lib/zlib_deflate/defutil.h

   1
   2
   3
   4 #define Assert(err, str)
   5 #define Trace(dummy)
   6 #define Tracev(dummy)
   7 #define Tracecv(err, dummy)
   8 #define Tracevv(dummy)
   9
  10
  11
  12 #define LENGTH_CODES 29
  13 /* number of length codes, not counting the special END_BLOCK code */
  14
  15 #define LITERALS  256
  16 /* number of literal bytes 0..255 */
  17
  18 #define L_CODES (LITERALS+1+LENGTH_CODES)
  19 /* number of Literal or Length codes, including the END_BLOCK code */
  20
  21 #define D_CODES   30
  22 /* number of distance codes */
  23
  24 #define BL_CODES  19
  25 /* number of codes used to transfer the bit lengths */
  26
  27 #define HEAP_SIZE (2*L_CODES+1)
  28 /* maximum heap size */
  29
  30 #define MAX_BITS 15
  31 /* All codes must not exceed MAX_BITS bits */
  32
  33 #define INIT_STATE    42
  34 #define BUSY_STATE   113
  35 #define FINISH_STATE 666
  36 /* Stream status */
  37
  38
  39 /* Data structure describing a single value and its code string. */
  40 typedef struct ct_data_s {
  41     union {
  42         ush  freq;       /* frequency count */
  43         ush  code;       /* bit string */
  44     } fc;
  45     union {
  46         ush  dad;        /* father node in Huffman tree */
  47         ush  len;        /* length of bit string */
  48     } dl;
  49 } ct_data;
  50
  51 #define Freq fc.freq
  52 #define Code fc.code
  53 #define Dad  dl.dad
  54 #define Len  dl.len
  55
  56 typedef struct static_tree_desc_s  static_tree_desc;
  57
  58 typedef struct tree_desc_s {
  59     ct_data *dyn_tree;           /* the dynamic tree */
  60     int     max_code;            /* largest code with non zero frequency */
  61     static_tree_desc *stat_desc; /* the corresponding static tree */
  62 } tree_desc;
  63
  64 typedef ush Pos;
  65 typedef unsigned IPos;
  66
  67 /* A Pos is an index in the character window. We use short instead of int to
  68  * save space in the various tables. IPos is used only for parameter passing.
  69  */
  70
  71 typedef struct deflate_state {
  72     z_streamp strm;      /* pointer back to this zlib stream */
  73     int   status;        /* as the name implies */
  74     Byte *pending_buf;   /* output still pending */
  75     ulg   pending_buf_size; /* size of pending_buf */
  76     Byte *pending_out;   /* next pending byte to output to the stream */
  77     int   pending;       /* nb of bytes in the pending buffer */
  78     int   noheader;      /* suppress zlib header and adler32 */
  79     Byte  data_type;     /* UNKNOWN, BINARY or ASCII */
  80     Byte  method;        /* STORED (for zip only) or DEFLATED */
  81     int   last_flush;    /* value of flush param for previous deflate call */
  82
  83                 /* used by deflate.c: */
  84
  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
  89     Byte *window;
  90     /* Sliding window. Input bytes are read into the second half of the window,
  91      * and move to the first half later to keep a dictionary of at least wSize
  92      * bytes. With this organization, matches are limited to a distance of
  93      * wSize-MAX_MATCH bytes, but this ensures that IO is always
  94      * performed with a length multiple of the block size. Also, it limits
  95      * the window size to 64K, which is quite useful on MSDOS.
  96      * To do: use the user input buffer as sliding window.
  97      */
  98
  99     ulg window_size;
 100     /* Actual size of window: 2*wSize, except when the user input buffer
 101      * is directly used as sliding window.
 102      */
 103
 104     Pos *prev;
 105     /* Link to older string with same hash index. To limit the size of this
 106      * array to 64K, this link is maintained only for the last 32K strings.
 107      * An index in this array is thus a window index modulo 32K.
 108      */
 109
 110     Pos *head; /* Heads of the hash chains or NIL. */
 111
 112     uInt  ins_h;          /* hash index of string to be inserted */
 113     uInt  hash_size;      /* number of elements in hash table */
 114     uInt  hash_bits;      /* log2(hash_size) */
 115     uInt  hash_mask;      /* hash_size-1 */
 116
 117     uInt  hash_shift;
 118     /* Number of bits by which ins_h must be shifted at each input
 119      * step. It must be such that after MIN_MATCH steps, the oldest
 120      * byte no longer takes part in the hash key, that is:
 121      *   hash_shift * MIN_MATCH >= hash_bits
 122      */
 123
 124     long block_start;
 125     /* Window position at the beginning of the current output block. Gets
 126      * negative when the window is moved backwards.
 127      */
 128
 129     uInt match_length;           /* length of best match */
 130     IPos prev_match;             /* previous match */
 131     int match_available;         /* set if previous match exists */
 132     uInt strstart;               /* start of string to insert */
 133     uInt match_start;            /* start of matching string */
 134     uInt lookahead;              /* number of valid bytes ahead in window */
 135
 136     uInt prev_length;
 137     /* Length of the best match at previous step. Matches not greater than this
 138      * are discarded. This is used in the lazy match evaluation.
 139      */
 140
 141     uInt max_chain_length;
 142     /* To speed up deflation, hash chains are never searched beyond this
 143      * length.  A higher limit improves compression ratio but degrades the
 144      * speed.
 145      */
 146
 147     uInt max_lazy_match;
 148     /* Attempt to find a better match only when the current match is strictly
 149      * smaller than this value. This mechanism is used only for compression
 150      * levels >= 4.
 151      */
 152 #   define max_insert_length  max_lazy_match
 153     /* Insert new strings in the hash table only if the match length is not
 154      * greater than this length. This saves time but degrades compression.
 155      * max_insert_length is used only for compression levels <= 3.
 156      */
 157
 158     int level;    /* compression level (1..9) */
 159     int strategy; /* favor or force Huffman coding*/
 160
 161     uInt good_match;
 162     /* Use a faster search when the previous match is longer than this */
 163
 164     int nice_match; /* Stop searching when current match exceeds this */
 165
 166                 /* used by trees.c: */
 167     /* Didn't use ct_data typedef below to supress compiler warning */
 168     struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
 169     struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
 170     struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
 171
 172     struct tree_desc_s l_desc;               /* desc. for literal tree */
 173     struct tree_desc_s d_desc;               /* desc. for distance tree */
 174     struct tree_desc_s bl_desc;              /* desc. for bit length tree */
 175
 176     ush bl_count[MAX_BITS+1];
 177     /* number of codes at each bit length for an optimal tree */
 178
 179     int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
 180     int heap_len;               /* number of elements in the heap */
 181     int heap_max;               /* element of largest frequency */
 182     /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
 183      * The same heap array is used to build all trees.
 184      */
 185
 186     uch depth[2*L_CODES+1];
 187     /* Depth of each subtree used as tie breaker for trees of equal frequency
 188      */
 189
 190     uch *l_buf;          /* buffer for literals or lengths */
 191
 192     uInt  lit_bufsize;
 193     /* Size of match buffer for literals/lengths.  There are 4 reasons for
 194      * limiting lit_bufsize to 64K:
 195      *   - frequencies can be kept in 16 bit counters
 196      *   - if compression is not successful for the first block, all input
 197      *     data is still in the window so we can still emit a stored block even
 198      *     when input comes from standard input.  (This can also be done for
 199      *     all blocks if lit_bufsize is not greater than 32K.)
 200      *   - if compression is not successful for a file smaller than 64K, we can
 201      *     even emit a stored file instead of a stored block (saving 5 bytes).
 202      *     This is applicable only for zip (not gzip or zlib).
 203      *   - creating new Huffman trees less frequently may not provide fast
 204      *     adaptation to changes in the input data statistics. (Take for
 205      *     example a binary file with poorly compressible code followed by
 206      *     a highly compressible string table.) Smaller buffer sizes give
 207      *     fast adaptation but have of course the overhead of transmitting
 208      *     trees more frequently.
 209      *   - I can't count above 4
 210      */
 211
 212     uInt last_lit;      /* running index in l_buf */
 213
 214     ush *d_buf;
 215     /* Buffer for distances. To simplify the code, d_buf and l_buf have
 216      * the same number of elements. To use different lengths, an extra flag
 217      * array would be necessary.
 218      */
 219
 220     ulg opt_len;        /* bit length of current block with optimal trees */
 221     ulg static_len;     /* bit length of current block with static trees */
 222     ulg compressed_len; /* total bit length of compressed file */
 223     uInt matches;       /* number of string matches in current block */
 224     int last_eob_len;   /* bit length of EOB code for last block */
 225
 226 #ifdef DEBUG_ZLIB
 227     ulg bits_sent;      /* bit length of the compressed data */
 228 #endif
 229
 230     ush bi_buf;
 231     /* Output buffer. bits are inserted starting at the bottom (least
 232      * significant bits).
 233      */
 234     int bi_valid;
 235     /* Number of valid bits in bi_buf.  All bits above the last valid bit
 236      * are always zero.
 237      */
 238
 239 } deflate_state;
 240
 241 typedef struct deflate_workspace {
 242     /* State memory for the deflator */
 243     deflate_state deflate_memory;
 244     Byte window_memory[2 * (1 << MAX_WBITS)];
 245     Pos prev_memory[1 << MAX_WBITS];
 246     Pos head_memory[1 << (MAX_MEM_LEVEL + 7)];
 247     char overlay_memory[(1 << (MAX_MEM_LEVEL + 6)) * (sizeof(ush)+2)];
 248 } deflate_workspace;
 249
 250 /* Output a byte on the stream.
 251  * IN assertion: there is enough room in pending_buf.
 252  */
 253 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
 254
 255
 256 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
 257 /* Minimum amount of lookahead, except at the end of the input file.
 258  * See deflate.c for comments about the MIN_MATCH+1.
 259  */
 260
 261 #define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
 262 /* In order to simplify the code, particularly on 16 bit machines, match
 263  * distances are limited to MAX_DIST instead of WSIZE.
 264  */
 265
 266         /* in trees.c */
 267 void zlib_tr_init         (deflate_state *s);
 268 int  zlib_tr_tally        (deflate_state *s, unsigned dist, unsigned lc);
 269 ulg  zlib_tr_flush_block  (deflate_state *s, char *buf, ulg stored_len,
 270                            int eof);
 271 void zlib_tr_align        (deflate_state *s);
 272 void zlib_tr_stored_block (deflate_state *s, char *buf, ulg stored_len,
 273                            int eof);
 274 void zlib_tr_stored_type_only (deflate_state *);
 275
 276
 277 /* ===========================================================================
 278  * Output a short LSB first on the stream.
 279  * IN assertion: there is enough room in pendingBuf.
 280  */
 281 #define put_short(s, w) { \
 282     put_byte(s, (uch)((w) & 0xff)); \
 283     put_byte(s, (uch)((ush)(w) >> 8)); \
 284 }
 285
 286 /* ===========================================================================
 287  * Reverse the first len bits of a code, using straightforward code (a faster
 288  * method would use a table)
 289  * IN assertion: 1 <= len <= 15
 290  */
 291 static inline unsigned bi_reverse(unsigned code, /* the value to invert */
 292                                   int len)       /* its bit length */
 293 {
 294     register unsigned res = 0;
 295     do {
 296         res |= code & 1;
 297         code >>= 1, res <<= 1;
 298     } while (--len > 0);
 299     return res >> 1;
 300 }
 301
 302 /* ===========================================================================
 303  * Flush the bit buffer, keeping at most 7 bits in it.
 304  */
 305 static inline void bi_flush(deflate_state *s)
 306 {
 307     if (s->bi_valid == 16) {
 308         put_short(s, s->bi_buf);
 309         s->bi_buf = 0;
 310         s->bi_valid = 0;
 311     } else if (s->bi_valid >= 8) {
 312         put_byte(s, (Byte)s->bi_buf);
 313         s->bi_buf >>= 8;
 314         s->bi_valid -= 8;
 315     }
 316 }
 317
 318 /* ===========================================================================
 319  * Flush the bit buffer and align the output on a byte boundary
 320  */
 321 static inline void bi_windup(deflate_state *s)
 322 {
 323     if (s->bi_valid > 8) {
 324         put_short(s, s->bi_buf);
 325     } else if (s->bi_valid > 0) {
 326         put_byte(s, (Byte)s->bi_buf);
 327     }
 328     s->bi_buf = 0;
 329     s->bi_valid = 0;
 330 #ifdef DEBUG_ZLIB
 331     s->bits_sent = (s->bits_sent+7) & ~7;
 332 #endif
 333 }
 334