cpython/Modules/zlib/inftrees.h at 3.5 · python/cpython · GitHub

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/* inftrees.h -- header to use inftrees.c

* 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));

cpython/Modules/zlib/inftrees.h at 3.5 · python/cpython · GitHub

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