1: /* inftrees.h -- header to use inftrees.c
2: * Copyright (C) 1995-2005, 2010 Mark Adler
3: * For conditions of distribution and use, see copyright notice in zlib.h
4: */
5:
6: /* WARNING: this file should *not* be used by applications. It is
7: part of the implementation of the compression library and is
8: subject to change. Applications should only use zlib.h.
9: */
10:
11: /* Structure for decoding tables. Each entry provides either the
12: information needed to do the operation requested by the code that
13: indexed that table entry, or it provides a pointer to another
14: table that indexes more bits of the code. op indicates whether
15: the entry is a pointer to another table, a literal, a length or
16: distance, an end-of-block, or an invalid code. For a table
17: pointer, the low four bits of op is the number of index bits of
18: that table. For a length or distance, the low four bits of op
19: is the number of extra bits to get after the code. bits is
20: the number of bits in this code or part of the code to drop off
21: of the bit buffer. val is the actual byte to output in the case
22: of a literal, the base length or distance, or the offset from
23: the current table to the next table. Each entry is four bytes. */
24: typedef struct {
25: unsigned char op; /* operation, extra bits, table bits */
26: unsigned char bits; /* bits in this part of the code */
27: unsigned short val; /* offset in table or code value */
28: } code;
29:
30: /* op values as set by inflate_table():
31: 00000000 - literal
32: 0000tttt - table link, tttt != 0 is the number of table index bits
33: 0001eeee - length or distance, eeee is the number of extra bits
34: 01100000 - end of block
35: 01000000 - invalid code
36: */
37:
38: /* Maximum size of the dynamic table. The maximum number of code structures is
39: 1444, which is the sum of 852 for literal/length codes and 592 for distance
40: codes. These values were found by exhaustive searches using the program
41: examples/enough.c found in the zlib distribtution. The arguments to that
42: program are the number of symbols, the initial root table size, and the
43: maximum bit length of a code. "enough 286 9 15" for literal/length codes
44: returns returns 852, and "enough 30 6 15" for distance codes returns 592.
45: The initial root table size (9 or 6) is found in the fifth argument of the
46: inflate_table() calls in inflate.c and infback.c. If the root table size is
47: changed, then these maximum sizes would be need to be recalculated and
48: updated. */
49: #define ENOUGH_LENS 852
50: #define ENOUGH_DISTS 592
51: #define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS)
52:
53: /* Type of code to build for inflate_table() */
54: typedef enum {
55: CODES,
56: LENS,
57: DISTS
58: } codetype;
59:
60: int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens,
61: unsigned codes, code FAR * FAR *table,
62: unsigned FAR *bits, unsigned short FAR *work));
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