1/* deflate.h -- internal compression state
2 * Copyright (C) 1995-2016 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    /* zlib header -> BUSY_STATE */
55#ifdef GZIP
56#  define GZIP_STATE  57    /* gzip header -> BUSY_STATE | EXTRA_STATE */
57#endif
58#define EXTRA_STATE   69    /* gzip extra block -> NAME_STATE */
59#define NAME_STATE    73    /* gzip file name -> COMMENT_STATE */
60#define COMMENT_STATE 91    /* gzip comment -> HCRC_STATE */
61#define HCRC_STATE   103    /* gzip header CRC -> BUSY_STATE */
62#define BUSY_STATE   113    /* deflate -> FINISH_STATE */
63#define FINISH_STATE 666    /* stream complete */
64/* Stream status */
65
66
67/* Data structure describing a single value and its code string. */
68typedef struct ct_data_s {
69    union {
70        ush  freq;       /* frequency count */
71        ush  code;       /* bit string */
72    } fc;
73    union {
74        ush  dad;        /* father node in Huffman tree */
75        ush  len;        /* length of bit string */
76    } dl;
77} FAR ct_data;
78
79#define Freq fc.freq
80#define Code fc.code
81#define Dad  dl.dad
82#define Len  dl.len
83
84typedef struct static_tree_desc_s  static_tree_desc;
85
86typedef struct tree_desc_s {
87    ct_data *dyn_tree;           /* the dynamic tree */
88    int     max_code;            /* largest code with non zero frequency */
89    const static_tree_desc *stat_desc;  /* the corresponding static tree */
90} FAR tree_desc;
91
92typedef ush Pos;
93typedef Pos FAR Posf;
94typedef unsigned IPos;
95
96/* A Pos is an index in the character window. We use short instead of int to
97 * save space in the various tables. IPos is used only for parameter passing.
98 */
99
100typedef struct internal_state {
101    z_streamp strm;      /* pointer back to this zlib stream */
102    int   status;        /* as the name implies */
103    Bytef *pending_buf;  /* output still pending */
104    ulg   pending_buf_size; /* size of pending_buf */
105    Bytef *pending_out;  /* next pending byte to output to the stream */
106    ulg   pending;       /* nb of bytes in the pending buffer */
107    int   wrap;          /* bit 0 true for zlib, bit 1 true for gzip */
108    gz_headerp  gzhead;  /* gzip header information to write */
109    ulg   gzindex;       /* where in extra, name, or comment */
110    Byte  method;        /* can only be DEFLATED */
111    int   last_flush;    /* value of flush param for previous deflate call */
112
113                /* used by deflate.c: */
114
115    uInt  w_size;        /* LZ77 window size (32K by default) */
116    uInt  w_bits;        /* log2(w_size)  (8..16) */
117    uInt  w_mask;        /* w_size - 1 */
118
119    Bytef *window;
120    /* Sliding window. Input bytes are read into the second half of the window,
121     * and move to the first half later to keep a dictionary of at least wSize
122     * bytes. With this organization, matches are limited to a distance of
123     * wSize-MAX_MATCH bytes, but this ensures that IO is always
124     * performed with a length multiple of the block size. Also, it limits
125     * the window size to 64K, which is quite useful on MSDOS.
126     * To do: use the user input buffer as sliding window.
127     */
128
129    ulg window_size;
130    /* Actual size of window: 2*wSize, except when the user input buffer
131     * is directly used as sliding window.
132     */
133
134    Posf *prev;
135    /* Link to older string with same hash index. To limit the size of this
136     * array to 64K, this link is maintained only for the last 32K strings.
137     * An index in this array is thus a window index modulo 32K.
138     */
139
140    Posf *head; /* Heads of the hash chains or NIL. */
141
142    uInt  ins_h;          /* hash index of string to be inserted */
143    uInt  hash_size;      /* number of elements in hash table */
144    uInt  hash_bits;      /* log2(hash_size) */
145    uInt  hash_mask;      /* hash_size-1 */
146
147    uInt  hash_shift;
148    /* Number of bits by which ins_h must be shifted at each input
149     * step. It must be such that after MIN_MATCH steps, the oldest
150     * byte no longer takes part in the hash key, that is:
151     *   hash_shift * MIN_MATCH >= hash_bits
152     */
153
154    long block_start;
155    /* Window position at the beginning of the current output block. Gets
156     * negative when the window is moved backwards.
157     */
158
159    uInt match_length;           /* length of best match */
160    IPos prev_match;             /* previous match */
161    int match_available;         /* set if previous match exists */
162    uInt strstart;               /* start of string to insert */
163    uInt match_start;            /* start of matching string */
164    uInt lookahead;              /* number of valid bytes ahead in window */
165
166    uInt prev_length;
167    /* Length of the best match at previous step. Matches not greater than this
168     * are discarded. This is used in the lazy match evaluation.
169     */
170
171    uInt max_chain_length;
172    /* To speed up deflation, hash chains are never searched beyond this
173     * length.  A higher limit improves compression ratio but degrades the
174     * speed.
175     */
176
177    uInt max_lazy_match;
178    /* Attempt to find a better match only when the current match is strictly
179     * smaller than this value. This mechanism is used only for compression
180     * levels >= 4.
181     */
182#   define max_insert_length  max_lazy_match
183    /* Insert new strings in the hash table only if the match length is not
184     * greater than this length. This saves time but degrades compression.
185     * max_insert_length is used only for compression levels <= 3.
186     */
187
188    int level;    /* compression level (1..9) */
189    int strategy; /* favor or force Huffman coding*/
190
191    uInt good_match;
192    /* Use a faster search when the previous match is longer than this */
193
194    int nice_match; /* Stop searching when current match exceeds this */
195
196                /* used by trees.c: */
197    /* Didn't use ct_data typedef below to suppress compiler warning */
198    struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
199    struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
200    struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
201
202    struct tree_desc_s l_desc;               /* desc. for literal tree */
203    struct tree_desc_s d_desc;               /* desc. for distance tree */
204    struct tree_desc_s bl_desc;              /* desc. for bit length tree */
205
206    ush bl_count[MAX_BITS+1];
207    /* number of codes at each bit length for an optimal tree */
208
209    int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
210    int heap_len;               /* number of elements in the heap */
211    int heap_max;               /* element of largest frequency */
212    /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
213     * The same heap array is used to build all trees.
214     */
215
216    uch depth[2*L_CODES+1];
217    /* Depth of each subtree used as tie breaker for trees of equal frequency
218     */
219
220    uchf *l_buf;          /* buffer for literals or lengths */
221
222    uInt  lit_bufsize;
223    /* Size of match buffer for literals/lengths.  There are 4 reasons for
224     * limiting lit_bufsize to 64K:
225     *   - frequencies can be kept in 16 bit counters
226     *   - if compression is not successful for the first block, all input
227     *     data is still in the window so we can still emit a stored block even
228     *     when input comes from standard input.  (This can also be done for
229     *     all blocks if lit_bufsize is not greater than 32K.)
230     *   - if compression is not successful for a file smaller than 64K, we can
231     *     even emit a stored file instead of a stored block (saving 5 bytes).
232     *     This is applicable only for zip (not gzip or zlib).
233     *   - creating new Huffman trees less frequently may not provide fast
234     *     adaptation to changes in the input data statistics. (Take for
235     *     example a binary file with poorly compressible code followed by
236     *     a highly compressible string table.) Smaller buffer sizes give
237     *     fast adaptation but have of course the overhead of transmitting
238     *     trees more frequently.
239     *   - I can't count above 4
240     */
241
242    uInt last_lit;      /* running index in l_buf */
243
244    ushf *d_buf;
245    /* Buffer for distances. To simplify the code, d_buf and l_buf have
246     * the same number of elements. To use different lengths, an extra flag
247     * array would be necessary.
248     */
249
250    ulg opt_len;        /* bit length of current block with optimal trees */
251    ulg static_len;     /* bit length of current block with static trees */
252    uInt matches;       /* number of string matches in current block */
253    uInt insert;        /* bytes at end of window left to insert */
254
255#ifdef ZLIB_DEBUG
256    ulg compressed_len; /* total bit length of compressed file mod 2^32 */
257    ulg bits_sent;      /* bit length of compressed data sent mod 2^32 */
258#endif
259
260    ush bi_buf;
261    /* Output buffer. bits are inserted starting at the bottom (least
262     * significant bits).
263     */
264    int bi_valid;
265    /* Number of valid bits in bi_buf.  All bits above the last valid bit
266     * are always zero.
267     */
268
269    ulg high_water;
270    /* High water mark offset in window for initialized bytes -- bytes above
271     * this are set to zero in order to avoid memory check warnings when
272     * longest match routines access bytes past the input.  This is then
273     * updated to the new high water mark.
274     */
275
276} FAR deflate_state;
277
278/* Output a byte on the stream.
279 * IN assertion: there is enough room in pending_buf.
280 */
281#define put_byte(s, c) {s->pending_buf[s->pending++] = (Bytef)(c);}
282
283
284#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
285/* Minimum amount of lookahead, except at the end of the input file.
286 * See deflate.c for comments about the MIN_MATCH+1.
287 */
288
289#define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
290/* In order to simplify the code, particularly on 16 bit machines, match
291 * distances are limited to MAX_DIST instead of WSIZE.
292 */
293
294#define WIN_INIT MAX_MATCH
295/* Number of bytes after end of data in window to initialize in order to avoid
296   memory checker errors from longest match routines */
297
298        /* in trees.c */
299void ZLIB_INTERNAL _tr_init OF((deflate_state *s));
300int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
301void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf,
302                        ulg stored_len, int last));
303void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s));
304void ZLIB_INTERNAL _tr_align OF((deflate_state *s));
305void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
306                        ulg stored_len, int last));
307
308#define d_code(dist) \
309   ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
310/* Mapping from a distance to a distance code. dist is the distance - 1 and
311 * must not have side effects. _dist_code[256] and _dist_code[257] are never
312 * used.
313 */
314
315#ifndef ZLIB_DEBUG
316/* Inline versions of _tr_tally for speed: */
317
318#if defined(GEN_TREES_H) || !defined(STDC)
319  extern uch ZLIB_INTERNAL _length_code[];
320  extern uch ZLIB_INTERNAL _dist_code[];
321#else
322  extern const uch ZLIB_INTERNAL _length_code[];
323  extern const uch ZLIB_INTERNAL _dist_code[];
324#endif
325
326# define _tr_tally_lit(s, c, flush) \
327  { uch cc = (c); \
328    s->d_buf[s->last_lit] = 0; \
329    s->l_buf[s->last_lit++] = cc; \
330    s->dyn_ltree[cc].Freq++; \
331    flush = (s->last_lit == s->lit_bufsize-1); \
332   }
333# define _tr_tally_dist(s, distance, length, flush) \
334  { uch len = (uch)(length); \
335    ush dist = (ush)(distance); \
336    s->d_buf[s->last_lit] = dist; \
337    s->l_buf[s->last_lit++] = len; \
338    dist--; \
339    s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
340    s->dyn_dtree[d_code(dist)].Freq++; \
341    flush = (s->last_lit == s->lit_bufsize-1); \
342  }
343#else
344# define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
345# define _tr_tally_dist(s, distance, length, flush) \
346              flush = _tr_tally(s, distance, length)
347#endif
348
349#endif /* DEFLATE_H */
350