inflate.h

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/* inflate.h -- internal inflate state definition
 * Copyright (C) 1995-2003 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 */
  #ifdef GUNZIP
    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) */
  #endif
  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 */
  #ifdef GUNZIP
    LENGTH,  /* i: waiting for 32-bit length (gzip) */
  #endif
  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 long check; /* protected copy of check value */
  unsigned long total; /* protected copy of output count */
  /* 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 */
};