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author | Mark Adler <madler@alumni.caltech.edu> | 2011-09-09 22:36:31 -0700 |
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committer | Mark Adler <madler@alumni.caltech.edu> | 2011-09-09 22:36:31 -0700 |
commit | bcf78a20978d76f64b7cd46d1a4d7a79a578c77b (patch) | |
tree | 1929db4ad12c15efc15ac123264a8a9046903a7a /deflate.h | |
download | zlib-bcf78a20978d76f64b7cd46d1a4d7a79a578c77b.tar.gz zlib-bcf78a20978d76f64b7cd46d1a4d7a79a578c77b.tar.bz2 zlib-bcf78a20978d76f64b7cd46d1a4d7a79a578c77b.zip |
zlib 0.71v0.71
Diffstat (limited to 'deflate.h')
-rw-r--r-- | deflate.h | 270 |
1 files changed, 270 insertions, 0 deletions
diff --git a/deflate.h b/deflate.h new file mode 100644 index 0000000..740c25a --- /dev/null +++ b/deflate.h | |||
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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 1.3 1995/04/14 12:39:45 jloup 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)); | ||