00001 /* inftree9.h -- header to use inftree9.c 00002 * Copyright (C) 1995-2008 Mark Adler 00003 * For conditions of distribution and use, see copyright notice in zlib.h 00004 */ 00005 00006 /* WARNING: this file should *not* be used by applications. It is 00007 part of the implementation of the compression library and is 00008 subject to change. Applications should only use zlib.h. 00009 */ 00010 00011 /* Structure for decoding tables. Each entry provides either the 00012 information needed to do the operation requested by the code that 00013 indexed that table entry, or it provides a pointer to another 00014 table that indexes more bits of the code. op indicates whether 00015 the entry is a pointer to another table, a literal, a length or 00016 distance, an end-of-block, or an invalid code. For a table 00017 pointer, the low four bits of op is the number of index bits of 00018 that table. For a length or distance, the low four bits of op 00019 is the number of extra bits to get after the code. bits is 00020 the number of bits in this code or part of the code to drop off 00021 of the bit buffer. val is the actual byte to output in the case 00022 of a literal, the base length or distance, or the offset from 00023 the current table to the next table. Each entry is four bytes. */ 00024 typedef struct { 00025 unsigned char op; /* operation, extra bits, table bits */ 00026 unsigned char bits; /* bits in this part of the code */ 00027 unsigned short val; /* offset in table or code value */ 00028 } code; 00029 00030 /* op values as set by inflate_table(): 00031 00000000 - literal 00032 0000tttt - table link, tttt != 0 is the number of table index bits 00033 100eeeee - length or distance, eeee is the number of extra bits 00034 01100000 - end of block 00035 01000000 - invalid code 00036 */ 00037 00038 /* Maximum size of the dynamic table. The maximum number of code structures is 00039 1446, which is the sum of 852 for literal/length codes and 594 for distance 00040 codes. These values were found by exhaustive searches using the program 00041 examples/enough.c found in the zlib distribtution. The arguments to that 00042 program are the number of symbols, the initial root table size, and the 00043 maximum bit length of a code. "enough 286 9 15" for literal/length codes 00044 returns returns 852, and "enough 32 6 15" for distance codes returns 594. 00045 The initial root table size (9 or 6) is found in the fifth argument of the 00046 inflate_table() calls in infback9.c. If the root table size is changed, 00047 then these maximum sizes would be need to be recalculated and updated. */ 00048 #define ENOUGH_LENS 852 00049 #define ENOUGH_DISTS 594 00050 #define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS) 00051 00052 /* Type of code to build for inflate_table9() */ 00053 typedef enum { 00054 CODES, 00055 LENS, 00056 DISTS 00057 } codetype; 00058 00059 extern int inflate_table9 OF((codetype type, unsigned short FAR *lens, 00060 unsigned codes, code FAR * FAR *table, 00061 unsigned FAR *bits, unsigned short FAR *work));