes ahead in window */
145
146 uInt prev_length;
147 /* Length of the best match at previous step. Matches not greater than this
148 * are discarded. This is used in the lazy match evaluation.
149 */
150
151 uInt max_chain_length;
152 /* To speed up deflation, hash chains are never searched beyond this
153 * length. A higher limit improves compression ratio but degrades the
154 * speed.
155 */
156
157 uInt max_lazy_match;
158 /* Attempt to find a better match only when the current match is strictly
159 * smaller than this value. This mechanism is used only for compression
160 * levels >= 4.
161 */
162 # define max_insert_length max_lazy_match
163 /* Insert new strings in the hash table only if the match length is not
164 * greater than this length. This saves time but degrades compression.
165 * max_insert_length is used only for compression levels <= 3.
166 */
167
168 int level; /* compression level (1..9) */
169 int strategy; /* favor or force Huffman coding*/
170
171 uInt good_match;
172 /* Use a faster search when the previous match is longer than this */
173
174 int nice_match; /* Stop searching when current match exceeds this */
175
176 /* used by trees.c: */
177
178 ct_data dyn_ltree[HEAP_SIZE]; /* literal and length tree */
179 ct_data dyn_dtree[2*D_CODES+1]; /* distance tree */
180 ct_data bl_tree[2*BL_CODES+1]; /* Huffman tree for the bit lengths */
181
182 tree_desc l_desc; /* descriptor for literal tree */
183 tree_desc d_desc; /* descriptor for distance tree */
184 tree_desc bl_desc; /* descriptor for bit length tree */
185
186 ush bl_count[MAX_BITS+1];
187 /* number of codes at each bit length for an optimal tree */
188
189 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
190 int heap_len; /* number of elements in the heap */
191 int heap_max; /* element of largest frequency */
192 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
193 * The same heap array is used to build all trees.
194 */
195
196 uch depth[2*L_CODES+1];
197 /* Depth of each subtree used as tie breaker for trees of equal frequency
198 */
199
200 uch *l_buf; /* buffer for literals or lengths */
201
202 uInt lit_bufsize;
203 /* Size of match buffer for literals/lengths. There are 4 reasons for
204 * limiting lit_bufsize to 64K:
205 * - frequencies can be kept in 16 bit counters
206 * - if compression is not successful for the first block, all input
207 * data is still in the window so we can still emit a stored block even
208 * when input comes from standard input. (This can also be done for
209 * all blocks if lit_bufsize is not greater than 32K.)
210 * - if compression is not successful for a file smaller than 64K, we can
211 * even emit a stored file instead of a stored block (saving 5 bytes).
212 * This is applicable only for zip (not gzip or zlib).
213 * - creating new Huffman trees less frequently may not provide fast
214 * adaptation to changes in the input data statistics. (Take for
215 * example a binary file with poorly compressible code followed by
216 * a highly compressible string table.) Smaller buffer sizes give
217 * fast adaptation but have of course the overhead of transmitting
218 * trees more frequently.
219 * - I can't count above 4
220 */
221
222 uInt last_lit; /* running index in l_buf */
223
224 ush *d_buf;
225 /* Buffer for distances. To simplify the code, d_buf and l_buf have
226 * the same number of elements. To use different lengths, an extra flag
227 * array would be necessary.
228 */
229
230 ulg opt_len; /* bit length of current block with optimal trees */
231 ulg static_len; /* bit length of current block with static trees */
232 ulg compressed_len; /* total bit length of compressed file */
233 uInt matches; /* number of string matches in current block */
234
235 #ifdef DEBUG
236 ulg bits_sent; /* bit length of the compressed data */
237 #endif
238
239 ush bi_buf;
240 /* Output buffer. bits are inserted starting at the bottom (least
241 * significant bits).
242 */
243 int bi_valid;
244 /* Number of valid bits in bi_buf. All bits above the last valid bit
245 * are always zero.
246 */
247
248 } deflate_state;
249
250
251 /* Output a byte on the stream.
252 * IN assertion: there is enough room in pending_buf.
253 */
254 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
255
256
257 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
258 /* Minimum amount of lookahead, except at the end of the input file.
259 * See deflate.c for comments about the MIN_MATCH+1.
260 */
261
262 #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
263 /* In order to simplify the code, particularly on 16 bit machines, match
264 * distances are limited to MAX_DIST instead of WSIZE.
265 */
266
267 /* in trees.c */
268 void ct_init __P((deflate_state *s));
269 int ct_tally __P((deflate_state *s, int dist, int lc));
270 ulg ct_flush_block __P((deflate_state *s, char *buf, ulg stored_len, int eof));
271 void ct_stored_block __P((deflate_state *s, char *buf, ulg stored_len,
272 int eof));