1 /* deflate.h -- internal compression state
2  * Copyright (C) 1995-2012 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 /* define NO_GZIP when compiling if you want to disable gzip header and
19    trailer creation by deflate().  NO_GZIP would be used to avoid linking in
20    the crc code when it is not needed.  For shared libraries, gzip encoding
21    should be left enabled. */
22 #ifndef NO_GZIP
23 #  define GZIP
24 #endif
25 
26 /* ===========================================================================
27  * Internal compression state.
28  */
29 
30 #define LENGTH_CODES 29
31 /* number of length codes, not counting the special END_BLOCK code */
32 
33 #define LITERALS  256
34 /* number of literal bytes 0..255 */
35 
36 #define L_CODES (LITERALS+1+LENGTH_CODES)
37 /* number of Literal or Length codes, including the END_BLOCK code */
38 
39 #define D_CODES   30
40 /* number of distance codes */
41 
42 #define BL_CODES  19
43 /* number of codes used to transfer the bit lengths */
44 
45 #define HEAP_SIZE (2*L_CODES+1)
46 /* maximum heap size */
47 
48 #define MAX_BITS 15
49 /* All codes must not exceed MAX_BITS bits */
50 
51 #define Buf_size 16
52 /* size of bit buffer in bi_buf */
53 
54 #define INIT_STATE    42
55 #define EXTRA_STATE   69
56 #define NAME_STATE    73
57 #define COMMENT_STATE 91
58 #define HCRC_STATE   103
59 #define BUSY_STATE   113
60 #define FINISH_STATE 666
61 /* Stream status */
62 
63 
64 /* Data structure describing a single value and its code string. */
65 typedef struct ct_data_s {
66     union {
67         ush  freq;       /* frequency count */
68         ush  code;       /* bit string */
69     } fc;
70     union {
71         ush  dad;        /* father node in Huffman tree */
72         ush  len;        /* length of bit string */
73     } dl;
74 } FAR ct_data;
75 
76 #define Freq fc.freq
77 #define Code fc.code
78 #define Dad  dl.dad
79 #define Len  dl.len
80 
81 typedef struct static_tree_desc_s  static_tree_desc;
82 
83 typedef struct tree_desc_s {
84     ct_data *dyn_tree;           /* the dynamic tree */
85     int     max_code;            /* largest code with non zero frequency */
86     static_tree_desc *stat_desc; /* the corresponding static tree */
87 } FAR tree_desc;
88 
89 typedef ush Pos;
90 typedef Pos FAR Posf;
91 typedef unsigned IPos;
92 
93 /* A Pos is an index in the character window. We use short instead of int to
94  * save space in the various tables. IPos is used only for parameter passing.
95  */
96 
97 typedef struct internal_state {
98     z_streamp strm;      /* pointer back to this zlib stream */
99     int   status;        /* as the name implies */
100     Bytef *pending_buf;  /* output still pending */
101     ulg   pending_buf_size; /* size of pending_buf */
102     Bytef *pending_out;  /* next pending byte to output to the stream */
103     uInt   pending;      /* nb of bytes in the pending buffer */
104     int   wrap;          /* bit 0 true for zlib, bit 1 true for gzip */
105     gz_headerp  gzhead;  /* gzip header information to write */
106     uInt   gzindex;      /* where in extra, name, or comment */
107     Byte  method;        /* can only be DEFLATED */
108     int   last_flush;    /* value of flush param for previous deflate call */
109 
110                 /* used by deflate.c: */
111 
112     uInt  w_size;        /* LZ77 window size (32K by default) */
113     uInt  w_bits;        /* log2(w_size)  (8..16) */
114     uInt  w_mask;        /* w_size - 1 */
115 
116     Bytef *window;
117     /* Sliding window. Input bytes are read into the second half of the window,
118      * and move to the first half later to keep a dictionary of at least wSize
119      * bytes. With this organization, matches are limited to a distance of
120      * wSize-MAX_MATCH bytes, but this ensures that IO is always
121      * performed with a length multiple of the block size. Also, it limits
122      * the window size to 64K, which is quite useful on MSDOS.
123      * To do: use the user input buffer as sliding window.
124      */
125 
126     ulg window_size;
127     /* Actual size of window: 2*wSize, except when the user input buffer
128      * is directly used as sliding window.
129      */
130 
131     Posf *prev;
132     /* Link to older string with same hash index. To limit the size of this
133      * array to 64K, this link is maintained only for the last 32K strings.
134      * An index in this array is thus a window index modulo 32K.
135      */
136 
137     Posf *head; /* Heads of the hash chains or NIL. */
138 
139     uInt  ins_h;          /* hash index of string to be inserted */
140     uInt  hash_size;      /* number of elements in hash table */
141     uInt  hash_bits;      /* log2(hash_size) */
142     uInt  hash_mask;      /* hash_size-1 */
143 
144     uInt  hash_shift;
145     /* Number of bits by which ins_h must be shifted at each input
146      * step. It must be such that after MIN_MATCH steps, the oldest
147      * byte no longer takes part in the hash key, that is:
148      *   hash_shift * MIN_MATCH >= hash_bits
149      */
150 
151     long block_start;
152     /* Window position at the beginning of the current output block. Gets
153      * negative when the window is moved backwards.
154      */
155 
156     uInt match_length;           /* length of best match */
157     IPos prev_match;             /* previous match */
158     int match_available;         /* set if previous match exists */
159     uInt strstart;               /* start of string to insert */
160     uInt match_start;            /* start of matching string */
161     uInt lookahead;              /* number of valid bytes ahead in window */
162 
163     uInt prev_length;
164     /* Length of the best match at previous step. Matches not greater than this
165      * are discarded. This is used in the lazy match evaluation.
166      */
167 
168     uInt max_chain_length;
169     /* To speed up deflation, hash chains are never searched beyond this
170      * length.  A higher limit improves compression ratio but degrades the
171      * speed.
172      */
173 
174     uInt max_lazy_match;
175     /* Attempt to find a better match only when the current match is strictly
176      * smaller than this value. This mechanism is used only for compression
177      * levels >= 4.
178      */
179 #   define max_insert_length  max_lazy_match
180     /* Insert new strings in the hash table only if the match length is not
181      * greater than this length. This saves time but degrades compression.
182      * max_insert_length is used only for compression levels <= 3.
183      */
184 
185     int level;    /* compression level (1..9) */
186     int strategy; /* favor or force Huffman coding*/
187 
188     uInt good_match;
189     /* Use a faster search when the previous match is longer than this */
190 
191     int nice_match; /* Stop searching when current match exceeds this */
192 
193                 /* used by trees.c: */
194     /* Didn't use ct_data typedef below to suppress compiler warning */
195     struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
196     struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
197     struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
198 
199     struct tree_desc_s l_desc;               /* desc. for literal tree */
200     struct tree_desc_s d_desc;               /* desc. for distance tree */
201     struct tree_desc_s bl_desc;              /* desc. for bit length tree */
202 
203     ush bl_count[MAX_BITS+1];
204     /* number of codes at each bit length for an optimal tree */
205 
206     int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
207     int heap_len;               /* number of elements in the heap */
208     int heap_max;               /* element of largest frequency */
209     /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
210      * The same heap array is used to build all trees.
211      */
212 
213     uch depth[2*L_CODES+1];
214     /* Depth of each subtree used as tie breaker for trees of equal frequency
215      */
216 
217     uchf *l_buf;          /* buffer for literals or lengths */
218 
219     uInt  lit_bufsize;
220     /* Size of match buffer for literals/lengths.  There are 4 reasons for
221      * limiting lit_bufsize to 64K:
222      *   - frequencies can be kept in 16 bit counters
223      *   - if compression is not successful for the first block, all input
224      *     data is still in the window so we can still emit a stored block even
225      *     when input comes from standard input.  (This can also be done for
226      *     all blocks if lit_bufsize is not greater than 32K.)
227      *   - if compression is not successful for a file smaller than 64K, we can
228      *     even emit a stored file instead of a stored block (saving 5 bytes).
229      *     This is applicable only for zip (not gzip or zlib).
230      *   - creating new Huffman trees less frequently may not provide fast
231      *     adaptation to changes in the input data statistics. (Take for
232      *     example a binary file with poorly compressible code followed by
233      *     a highly compressible string table.) Smaller buffer sizes give
234      *     fast adaptation but have of course the overhead of transmitting
235      *     trees more frequently.
236      *   - I can't count above 4
237      */
238 
239     uInt last_lit;      /* running index in l_buf */
240 
241     ushf *d_buf;
242     /* Buffer for distances. To simplify the code, d_buf and l_buf have
243      * the same number of elements. To use different lengths, an extra flag
244      * array would be necessary.
245      */
246 
247     ulg opt_len;        /* bit length of current block with optimal trees */
248     ulg static_len;     /* bit length of current block with static trees */
249     uInt matches;       /* number of string matches in current block */
250     uInt insert;        /* bytes at end of window left to insert */
251 
252 #ifdef DEBUG
253     ulg compressed_len; /* total bit length of compressed file mod 2^32 */
254     ulg bits_sent;      /* bit length of compressed data sent mod 2^32 */
255 #endif
256 
257     ush bi_buf;
258     /* Output buffer. bits are inserted starting at the bottom (least
259      * significant bits).
260      */
261     int bi_valid;
262     /* Number of valid bits in bi_buf.  All bits above the last valid bit
263      * are always zero.
264      */
265 
266     ulg high_water;
267     /* High water mark offset in window for initialized bytes -- bytes above
268      * this are set to zero in order to avoid memory check warnings when
269      * longest match routines access bytes past the input.  This is then
270      * updated to the new high water mark.
271      */
272 
273 } FAR deflate_state;
274 
275 /* Output a byte on the stream.
276  * IN assertion: there is enough room in pending_buf.
277  */
278 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
279 
280 
281 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
282 /* Minimum amount of lookahead, except at the end of the input file.
283  * See deflate.c for comments about the MIN_MATCH+1.
284  */
285 
286 #define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
287 /* In order to simplify the code, particularly on 16 bit machines, match
288  * distances are limited to MAX_DIST instead of WSIZE.
289  */
290 
291 #define WIN_INIT MAX_MATCH
292 /* Number of bytes after end of data in window to initialize in order to avoid
293    memory checker errors from longest match routines */
294 
295         /* in trees.c */
296 void ZLIB_INTERNAL _tr_init OF((deflate_state *s));
297 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
298 void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf,
299                         ulg stored_len, int last));
300 void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s));
301 void ZLIB_INTERNAL _tr_align OF((deflate_state *s));
302 void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
303                         ulg stored_len, int last));
304 
305 #define d_code(dist) \
306    ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
307 /* Mapping from a distance to a distance code. dist is the distance - 1 and
308  * must not have side effects. _dist_code[256] and _dist_code[257] are never
309  * used.
310  */
311 
312 #ifndef DEBUG
313 /* Inline versions of _tr_tally for speed: */
314 
315 #if defined(GEN_TREES_H) || !defined(STDC)
316   extern uch ZLIB_INTERNAL _length_code[];
317   extern uch ZLIB_INTERNAL _dist_code[];
318 #else
319   extern const uch ZLIB_INTERNAL _length_code[];
320   extern const uch ZLIB_INTERNAL _dist_code[];
321 #endif
322 
323 # define _tr_tally_lit(s, c, flush) \
324   { uch cc = (c); \
325     s->d_buf[s->last_lit] = 0; \
326     s->l_buf[s->last_lit++] = cc; \
327     s->dyn_ltree[cc].Freq++; \
328     flush = (s->last_lit == s->lit_bufsize-1); \
329    }
330 # define _tr_tally_dist(s, distance, length, flush) \
331   { uch len = (length); \
332     ush dist = (distance); \
333     s->d_buf[s->last_lit] = dist; \
334     s->l_buf[s->last_lit++] = len; \
335     dist--; \
336     s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
337     s->dyn_dtree[d_code(dist)].Freq++; \
338     flush = (s->last_lit == s->lit_bufsize-1); \
339   }
340 #else
341 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
342 # define _tr_tally_dist(s, distance, length, flush) \
343               flush = _tr_tally(s, distance, length)
344 #endif
345 
346 #endif /* DEFLATE_H */
347