zlib/inflate.h

   1 /* inflate.h -- internal inflate state definition
   2  * Copyright (C) 1995-2016 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 = 16180,   /* 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: same as COPY below, but only first time in */
  36         COPY,       /* i/o: waiting for input or output to copy stored block */
  37         TABLE,      /* i: waiting for dynamic block table lengths */
  38         LENLENS,    /* i: waiting for code length code lengths */
  39         CODELENS,   /* i: waiting for length/lit and distance code lengths */
  40             LEN_,       /* i: same as LEN below, but only first time in */
  41             LEN,        /* i: waiting for length/lit/eob code */
  42             LENEXT,     /* i: waiting for length extra bits */
  43             DIST,       /* i: waiting for distance code */
  44             DISTEXT,    /* i: waiting for distance extra bits */
  45             MATCH,      /* o: waiting for output space to copy string */
  46             LIT,        /* o: waiting for output space to write literal */
  47     CHECK,      /* i: waiting for 32-bit check value */
  48     LENGTH,     /* i: waiting for 32-bit length (gzip) */
  49     DONE,       /* finished check, done -- remain here until reset */
  50     BAD,        /* got a data error -- remain here until reset */
  51     MEM,        /* got an inflate() memory error -- remain here until reset */
  52     SYNC        /* looking for synchronization bytes to restart inflate() */
  53 } inflate_mode;
  54
  55 /*
  56     State transitions between above modes -
  57
  58     (most modes can go to BAD or MEM on error -- not shown for clarity)
  59
  60     Process header:
  61         HEAD -> (gzip) or (zlib) or (raw)
  62         (gzip) -> FLAGS -> TIME -> OS -> EXLEN -> EXTRA -> NAME -> COMMENT ->
  63                   HCRC -> TYPE
  64         (zlib) -> DICTID or TYPE
  65         DICTID -> DICT -> TYPE
  66         (raw) -> TYPEDO
  67     Read deflate blocks:
  68             TYPE -> TYPEDO -> STORED or TABLE or LEN_ or CHECK
  69             STORED -> COPY_ -> COPY -> TYPE
  70             TABLE -> LENLENS -> CODELENS -> LEN_
  71             LEN_ -> LEN
  72     Read deflate codes in fixed or dynamic block:
  73                 LEN -> LENEXT or LIT or TYPE
  74                 LENEXT -> DIST -> DISTEXT -> MATCH -> LEN
  75                 LIT -> LEN
  76     Process trailer:
  77         CHECK -> LENGTH -> DONE
  78  */
  79
  80 /* State maintained between inflate() calls -- approximately 7K bytes, not
  81    including the allocated sliding window, which is up to 32K bytes. */
  82 struct inflate_state {
  83     z_streamp strm;             /* pointer back to this zlib stream */
  84     inflate_mode mode;          /* current inflate mode */
  85     int last;                   /* true if processing last block */
  86     int wrap;                   /* bit 0 true for zlib, bit 1 true for gzip,
  87                                    bit 2 true to validate check value */
  88     int havedict;               /* true if dictionary provided */
  89     int flags;                  /* gzip header method and flags (0 if zlib) */
  90     unsigned dmax;              /* zlib header max distance (INFLATE_STRICT) */
  91     unsigned long check;        /* protected copy of check value */
  92     unsigned long total;        /* protected copy of output count */
  93     gz_headerp head;            /* where to save gzip header information */
  94         /* sliding window */
  95     unsigned wbits;             /* log base 2 of requested window size */
  96     unsigned wsize;             /* window size or zero if not using window */
  97     unsigned whave;             /* valid bytes in the window */
  98     unsigned wnext;             /* window write index */
  99     unsigned char FAR *window;  /* allocated sliding window, if needed */
 100         /* bit accumulator */
 101     unsigned long hold;         /* input bit accumulator */
 102     unsigned bits;              /* number of bits in "in" */
 103         /* for string and stored block copying */
 104     unsigned length;            /* literal or length of data to copy */
 105     unsigned offset;            /* distance back to copy string from */
 106         /* for table and code decoding */
 107     unsigned extra;             /* extra bits needed */
 108         /* fixed and dynamic code tables */
 109     code const FAR *lencode;    /* starting table for length/literal codes */
 110     code const FAR *distcode;   /* starting table for distance codes */
 111     unsigned lenbits;           /* index bits for lencode */
 112     unsigned distbits;          /* index bits for distcode */
 113         /* dynamic table building */
 114     unsigned ncode;             /* number of code length code lengths */
 115     unsigned nlen;              /* number of length code lengths */
 116     unsigned ndist;             /* number of distance code lengths */
 117     unsigned have;              /* number of code lengths in lens[] */
 118     code FAR *next;             /* next available space in codes[] */
 119     unsigned short lens[320];   /* temporary storage for code lengths */
 120     unsigned short work[288];   /* work area for code table building */
 121     code codes[ENOUGH];         /* space for code tables */
 122     int sane;                   /* if false, allow invalid distance too far */
 123     int back;                   /* bits back of last unprocessed length/lit */
 124     unsigned was;               /* initial length of match */
 125 };