src/zlib/inflate.h

   1 /* inflate.h -- internal inflate state definition
   2  * Copyright (C) 1995-2004 Mark Adler
   3  * For conditions of distribution and use, see copyright notice in zlib.h
   4  */
   5
   6 /* WARNING: this file should *not* be used by applications. It is
   7    part of the implementation of the compression library and is
   8    subject to change. Applications should only use zlib.h.
   9  */
  10
  11 /* define NO_GZIP when compiling if you want to disable gzip header and
  12    trailer decoding by inflate().  NO_GZIP would be used to avoid linking in
  13    the crc code when it is not needed.  For shared libraries, gzip decoding
  14    should be left enabled. */
  15 #ifndef NO_GZIP
  16 #  define GUNZIP
  17 #endif
  18
  19 /* Possible inflate modes between inflate() calls */
  20 typedef enum {
  21     HEAD,       /* i: waiting for magic header */
  22     FLAGS,      /* i: waiting for method and flags (gzip) */
  23     TIME,       /* i: waiting for modification time (gzip) */
  24     OS,         /* i: waiting for extra flags and operating system (gzip) */
  25     EXLEN,      /* i: waiting for extra length (gzip) */
  26     EXTRA,      /* i: waiting for extra bytes (gzip) */
  27     NAME,       /* i: waiting for end of file name (gzip) */
  28     COMMENT,    /* i: waiting for end of comment (gzip) */
  29     HCRC,       /* i: waiting for header crc (gzip) */
  30     DICTID,     /* i: waiting for dictionary check value */
  31     DICT,       /* waiting for inflateSetDictionary() call */
  32         TYPE,       /* i: waiting for type bits, including last-flag bit */
  33         TYPEDO,     /* i: same, but skip check to exit inflate on new block */
  34         STORED,     /* i: waiting for stored size (length and complement) */
  35         COPY,       /* i/o: waiting for input or output to copy stored block */
  36         TABLE,      /* i: waiting for dynamic block table lengths */
  37         LENLENS,    /* i: waiting for code length code lengths */
  38         CODELENS,   /* i: waiting for length/lit and distance code lengths */
  39             LEN,        /* i: waiting for length/lit code */
  40             LENEXT,     /* i: waiting for length extra bits */
  41             DIST,       /* i: waiting for distance code */
  42             DISTEXT,    /* i: waiting for distance extra bits */
  43             MATCH,      /* o: waiting for output space to copy string */
  44             LIT,        /* o: waiting for output space to write literal */
  45     CHECK,      /* i: waiting for 32-bit check value */
  46     LENGTH,     /* i: waiting for 32-bit length (gzip) */
  47     DONE,       /* finished check, done -- remain here until reset */
  48     BAD,        /* got a data error -- remain here until reset */
  49     MEM,        /* got an inflate() memory error -- remain here until reset */
  50     SYNC        /* looking for synchronization bytes to restart inflate() */
  51 } inflate_mode;
  52
  53 /*
  54     State transitions between above modes -
  55
  56     (most modes can go to the BAD or MEM mode -- not shown for clarity)
  57
  58     Process header:
  59         HEAD -> (gzip) or (zlib)
  60         (gzip) -> FLAGS -> TIME -> OS -> EXLEN -> EXTRA -> NAME
  61         NAME -> COMMENT -> HCRC -> TYPE
  62         (zlib) -> DICTID or TYPE
  63         DICTID -> DICT -> TYPE
  64     Read deflate blocks:
  65             TYPE -> STORED or TABLE or LEN or CHECK
  66             STORED -> COPY -> TYPE
  67             TABLE -> LENLENS -> CODELENS -> LEN
  68     Read deflate codes:
  69                 LEN -> LENEXT or LIT or TYPE
  70                 LENEXT -> DIST -> DISTEXT -> MATCH -> LEN
  71                 LIT -> LEN
  72     Process trailer:
  73         CHECK -> LENGTH -> DONE
  74  */
  75
  76 /* state maintained between inflate() calls.  Approximately 7K bytes. */
  77 struct inflate_state {
  78     inflate_mode mode;          /* current inflate mode */
  79     int last;                   /* true if processing last block */
  80     int wrap;                   /* bit 0 true for zlib, bit 1 true for gzip */
  81     int havedict;               /* true if dictionary provided */
  82     int flags;                  /* gzip header method and flags (0 if zlib) */
  83     unsigned dmax;              /* zlib header max distance (INFLATE_STRICT) */
  84     unsigned long check;        /* protected copy of check value */
  85     unsigned long total;        /* protected copy of output count */
  86     gz_headerp head;            /* where to save gzip header information */
  87         /* sliding window */
  88     unsigned wbits;             /* log base 2 of requested window size */
  89     unsigned wsize;             /* window size or zero if not using window */
  90     unsigned whave;             /* valid bytes in the window */
  91     unsigned write;             /* window write index */
  92     unsigned char FAR *window;  /* allocated sliding window, if needed */
  93         /* bit accumulator */
  94     unsigned long hold;         /* input bit accumulator */
  95     unsigned bits;              /* number of bits in "in" */
  96         /* for string and stored block copying */
  97     unsigned length;            /* literal or length of data to copy */
  98     unsigned offset;            /* distance back to copy string from */
  99         /* for table and code decoding */
 100     unsigned extra;             /* extra bits needed */
 101         /* fixed and dynamic code tables */
 102     code const FAR *lencode;    /* starting table for length/literal codes */
 103     code const FAR *distcode;   /* starting table for distance codes */
 104     unsigned lenbits;           /* index bits for lencode */
 105     unsigned distbits;          /* index bits for distcode */
 106         /* dynamic table building */
 107     unsigned ncode;             /* number of code length code lengths */
 108     unsigned nlen;              /* number of length code lengths */
 109     unsigned ndist;             /* number of distance code lengths */
 110     unsigned have;              /* number of code lengths in lens[] */
 111     code FAR *next;             /* next available space in codes[] */
 112     unsigned short lens[320];   /* temporary storage for code lengths */
 113     unsigned short work[288];   /* work area for code table building */
 114     code codes[ENOUGH];         /* space for code tables */
 115 };