inftrees.h revision 206924
1193326Sed/* inftrees.h -- header to use inftrees.c 2193326Sed * Copyright (C) 1995-2005, 2010 Mark Adler 3193326Sed * For conditions of distribution and use, see copyright notice in zlib.h 4193326Sed */ 5193326Sed 6193326Sed/* WARNING: this file should *not* be used by applications. It is 7193326Sed part of the implementation of the compression library and is 8193326Sed subject to change. Applications should only use zlib.h. 9193326Sed */ 10193326Sed 11193326Sed/* Structure for decoding tables. Each entry provides either the 12193326Sed information needed to do the operation requested by the code that 13193326Sed indexed that table entry, or it provides a pointer to another 14193326Sed table that indexes more bits of the code. op indicates whether 15212904Sdim the entry is a pointer to another table, a literal, a length or 16252723Sdim distance, an end-of-block, or an invalid code. For a table 17198092Srdivacky pointer, the low four bits of op is the number of index bits of 18193326Sed that table. For a length or distance, the low four bits of op 19193326Sed is the number of extra bits to get after the code. bits is 20193326Sed the number of bits in this code or part of the code to drop off 21193326Sed of the bit buffer. val is the actual byte to output in the case 22193326Sed of a literal, the base length or distance, or the offset from 23193326Sed the current table to the next table. Each entry is four bytes. */ 24252723Sdimtypedef struct { 25252723Sdim unsigned char op; /* operation, extra bits, table bits */ 26252723Sdim unsigned char bits; /* bits in this part of the code */ 27252723Sdim unsigned short val; /* offset in table or code value */ 28252723Sdim} code; 29252723Sdim 30252723Sdim/* op values as set by inflate_table(): 31193326Sed 00000000 - literal 32193326Sed 0000tttt - table link, tttt != 0 is the number of table index bits 33193326Sed 0001eeee - length or distance, eeee is the number of extra bits 34193326Sed 01100000 - end of block 35193326Sed 01000000 - invalid code 36193326Sed */ 37193326Sed 38193326Sed/* Maximum size of the dynamic table. The maximum number of code structures is 39193326Sed 1444, which is the sum of 852 for literal/length codes and 592 for distance 40193326Sed codes. These values were found by exhaustive searches using the program 41193326Sed examples/enough.c found in the zlib distribtution. The arguments to that 42218893Sdim program are the number of symbols, the initial root table size, and the 43193326Sed maximum bit length of a code. "enough 286 9 15" for literal/length codes 44193326Sed returns returns 852, and "enough 30 6 15" for distance codes returns 592. 45193326Sed The initial root table size (9 or 6) is found in the fifth argument of the 46193326Sed inflate_table() calls in inflate.c and infback.c. If the root table size is 47210299Sed changed, then these maximum sizes would be need to be recalculated and 48245431Sdim updated. */ 49210299Sed#define ENOUGH_LENS 852 50193326Sed#define ENOUGH_DISTS 592 51193326Sed#define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS) 52218893Sdim 53218893Sdim/* Type of code to build for inflate_table() */ 54218893Sdimtypedef enum { 55218893Sdim CODES, 56218893Sdim LENS, 57218893Sdim DISTS 58218893Sdim} codetype; 59199990Srdivacky 60193326Sedint ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens, 61193326Sed unsigned codes, code FAR * FAR *table, 62193326Sed unsigned FAR *bits, unsigned short FAR *work)); 63193326Sed