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deflate.h
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00001 /* deflate.h -- internal compression state
00002  * Copyright (C) 1995-2004 Jean-loup Gailly
00003  * For conditions of distribution and use, see copyright notice in zlib.h
00004  */
00005 
00006 /* WARNING: this file should *not* be used by applications. It is
00007    part of the implementation of the compression library and is
00008    subject to change. Applications should only use zlib.h.
00009  */
00010 
00011 /* @(#) $Id: deflate.h,v 1.5 2005/07/20 20:32:42 wtchang%redhat.com Exp $ */
00012 
00013 #ifndef DEFLATE_H
00014 #define DEFLATE_H
00015 
00016 #include "zutil.h"
00017 
00018 /* define NO_GZIP when compiling if you want to disable gzip header and
00019    trailer creation by deflate().  NO_GZIP would be used to avoid linking in
00020    the crc code when it is not needed.  For shared libraries, gzip encoding
00021    should be left enabled. */
00022 #ifndef NO_GZIP
00023 #  define GZIP
00024 #endif
00025 
00026 /* ===========================================================================
00027  * Internal compression state.
00028  */
00029 
00030 #define LENGTH_CODES 29
00031 /* number of length codes, not counting the special END_BLOCK code */
00032 
00033 #define LITERALS  256
00034 /* number of literal bytes 0..255 */
00035 
00036 #define L_CODES (LITERALS+1+LENGTH_CODES)
00037 /* number of Literal or Length codes, including the END_BLOCK code */
00038 
00039 #define D_CODES   30
00040 /* number of distance codes */
00041 
00042 #define BL_CODES  19
00043 /* number of codes used to transfer the bit lengths */
00044 
00045 #define HEAP_SIZE (2*L_CODES+1)
00046 /* maximum heap size */
00047 
00048 #define MAX_BITS 15
00049 /* All codes must not exceed MAX_BITS bits */
00050 
00051 #define INIT_STATE    42
00052 #define EXTRA_STATE   69
00053 #define NAME_STATE    73
00054 #define COMMENT_STATE 91
00055 #define HCRC_STATE   103
00056 #define BUSY_STATE   113
00057 #define FINISH_STATE 666
00058 /* Stream status */
00059 
00060 
00061 /* Data structure describing a single value and its code string. */
00062 typedef struct ct_data_s {
00063     union {
00064         ush  freq;       /* frequency count */
00065         ush  code;       /* bit string */
00066     } fc;
00067     union {
00068         ush  dad;        /* father node in Huffman tree */
00069         ush  len;        /* length of bit string */
00070     } dl;
00071 } FAR ct_data;
00072 
00073 #define Freq fc.freq
00074 #define Code fc.code
00075 #define Dad  dl.dad
00076 #define Len  dl.len
00077 
00078 typedef struct static_tree_desc_s  static_tree_desc;
00079 
00080 typedef struct tree_desc_s {
00081     ct_data *dyn_tree;           /* the dynamic tree */
00082     int     max_code;            /* largest code with non zero frequency */
00083     static_tree_desc *stat_desc; /* the corresponding static tree */
00084 } FAR tree_desc;
00085 
00086 typedef ush Pos;
00087 typedef Pos FAR Posf;
00088 typedef unsigned IPos;
00089 
00090 /* A Pos is an index in the character window. We use short instead of int to
00091  * save space in the various tables. IPos is used only for parameter passing.
00092  */
00093 
00094 typedef struct internal_state {
00095     z_streamp strm;      /* pointer back to this zlib stream */
00096     int   status;        /* as the name implies */
00097     Bytef *pending_buf;  /* output still pending */
00098     ulg   pending_buf_size; /* size of pending_buf */
00099     Bytef *pending_out;  /* next pending byte to output to the stream */
00100     uInt   pending;      /* nb of bytes in the pending buffer */
00101     int   wrap;          /* bit 0 true for zlib, bit 1 true for gzip */
00102     gz_headerp  gzhead;  /* gzip header information to write */
00103     uInt   gzindex;      /* where in extra, name, or comment */
00104     Byte  method;        /* STORED (for zip only) or DEFLATED */
00105     int   last_flush;    /* value of flush param for previous deflate call */
00106 
00107                 /* used by deflate.c: */
00108 
00109     uInt  w_size;        /* LZ77 window size (32K by default) */
00110     uInt  w_bits;        /* log2(w_size)  (8..16) */
00111     uInt  w_mask;        /* w_size - 1 */
00112 
00113     Bytef *window;
00114     /* Sliding window. Input bytes are read into the second half of the window,
00115      * and move to the first half later to keep a dictionary of at least wSize
00116      * bytes. With this organization, matches are limited to a distance of
00117      * wSize-MAX_MATCH bytes, but this ensures that IO is always
00118      * performed with a length multiple of the block size. Also, it limits
00119      * the window size to 64K, which is quite useful on MSDOS.
00120      * To do: use the user input buffer as sliding window.
00121      */
00122 
00123     ulg window_size;
00124     /* Actual size of window: 2*wSize, except when the user input buffer
00125      * is directly used as sliding window.
00126      */
00127 
00128     Posf *prev;
00129     /* Link to older string with same hash index. To limit the size of this
00130      * array to 64K, this link is maintained only for the last 32K strings.
00131      * An index in this array is thus a window index modulo 32K.
00132      */
00133 
00134     Posf *head; /* Heads of the hash chains or NIL. */
00135 
00136     uInt  ins_h;          /* hash index of string to be inserted */
00137     uInt  hash_size;      /* number of elements in hash table */
00138     uInt  hash_bits;      /* log2(hash_size) */
00139     uInt  hash_mask;      /* hash_size-1 */
00140 
00141     uInt  hash_shift;
00142     /* Number of bits by which ins_h must be shifted at each input
00143      * step. It must be such that after MIN_MATCH steps, the oldest
00144      * byte no longer takes part in the hash key, that is:
00145      *   hash_shift * MIN_MATCH >= hash_bits
00146      */
00147 
00148     long block_start;
00149     /* Window position at the beginning of the current output block. Gets
00150      * negative when the window is moved backwards.
00151      */
00152 
00153     uInt match_length;           /* length of best match */
00154     IPos prev_match;             /* previous match */
00155     int match_available;         /* set if previous match exists */
00156     uInt strstart;               /* start of string to insert */
00157     uInt match_start;            /* start of matching string */
00158     uInt lookahead;              /* number of valid bytes ahead in window */
00159 
00160     uInt prev_length;
00161     /* Length of the best match at previous step. Matches not greater than this
00162      * are discarded. This is used in the lazy match evaluation.
00163      */
00164 
00165     uInt max_chain_length;
00166     /* To speed up deflation, hash chains are never searched beyond this
00167      * length.  A higher limit improves compression ratio but degrades the
00168      * speed.
00169      */
00170 
00171     uInt max_lazy_match;
00172     /* Attempt to find a better match only when the current match is strictly
00173      * smaller than this value. This mechanism is used only for compression
00174      * levels >= 4.
00175      */
00176 #   define max_insert_length  max_lazy_match
00177     /* Insert new strings in the hash table only if the match length is not
00178      * greater than this length. This saves time but degrades compression.
00179      * max_insert_length is used only for compression levels <= 3.
00180      */
00181 
00182     int level;    /* compression level (1..9) */
00183     int strategy; /* favor or force Huffman coding*/
00184 
00185     uInt good_match;
00186     /* Use a faster search when the previous match is longer than this */
00187 
00188     int nice_match; /* Stop searching when current match exceeds this */
00189 
00190                 /* used by trees.c: */
00191     /* Didn't use ct_data typedef below to supress compiler warning */
00192     struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
00193     struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
00194     struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
00195 
00196     struct tree_desc_s l_desc;               /* desc. for literal tree */
00197     struct tree_desc_s d_desc;               /* desc. for distance tree */
00198     struct tree_desc_s bl_desc;              /* desc. for bit length tree */
00199 
00200     ush bl_count[MAX_BITS+1];
00201     /* number of codes at each bit length for an optimal tree */
00202 
00203     int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
00204     int heap_len;               /* number of elements in the heap */
00205     int heap_max;               /* element of largest frequency */
00206     /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
00207      * The same heap array is used to build all trees.
00208      */
00209 
00210     uch depth[2*L_CODES+1];
00211     /* Depth of each subtree used as tie breaker for trees of equal frequency
00212      */
00213 
00214     uchf *l_buf;          /* buffer for literals or lengths */
00215 
00216     uInt  lit_bufsize;
00217     /* Size of match buffer for literals/lengths.  There are 4 reasons for
00218      * limiting lit_bufsize to 64K:
00219      *   - frequencies can be kept in 16 bit counters
00220      *   - if compression is not successful for the first block, all input
00221      *     data is still in the window so we can still emit a stored block even
00222      *     when input comes from standard input.  (This can also be done for
00223      *     all blocks if lit_bufsize is not greater than 32K.)
00224      *   - if compression is not successful for a file smaller than 64K, we can
00225      *     even emit a stored file instead of a stored block (saving 5 bytes).
00226      *     This is applicable only for zip (not gzip or zlib).
00227      *   - creating new Huffman trees less frequently may not provide fast
00228      *     adaptation to changes in the input data statistics. (Take for
00229      *     example a binary file with poorly compressible code followed by
00230      *     a highly compressible string table.) Smaller buffer sizes give
00231      *     fast adaptation but have of course the overhead of transmitting
00232      *     trees more frequently.
00233      *   - I can't count above 4
00234      */
00235 
00236     uInt last_lit;      /* running index in l_buf */
00237 
00238     ushf *d_buf;
00239     /* Buffer for distances. To simplify the code, d_buf and l_buf have
00240      * the same number of elements. To use different lengths, an extra flag
00241      * array would be necessary.
00242      */
00243 
00244     ulg opt_len;        /* bit length of current block with optimal trees */
00245     ulg static_len;     /* bit length of current block with static trees */
00246     uInt matches;       /* number of string matches in current block */
00247     int last_eob_len;   /* bit length of EOB code for last block */
00248 
00249 #ifdef DEBUG
00250     ulg compressed_len; /* total bit length of compressed file mod 2^32 */
00251     ulg bits_sent;      /* bit length of compressed data sent mod 2^32 */
00252 #endif
00253 
00254     ush bi_buf;
00255     /* Output buffer. bits are inserted starting at the bottom (least
00256      * significant bits).
00257      */
00258     int bi_valid;
00259     /* Number of valid bits in bi_buf.  All bits above the last valid bit
00260      * are always zero.
00261      */
00262 
00263 } FAR deflate_state;
00264 
00265 /* Output a byte on the stream.
00266  * IN assertion: there is enough room in pending_buf.
00267  */
00268 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
00269 
00270 
00271 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
00272 /* Minimum amount of lookahead, except at the end of the input file.
00273  * See deflate.c for comments about the MIN_MATCH+1.
00274  */
00275 
00276 #define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
00277 /* In order to simplify the code, particularly on 16 bit machines, match
00278  * distances are limited to MAX_DIST instead of WSIZE.
00279  */
00280 
00281         /* in trees.c */
00282 void _tr_init         OF((deflate_state *s));
00283 int  _tr_tally        OF((deflate_state *s, unsigned dist, unsigned lc));
00284 void _tr_flush_block  OF((deflate_state *s, charf *buf, ulg stored_len,
00285                           int eof));
00286 void _tr_align        OF((deflate_state *s));
00287 void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
00288                           int eof));
00289 
00290 #define d_code(dist) \
00291    ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
00292 /* Mapping from a distance to a distance code. dist is the distance - 1 and
00293  * must not have side effects. _dist_code[256] and _dist_code[257] are never
00294  * used.
00295  */
00296 
00297 #ifndef DEBUG
00298 /* Inline versions of _tr_tally for speed: */
00299 
00300 #if defined(GEN_TREES_H) || !defined(STDC)
00301   extern uch _length_code[];
00302   extern uch _dist_code[];
00303 #else
00304   extern const uch _length_code[];
00305   extern const uch _dist_code[];
00306 #endif
00307 
00308 # define _tr_tally_lit(s, c, flush) \
00309   { uch cc = (c); \
00310     s->d_buf[s->last_lit] = 0; \
00311     s->l_buf[s->last_lit++] = cc; \
00312     s->dyn_ltree[cc].Freq++; \
00313     flush = (s->last_lit == s->lit_bufsize-1); \
00314    }
00315 # define _tr_tally_dist(s, distance, length, flush) \
00316   { uch len = (length); \
00317     ush dist = (distance); \
00318     s->d_buf[s->last_lit] = dist; \
00319     s->l_buf[s->last_lit++] = len; \
00320     dist--; \
00321     s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
00322     s->dyn_dtree[d_code(dist)].Freq++; \
00323     flush = (s->last_lit == s->lit_bufsize-1); \
00324   }
00325 #else
00326 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
00327 # define _tr_tally_dist(s, distance, length, flush) \
00328               flush = _tr_tally(s, distance, length)
00329 #endif
00330 
00331 #endif /* DEFLATE_H */