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inflate.h
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1 /* inflate.h -- internal inflate state definition
2  * Copyright (C) 1995-2009 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: 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 10K bytes. */
81 struct inflate_state {
82  inflate_mode mode; /* current inflate mode */
83  int last; /* true if processing last block */
84  int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
85  int havedict; /* true if dictionary provided */
86  int flags; /* gzip header method and flags (0 if zlib) */
87  unsigned dmax; /* zlib header max distance (INFLATE_STRICT) */
88  unsigned long check; /* protected copy of check value */
89  unsigned long total; /* protected copy of output count */
90  gz_headerp head; /* where to save gzip header information */
91  /* sliding window */
92  unsigned wbits; /* log base 2 of requested window size */
93  unsigned wsize; /* window size or zero if not using window */
94  unsigned whave; /* valid bytes in the window */
95  unsigned wnext; /* window write index */
96  unsigned char FAR *window; /* allocated sliding window, if needed */
97  /* bit accumulator */
98  unsigned long hold; /* input bit accumulator */
99  unsigned bits; /* number of bits in "in" */
100  /* for string and stored block copying */
101  unsigned length; /* literal or length of data to copy */
102  unsigned offset; /* distance back to copy string from */
103  /* for table and code decoding */
104  unsigned extra; /* extra bits needed */
105  /* fixed and dynamic code tables */
106  code const FAR *lencode; /* starting table for length/literal codes */
107  code const FAR *distcode; /* starting table for distance codes */
108  unsigned lenbits; /* index bits for lencode */
109  unsigned distbits; /* index bits for distcode */
110  /* dynamic table building */
111  unsigned ncode; /* number of code length code lengths */
112  unsigned nlen; /* number of length code lengths */
113  unsigned ndist; /* number of distance code lengths */
114  unsigned have; /* number of code lengths in lens[] */
115  code FAR *next; /* next available space in codes[] */
116  unsigned short lens[320]; /* temporary storage for code lengths */
117  unsigned short work[288]; /* work area for code table building */
118  code codes[ENOUGH]; /* space for code tables */
119  int sane; /* if false, allow invalid distance too far */
120  int back; /* bits back of last unprocessed length/lit */
121  unsigned was; /* initial length of match */
122 };
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