1*212397c6Schristos /* inftrees.h -- header to use inftrees.c 2*212397c6Schristos * Copyright (C) 1995-2005, 2010 Mark Adler 3*212397c6Schristos * For conditions of distribution and use, see copyright notice in zlib.h 4*212397c6Schristos */ 5*212397c6Schristos 6*212397c6Schristos /* WARNING: this file should *not* be used by applications. It is 7*212397c6Schristos part of the implementation of the compression library and is 8*212397c6Schristos subject to change. Applications should only use zlib.h. 9*212397c6Schristos */ 10*212397c6Schristos 11*212397c6Schristos /* Structure for decoding tables. Each entry provides either the 12*212397c6Schristos information needed to do the operation requested by the code that 13*212397c6Schristos indexed that table entry, or it provides a pointer to another 14*212397c6Schristos table that indexes more bits of the code. op indicates whether 15*212397c6Schristos the entry is a pointer to another table, a literal, a length or 16*212397c6Schristos distance, an end-of-block, or an invalid code. For a table 17*212397c6Schristos pointer, the low four bits of op is the number of index bits of 18*212397c6Schristos that table. For a length or distance, the low four bits of op 19*212397c6Schristos is the number of extra bits to get after the code. bits is 20*212397c6Schristos the number of bits in this code or part of the code to drop off 21*212397c6Schristos of the bit buffer. val is the actual byte to output in the case 22*212397c6Schristos of a literal, the base length or distance, or the offset from 23*212397c6Schristos the current table to the next table. Each entry is four bytes. */ 24*212397c6Schristos typedef struct { 25*212397c6Schristos unsigned char op; /* operation, extra bits, table bits */ 26*212397c6Schristos unsigned char bits; /* bits in this part of the code */ 27*212397c6Schristos unsigned short val; /* offset in table or code value */ 28*212397c6Schristos } code; 29*212397c6Schristos 30*212397c6Schristos /* op values as set by inflate_table(): 31*212397c6Schristos 00000000 - literal 32*212397c6Schristos 0000tttt - table link, tttt != 0 is the number of table index bits 33*212397c6Schristos 0001eeee - length or distance, eeee is the number of extra bits 34*212397c6Schristos 01100000 - end of block 35*212397c6Schristos 01000000 - invalid code 36*212397c6Schristos */ 37*212397c6Schristos 38*212397c6Schristos /* Maximum size of the dynamic table. The maximum number of code structures is 39*212397c6Schristos 1444, which is the sum of 852 for literal/length codes and 592 for distance 40*212397c6Schristos codes. These values were found by exhaustive searches using the program 41*212397c6Schristos examples/enough.c found in the zlib distribtution. The arguments to that 42*212397c6Schristos program are the number of symbols, the initial root table size, and the 43*212397c6Schristos maximum bit length of a code. "enough 286 9 15" for literal/length codes 44*212397c6Schristos returns returns 852, and "enough 30 6 15" for distance codes returns 592. 45*212397c6Schristos The initial root table size (9 or 6) is found in the fifth argument of the 46*212397c6Schristos inflate_table() calls in inflate.c and infback.c. If the root table size is 47*212397c6Schristos changed, then these maximum sizes would be need to be recalculated and 48*212397c6Schristos updated. */ 49*212397c6Schristos #define ENOUGH_LENS 852 50*212397c6Schristos #define ENOUGH_DISTS 592 51*212397c6Schristos #define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS) 52*212397c6Schristos 53*212397c6Schristos /* Type of code to build for inflate_table() */ 54*212397c6Schristos typedef enum { 55*212397c6Schristos CODES, 56*212397c6Schristos LENS, 57*212397c6Schristos DISTS 58*212397c6Schristos } codetype; 59*212397c6Schristos 60*212397c6Schristos int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens, 61*212397c6Schristos unsigned codes, code FAR * FAR *table, 62*212397c6Schristos unsigned FAR *bits, unsigned short FAR *work)); 63