inflate.h

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/* inflate.h -- internal inflate state definition
 * Copyright (C) 1995-2009 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, /* 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 10K 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 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 */
};