The Tor Browser / file revision

 /* deflate.h -- internal compression state

  * Copyright (C) 1995-2010 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.

      */

     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_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 */