File indexing completed on 2024-04-21 03:48:32
0001 /* inftrees.h -- header to use inftrees.c 0002 * Copyright (C) 1995-2005, 2010 Mark Adler 0003 * For conditions of distribution and use, see copyright notice in zlib.h 0004 */ 0005 0006 /* WARNING: this file should *not* be used by applications. It is 0007 part of the implementation of the compression library and is 0008 subject to change. Applications should only use zlib.h. 0009 */ 0010 0011 /* Structure for decoding tables. Each entry provides either the 0012 information needed to do the operation requested by the code that 0013 indexed that table entry, or it provides a pointer to another 0014 table that indexes more bits of the code. op indicates whether 0015 the entry is a pointer to another table, a literal, a length or 0016 distance, an end-of-block, or an invalid code. For a table 0017 pointer, the low four bits of op is the number of index bits of 0018 that table. For a length or distance, the low four bits of op 0019 is the number of extra bits to get after the code. bits is 0020 the number of bits in this code or part of the code to drop off 0021 of the bit buffer. val is the actual byte to output in the case 0022 of a literal, the base length or distance, or the offset from 0023 the current table to the next table. Each entry is four bytes. */ 0024 typedef struct { 0025 unsigned char op; /* operation, extra bits, table bits */ 0026 unsigned char bits; /* bits in this part of the code */ 0027 unsigned short val; /* offset in table or code value */ 0028 } code; 0029 0030 /* op values as set by inflate_table(): 0031 00000000 - literal 0032 0000tttt - table link, tttt != 0 is the number of table index bits 0033 0001eeee - length or distance, eeee is the number of extra bits 0034 01100000 - end of block 0035 01000000 - invalid code 0036 */ 0037 0038 /* Maximum size of the dynamic table. The maximum number of code structures is 0039 1444, which is the sum of 852 for literal/length codes and 592 for distance 0040 codes. These values were found by exhaustive searches using the program 0041 examples/enough.c found in the zlib distribtution. The arguments to that 0042 program are the number of symbols, the initial root table size, and the 0043 maximum bit length of a code. "enough 286 9 15" for literal/length codes 0044 returns returns 852, and "enough 30 6 15" for distance codes returns 592. 0045 The initial root table size (9 or 6) is found in the fifth argument of the 0046 inflate_table() calls in inflate.c and infback.c. If the root table size is 0047 changed, then these maximum sizes would be need to be recalculated and 0048 updated. */ 0049 #define ENOUGH_LENS 852 0050 #define ENOUGH_DISTS 592 0051 #define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS) 0052 0053 /* Type of code to build for inflate_table() */ 0054 typedef enum { 0055 CODES, 0056 LENS, 0057 DISTS 0058 } codetype; 0059 0060 int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens, 0061 unsigned codes, code FAR * FAR *table, 0062 unsigned FAR *bits, unsigned short FAR *work));