inftrees.h
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/* inftrees.h -- header to use inftrees.c
* Copyright (C) 1995-2005, 2010 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.
*/
/* Structure for decoding tables. Each entry provides either the
information needed to do the operation requested by the code that
indexed that table entry, or it provides a pointer to another
table that indexes more bits of the code. op indicates whether
the entry is a pointer to another table, a literal, a length or
distance, an end-of-block, or an invalid code. For a table
pointer, the low four bits of op is the number of index bits of
that table. For a length or distance, the low four bits of op
is the number of extra bits to get after the code. bits is
the number of bits in this code or part of the code to drop off
of the bit buffer. val is the actual byte to output in the case
of a literal, the base length or distance, or the offset from
the current table to the next table. Each entry is four bytes. */
typedef struct {
unsigned char op; /* operation, extra bits, table bits */
unsigned char bits; /* bits in this part of the code */
unsigned short val; /* offset in table or code value */
} code;
/* op values as set by inflate_table():
00000000 - literal
0000tttt - table link, tttt != 0 is the number of table index bits
0001eeee - length or distance, eeee is the number of extra bits
01100000 - end of block
01000000 - invalid code
*/
/* Maximum size of the dynamic table. The maximum number of code structures is
1444, which is the sum of 852 for literal/length codes and 592 for distance
codes. These values were found by exhaustive searches using the program
examples/enough.c found in the zlib distribtution. The arguments to that
program are the number of symbols, the initial root table size, and the
maximum bit length of a code. "enough 286 9 15" for literal/length codes
returns returns 852, and "enough 30 6 15" for distance codes returns 592.
The initial root table size (9 or 6) is found in the fifth argument of the
inflate_table() calls in inflate.c and infback.c. If the root table size is
changed, then these maximum sizes would be need to be recalculated and
updated. */
#define ENOUGH_LENS 852
#define ENOUGH_DISTS 592
#define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS)
/* Type of code to build for inflate_table() */
typedef enum {
CODES,
LENS,
DISTS
} codetype;
int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens,
unsigned codes, code FAR * FAR *table,
unsigned FAR *bits, unsigned short FAR *work));
ZLIB_INTERNAL
#define ZLIB_INTERNAL
Definition: compress.c:8
inflate_table
int ZLIB_INTERNAL inflate_table(codetype type, unsigned short FAR *lens, unsigned codes, code FAR *FAR *table, unsigned FAR *bits, unsigned short FAR *work)
Definition: inftrees.c:32
codetype
codetype
Definition: inftrees.h:54
CODES
@ CODES
Definition: inftrees.h:55
LENS
@ LENS
Definition: inftrees.h:56
DISTS
@ DISTS
Definition: inftrees.h:57
OF
int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens, unsigned codes, code FAR *FAR *table, unsigned FAR *bits, unsigned short FAR *work))
code
Definition: inftrees.h:24
code::op
unsigned char op
Definition: inftrees.h:25
code::bits
unsigned char bits
Definition: inftrees.h:26
code::val
unsigned short val
Definition: inftrees.h:27
FAR
#define FAR
Definition: zconf.h:387