source: rtems/cpukit/zlib/deflate.h @ 89bace6

4.104.11
Last change on this file since 89bace6 was 959f7df2, checked in by Ralf Corsepius <ralf.corsepius@…>, on Oct 28, 2005 at 7:22:42 AM

Import of zlib-1.2.2.2.tar.gz

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1/* deflate.h -- internal compression state
2 * Copyright (C) 1995-2004 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 INIT_STATE    42
52#define EXTRA_STATE   69
53#define NAME_STATE    73
54#define COMMENT_STATE 91
55#define HCRC_STATE   103
56#define BUSY_STATE   113
57#define FINISH_STATE 666
58/* Stream status */
59
60
61/* Data structure describing a single value and its code string. */
62typedef struct ct_data_s {
63    union {
64        ush  freq;       /* frequency count */
65        ush  code;       /* bit string */
66    } fc;
67    union {
68        ush  dad;        /* father node in Huffman tree */
69        ush  len;        /* length of bit string */
70    } dl;
71} FAR ct_data;
72
73#define Freq fc.freq
74#define Code fc.code
75#define Dad  dl.dad
76#define Len  dl.len
77
78typedef struct static_tree_desc_s  static_tree_desc;
79
80typedef struct tree_desc_s {
81    ct_data *dyn_tree;           /* the dynamic tree */
82    int     max_code;            /* largest code with non zero frequency */
83    static_tree_desc *stat_desc; /* the corresponding static tree */
84} FAR tree_desc;
85
86typedef ush Pos;
87typedef Pos FAR Posf;
88typedef unsigned IPos;
89
90/* A Pos is an index in the character window. We use short instead of int to
91 * save space in the various tables. IPos is used only for parameter passing.
92 */
93
94typedef struct internal_state {
95    z_streamp strm;      /* pointer back to this zlib stream */
96    int   status;        /* as the name implies */
97    Bytef *pending_buf;  /* output still pending */
98    ulg   pending_buf_size; /* size of pending_buf */
99    Bytef *pending_out;  /* next pending byte to output to the stream */
100    int   pending;       /* nb of bytes in the pending buffer */
101    int   wrap;          /* bit 0 true for zlib, bit 1 true for gzip */
102    gz_headerp  gzhead;  /* gzip header information to write */
103    int   gzindex;       /* where in extra, name, or comment */
104    Byte  method;        /* STORED (for zip only) or DEFLATED */
105    int   last_flush;    /* value of flush param for previous deflate call */
106
107                /* used by deflate.c: */
108
109    uInt  w_size;        /* LZ77 window size (32K by default) */
110    uInt  w_bits;        /* log2(w_size)  (8..16) */
111    uInt  w_mask;        /* w_size - 1 */
112
113    Bytef *window;
114    /* Sliding window. Input bytes are read into the second half of the window,
115     * and move to the first half later to keep a dictionary of at least wSize
116     * bytes. With this organization, matches are limited to a distance of
117     * wSize-MAX_MATCH bytes, but this ensures that IO is always
118     * performed with a length multiple of the block size. Also, it limits
119     * the window size to 64K, which is quite useful on MSDOS.
120     * To do: use the user input buffer as sliding window.
121     */
122
123    ulg window_size;
124    /* Actual size of window: 2*wSize, except when the user input buffer
125     * is directly used as sliding window.
126     */
127
128    Posf *prev;
129    /* Link to older string with same hash index. To limit the size of this
130     * array to 64K, this link is maintained only for the last 32K strings.
131     * An index in this array is thus a window index modulo 32K.
132     */
133
134    Posf *head; /* Heads of the hash chains or NIL. */
135
136    uInt  ins_h;          /* hash index of string to be inserted */
137    uInt  hash_size;      /* number of elements in hash table */
138    uInt  hash_bits;      /* log2(hash_size) */
139    uInt  hash_mask;      /* hash_size-1 */
140
141    uInt  hash_shift;
142    /* Number of bits by which ins_h must be shifted at each input
143     * step. It must be such that after MIN_MATCH steps, the oldest
144     * byte no longer takes part in the hash key, that is:
145     *   hash_shift * MIN_MATCH >= hash_bits
146     */
147
148    long block_start;
149    /* Window position at the beginning of the current output block. Gets
150     * negative when the window is moved backwards.
151     */
152
153    uInt match_length;           /* length of best match */
154    IPos prev_match;             /* previous match */
155    int match_available;         /* set if previous match exists */
156    uInt strstart;               /* start of string to insert */
157    uInt match_start;            /* start of matching string */
158    uInt lookahead;              /* number of valid bytes ahead in window */
159
160    uInt prev_length;
161    /* Length of the best match at previous step. Matches not greater than this
162     * are discarded. This is used in the lazy match evaluation.
163     */
164
165    uInt max_chain_length;
166    /* To speed up deflation, hash chains are never searched beyond this
167     * length.  A higher limit improves compression ratio but degrades the
168     * speed.
169     */
170
171    uInt max_lazy_match;
172    /* Attempt to find a better match only when the current match is strictly
173     * smaller than this value. This mechanism is used only for compression
174     * levels >= 4.
175     */
176#   define max_insert_length  max_lazy_match
177    /* Insert new strings in the hash table only if the match length is not
178     * greater than this length. This saves time but degrades compression.
179     * max_insert_length is used only for compression levels <= 3.
180     */
181
182    int level;    /* compression level (1..9) */
183    int strategy; /* favor or force Huffman coding*/
184
185    uInt good_match;
186    /* Use a faster search when the previous match is longer than this */
187
188    int nice_match; /* Stop searching when current match exceeds this */
189
190                /* used by trees.c: */
191    /* Didn't use ct_data typedef below to supress compiler warning */
192    struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
193    struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
194    struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
195
196    struct tree_desc_s l_desc;               /* desc. for literal tree */
197    struct tree_desc_s d_desc;               /* desc. for distance tree */
198    struct tree_desc_s bl_desc;              /* desc. for bit length tree */
199
200    ush bl_count[MAX_BITS+1];
201    /* number of codes at each bit length for an optimal tree */
202
203    int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
204    int heap_len;               /* number of elements in the heap */
205    int heap_max;               /* element of largest frequency */
206    /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
207     * The same heap array is used to build all trees.
208     */
209
210    uch depth[2*L_CODES+1];
211    /* Depth of each subtree used as tie breaker for trees of equal frequency
212     */
213
214    uchf *l_buf;          /* buffer for literals or lengths */
215
216    uInt  lit_bufsize;
217    /* Size of match buffer for literals/lengths.  There are 4 reasons for
218     * limiting lit_bufsize to 64K:
219     *   - frequencies can be kept in 16 bit counters
220     *   - if compression is not successful for the first block, all input
221     *     data is still in the window so we can still emit a stored block even
222     *     when input comes from standard input.  (This can also be done for
223     *     all blocks if lit_bufsize is not greater than 32K.)
224     *   - if compression is not successful for a file smaller than 64K, we can
225     *     even emit a stored file instead of a stored block (saving 5 bytes).
226     *     This is applicable only for zip (not gzip or zlib).
227     *   - creating new Huffman trees less frequently may not provide fast
228     *     adaptation to changes in the input data statistics. (Take for
229     *     example a binary file with poorly compressible code followed by
230     *     a highly compressible string table.) Smaller buffer sizes give
231     *     fast adaptation but have of course the overhead of transmitting
232     *     trees more frequently.
233     *   - I can't count above 4
234     */
235
236    uInt last_lit;      /* running index in l_buf */
237
238    ushf *d_buf;
239    /* Buffer for distances. To simplify the code, d_buf and l_buf have
240     * the same number of elements. To use different lengths, an extra flag
241     * array would be necessary.
242     */
243
244    ulg opt_len;        /* bit length of current block with optimal trees */
245    ulg static_len;     /* bit length of current block with static trees */
246    uInt matches;       /* number of string matches in current block */
247    int last_eob_len;   /* bit length of EOB code for last block */
248
249#ifdef DEBUG
250    ulg compressed_len; /* total bit length of compressed file mod 2^32 */
251    ulg bits_sent;      /* bit length of compressed data sent mod 2^32 */
252#endif
253
254    ush bi_buf;
255    /* Output buffer. bits are inserted starting at the bottom (least
256     * significant bits).
257     */
258    int bi_valid;
259    /* Number of valid bits in bi_buf.  All bits above the last valid bit
260     * are always zero.
261     */
262
263} FAR deflate_state;
264
265/* Output a byte on the stream.
266 * IN assertion: there is enough room in pending_buf.
267 */
268#define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
269
270
271#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
272/* Minimum amount of lookahead, except at the end of the input file.
273 * See deflate.c for comments about the MIN_MATCH+1.
274 */
275
276#define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
277/* In order to simplify the code, particularly on 16 bit machines, match
278 * distances are limited to MAX_DIST instead of WSIZE.
279 */
280
281        /* in trees.c */
282void _tr_init         OF((deflate_state *s));
283int  _tr_tally        OF((deflate_state *s, unsigned dist, unsigned lc));
284void _tr_flush_block  OF((deflate_state *s, charf *buf, ulg stored_len,
285                          int eof));
286void _tr_align        OF((deflate_state *s));
287void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
288                          int eof));
289
290#define d_code(dist) \
291   ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
292/* Mapping from a distance to a distance code. dist is the distance - 1 and
293 * must not have side effects. _dist_code[256] and _dist_code[257] are never
294 * used.
295 */
296
297#ifndef DEBUG
298/* Inline versions of _tr_tally for speed: */
299
300#if defined(GEN_TREES_H) || !defined(STDC)
301  extern uch _length_code[];
302  extern uch _dist_code[];
303#else
304  extern const uch _length_code[];
305  extern const uch _dist_code[];
306#endif
307
308# define _tr_tally_lit(s, c, flush) \
309  { uch cc = (c); \
310    s->d_buf[s->last_lit] = 0; \
311    s->l_buf[s->last_lit++] = cc; \
312    s->dyn_ltree[cc].Freq++; \
313    flush = (s->last_lit == s->lit_bufsize-1); \
314   }
315# define _tr_tally_dist(s, distance, length, flush) \
316  { uch len = (length); \
317    ush dist = (distance); \
318    s->d_buf[s->last_lit] = dist; \
319    s->l_buf[s->last_lit++] = len; \
320    dist--; \
321    s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
322    s->dyn_dtree[d_code(dist)].Freq++; \
323    flush = (s->last_lit == s->lit_bufsize-1); \
324  }
325#else
326# define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
327# define _tr_tally_dist(s, distance, length, flush) \
328              flush = _tr_tally(s, distance, length)
329#endif
330
331#endif /* DEFLATE_H */
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