text: /* deflate.h -- internal compression state
   * Copyright (C) 1995-2004 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 INIT_STATE    42
  #define EXTRA_STATE   69
  #define NAME_STATE    73
  #define COMMENT_STATE 91
  #define HCRC_STATE   103
  #define BUSY_STATE   113
  #define FINISH_STATE 666
  /* 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 */
     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 */
     uInt   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 */
     uInt   gzindex;      /* where in extra, name, or comment */
     Byte  method;        /* STORED (for zip only) or 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 supress 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 *l_buf;          /* buffer for literals or 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 last_lit;      /* running index in l_buf */
  
     ushf *d_buf;
     /* Buffer for distances. To simplify the code, d_buf and l_buf have
      * the same number of elements. To use different lengths, an extra flag
      * array would be necessary.
      */
  
     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 */
     int last_eob_len;   /* bit length of EOB code for last block */
  
  #ifdef 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.
      */
  
  } 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++] = (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.
   */
  
  /* in trees.c */
  void _tr_init         OF((deflate_state *s));
  int  _tr_tally        OF((deflate_state *s, unsigned dist, unsigned lc));
  void _tr_flush_block  OF((deflate_state *s, charf *buf, ulg stored_len,
                            int eof));
  void _tr_align        OF((deflate_state *s));
  void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
                            int eof));
  
  #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 DEBUG
  /* Inline versions of _tr_tally for speed: */
  
  #if defined(GEN_TREES_H) || !defined(STDC)
  extern uch _length_code[];
  extern uch _dist_code[];
  #else
  extern const uch _length_code[];
  extern const uch _dist_code[];
  #endif
  
  # define _tr_tally_lit(s, c, flush) \
    { uch cc = (c); \
      s->d_buf[s->last_lit] = 0; \
      s->l_buf[s->last_lit++] = cc; \
      s->dyn_ltree[cc].Freq++; \
      flush = (s->last_lit == s->lit_bufsize-1); \
     }
  # define _tr_tally_dist(s, distance, length, flush) \
    { uch len = (length); \
      ush dist = (distance); \
      s->d_buf[s->last_lit] = dist; \
      s->l_buf[s->last_lit++] = len; \
      dist--; \
      s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
      s->dyn_dtree[d_code(dist)].Freq++; \
      flush = (s->last_lit == s->lit_bufsize-1); \
    }
  #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 */
  