FreeBSD/Linux Kernel Cross Reference
sys/contrib/zlib/deflate.h

     /* deflate.h -- internal compression state
      * Copyright (C) 1995-2018 Jean-loup Gailly
      * For conditions of distribution and use, see copyright notice in zlib.h
      */
     
     /* WARNING: this file should *not* be used by applications. It is
        part of the implementation of the compression library and is
        subject to change. Applications should only use zlib.h.
      */
    
    /* @(#) $Id$ */
    
    #ifndef DEFLATE_H
    #define DEFLATE_H
    
    #include "zutil.h"
    
    /* define NO_GZIP when compiling if you want to disable gzip header and
       trailer creation by deflate().  NO_GZIP would be used to avoid linking in
       the crc code when it is not needed.  For shared libraries, gzip encoding
       should be left enabled. */
    #ifndef NO_GZIP
    #  define GZIP
    #endif
    
    /* ===========================================================================
     * Internal compression state.
     */
    
    #define LENGTH_CODES 29
    /* number of length codes, not counting the special END_BLOCK code */
    
    #define LITERALS  256
    /* number of literal bytes 0..255 */
    
    #define L_CODES (LITERALS+1+LENGTH_CODES)
    /* number of Literal or Length codes, including the END_BLOCK code */
    
    #define D_CODES   30
    /* number of distance codes */
    
    #define BL_CODES  19
    /* number of codes used to transfer the bit lengths */
    
    #define HEAP_SIZE (2*L_CODES+1)
    /* maximum heap size */
    
    #define MAX_BITS 15
    /* All codes must not exceed MAX_BITS bits */
    
    #define Buf_size 16
    /* size of bit buffer in bi_buf */
    
    #define INIT_STATE    42    /* zlib header -> BUSY_STATE */
    #ifdef GZIP
    #  define GZIP_STATE  57    /* gzip header -> BUSY_STATE | EXTRA_STATE */
    #endif
    #define EXTRA_STATE   69    /* gzip extra block -> NAME_STATE */
    #define NAME_STATE    73    /* gzip file name -> COMMENT_STATE */
    #define COMMENT_STATE 91    /* gzip comment -> HCRC_STATE */
    #define HCRC_STATE   103    /* gzip header CRC -> BUSY_STATE */
    #define BUSY_STATE   113    /* deflate -> FINISH_STATE */
    #define FINISH_STATE 666    /* stream complete */
    /* Stream status */
    
    
    /* Data structure describing a single value and its code string. */
    typedef struct ct_data_s {
        union {
            ush  freq;       /* frequency count */
            ush  code;       /* bit string */
        } fc;
        union {
            ush  dad;        /* father node in Huffman tree */
            ush  len;        /* length of bit string */
        } dl;
    } FAR ct_data;
    
    #define Freq fc.freq
    #define Code fc.code
    #define Dad  dl.dad
    #define Len  dl.len
    
    typedef struct static_tree_desc_s  static_tree_desc;
    
    typedef struct tree_desc_s {
        ct_data *dyn_tree;           /* the dynamic tree */
        int     max_code;            /* largest code with non zero frequency */
        const static_tree_desc *stat_desc;  /* the corresponding static tree */
    } FAR tree_desc;
    
    typedef ush Pos;
    typedef Pos FAR Posf;
    typedef unsigned IPos;
    
    /* A Pos is an index in the character window. We use short instead of int to
     * save space in the various tables. IPos is used only for parameter passing.
     */
    
   typedef struct internal_state {
       z_streamp strm;      /* pointer back to this zlib stream */
       int   status;        /* as the name implies */
       Bytef *pending_buf;  /* output still pending */
       ulg   pending_buf_size; /* size of pending_buf */
       Bytef *pending_out;  /* next pending byte to output to the stream */
       ulg   pending;       /* nb of bytes in the pending buffer */
       int   wrap;          /* bit 0 true for zlib, bit 1 true for gzip */
       gz_headerp  gzhead;  /* gzip header information to write */
       ulg   gzindex;       /* where in extra, name, or comment */
       Byte  method;        /* can only be DEFLATED */
       int   last_flush;    /* value of flush param for previous deflate call */
   
                   /* used by deflate.c: */
   
       uInt  w_size;        /* LZ77 window size (32K by default) */
       uInt  w_bits;        /* log2(w_size)  (8..16) */
       uInt  w_mask;        /* w_size - 1 */
   
       Bytef *window;
       /* Sliding window. Input bytes are read into the second half of the window,
        * and move to the first half later to keep a dictionary of at least wSize
        * bytes. With this organization, matches are limited to a distance of
        * wSize-MAX_MATCH bytes, but this ensures that IO is always
        * performed with a length multiple of the block size. Also, it limits
        * the window size to 64K, which is quite useful on MSDOS.
        * To do: use the user input buffer as sliding window.
        */
   
       ulg window_size;
       /* Actual size of window: 2*wSize, except when the user input buffer
        * is directly used as sliding window.
        */
   
       Posf *prev;
       /* Link to older string with same hash index. To limit the size of this
        * array to 64K, this link is maintained only for the last 32K strings.
        * An index in this array is thus a window index modulo 32K.
        */
   
       Posf *head; /* Heads of the hash chains or NIL. */
   
       uInt  ins_h;          /* hash index of string to be inserted */
       uInt  hash_size;      /* number of elements in hash table */
       uInt  hash_bits;      /* log2(hash_size) */
       uInt  hash_mask;      /* hash_size-1 */
   
       uInt  hash_shift;
       /* Number of bits by which ins_h must be shifted at each input
        * step. It must be such that after MIN_MATCH steps, the oldest
        * byte no longer takes part in the hash key, that is:
        *   hash_shift * MIN_MATCH >= hash_bits
        */
   
       long block_start;
       /* Window position at the beginning of the current output block. Gets
        * negative when the window is moved backwards.
        */
   
       uInt match_length;           /* length of best match */
       IPos prev_match;             /* previous match */
       int match_available;         /* set if previous match exists */
       uInt strstart;               /* start of string to insert */
       uInt match_start;            /* start of matching string */
       uInt lookahead;              /* number of valid bytes ahead in window */
   
       uInt prev_length;
       /* Length of the best match at previous step. Matches not greater than this
        * are discarded. This is used in the lazy match evaluation.
        */
   
       uInt max_chain_length;
       /* To speed up deflation, hash chains are never searched beyond this
        * length.  A higher limit improves compression ratio but degrades the
        * speed.
        */
   
       uInt max_lazy_match;
       /* Attempt to find a better match only when the current match is strictly
        * smaller than this value. This mechanism is used only for compression
        * levels >= 4.
        */
   #   define max_insert_length  max_lazy_match
       /* Insert new strings in the hash table only if the match length is not
        * greater than this length. This saves time but degrades compression.
        * max_insert_length is used only for compression levels <= 3.
        */
   
       int level;    /* compression level (1..9) */
       int strategy; /* favor or force Huffman coding*/
   
       uInt good_match;
       /* Use a faster search when the previous match is longer than this */
   
       int nice_match; /* Stop searching when current match exceeds this */
   
                   /* used by trees.c: */
       /* Didn't use ct_data typedef below to suppress compiler warning */
       struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
       struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
       struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
   
       struct tree_desc_s l_desc;               /* desc. for literal tree */
       struct tree_desc_s d_desc;               /* desc. for distance tree */
       struct tree_desc_s bl_desc;              /* desc. for bit length tree */
   
       ush bl_count[MAX_BITS+1];
       /* number of codes at each bit length for an optimal tree */
   
       int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
       int heap_len;               /* number of elements in the heap */
       int heap_max;               /* element of largest frequency */
       /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
        * The same heap array is used to build all trees.
        */
   
       uch depth[2*L_CODES+1];
       /* Depth of each subtree used as tie breaker for trees of equal frequency
        */
   
       uchf *sym_buf;        /* buffer for distances and literals/lengths */
   
       uInt  lit_bufsize;
       /* Size of match buffer for literals/lengths.  There are 4 reasons for
        * limiting lit_bufsize to 64K:
        *   - frequencies can be kept in 16 bit counters
        *   - if compression is not successful for the first block, all input
        *     data is still in the window so we can still emit a stored block even
        *     when input comes from standard input.  (This can also be done for
        *     all blocks if lit_bufsize is not greater than 32K.)
        *   - if compression is not successful for a file smaller than 64K, we can
        *     even emit a stored file instead of a stored block (saving 5 bytes).
        *     This is applicable only for zip (not gzip or zlib).
        *   - creating new Huffman trees less frequently may not provide fast
        *     adaptation to changes in the input data statistics. (Take for
        *     example a binary file with poorly compressible code followed by
        *     a highly compressible string table.) Smaller buffer sizes give
        *     fast adaptation but have of course the overhead of transmitting
        *     trees more frequently.
        *   - I can't count above 4
        */
   
       uInt sym_next;      /* running index in sym_buf */
       uInt sym_end;       /* symbol table full when sym_next reaches this */
   
       ulg opt_len;        /* bit length of current block with optimal trees */
       ulg static_len;     /* bit length of current block with static trees */
       uInt matches;       /* number of string matches in current block */
       uInt insert;        /* bytes at end of window left to insert */
   
   #ifdef ZLIB_DEBUG
       ulg compressed_len; /* total bit length of compressed file mod 2^32 */
       ulg bits_sent;      /* bit length of compressed data sent mod 2^32 */
   #endif
   
       ush bi_buf;
       /* Output buffer. bits are inserted starting at the bottom (least
        * significant bits).
        */
       int bi_valid;
       /* Number of valid bits in bi_buf.  All bits above the last valid bit
        * are always zero.
        */
   
       ulg high_water;
       /* High water mark offset in window for initialized bytes -- bytes above
        * this are set to zero in order to avoid memory check warnings when
        * longest match routines access bytes past the input.  This is then
        * updated to the new high water mark.
        */
   
   } FAR deflate_state;
   
   /* Output a byte on the stream.
    * IN assertion: there is enough room in pending_buf.
    */
   #define put_byte(s, c) {s->pending_buf[s->pending++] = (Bytef)(c);}
   
   
   #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
   /* Minimum amount of lookahead, except at the end of the input file.
    * See deflate.c for comments about the MIN_MATCH+1.
    */
   
   #define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
   /* In order to simplify the code, particularly on 16 bit machines, match
    * distances are limited to MAX_DIST instead of WSIZE.
    */
   
   #define WIN_INIT MAX_MATCH
   /* Number of bytes after end of data in window to initialize in order to avoid
      memory checker errors from longest match routines */
   
           /* in trees.c */
   void ZLIB_INTERNAL _tr_init OF((deflate_state *s));
   int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
   void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf,
                           ulg stored_len, int last));
   void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s));
   void ZLIB_INTERNAL _tr_align OF((deflate_state *s));
   void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
                           ulg stored_len, int last));
   
   #define d_code(dist) \
      ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
   /* Mapping from a distance to a distance code. dist is the distance - 1 and
    * must not have side effects. _dist_code[256] and _dist_code[257] are never
    * used.
    */
   
   #ifndef ZLIB_DEBUG
   /* Inline versions of _tr_tally for speed: */
   
   #if defined(GEN_TREES_H) || !defined(STDC)
     extern uch ZLIB_INTERNAL _length_code[];
     extern uch ZLIB_INTERNAL _dist_code[];
   #else
     extern const uch ZLIB_INTERNAL _length_code[];
     extern const uch ZLIB_INTERNAL _dist_code[];
   #endif
   
   # define _tr_tally_lit(s, c, flush) \
     { uch cc = (c); \
       s->sym_buf[s->sym_next++] = 0; \
       s->sym_buf[s->sym_next++] = 0; \
       s->sym_buf[s->sym_next++] = cc; \
       s->dyn_ltree[cc].Freq++; \
       flush = (s->sym_next == s->sym_end); \
      }
   # define _tr_tally_dist(s, distance, length, flush) \
     { uch len = (uch)(length); \
       ush dist = (ush)(distance); \
       s->sym_buf[s->sym_next++] = dist; \
       s->sym_buf[s->sym_next++] = dist >> 8; \
       s->sym_buf[s->sym_next++] = len; \
       dist--; \
       s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
       s->dyn_dtree[d_code(dist)].Freq++; \
       flush = (s->sym_next == s->sym_end); \
     }
   #else
   # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
   # define _tr_tally_dist(s, distance, length, flush) \
                 flush = _tr_tally(s, distance, length)
   #endif
   
   #endif /* DEFLATE_H */

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