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));␊ |
63 | |