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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)); |
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