kernel/zmod/deflate.h

   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 #ifndef _DEFLATE_H
  12 #define _DEFLATE_H
  13
  14 #include "zutil.h"
  15
  16 /* define NO_GZIP when compiling if you want to disable gzip header and
  17    trailer creation by deflate().  NO_GZIP would be used to avoid linking in
  18    the crc code when it is not needed.  For shared libraries, gzip encoding
  19    should be left enabled. */
  20 #ifndef NO_GZIP
  21 #  define GZIP
  22 #endif
  23
  24 /* ===========================================================================
  25  * Internal compression state.
  26  */
  27
  28 #define LENGTH_CODES 29
  29 /* number of length codes, not counting the special END_BLOCK code */
  30
  31 #define LITERALS  256
  32 /* number of literal bytes 0..255 */
  33
  34 #define L_CODES (LITERALS+1+LENGTH_CODES)
  35 /* number of Literal or Length codes, including the END_BLOCK code */
  36
  37 #define D_CODES   30
  38 /* number of distance codes */
  39
  40 #define BL_CODES  19
  41 /* number of codes used to transfer the bit lengths */
  42
  43 #define HEAP_SIZE (2*L_CODES+1)
  44 /* maximum heap size */
  45
  46 #define MAX_BITS 15
  47 /* All codes must not exceed MAX_BITS bits */
  48
  49 #define INIT_STATE    42
  50 #define EXTRA_STATE   69
  51 #define NAME_STATE    73
  52 #define COMMENT_STATE 91
  53 #define HCRC_STATE   103
  54 #define BUSY_STATE   113
  55 #define FINISH_STATE 666
  56 /* Stream status */
  57
  58
  59 /* Data structure describing a single value and its code string. */
  60 typedef struct ct_data_s {
  61     union {
  62         ush  freq;       /* frequency count */
  63         ush  code;       /* bit string */
  64     } fc;
  65     union {
  66         ush  dad;        /* father node in Huffman tree */
  67         ush  len;        /* length of bit string */
  68     } dl;
  69 } FAR ct_data;
  70
  71 #define Freq fc.freq
  72 #define Code fc.code
  73 #define Dad  dl.dad
  74 #define Len  dl.len
  75
  76 typedef struct static_tree_desc_s  static_tree_desc;
  77
  78 typedef struct tree_desc_s {
  79     ct_data *dyn_tree;           /* the dynamic tree */
  80     int     max_code;            /* largest code with non zero frequency */
  81     static_tree_desc *stat_desc; /* the corresponding static tree */
  82 } FAR tree_desc;
  83
  84 typedef ush Pos;
  85 typedef Pos FAR Posf;
  86 typedef unsigned IPos;
  87
  88 /* A Pos is an index in the character window. We use short instead of int to
  89  * save space in the various tables. IPos is used only for parameter passing.
  90  */
  91
  92 typedef struct internal_state {
  93     z_streamp strm;      /* pointer back to this zlib stream */
  94     int   status;        /* as the name implies */
  95     Bytef *pending_buf;  /* output still pending */
  96     ulg   pending_buf_size; /* size of pending_buf */
  97     Bytef *pending_out;  /* next pending byte to output to the stream */
  98     uInt   pending;      /* nb of bytes in the pending buffer */
  99     int   wrap;          /* bit 0 true for zlib, bit 1 true for gzip */
 100     gz_headerp  gzhead;  /* gzip header information to write */
 101     uInt   gzindex;      /* where in extra, name, or comment */
 102     Byte  method;        /* STORED (for zip only) or DEFLATED */
 103     int   last_flush;    /* value of flush param for previous deflate call */
 104
 105                 /* used by deflate.c: */
 106
 107     uInt  w_size;        /* LZ77 window size (32K by default) */
 108     uInt  w_bits;        /* log2(w_size)  (8..16) */
 109     uInt  w_mask;        /* w_size - 1 */
 110
 111     Bytef *window;
 112     /* Sliding window. Input bytes are read into the second half of the window,
 113      * and move to the first half later to keep a dictionary of at least wSize
 114      * bytes. With this organization, matches are limited to a distance of
 115      * wSize-MAX_MATCH bytes, but this ensures that IO is always
 116      * performed with a length multiple of the block size. Also, it limits
 117      * the window size to 64K, which is quite useful on MSDOS.
 118      * To do: use the user input buffer as sliding window.
 119      */
 120
 121     ulg window_size;
 122     /* Actual size of window: 2*wSize, except when the user input buffer
 123      * is directly used as sliding window.
 124      */
 125
 126     Posf *prev;
 127     /* Link to older string with same hash index. To limit the size of this
 128      * array to 64K, this link is maintained only for the last 32K strings.
 129      * An index in this array is thus a window index modulo 32K.
 130      */
 131
 132     Posf *head; /* Heads of the hash chains or NIL. */
 133
 134     uInt  ins_h;          /* hash index of string to be inserted */
 135     uInt  hash_size;      /* number of elements in hash table */
 136     uInt  hash_bits;      /* log2(hash_size) */
 137     uInt  hash_mask;      /* hash_size-1 */
 138
 139     uInt  hash_shift;
 140     /* Number of bits by which ins_h must be shifted at each input
 141      * step. It must be such that after MIN_MATCH steps, the oldest
 142      * byte no longer takes part in the hash key, that is:
 143      *   hash_shift * MIN_MATCH >= hash_bits
 144      */
 145
 146     long block_start;
 147     /* Window position at the beginning of the current output block. Gets
 148      * negative when the window is moved backwards.
 149      */
 150
 151     uInt match_length;           /* length of best match */
 152     IPos prev_match;             /* previous match */
 153     int match_available;         /* set if previous match exists */
 154     uInt strstart;               /* start of string to insert */
 155     uInt match_start;            /* start of matching string */
 156     uInt lookahead;              /* number of valid bytes ahead in window */
 157
 158     uInt prev_length;
 159     /* Length of the best match at previous step. Matches not greater than this
 160      * are discarded. This is used in the lazy match evaluation.
 161      */
 162
 163     uInt max_chain_length;
 164     /* To speed up deflation, hash chains are never searched beyond this
 165      * length.  A higher limit improves compression ratio but degrades the
 166      * speed.
 167      */
 168
 169     uInt max_lazy_match;
 170     /* Attempt to find a better match only when the current match is strictly
 171      * smaller than this value. This mechanism is used only for compression
 172      * levels >= 4.
 173      */
 174 #   define max_insert_length  max_lazy_match
 175     /* Insert new strings in the hash table only if the match length is not
 176      * greater than this length. This saves time but degrades compression.
 177      * max_insert_length is used only for compression levels <= 3.
 178      */
 179
 180     int level;    /* compression level (1..9) */
 181     int strategy; /* favor or force Huffman coding*/
 182
 183     uInt good_match;
 184     /* Use a faster search when the previous match is longer than this */
 185
 186     int nice_match; /* Stop searching when current match exceeds this */
 187
 188                 /* used by trees.c: */
 189     /* Didn't use ct_data typedef below to supress compiler warning */
 190     struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
 191     struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
 192     struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
 193
 194     struct tree_desc_s l_desc;               /* desc. for literal tree */
 195     struct tree_desc_s d_desc;               /* desc. for distance tree */
 196     struct tree_desc_s bl_desc;              /* desc. for bit length tree */
 197
 198     ush bl_count[MAX_BITS+1];
 199     /* number of codes at each bit length for an optimal tree */
 200
 201     int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
 202     int heap_len;               /* number of elements in the heap */
 203     int heap_max;               /* element of largest frequency */
 204     /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
 205      * The same heap array is used to build all trees.
 206      */
 207
 208     uch depth[2*L_CODES+1];
 209     /* Depth of each subtree used as tie breaker for trees of equal frequency
 210      */
 211
 212     uchf *l_buf;          /* buffer for literals or lengths */
 213
 214     uInt  lit_bufsize;
 215     /* Size of match buffer for literals/lengths.  There are 4 reasons for
 216      * limiting lit_bufsize to 64K:
 217      *   - frequencies can be kept in 16 bit counters
 218      *   - if compression is not successful for the first block, all input
 219      *     data is still in the window so we can still emit a stored block even
 220      *     when input comes from standard input.  (This can also be done for
 221      *     all blocks if lit_bufsize is not greater than 32K.)
 222      *   - if compression is not successful for a file smaller than 64K, we can
 223      *     even emit a stored file instead of a stored block (saving 5 bytes).
 224      *     This is applicable only for zip (not gzip or zlib).
 225      *   - creating new Huffman trees less frequently may not provide fast
 226      *     adaptation to changes in the input data statistics. (Take for
 227      *     example a binary file with poorly compressible code followed by
 228      *     a highly compressible string table.) Smaller buffer sizes give
 229      *     fast adaptation but have of course the overhead of transmitting
 230      *     trees more frequently.
 231      *   - I can't count above 4
 232      */
 233
 234     uInt last_lit;      /* running index in l_buf */
 235
 236     ushf *d_buf;
 237     /* Buffer for distances. To simplify the code, d_buf and l_buf have
 238      * the same number of elements. To use different lengths, an extra flag
 239      * array would be necessary.
 240      */
 241
 242     ulg opt_len;        /* bit length of current block with optimal trees */
 243     ulg static_len;     /* bit length of current block with static trees */
 244     uInt matches;       /* number of string matches in current block */
 245     int last_eob_len;   /* bit length of EOB code for last block */
 246
 247 #ifdef DEBUG
 248     ulg compressed_len; /* total bit length of compressed file mod 2^32 */
 249     ulg bits_sent;      /* bit length of compressed data sent mod 2^32 */
 250 #endif
 251
 252     ush bi_buf;
 253     /* Output buffer. bits are inserted starting at the bottom (least
 254      * significant bits).
 255      */
 256     int bi_valid;
 257     /* Number of valid bits in bi_buf.  All bits above the last valid bit
 258      * are always zero.
 259      */
 260
 261 } FAR deflate_state;
 262
 263 /* Output a byte on the stream.
 264  * IN assertion: there is enough room in pending_buf.
 265  */
 266 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
 267
 268
 269 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
 270 /* Minimum amount of lookahead, except at the end of the input file.
 271  * See deflate.c for comments about the MIN_MATCH+1.
 272  */
 273
 274 #define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
 275 /* In order to simplify the code, particularly on 16 bit machines, match
 276  * distances are limited to MAX_DIST instead of WSIZE.
 277  */
 278
 279         /* in trees.c */
 280 void _tr_init         OF((deflate_state *s));
 281 int  _tr_tally        OF((deflate_state *s, unsigned dist, unsigned lc));
 282 void _tr_flush_block  OF((deflate_state *s, charf *buf, ulg stored_len,
 283                           int eof));
 284 void _tr_align        OF((deflate_state *s));
 285 void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
 286                           int eof));
 287
 288 #define d_code(dist) \
 289    ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
 290 /* Mapping from a distance to a distance code. dist is the distance - 1 and
 291  * must not have side effects. _dist_code[256] and _dist_code[257] are never
 292  * used.
 293  */
 294
 295 #ifndef DEBUG
 296 /* Inline versions of _tr_tally for speed: */
 297
 298 #if defined(GEN_TREES_H) || !defined(STDC)
 299   extern uch _length_code[];
 300   extern uch _dist_code[];
 301 #else
 302   extern const uch _length_code[];
 303   extern const uch _dist_code[];
 304 #endif
 305
 306 # define _tr_tally_lit(s, c, flush) \
 307   { uch cc = (c); \
 308     s->d_buf[s->last_lit] = 0; \
 309     s->l_buf[s->last_lit++] = cc; \
 310     s->dyn_ltree[cc].Freq++; \
 311     flush = (s->last_lit == s->lit_bufsize-1); \
 312    }
 313 # define _tr_tally_dist(s, distance, length, flush) \
 314   { uch len = (length); \
 315     ush dist = (distance); \
 316     s->d_buf[s->last_lit] = dist; \
 317     s->l_buf[s->last_lit++] = len; \
 318     dist--; \
 319     s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
 320     s->dyn_dtree[d_code(dist)].Freq++; \
 321     flush = (s->last_lit == s->lit_bufsize-1); \
 322   }
 323 #else
 324 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
 325 # define _tr_tally_dist(s, distance, length, flush) \
 326               flush = _tr_tally(s, distance, length)
 327 #endif
 328
 329 #endif /* _DEFLATE_H */