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      1 /* deflate.h -- internal compression state
      2  * Copyright (C) 1995-2012 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 /* ===========================================================================
     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 Buf_size 16
     52 /* size of bit buffer in bi_buf */
     53 
     54 #define INIT_STATE    42
     55 #define EXTRA_STATE   69
     56 #define NAME_STATE    73
     57 #define COMMENT_STATE 91
     58 #define HCRC_STATE   103
     59 #define BUSY_STATE   113
     60 #define FINISH_STATE 666
     61 /* Stream status */
     62 
     63 
     64 /* Data structure describing a single value and its code string. */
     65 typedef struct ct_data_s {
     66     union {
     67         ush  freq;       /* frequency count */
     68         ush  code;       /* bit string */
     69     } fc;
     70     union {
     71         ush  dad;        /* father node in Huffman tree */
     72         ush  len;        /* length of bit string */
     73     } dl;
     74 } FAR ct_data;
     75 
     76 #define Freq fc.freq
     77 #define Code fc.code
     78 #define Dad  dl.dad
     79 #define Len  dl.len
     80 
     81 typedef struct static_tree_desc_s  static_tree_desc;
     82 
     83 typedef struct tree_desc_s {
     84     ct_data *dyn_tree;           /* the dynamic tree */
     85     int     max_code;            /* largest code with non zero frequency */
     86     static_tree_desc *stat_desc; /* the corresponding static tree */
     87 } FAR tree_desc;
     88 
     89 typedef ush Pos;
     90 typedef Pos FAR Posf;
     91 typedef unsigned IPos;
     92 
     93 /* A Pos is an index in the character window. We use short instead of int to
     94  * save space in the various tables. IPos is used only for parameter passing.
     95  */
     96 
     97 typedef struct internal_state {
     98     z_streamp strm;      /* pointer back to this zlib stream */
     99     int   status;        /* as the name implies */
    100     Bytef *pending_buf;  /* output still pending */
    101     ulg   pending_buf_size; /* size of pending_buf */
    102     Bytef *pending_out;  /* next pending byte to output to the stream */
    103     uInt   pending;      /* nb of bytes in the pending buffer */
    104     int   wrap;          /* bit 0 true for zlib, bit 1 true for gzip */
    105     gz_headerp  gzhead;  /* gzip header information to write */
    106     uInt   gzindex;      /* where in extra, name, or comment */
    107     Byte  method;        /* can only be DEFLATED */
    108     int   last_flush;    /* value of flush param for previous deflate call */
    109 
    110                 /* used by deflate.c: */
    111 
    112     uInt  w_size;        /* LZ77 window size (32K by default) */
    113     uInt  w_bits;        /* log2(w_size)  (8..16) */
    114     uInt  w_mask;        /* w_size - 1 */
    115 
    116     Bytef *window;
    117     /* Sliding window. Input bytes are read into the second half of the window,
    118      * and move to the first half later to keep a dictionary of at least wSize
    119      * bytes. With this organization, matches are limited to a distance of
    120      * wSize-MAX_MATCH bytes, but this ensures that IO is always
    121      * performed with a length multiple of the block size. Also, it limits
    122      * the window size to 64K, which is quite useful on MSDOS.
    123      * To do: use the user input buffer as sliding window.
    124      */
    125 
    126     ulg window_size;
    127     /* Actual size of window: 2*wSize, except when the user input buffer
    128      * is directly used as sliding window.
    129      */
    130 
    131     Posf *prev;
    132     /* Link to older string with same hash index. To limit the size of this
    133      * array to 64K, this link is maintained only for the last 32K strings.
    134      * An index in this array is thus a window index modulo 32K.
    135      */
    136 
    137     Posf *head; /* Heads of the hash chains or NIL. */
    138 
    139     uInt  ins_h;          /* hash index of string to be inserted */
    140     uInt  hash_size;      /* number of elements in hash table */
    141     uInt  hash_bits;      /* log2(hash_size) */
    142     uInt  hash_mask;      /* hash_size-1 */
    143 
    144     uInt  hash_shift;
    145     /* Number of bits by which ins_h must be shifted at each input
    146      * step. It must be such that after MIN_MATCH steps, the oldest
    147      * byte no longer takes part in the hash key, that is:
    148      *   hash_shift * MIN_MATCH >= hash_bits
    149      */
    150 
    151     long block_start;
    152     /* Window position at the beginning of the current output block. Gets
    153      * negative when the window is moved backwards.
    154      */
    155 
    156     uInt match_length;           /* length of best match */
    157     IPos prev_match;             /* previous match */
    158     int match_available;         /* set if previous match exists */
    159     uInt strstart;               /* start of string to insert */
    160     uInt match_start;            /* start of matching string */
    161     uInt lookahead;              /* number of valid bytes ahead in window */
    162 
    163     uInt prev_length;
    164     /* Length of the best match at previous step. Matches not greater than this
    165      * are discarded. This is used in the lazy match evaluation.
    166      */
    167 
    168     uInt max_chain_length;
    169     /* To speed up deflation, hash chains are never searched beyond this
    170      * length.  A higher limit improves compression ratio but degrades the
    171      * speed.
    172      */
    173 
    174     uInt max_lazy_match;
    175     /* Attempt to find a better match only when the current match is strictly
    176      * smaller than this value. This mechanism is used only for compression
    177      * levels >= 4.
    178      */
    179 #   define max_insert_length  max_lazy_match
    180     /* Insert new strings in the hash table only if the match length is not
    181      * greater than this length. This saves time but degrades compression.
    182      * max_insert_length is used only for compression levels <= 3.
    183      */
    184 
    185     int level;    /* compression level (1..9) */
    186     int strategy; /* favor or force Huffman coding*/
    187 
    188     uInt good_match;
    189     /* Use a faster search when the previous match is longer than this */
    190 
    191     int nice_match; /* Stop searching when current match exceeds this */
    192 
    193                 /* used by trees.c: */
    194     /* Didn't use ct_data typedef below to suppress compiler warning */
    195     struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
    196     struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
    197     struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
    198 
    199     struct tree_desc_s l_desc;               /* desc. for literal tree */
    200     struct tree_desc_s d_desc;               /* desc. for distance tree */
    201     struct tree_desc_s bl_desc;              /* desc. for bit length tree */
    202 
    203     ush bl_count[MAX_BITS+1];
    204     /* number of codes at each bit length for an optimal tree */
    205 
    206     int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
    207     int heap_len;               /* number of elements in the heap */
    208     int heap_max;               /* element of largest frequency */
    209     /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
    210      * The same heap array is used to build all trees.
    211      */
    212 
    213     uch depth[2*L_CODES+1];
    214     /* Depth of each subtree used as tie breaker for trees of equal frequency
    215      */
    216 
    217     uchf *l_buf;          /* buffer for literals or lengths */
    218 
    219     uInt  lit_bufsize;
    220     /* Size of match buffer for literals/lengths.  There are 4 reasons for
    221      * limiting lit_bufsize to 64K:
    222      *   - frequencies can be kept in 16 bit counters
    223      *   - if compression is not successful for the first block, all input
    224      *     data is still in the window so we can still emit a stored block even
    225      *     when input comes from standard input.  (This can also be done for
    226      *     all blocks if lit_bufsize is not greater than 32K.)
    227      *   - if compression is not successful for a file smaller than 64K, we can
    228      *     even emit a stored file instead of a stored block (saving 5 bytes).
    229      *     This is applicable only for zip (not gzip or zlib).
    230      *   - creating new Huffman trees less frequently may not provide fast
    231      *     adaptation to changes in the input data statistics. (Take for
    232      *     example a binary file with poorly compressible code followed by
    233      *     a highly compressible string table.) Smaller buffer sizes give
    234      *     fast adaptation but have of course the overhead of transmitting
    235      *     trees more frequently.
    236      *   - I can't count above 4
    237      */
    238 
    239     uInt last_lit;      /* running index in l_buf */
    240 
    241     ushf *d_buf;
    242     /* Buffer for distances. To simplify the code, d_buf and l_buf have
    243      * the same number of elements. To use different lengths, an extra flag
    244      * array would be necessary.
    245      */
    246 
    247     ulg opt_len;        /* bit length of current block with optimal trees */
    248     ulg static_len;     /* bit length of current block with static trees */
    249     uInt matches;       /* number of string matches in current block */
    250     uInt insert;        /* bytes at end of window left to insert */
    251 
    252 #ifdef DEBUG
    253     ulg compressed_len; /* total bit length of compressed file mod 2^32 */
    254     ulg bits_sent;      /* bit length of compressed data sent mod 2^32 */
    255 #endif
    256 
    257     ush bi_buf;
    258     /* Output buffer. bits are inserted starting at the bottom (least
    259      * significant bits).
    260      */
    261     int bi_valid;
    262     /* Number of valid bits in bi_buf.  All bits above the last valid bit
    263      * are always zero.
    264      */
    265 
    266     ulg high_water;
    267     /* High water mark offset in window for initialized bytes -- bytes above
    268      * this are set to zero in order to avoid memory check warnings when
    269      * longest match routines access bytes past the input.  This is then
    270      * updated to the new high water mark.
    271      */
    272 
    273 } FAR deflate_state;
    274 
    275 /* Output a byte on the stream.
    276  * IN assertion: there is enough room in pending_buf.
    277  */
    278 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
    279 
    280 
    281 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
    282 /* Minimum amount of lookahead, except at the end of the input file.
    283  * See deflate.c for comments about the MIN_MATCH+1.
    284  */
    285 
    286 #define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
    287 /* In order to simplify the code, particularly on 16 bit machines, match
    288  * distances are limited to MAX_DIST instead of WSIZE.
    289  */
    290 
    291 #define WIN_INIT MAX_MATCH
    292 /* Number of bytes after end of data in window to initialize in order to avoid
    293    memory checker errors from longest match routines */
    294 
    295         /* in trees.c */
    296 void ZLIB_INTERNAL _tr_init OF((deflate_state *s));
    297 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
    298 void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf,
    299                         ulg stored_len, int last));
    300 void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s));
    301 void ZLIB_INTERNAL _tr_align OF((deflate_state *s));
    302 void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
    303                         ulg stored_len, int last));
    304 
    305 #define d_code(dist) \
    306    ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
    307 /* Mapping from a distance to a distance code. dist is the distance - 1 and
    308  * must not have side effects. _dist_code[256] and _dist_code[257] are never
    309  * used.
    310  */
    311 
    312 #ifndef DEBUG
    313 /* Inline versions of _tr_tally for speed: */
    314 
    315 #if defined(GEN_TREES_H) || !defined(STDC)
    316   extern uch ZLIB_INTERNAL _length_code[];
    317   extern uch ZLIB_INTERNAL _dist_code[];
    318 #else
    319   extern const uch ZLIB_INTERNAL _length_code[];
    320   extern const uch ZLIB_INTERNAL _dist_code[];
    321 #endif
    322 
    323 # define _tr_tally_lit(s, c, flush) \
    324   { uch cc = (c); \
    325     s->d_buf[s->last_lit] = 0; \
    326     s->l_buf[s->last_lit++] = cc; \
    327     s->dyn_ltree[cc].Freq++; \
    328     flush = (s->last_lit == s->lit_bufsize-1); \
    329    }
    330 # define _tr_tally_dist(s, distance, length, flush) \
    331   { uch len = (length); \
    332     ush dist = (distance); \
    333     s->d_buf[s->last_lit] = dist; \
    334     s->l_buf[s->last_lit++] = len; \
    335     dist--; \
    336     s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
    337     s->dyn_dtree[d_code(dist)].Freq++; \
    338     flush = (s->last_lit == s->lit_bufsize-1); \
    339   }
    340 #else
    341 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
    342 # define _tr_tally_dist(s, distance, length, flush) \
    343               flush = _tr_tally(s, distance, length)
    344 #endif
    345 
    346 #endif /* DEFLATE_H */
    347