inflate.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2019, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

/* WARNING: this file should *not* be used by applications. It is
   part of the implementation of the compression library and is
   subject to change. Applications should only use zlib.h.
 */

/* define NO_GZIP when compiling if you want to disable gzip header and
   trailer decoding by inflate().  NO_GZIP would be used to avoid linking in
   the crc code when it is not needed.  For shared libraries, gzip decoding
   should be left enabled. */
#ifndef NO_GZIP
#define GUNZIP
#endif

/* Possible inflate modes between inflate() calls */
typedef enum
{
    HEAD, /* i: waiting for magic header */
    FLAGS, /* i: waiting for method and flags (gzip) */
    TIME, /* i: waiting for modification time (gzip) */
    OS, /* i: waiting for extra flags and operating system (gzip) */
    EXLEN, /* i: waiting for extra length (gzip) */
    EXTRA, /* i: waiting for extra bytes (gzip) */
    NAME, /* i: waiting for end of file name (gzip) */
    COMMENT, /* i: waiting for end of comment (gzip) */
    HCRC, /* i: waiting for header crc (gzip) */
    DICTID, /* i: waiting for dictionary check value */
    DICT, /* waiting for inflateSetDictionary() call */
    TYPE, /* i: waiting for type bits, including last-flag bit */
    TYPEDO, /* i: same, but skip check to exit inflate on new block */
    STORED, /* i: waiting for stored size (length and complement) */
    COPY, /* i/o: waiting for input or output to copy stored block */
    TABLE, /* i: waiting for dynamic block table lengths */
    LENLENS, /* i: waiting for code length code lengths */
    CODELENS, /* i: waiting for length/lit and distance code lengths */
    LEN, /* i: waiting for length/lit code */
    LENEXT, /* i: waiting for length extra bits */
    DIST, /* i: waiting for distance code */
    DISTEXT, /* i: waiting for distance extra bits */
    MATCH, /* o: waiting for output space to copy string */
    LIT, /* o: waiting for output space to write literal */
    CHECK, /* i: waiting for 32-bit check value */
    LENGTH, /* i: waiting for 32-bit length (gzip) */
    DONE, /* finished check, done -- remain here until reset */
    BAD, /* got a data error -- remain here until reset */
    MEM, /* got an inflate() memory error -- remain here until reset */
    SYNC /* looking for synchronization bytes to restart inflate() */
} inflate_mode;

/*
    State transitions between above modes -

    (most modes can go to the BAD or MEM mode -- not shown for clarity)

    Process header:
        HEAD -> (gzip) or (zlib)
        (gzip) -> FLAGS -> TIME -> OS -> EXLEN -> EXTRA -> NAME
        NAME -> COMMENT -> HCRC -> TYPE
        (zlib) -> DICTID or TYPE
        DICTID -> DICT -> TYPE
    Read deflate blocks:
            TYPE -> STORED or TABLE or LEN or CHECK
            STORED -> COPY -> TYPE
            TABLE -> LENLENS -> CODELENS -> LEN
    Read deflate codes:
                LEN -> LENEXT or LIT or TYPE
                LENEXT -> DIST -> DISTEXT -> MATCH -> LEN
                LIT -> LEN
    Process trailer:
        CHECK -> LENGTH -> DONE
 */

/* state maintained between inflate() calls.  Approximately 7K bytes. */
struct inflate_state
{
    inflate_mode mode; /* current inflate mode */
    int last; /* true if processing last block */
    int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
    int havedict; /* true if dictionary provided */
    int flags; /* gzip header method and flags (0 if zlib) */
    unsigned dmax; /* zlib header max distance (INFLATE_STRICT) */
    unsigned long check; /* protected copy of check value */
    unsigned long total; /* protected copy of output count */
    gz_headerp head; /* where to save gzip header information */
    /* sliding window */
    unsigned wbits; /* log base 2 of requested window size */
    unsigned wsize; /* window size or zero if not using window */
    unsigned whave; /* valid bytes in the window */
    unsigned write; /* window write index */
    unsigned char FAR* window; /* allocated sliding window, if needed */
    /* bit accumulator */
    unsigned long hold; /* input bit accumulator */
    unsigned bits; /* number of bits in "in" */
    /* for string and stored block copying */
    unsigned length; /* literal or length of data to copy */
    unsigned offset; /* distance back to copy string from */
    /* for table and code decoding */
    unsigned extra; /* extra bits needed */
    /* fixed and dynamic code tables */
    code const FAR* lencode; /* starting table for length/literal codes */
    code const FAR* distcode; /* starting table for distance codes */
    unsigned lenbits; /* index bits for lencode */
    unsigned distbits; /* index bits for distcode */
    /* dynamic table building */
    unsigned ncode; /* number of code length code lengths */
    unsigned nlen; /* number of length code lengths */
    unsigned ndist; /* number of distance code lengths */
    unsigned have; /* number of code lengths in lens[] */
    code FAR* next; /* next available space in codes[] */
    unsigned short lens[320]; /* temporary storage for code lengths */
    unsigned short work[288]; /* work area for code table building */
    code codes[ENOUGH]; /* space for code tables */
};