inflate.h revision 131377 
1/* inflate.h -- internal inflate state definition
2 * Copyright (C) 1995-2003 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 */
20typedef enum {
21    HEAD,       /* i: waiting for magic header */
22#ifdef GUNZIP
23    FLAGS,      /* i: waiting for method and flags (gzip) */
24    TIME,       /* i: waiting for modification time (gzip) */
25    OS,         /* i: waiting for extra flags and operating system (gzip) */
26    EXLEN,      /* i: waiting for extra length (gzip) */
27    EXTRA,      /* i: waiting for extra bytes (gzip) */
28    NAME,       /* i: waiting for end of file name (gzip) */
29    COMMENT,    /* i: waiting for end of comment (gzip) */
30    HCRC,       /* i: waiting for header crc (gzip) */
31#endif
32    DICTID,     /* i: waiting for dictionary check value */
33    DICT,       /* waiting for inflateSetDictionary() call */
34        TYPE,       /* i: waiting for type bits, including last-flag bit */
35        TYPEDO,     /* i: same, but skip check to exit inflate on new block */
36        STORED,     /* i: waiting for stored size (length and complement) */
37        COPY,       /* i/o: waiting for input or output to copy stored block */
38        TABLE,      /* i: waiting for dynamic block table lengths */
39        LENLENS,    /* i: waiting for code length code lengths */
40        CODELENS,   /* i: waiting for length/lit and distance code lengths */
41            LEN,        /* i: waiting for length/lit 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#ifdef GUNZIP
49    LENGTH,     /* i: waiting for 32-bit length (gzip) */
50#endif
51    DONE,       /* finished check, done -- remain here until reset */
52    BAD,        /* got a data error -- remain here until reset */
53    MEM,        /* got an inflate() memory error -- remain here until reset */
54    SYNC        /* looking for synchronization bytes to restart inflate() */
55} inflate_mode;
56
57/*
58    State transitions between above modes -
59
60    (most modes can go to the BAD or MEM mode -- not shown for clarity)
61
62    Process header:
63        HEAD -> (gzip) or (zlib)
64        (gzip) -> FLAGS -> TIME -> OS -> EXLEN -> EXTRA -> NAME
65        NAME -> COMMENT -> HCRC -> TYPE
66        (zlib) -> DICTID or TYPE
67        DICTID -> DICT -> TYPE
68    Read deflate blocks:
69            TYPE -> STORED or TABLE or LEN or CHECK
70            STORED -> COPY -> TYPE
71            TABLE -> LENLENS -> CODELENS -> LEN
72    Read deflate codes:
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. */
81struct 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 long check;        /* protected copy of check value */
88    unsigned long total;        /* protected copy of output count */
89        /* sliding window */
90    unsigned wbits;             /* log base 2 of requested window size */
91    unsigned wsize;             /* window size or zero if not using window */
92    unsigned whave;             /* valid bytes in the window */
93    unsigned write;             /* window write index */
94    unsigned char FAR *window;  /* allocated sliding window, if needed */
95        /* bit accumulator */
96    unsigned long hold;         /* input bit accumulator */
97    unsigned bits;              /* number of bits in "in" */
98        /* for string and stored block copying */
99    unsigned length;            /* literal or length of data to copy */
100    unsigned offset;            /* distance back to copy string from */
101        /* for table and code decoding */
102    unsigned extra;             /* extra bits needed */
103        /* fixed and dynamic code tables */
104    code const FAR *lencode;    /* starting table for length/literal codes */
105    code const FAR *distcode;   /* starting table for distance codes */
106    unsigned lenbits;           /* index bits for lencode */
107    unsigned distbits;          /* index bits for distcode */
108        /* dynamic table building */
109    unsigned ncode;             /* number of code length code lengths */
110    unsigned nlen;              /* number of length code lengths */
111    unsigned ndist;             /* number of distance code lengths */
112    unsigned have;              /* number of code lengths in lens[] */
113    code FAR *next;             /* next available space in codes[] */
114    unsigned short lens[320];   /* temporary storage for code lengths */
115    unsigned short work[288];   /* work area for code table building */
116    code codes[ENOUGH];         /* space for code tables */
117};
118