1 /* inflate.h -- internal inflate state definition
2  * Copyright (C) 1995-2019 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, or
90                                    -1 if raw or no header yet */
91     unsigned dmax;              /* zlib header max distance (INFLATE_STRICT) */
92     unsigned long check;        /* protected copy of check value */
93     unsigned long total;        /* protected copy of output count */
94     gz_headerp head;            /* where to save gzip header information */
95         /* sliding window */
96     unsigned wbits;             /* log base 2 of requested window size */
97     unsigned wsize;             /* window size or zero if not using window */
98     unsigned whave;             /* valid bytes in the window */
99     unsigned wnext;             /* window write index */
100     unsigned char FAR *window;  /* allocated sliding window, if needed */
101         /* bit accumulator */
102     unsigned long hold;         /* input bit accumulator */
103     unsigned bits;              /* number of bits in "in" */
104         /* for string and stored block copying */
105     unsigned length;            /* literal or length of data to copy */
106     unsigned offset;            /* distance back to copy string from */
107         /* for table and code decoding */
108     unsigned extra;             /* extra bits needed */
109         /* fixed and dynamic code tables */
110     code const FAR *lencode;    /* starting table for length/literal codes */
111     code const FAR *distcode;   /* starting table for distance codes */
112     unsigned lenbits;           /* index bits for lencode */
113     unsigned distbits;          /* index bits for distcode */
114         /* dynamic table building */
115     unsigned ncode;             /* number of code length code lengths */
116     unsigned nlen;              /* number of length code lengths */
117     unsigned ndist;             /* number of distance code lengths */
118     unsigned have;              /* number of code lengths in lens[] */
119     code FAR *next;             /* next available space in codes[] */
120     unsigned short lens[320];   /* temporary storage for code lengths */
121     unsigned short work[288];   /* work area for code table building */
122     code codes[ENOUGH];         /* space for code tables */
123     int sane;                   /* if false, allow invalid distance too far */
124     int back;                   /* bits back of last unprocessed length/lit */
125     unsigned was;               /* initial length of match */
126 };
127