deflate.h 12 KB

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