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: deflate.h,v 1.1.1.1 2012/02/17 15:09:30 misho Exp $ */
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. */
62: typedef 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:
78: typedef struct static_tree_desc_s static_tree_desc;
79:
80: typedef 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:
86: typedef ush Pos;
87: typedef Pos FAR Posf;
88: typedef 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:
94: typedef 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: uInt 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: uInt 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 */
282: void _tr_init OF((deflate_state *s));
283: int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
284: void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len,
285: int eof));
286: void _tr_align OF((deflate_state *s));
287: void _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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