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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)); |