zlib/inflate.h

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/* inflate.h -- internal inflate state definition
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* Copyright (C) 1995-2019 Mark Adler
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* 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.
*/
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/* 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
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the crc code when it is not needed. For shared libraries, gzip decoding
should be left enabled. */
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#ifndef NO_GZIP
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# define GUNZIP
#endif
/* Possible inflate modes between inflate() calls */
typedef enum {
HEAD = 16180, /* i: waiting for magic header */
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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 */
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TYPEDO, /* i: same, but skip check to exit inflate on new block */
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STORED, /* i: waiting for stored size (length and complement) */
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COPY_, /* i/o: same as COPY below, but only first time in */
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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 */
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LEN_, /* i: same as LEN below, but only first time in */
LEN, /* i: waiting for length/lit/eob code */
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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 -
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(most modes can go to BAD or MEM on error -- not shown for clarity)
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Process header:
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HEAD -> (gzip) or (zlib) or (raw)
(gzip) -> FLAGS -> TIME -> OS -> EXLEN -> EXTRA -> NAME -> COMMENT ->
HCRC -> TYPE
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(zlib) -> DICTID or TYPE
DICTID -> DICT -> TYPE
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(raw) -> TYPEDO
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Read deflate blocks:
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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:
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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
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including the allocated sliding window, which is up to 32K bytes. */
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struct inflate_state {
z_streamp strm; /* pointer back to this zlib stream */
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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 */
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int havedict; /* true if dictionary provided */
int flags; /* gzip header method and flags, 0 if zlib, or
-1 if raw or no header yet */
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unsigned dmax; /* zlib header max distance (INFLATE_STRICT) */
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unsigned long check; /* protected copy of check value */
unsigned long total; /* protected copy of output count */
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gz_headerp head; /* where to save gzip header information */
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/* sliding window */
unsigned wbits; /* log base 2 of requested window size */
unsigned wsize; /* window size or zero if not using window */
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unsigned whave; /* valid bytes in the window */
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unsigned wnext; /* window write index */
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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 */
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int sane; /* if false, allow invalid distance too far */
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int back; /* bits back of last unprocessed length/lit */
unsigned was; /* initial length of match */
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};