external/zlib-1.2.11/deflate.h
author Sam Lantinga <slouken@libsdl.org>
Fri, 26 Oct 2018 14:58:01 -0700
changeset 617 d64228a395fc
parent 521 9ed2f7d4a251
permissions -rw-r--r--
Fixed webp library detection when cross-compiling for Windows
     1 /* deflate.h -- internal compression state
     2  * Copyright (C) 1995-2016 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    /* zlib header -> BUSY_STATE */
    55 #ifdef GZIP
    56 #  define GZIP_STATE  57    /* gzip header -> BUSY_STATE | EXTRA_STATE */
    57 #endif
    58 #define EXTRA_STATE   69    /* gzip extra block -> NAME_STATE */
    59 #define NAME_STATE    73    /* gzip file name -> COMMENT_STATE */
    60 #define COMMENT_STATE 91    /* gzip comment -> HCRC_STATE */
    61 #define HCRC_STATE   103    /* gzip header CRC -> BUSY_STATE */
    62 #define BUSY_STATE   113    /* deflate -> FINISH_STATE */
    63 #define FINISH_STATE 666    /* stream complete */
    64 /* Stream status */
    65 
    66 
    67 /* Data structure describing a single value and its code string. */
    68 typedef struct ct_data_s {
    69     union {
    70         ush  freq;       /* frequency count */
    71         ush  code;       /* bit string */
    72     } fc;
    73     union {
    74         ush  dad;        /* father node in Huffman tree */
    75         ush  len;        /* length of bit string */
    76     } dl;
    77 } FAR ct_data;
    78 
    79 #define Freq fc.freq
    80 #define Code fc.code
    81 #define Dad  dl.dad
    82 #define Len  dl.len
    83 
    84 typedef struct static_tree_desc_s  static_tree_desc;
    85 
    86 typedef struct tree_desc_s {
    87     ct_data *dyn_tree;           /* the dynamic tree */
    88     int     max_code;            /* largest code with non zero frequency */
    89     const static_tree_desc *stat_desc;  /* the corresponding static tree */
    90 } FAR tree_desc;
    91 
    92 typedef ush Pos;
    93 typedef Pos FAR Posf;
    94 typedef unsigned IPos;
    95 
    96 /* A Pos is an index in the character window. We use short instead of int to
    97  * save space in the various tables. IPos is used only for parameter passing.
    98  */
    99 
   100 typedef struct internal_state {
   101     z_streamp strm;      /* pointer back to this zlib stream */
   102     int   status;        /* as the name implies */
   103     Bytef *pending_buf;  /* output still pending */
   104     ulg   pending_buf_size; /* size of pending_buf */
   105     Bytef *pending_out;  /* next pending byte to output to the stream */
   106     ulg   pending;       /* nb of bytes in the pending buffer */
   107     int   wrap;          /* bit 0 true for zlib, bit 1 true for gzip */
   108     gz_headerp  gzhead;  /* gzip header information to write */
   109     ulg   gzindex;       /* where in extra, name, or comment */
   110     Byte  method;        /* can only be DEFLATED */
   111     int   last_flush;    /* value of flush param for previous deflate call */
   112 
   113                 /* used by deflate.c: */
   114 
   115     uInt  w_size;        /* LZ77 window size (32K by default) */
   116     uInt  w_bits;        /* log2(w_size)  (8..16) */
   117     uInt  w_mask;        /* w_size - 1 */
   118 
   119     Bytef *window;
   120     /* Sliding window. Input bytes are read into the second half of the window,
   121      * and move to the first half later to keep a dictionary of at least wSize
   122      * bytes. With this organization, matches are limited to a distance of
   123      * wSize-MAX_MATCH bytes, but this ensures that IO is always
   124      * performed with a length multiple of the block size. Also, it limits
   125      * the window size to 64K, which is quite useful on MSDOS.
   126      * To do: use the user input buffer as sliding window.
   127      */
   128 
   129     ulg window_size;
   130     /* Actual size of window: 2*wSize, except when the user input buffer
   131      * is directly used as sliding window.
   132      */
   133 
   134     Posf *prev;
   135     /* Link to older string with same hash index. To limit the size of this
   136      * array to 64K, this link is maintained only for the last 32K strings.
   137      * An index in this array is thus a window index modulo 32K.
   138      */
   139 
   140     Posf *head; /* Heads of the hash chains or NIL. */
   141 
   142     uInt  ins_h;          /* hash index of string to be inserted */
   143     uInt  hash_size;      /* number of elements in hash table */
   144     uInt  hash_bits;      /* log2(hash_size) */
   145     uInt  hash_mask;      /* hash_size-1 */
   146 
   147     uInt  hash_shift;
   148     /* Number of bits by which ins_h must be shifted at each input
   149      * step. It must be such that after MIN_MATCH steps, the oldest
   150      * byte no longer takes part in the hash key, that is:
   151      *   hash_shift * MIN_MATCH >= hash_bits
   152      */
   153 
   154     long block_start;
   155     /* Window position at the beginning of the current output block. Gets
   156      * negative when the window is moved backwards.
   157      */
   158 
   159     uInt match_length;           /* length of best match */
   160     IPos prev_match;             /* previous match */
   161     int match_available;         /* set if previous match exists */
   162     uInt strstart;               /* start of string to insert */
   163     uInt match_start;            /* start of matching string */
   164     uInt lookahead;              /* number of valid bytes ahead in window */
   165 
   166     uInt prev_length;
   167     /* Length of the best match at previous step. Matches not greater than this
   168      * are discarded. This is used in the lazy match evaluation.
   169      */
   170 
   171     uInt max_chain_length;
   172     /* To speed up deflation, hash chains are never searched beyond this
   173      * length.  A higher limit improves compression ratio but degrades the
   174      * speed.
   175      */
   176 
   177     uInt max_lazy_match;
   178     /* Attempt to find a better match only when the current match is strictly
   179      * smaller than this value. This mechanism is used only for compression
   180      * levels >= 4.
   181      */
   182 #   define max_insert_length  max_lazy_match
   183     /* Insert new strings in the hash table only if the match length is not
   184      * greater than this length. This saves time but degrades compression.
   185      * max_insert_length is used only for compression levels <= 3.
   186      */
   187 
   188     int level;    /* compression level (1..9) */
   189     int strategy; /* favor or force Huffman coding*/
   190 
   191     uInt good_match;
   192     /* Use a faster search when the previous match is longer than this */
   193 
   194     int nice_match; /* Stop searching when current match exceeds this */
   195 
   196                 /* used by trees.c: */
   197     /* Didn't use ct_data typedef below to suppress compiler warning */
   198     struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
   199     struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
   200     struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
   201 
   202     struct tree_desc_s l_desc;               /* desc. for literal tree */
   203     struct tree_desc_s d_desc;               /* desc. for distance tree */
   204     struct tree_desc_s bl_desc;              /* desc. for bit length tree */
   205 
   206     ush bl_count[MAX_BITS+1];
   207     /* number of codes at each bit length for an optimal tree */
   208 
   209     int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
   210     int heap_len;               /* number of elements in the heap */
   211     int heap_max;               /* element of largest frequency */
   212     /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
   213      * The same heap array is used to build all trees.
   214      */
   215 
   216     uch depth[2*L_CODES+1];
   217     /* Depth of each subtree used as tie breaker for trees of equal frequency
   218      */
   219 
   220     uchf *l_buf;          /* buffer for literals or lengths */
   221 
   222     uInt  lit_bufsize;
   223     /* Size of match buffer for literals/lengths.  There are 4 reasons for
   224      * limiting lit_bufsize to 64K:
   225      *   - frequencies can be kept in 16 bit counters
   226      *   - if compression is not successful for the first block, all input
   227      *     data is still in the window so we can still emit a stored block even
   228      *     when input comes from standard input.  (This can also be done for
   229      *     all blocks if lit_bufsize is not greater than 32K.)
   230      *   - if compression is not successful for a file smaller than 64K, we can
   231      *     even emit a stored file instead of a stored block (saving 5 bytes).
   232      *     This is applicable only for zip (not gzip or zlib).
   233      *   - creating new Huffman trees less frequently may not provide fast
   234      *     adaptation to changes in the input data statistics. (Take for
   235      *     example a binary file with poorly compressible code followed by
   236      *     a highly compressible string table.) Smaller buffer sizes give
   237      *     fast adaptation but have of course the overhead of transmitting
   238      *     trees more frequently.
   239      *   - I can't count above 4
   240      */
   241 
   242     uInt last_lit;      /* running index in l_buf */
   243 
   244     ushf *d_buf;
   245     /* Buffer for distances. To simplify the code, d_buf and l_buf have
   246      * the same number of elements. To use different lengths, an extra flag
   247      * array would be necessary.
   248      */
   249 
   250     ulg opt_len;        /* bit length of current block with optimal trees */
   251     ulg static_len;     /* bit length of current block with static trees */
   252     uInt matches;       /* number of string matches in current block */
   253     uInt insert;        /* bytes at end of window left to insert */
   254 
   255 #ifdef ZLIB_DEBUG
   256     ulg compressed_len; /* total bit length of compressed file mod 2^32 */
   257     ulg bits_sent;      /* bit length of compressed data sent mod 2^32 */
   258 #endif
   259 
   260     ush bi_buf;
   261     /* Output buffer. bits are inserted starting at the bottom (least
   262      * significant bits).
   263      */
   264     int bi_valid;
   265     /* Number of valid bits in bi_buf.  All bits above the last valid bit
   266      * are always zero.
   267      */
   268 
   269     ulg high_water;
   270     /* High water mark offset in window for initialized bytes -- bytes above
   271      * this are set to zero in order to avoid memory check warnings when
   272      * longest match routines access bytes past the input.  This is then
   273      * updated to the new high water mark.
   274      */
   275 
   276 } FAR deflate_state;
   277 
   278 /* Output a byte on the stream.
   279  * IN assertion: there is enough room in pending_buf.
   280  */
   281 #define put_byte(s, c) {s->pending_buf[s->pending++] = (Bytef)(c);}
   282 
   283 
   284 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
   285 /* Minimum amount of lookahead, except at the end of the input file.
   286  * See deflate.c for comments about the MIN_MATCH+1.
   287  */
   288 
   289 #define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
   290 /* In order to simplify the code, particularly on 16 bit machines, match
   291  * distances are limited to MAX_DIST instead of WSIZE.
   292  */
   293 
   294 #define WIN_INIT MAX_MATCH
   295 /* Number of bytes after end of data in window to initialize in order to avoid
   296    memory checker errors from longest match routines */
   297 
   298         /* in trees.c */
   299 void ZLIB_INTERNAL _tr_init OF((deflate_state *s));
   300 int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
   301 void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf,
   302                         ulg stored_len, int last));
   303 void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s));
   304 void ZLIB_INTERNAL _tr_align OF((deflate_state *s));
   305 void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
   306                         ulg stored_len, int last));
   307 
   308 #define d_code(dist) \
   309    ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
   310 /* Mapping from a distance to a distance code. dist is the distance - 1 and
   311  * must not have side effects. _dist_code[256] and _dist_code[257] are never
   312  * used.
   313  */
   314 
   315 #ifndef ZLIB_DEBUG
   316 /* Inline versions of _tr_tally for speed: */
   317 
   318 #if defined(GEN_TREES_H) || !defined(STDC)
   319   extern uch ZLIB_INTERNAL _length_code[];
   320   extern uch ZLIB_INTERNAL _dist_code[];
   321 #else
   322   extern const uch ZLIB_INTERNAL _length_code[];
   323   extern const uch ZLIB_INTERNAL _dist_code[];
   324 #endif
   325 
   326 # define _tr_tally_lit(s, c, flush) \
   327   { uch cc = (c); \
   328     s->d_buf[s->last_lit] = 0; \
   329     s->l_buf[s->last_lit++] = cc; \
   330     s->dyn_ltree[cc].Freq++; \
   331     flush = (s->last_lit == s->lit_bufsize-1); \
   332    }
   333 # define _tr_tally_dist(s, distance, length, flush) \
   334   { uch len = (uch)(length); \
   335     ush dist = (ush)(distance); \
   336     s->d_buf[s->last_lit] = dist; \
   337     s->l_buf[s->last_lit++] = len; \
   338     dist--; \
   339     s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
   340     s->dyn_dtree[d_code(dist)].Freq++; \
   341     flush = (s->last_lit == s->lit_bufsize-1); \
   342   }
   343 #else
   344 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
   345 # define _tr_tally_dist(s, distance, length, flush) \
   346               flush = _tr_tally(s, distance, length)
   347 #endif
   348 
   349 #endif /* DEFLATE_H */