modules/zlib/src/deflate.h

   1 /* deflate.h -- internal compression state
   2  * Copyright (C) 1995-2024 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 /* define LIT_MEM to slightly increase the speed of deflate (order 1% to 2%) at
  27    the cost of a larger memory footprint */
  28 /* #define LIT_MEM */
  29
  30 /* ===========================================================================
  31  * Internal compression state.
  32  */
  33
  34 #define LENGTH_CODES 29
  35 /* number of length codes, not counting the special END_BLOCK code */
  36
  37 #define LITERALS  256
  38 /* number of literal bytes 0..255 */
  39
  40 #define L_CODES (LITERALS+1+LENGTH_CODES)
  41 /* number of Literal or Length codes, including the END_BLOCK code */
  42
  43 #define D_CODES   30
  44 /* number of distance codes */
  45
  46 #define BL_CODES  19
  47 /* number of codes used to transfer the bit lengths */
  48
  49 #define HEAP_SIZE (2*L_CODES+1)
  50 /* maximum heap size */
  51
  52 #define MAX_BITS 15
  53 /* All codes must not exceed MAX_BITS bits */
  54
  55 #define Buf_size 16
  56 /* size of bit buffer in bi_buf */
  57
  58 #define INIT_STATE    42    /* zlib header -> BUSY_STATE */
  59 #ifdef GZIP
  60 #  define GZIP_STATE  57    /* gzip header -> BUSY_STATE | EXTRA_STATE */
  61 #endif
  62 #define EXTRA_STATE   69    /* gzip extra block -> NAME_STATE */
  63 #define NAME_STATE    73    /* gzip file name -> COMMENT_STATE */
  64 #define COMMENT_STATE 91    /* gzip comment -> HCRC_STATE */
  65 #define HCRC_STATE   103    /* gzip header CRC -> BUSY_STATE */
  66 #define BUSY_STATE   113    /* deflate -> FINISH_STATE */
  67 #define FINISH_STATE 666    /* stream complete */
  68 /* Stream status */
  69
  70
  71 /* Data structure describing a single value and its code string. */
  72 typedef struct ct_data_s {
  73     union {
  74         ush  freq;       /* frequency count */
  75         ush  code;       /* bit string */
  76     } fc;
  77     union {
  78         ush  dad;        /* father node in Huffman tree */
  79         ush  len;        /* length of bit string */
  80     } dl;
  81 } FAR ct_data;
  82
  83 #define Freq fc.freq
  84 #define Code fc.code
  85 #define Dad  dl.dad
  86 #define Len  dl.len
  87
  88 typedef struct static_tree_desc_s  static_tree_desc;
  89
  90 typedef struct tree_desc_s {
  91     ct_data *dyn_tree;           /* the dynamic tree */
  92     int     max_code;            /* largest code with non zero frequency */
  93     const static_tree_desc *stat_desc;  /* the corresponding static tree */
  94 } FAR tree_desc;
  95
  96 typedef ush Pos;
  97 typedef Pos FAR Posf;
  98 typedef unsigned IPos;
  99
 100 /* A Pos is an index in the character window. We use short instead of int to
 101  * save space in the various tables. IPos is used only for parameter passing.
 102  */
 103
 104 typedef struct internal_state {
 105     z_streamp strm;      /* pointer back to this zlib stream */
 106     int   status;        /* as the name implies */
 107     Bytef *pending_buf;  /* output still pending */
 108     ulg   pending_buf_size; /* size of pending_buf */
 109     Bytef *pending_out;  /* next pending byte to output to the stream */
 110     ulg   pending;       /* nb of bytes in the pending buffer */
 111     int   wrap;          /* bit 0 true for zlib, bit 1 true for gzip */
 112     gz_headerp  gzhead;  /* gzip header information to write */
 113     ulg   gzindex;       /* where in extra, name, or comment */
 114     Byte  method;        /* can only be DEFLATED */
 115     int   last_flush;    /* value of flush param for previous deflate call */
 116
 117                 /* used by deflate.c: */
 118
 119     uInt  w_size;        /* LZ77 window size (32K by default) */
 120     uInt  w_bits;        /* log2(w_size)  (8..16) */
 121     uInt  w_mask;        /* w_size - 1 */
 122
 123     Bytef *window;
 124     /* Sliding window. Input bytes are read into the second half of the window,
 125      * and move to the first half later to keep a dictionary of at least wSize
 126      * bytes. With this organization, matches are limited to a distance of
 127      * wSize-MAX_MATCH bytes, but this ensures that IO is always
 128      * performed with a length multiple of the block size. Also, it limits
 129      * the window size to 64K, which is quite useful on MSDOS.
 130      * To do: use the user input buffer as sliding window.
 131      */
 132
 133     ulg window_size;
 134     /* Actual size of window: 2*wSize, except when the user input buffer
 135      * is directly used as sliding window.
 136      */
 137
 138     Posf *prev;
 139     /* Link to older string with same hash index. To limit the size of this
 140      * array to 64K, this link is maintained only for the last 32K strings.
 141      * An index in this array is thus a window index modulo 32K.
 142      */
 143
 144     Posf *head; /* Heads of the hash chains or NIL. */
 145
 146     uInt  ins_h;          /* hash index of string to be inserted */
 147     uInt  hash_size;      /* number of elements in hash table */
 148     uInt  hash_bits;      /* log2(hash_size) */
 149     uInt  hash_mask;      /* hash_size-1 */
 150
 151     uInt  hash_shift;
 152     /* Number of bits by which ins_h must be shifted at each input
 153      * step. It must be such that after MIN_MATCH steps, the oldest
 154      * byte no longer takes part in the hash key, that is:
 155      *   hash_shift * MIN_MATCH >= hash_bits
 156      */
 157
 158     long block_start;
 159     /* Window position at the beginning of the current output block. Gets
 160      * negative when the window is moved backwards.
 161      */
 162
 163     uInt match_length;           /* length of best match */
 164     IPos prev_match;             /* previous match */
 165     int match_available;         /* set if previous match exists */
 166     uInt strstart;               /* start of string to insert */
 167     uInt match_start;            /* start of matching string */
 168     uInt lookahead;              /* number of valid bytes ahead in window */
 169
 170     uInt prev_length;
 171     /* Length of the best match at previous step. Matches not greater than this
 172      * are discarded. This is used in the lazy match evaluation.
 173      */
 174
 175     uInt max_chain_length;
 176     /* To speed up deflation, hash chains are never searched beyond this
 177      * length.  A higher limit improves compression ratio but degrades the
 178      * speed.
 179      */
 180
 181     uInt max_lazy_match;
 182     /* Attempt to find a better match only when the current match is strictly
 183      * smaller than this value. This mechanism is used only for compression
 184      * levels >= 4.
 185      */
 186 #   define max_insert_length  max_lazy_match
 187     /* Insert new strings in the hash table only if the match length is not
 188      * greater than this length. This saves time but degrades compression.
 189      * max_insert_length is used only for compression levels <= 3.
 190      */
 191
 192     int level;    /* compression level (1..9) */
 193     int strategy; /* favor or force Huffman coding*/
 194
 195     uInt good_match;
 196     /* Use a faster search when the previous match is longer than this */
 197
 198     int nice_match; /* Stop searching when current match exceeds this */
 199
 200                 /* used by trees.c: */
 201     /* Didn't use ct_data typedef below to suppress compiler warning */
 202     struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
 203     struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
 204     struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
 205
 206     struct tree_desc_s l_desc;               /* desc. for literal tree */
 207     struct tree_desc_s d_desc;               /* desc. for distance tree */
 208     struct tree_desc_s bl_desc;              /* desc. for bit length tree */
 209
 210     ush bl_count[MAX_BITS+1];
 211     /* number of codes at each bit length for an optimal tree */
 212
 213     int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
 214     int heap_len;               /* number of elements in the heap */
 215     int heap_max;               /* element of largest frequency */
 216     /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
 217      * The same heap array is used to build all trees.
 218      */
 219
 220     uch depth[2*L_CODES+1];
 221     /* Depth of each subtree used as tie breaker for trees of equal frequency
 222      */
 223
 224 #ifdef LIT_MEM
 225 #   define LIT_BUFS 5
 226     ushf *d_buf;          /* buffer for distances */
 227     uchf *l_buf;          /* buffer for literals/lengths */
 228 #else
 229 #   define LIT_BUFS 4
 230     uchf *sym_buf;        /* buffer for distances and literals/lengths */
 231 #endif
 232
 233     uInt  lit_bufsize;
 234     /* Size of match buffer for literals/lengths.  There are 4 reasons for
 235      * limiting lit_bufsize to 64K:
 236      *   - frequencies can be kept in 16 bit counters
 237      *   - if compression is not successful for the first block, all input
 238      *     data is still in the window so we can still emit a stored block even
 239      *     when input comes from standard input.  (This can also be done for
 240      *     all blocks if lit_bufsize is not greater than 32K.)
 241      *   - if compression is not successful for a file smaller than 64K, we can
 242      *     even emit a stored file instead of a stored block (saving 5 bytes).
 243      *     This is applicable only for zip (not gzip or zlib).
 244      *   - creating new Huffman trees less frequently may not provide fast
 245      *     adaptation to changes in the input data statistics. (Take for
 246      *     example a binary file with poorly compressible code followed by
 247      *     a highly compressible string table.) Smaller buffer sizes give
 248      *     fast adaptation but have of course the overhead of transmitting
 249      *     trees more frequently.
 250      *   - I can't count above 4
 251      */
 252
 253     uInt sym_next;      /* running index in symbol buffer */
 254     uInt sym_end;       /* symbol table full when sym_next reaches this */
 255
 256     ulg opt_len;        /* bit length of current block with optimal trees */
 257     ulg static_len;     /* bit length of current block with static trees */
 258     uInt matches;       /* number of string matches in current block */
 259     uInt insert;        /* bytes at end of window left to insert */
 260
 261 #ifdef ZLIB_DEBUG
 262     ulg compressed_len; /* total bit length of compressed file mod 2^32 */
 263     ulg bits_sent;      /* bit length of compressed data sent mod 2^32 */
 264 #endif
 265
 266     ush bi_buf;
 267     /* Output buffer. bits are inserted starting at the bottom (least
 268      * significant bits).
 269      */
 270     int bi_valid;
 271     /* Number of valid bits in bi_buf.  All bits above the last valid bit
 272      * are always zero.
 273      */
 274
 275     ulg high_water;
 276     /* High water mark offset in window for initialized bytes -- bytes above
 277      * this are set to zero in order to avoid memory check warnings when
 278      * longest match routines access bytes past the input.  This is then
 279      * updated to the new high water mark.
 280      */
 281
 282 } FAR deflate_state;
 283
 284 /* Output a byte on the stream.
 285  * IN assertion: there is enough room in pending_buf.
 286  */
 287 #define put_byte(s, c) {s->pending_buf[s->pending++] = (Bytef)(c);}
 288
 289
 290 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
 291 /* Minimum amount of lookahead, except at the end of the input file.
 292  * See deflate.c for comments about the MIN_MATCH+1.
 293  */
 294
 295 #define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
 296 /* In order to simplify the code, particularly on 16 bit machines, match
 297  * distances are limited to MAX_DIST instead of WSIZE.
 298  */
 299
 300 #define WIN_INIT MAX_MATCH
 301 /* Number of bytes after end of data in window to initialize in order to avoid
 302    memory checker errors from longest match routines */
 303
 304         /* in trees.c */
 305 void ZLIB_INTERNAL _tr_init(deflate_state *s);
 306 int ZLIB_INTERNAL _tr_tally(deflate_state *s, unsigned dist, unsigned lc);
 307 void ZLIB_INTERNAL _tr_flush_block(deflate_state *s, charf *buf,
 308                                    ulg stored_len, int last);
 309 void ZLIB_INTERNAL _tr_flush_bits(deflate_state *s);
 310 void ZLIB_INTERNAL _tr_align(deflate_state *s);
 311 void ZLIB_INTERNAL _tr_stored_block(deflate_state *s, charf *buf,
 312                                     ulg stored_len, int last);
 313
 314 #define d_code(dist) \
 315    ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
 316 /* Mapping from a distance to a distance code. dist is the distance - 1 and
 317  * must not have side effects. _dist_code[256] and _dist_code[257] are never
 318  * used.
 319  */
 320
 321 #ifndef ZLIB_DEBUG
 322 /* Inline versions of _tr_tally for speed: */
 323
 324 #if defined(GEN_TREES_H) || !defined(STDC)
 325   extern uch ZLIB_INTERNAL _length_code[];
 326   extern uch ZLIB_INTERNAL _dist_code[];
 327 #else
 328   extern const uch ZLIB_INTERNAL _length_code[];
 329   extern const uch ZLIB_INTERNAL _dist_code[];
 330 #endif
 331
 332 #ifdef LIT_MEM
 333 # define _tr_tally_lit(s, c, flush) \
 334   { uch cc = (c); \
 335     s->d_buf[s->sym_next] = 0; \
 336     s->l_buf[s->sym_next++] = cc; \
 337     s->dyn_ltree[cc].Freq++; \
 338     flush = (s->sym_next == s->sym_end); \
 339    }
 340 # define _tr_tally_dist(s, distance, length, flush) \
 341   { uch len = (uch)(length); \
 342     ush dist = (ush)(distance); \
 343     s->d_buf[s->sym_next] = dist; \
 344     s->l_buf[s->sym_next++] = len; \
 345     dist--; \
 346     s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
 347     s->dyn_dtree[d_code(dist)].Freq++; \
 348     flush = (s->sym_next == s->sym_end); \
 349   }
 350 #else
 351 # define _tr_tally_lit(s, c, flush) \
 352   { uch cc = (c); \
 353     s->sym_buf[s->sym_next++] = 0; \
 354     s->sym_buf[s->sym_next++] = 0; \
 355     s->sym_buf[s->sym_next++] = cc; \
 356     s->dyn_ltree[cc].Freq++; \
 357     flush = (s->sym_next == s->sym_end); \
 358    }
 359 # define _tr_tally_dist(s, distance, length, flush) \
 360   { uch len = (uch)(length); \
 361     ush dist = (ush)(distance); \
 362     s->sym_buf[s->sym_next++] = (uch)dist; \
 363     s->sym_buf[s->sym_next++] = (uch)(dist >> 8); \
 364     s->sym_buf[s->sym_next++] = len; \
 365     dist--; \
 366     s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
 367     s->dyn_dtree[d_code(dist)].Freq++; \
 368     flush = (s->sym_next == s->sym_end); \
 369   }
 370 #endif
 371 #else
 372 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
 373 # define _tr_tally_dist(s, distance, length, flush) \
 374               flush = _tr_tally(s, distance, length)
 375 #endif
 376
 377 #endif /* DEFLATE_H */