File indexing completed on 2024-04-14 03:46:46

 /* deflate.h -- internal compression state
  * Copyright (C) 1995-2012 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
 #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;        /* 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 *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 */
     uInt insert;        /* bytes at end of window left to insert */
 
 #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.
      */
 
     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++] = (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 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->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 */