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avfs  1.0.1
deflate.h
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00001 /* deflate.h -- internal compression state
00002  * Copyright (C) 1995-2002 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 1.2 2002/12/03 18:50:25 mszeredi Exp $ */
00012 
00013 #ifndef _DEFLATE_H
00014 #define _DEFLATE_H
00015 
00016 #include "zutil.h"
00017 
00018 /* ===========================================================================
00019  * Internal compression state.
00020  */
00021 
00022 #define LENGTH_CODES 29
00023 /* number of length codes, not counting the special END_BLOCK code */
00024 
00025 #define LITERALS  256
00026 /* number of literal bytes 0..255 */
00027 
00028 #define L_CODES (LITERALS+1+LENGTH_CODES)
00029 /* number of Literal or Length codes, including the END_BLOCK code */
00030 
00031 #define D_CODES   30
00032 /* number of distance codes */
00033 
00034 #define BL_CODES  19
00035 /* number of codes used to transfer the bit lengths */
00036 
00037 #define HEAP_SIZE (2*L_CODES+1)
00038 /* maximum heap size */
00039 
00040 #define MAX_BITS 15
00041 /* All codes must not exceed MAX_BITS bits */
00042 
00043 #define INIT_STATE    42
00044 #define BUSY_STATE   113
00045 #define FINISH_STATE 666
00046 /* Stream status */
00047 
00048 
00049 /* Data structure describing a single value and its code string. */
00050 typedef struct ct_data_s {
00051     union {
00052         ush  freq;       /* frequency count */
00053         ush  code;       /* bit string */
00054     } fc;
00055     union {
00056         ush  dad;        /* father node in Huffman tree */
00057         ush  len;        /* length of bit string */
00058     } dl;
00059 } FAR ct_data;
00060 
00061 #define Freq fc.freq
00062 #define Code fc.code
00063 #define Dad  dl.dad
00064 #define Len  dl.len
00065 
00066 typedef struct static_tree_desc_s  static_tree_desc;
00067 
00068 typedef struct tree_desc_s {
00069     ct_data *dyn_tree;           /* the dynamic tree */
00070     int     max_code;            /* largest code with non zero frequency */
00071     static_tree_desc *stat_desc; /* the corresponding static tree */
00072 } FAR tree_desc;
00073 
00074 typedef ush Pos;
00075 typedef Pos FAR Posf;
00076 typedef unsigned IPos;
00077 
00078 /* A Pos is an index in the character window. We use short instead of int to
00079  * save space in the various tables. IPos is used only for parameter passing.
00080  */
00081 
00082 typedef struct internal_state {
00083     z_streamp strm;      /* pointer back to this zlib stream */
00084     int   status;        /* as the name implies */
00085     Bytef *pending_buf;  /* output still pending */
00086     ulg   pending_buf_size; /* size of pending_buf */
00087     Bytef *pending_out;  /* next pending byte to output to the stream */
00088     int   pending;       /* nb of bytes in the pending buffer */
00089     int   noheader;      /* suppress zlib header and adler32 */
00090     Byte  data_type;     /* UNKNOWN, BINARY or ASCII */
00091     Byte  method;        /* STORED (for zip only) or DEFLATED */
00092     int   last_flush;    /* value of flush param for previous deflate call */
00093 
00094                 /* used by deflate.c: */
00095 
00096     uInt  w_size;        /* LZ77 window size (32K by default) */
00097     uInt  w_bits;        /* log2(w_size)  (8..16) */
00098     uInt  w_mask;        /* w_size - 1 */
00099 
00100     Bytef *window;
00101     /* Sliding window. Input bytes are read into the second half of the window,
00102      * and move to the first half later to keep a dictionary of at least wSize
00103      * bytes. With this organization, matches are limited to a distance of
00104      * wSize-MAX_MATCH bytes, but this ensures that IO is always
00105      * performed with a length multiple of the block size. Also, it limits
00106      * the window size to 64K, which is quite useful on MSDOS.
00107      * To do: use the user input buffer as sliding window.
00108      */
00109 
00110     ulg window_size;
00111     /* Actual size of window: 2*wSize, except when the user input buffer
00112      * is directly used as sliding window.
00113      */
00114 
00115     Posf *prev;
00116     /* Link to older string with same hash index. To limit the size of this
00117      * array to 64K, this link is maintained only for the last 32K strings.
00118      * An index in this array is thus a window index modulo 32K.
00119      */
00120 
00121     Posf *head; /* Heads of the hash chains or NIL. */
00122 
00123     uInt  ins_h;          /* hash index of string to be inserted */
00124     uInt  hash_size;      /* number of elements in hash table */
00125     uInt  hash_bits;      /* log2(hash_size) */
00126     uInt  hash_mask;      /* hash_size-1 */
00127 
00128     uInt  hash_shift;
00129     /* Number of bits by which ins_h must be shifted at each input
00130      * step. It must be such that after MIN_MATCH steps, the oldest
00131      * byte no longer takes part in the hash key, that is:
00132      *   hash_shift * MIN_MATCH >= hash_bits
00133      */
00134 
00135     long block_start;
00136     /* Window position at the beginning of the current output block. Gets
00137      * negative when the window is moved backwards.
00138      */
00139 
00140     uInt match_length;           /* length of best match */
00141     IPos prev_match;             /* previous match */
00142     int match_available;         /* set if previous match exists */
00143     uInt strstart;               /* start of string to insert */
00144     uInt match_start;            /* start of matching string */
00145     uInt lookahead;              /* number of valid bytes ahead in window */
00146 
00147     uInt prev_length;
00148     /* Length of the best match at previous step. Matches not greater than this
00149      * are discarded. This is used in the lazy match evaluation.
00150      */
00151 
00152     uInt max_chain_length;
00153     /* To speed up deflation, hash chains are never searched beyond this
00154      * length.  A higher limit improves compression ratio but degrades the
00155      * speed.
00156      */
00157 
00158     uInt max_lazy_match;
00159     /* Attempt to find a better match only when the current match is strictly
00160      * smaller than this value. This mechanism is used only for compression
00161      * levels >= 4.
00162      */
00163 #   define max_insert_length  max_lazy_match
00164     /* Insert new strings in the hash table only if the match length is not
00165      * greater than this length. This saves time but degrades compression.
00166      * max_insert_length is used only for compression levels <= 3.
00167      */
00168 
00169     int level;    /* compression level (1..9) */
00170     int strategy; /* favor or force Huffman coding*/
00171 
00172     uInt good_match;
00173     /* Use a faster search when the previous match is longer than this */
00174 
00175     int nice_match; /* Stop searching when current match exceeds this */
00176 
00177                 /* used by trees.c: */
00178     /* Didn't use ct_data typedef below to supress compiler warning */
00179     struct ct_data_s dyn_ltree[HEAP_SIZE];   /* literal and length tree */
00180     struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
00181     struct ct_data_s bl_tree[2*BL_CODES+1];  /* Huffman tree for bit lengths */
00182 
00183     struct tree_desc_s l_desc;               /* desc. for literal tree */
00184     struct tree_desc_s d_desc;               /* desc. for distance tree */
00185     struct tree_desc_s bl_desc;              /* desc. for bit length tree */
00186 
00187     ush bl_count[MAX_BITS+1];
00188     /* number of codes at each bit length for an optimal tree */
00189 
00190     int heap[2*L_CODES+1];      /* heap used to build the Huffman trees */
00191     int heap_len;               /* number of elements in the heap */
00192     int heap_max;               /* element of largest frequency */
00193     /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
00194      * The same heap array is used to build all trees.
00195      */
00196 
00197     uch depth[2*L_CODES+1];
00198     /* Depth of each subtree used as tie breaker for trees of equal frequency
00199      */
00200 
00201     uchf *l_buf;          /* buffer for literals or lengths */
00202 
00203     uInt  lit_bufsize;
00204     /* Size of match buffer for literals/lengths.  There are 4 reasons for
00205      * limiting lit_bufsize to 64K:
00206      *   - frequencies can be kept in 16 bit counters
00207      *   - if compression is not successful for the first block, all input
00208      *     data is still in the window so we can still emit a stored block even
00209      *     when input comes from standard input.  (This can also be done for
00210      *     all blocks if lit_bufsize is not greater than 32K.)
00211      *   - if compression is not successful for a file smaller than 64K, we can
00212      *     even emit a stored file instead of a stored block (saving 5 bytes).
00213      *     This is applicable only for zip (not gzip or zlib).
00214      *   - creating new Huffman trees less frequently may not provide fast
00215      *     adaptation to changes in the input data statistics. (Take for
00216      *     example a binary file with poorly compressible code followed by
00217      *     a highly compressible string table.) Smaller buffer sizes give
00218      *     fast adaptation but have of course the overhead of transmitting
00219      *     trees more frequently.
00220      *   - I can't count above 4
00221      */
00222 
00223     uInt last_lit;      /* running index in l_buf */
00224 
00225     ushf *d_buf;
00226     /* Buffer for distances. To simplify the code, d_buf and l_buf have
00227      * the same number of elements. To use different lengths, an extra flag
00228      * array would be necessary.
00229      */
00230 
00231     ulg opt_len;        /* bit length of current block with optimal trees */
00232     ulg static_len;     /* bit length of current block with static trees */
00233     uInt matches;       /* number of string matches in current block */
00234     int last_eob_len;   /* bit length of EOB code for last block */
00235 
00236 #ifdef DEBUG
00237     ulg compressed_len; /* total bit length of compressed file mod 2^32 */
00238     ulg bits_sent;      /* bit length of compressed data sent mod 2^32 */
00239 #endif
00240 
00241     ush bi_buf;
00242     /* Output buffer. bits are inserted starting at the bottom (least
00243      * significant bits).
00244      */
00245     int bi_valid;
00246     /* Number of valid bits in bi_buf.  All bits above the last valid bit
00247      * are always zero.
00248      */
00249 
00250 } FAR deflate_state;
00251 
00252 /* Output a byte on the stream.
00253  * IN assertion: there is enough room in pending_buf.
00254  */
00255 #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
00256 
00257 
00258 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
00259 /* Minimum amount of lookahead, except at the end of the input file.
00260  * See deflate.c for comments about the MIN_MATCH+1.
00261  */
00262 
00263 #define MAX_DIST(s)  ((s)->w_size-MIN_LOOKAHEAD)
00264 /* In order to simplify the code, particularly on 16 bit machines, match
00265  * distances are limited to MAX_DIST instead of WSIZE.
00266  */
00267 
00268         /* in trees.c */
00269 void _tr_init         OF((deflate_state *s));
00270 int  _tr_tally        OF((deflate_state *s, unsigned dist, unsigned lc));
00271 void _tr_flush_block  OF((deflate_state *s, charf *buf, ulg stored_len,
00272                        int eof));
00273 void _tr_align        OF((deflate_state *s));
00274 void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
00275                           int eof));
00276 
00277 #define d_code(dist) \
00278    ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
00279 /* Mapping from a distance to a distance code. dist is the distance - 1 and
00280  * must not have side effects. _dist_code[256] and _dist_code[257] are never
00281  * used.
00282  */
00283 
00284 #ifndef DEBUG
00285 /* Inline versions of _tr_tally for speed: */
00286 
00287 #if defined(GEN_TREES_H) || !defined(STDC)
00288   extern uch _length_code[];
00289   extern uch _dist_code[];
00290 #else
00291   extern const uch _length_code[];
00292   extern const uch _dist_code[];
00293 #endif
00294 
00295 # define _tr_tally_lit(s, c, flush) \
00296   { uch cc = (c); \
00297     s->d_buf[s->last_lit] = 0; \
00298     s->l_buf[s->last_lit++] = cc; \
00299     s->dyn_ltree[cc].Freq++; \
00300     flush = (s->last_lit == s->lit_bufsize-1); \
00301    }
00302 # define _tr_tally_dist(s, distance, length, flush) \
00303   { uch len = (length); \
00304     ush dist = (distance); \
00305     s->d_buf[s->last_lit] = dist; \
00306     s->l_buf[s->last_lit++] = len; \
00307     dist--; \
00308     s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
00309     s->dyn_dtree[d_code(dist)].Freq++; \
00310     flush = (s->last_lit == s->lit_bufsize-1); \
00311   }
00312 #else
00313 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
00314 # define _tr_tally_dist(s, distance, length, flush) \
00315               flush = _tr_tally(s, distance, length) 
00316 #endif
00317 
00318 #endif