FreeBSD/Linux Kernel Cross Reference
sys/contrib/zlib/inflate.h

     /* inflate.h -- internal inflate state definition
      * Copyright (C) 1995-2019 Mark Adler
      * For conditions of distribution and use, see copyright notice in zlib.h
      */
     
     /* 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 = 16180,   /* 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: same as COPY below, but only first time in */
            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: same as LEN below, but only first time in */
                LEN,        /* i: waiting for length/lit/eob 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 BAD or MEM on error -- not shown for clarity)
    
        Process header:
            HEAD -> (gzip) or (zlib) or (raw)
            (gzip) -> FLAGS -> TIME -> OS -> EXLEN -> EXTRA -> NAME -> COMMENT ->
                      HCRC -> TYPE
            (zlib) -> DICTID or TYPE
            DICTID -> DICT -> TYPE
            (raw) -> TYPEDO
        Read deflate blocks:
                TYPE -> TYPEDO -> STORED or TABLE or LEN_ or CHECK
                STORED -> COPY_ -> COPY -> TYPE
                TABLE -> LENLENS -> CODELENS -> LEN_
                LEN_ -> LEN
        Read deflate codes in fixed or dynamic block:
                    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, not
       including the allocated sliding window, which is up to 32K bytes. */
    struct inflate_state {
        z_streamp strm;             /* pointer back to this zlib stream */
        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,
                                       bit 2 true to validate check value */
        int havedict;               /* true if dictionary provided */
        int flags;                  /* gzip header method and flags, 0 if zlib, or
                                       -1 if raw or no header yet */
        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 wnext;             /* 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 */
       int sane;                   /* if false, allow invalid distance too far */
       int back;                   /* bits back of last unprocessed length/lit */
       unsigned was;               /* initial length of match */
   };

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