1*75fd0b74Schristos /* inftrees.h -- header to use inftrees.c 2*75fd0b74Schristos * Copyright (C) 1995-2005, 2010 Mark Adler 3*75fd0b74Schristos * For conditions of distribution and use, see copyright notice in zlib.h 4*75fd0b74Schristos */ 5*75fd0b74Schristos 6*75fd0b74Schristos /* WARNING: this file should *not* be used by applications. It is 7*75fd0b74Schristos part of the implementation of the compression library and is 8*75fd0b74Schristos subject to change. Applications should only use zlib.h. 9*75fd0b74Schristos */ 10*75fd0b74Schristos 11*75fd0b74Schristos /* Structure for decoding tables. Each entry provides either the 12*75fd0b74Schristos information needed to do the operation requested by the code that 13*75fd0b74Schristos indexed that table entry, or it provides a pointer to another 14*75fd0b74Schristos table that indexes more bits of the code. op indicates whether 15*75fd0b74Schristos the entry is a pointer to another table, a literal, a length or 16*75fd0b74Schristos distance, an end-of-block, or an invalid code. For a table 17*75fd0b74Schristos pointer, the low four bits of op is the number of index bits of 18*75fd0b74Schristos that table. For a length or distance, the low four bits of op 19*75fd0b74Schristos is the number of extra bits to get after the code. bits is 20*75fd0b74Schristos the number of bits in this code or part of the code to drop off 21*75fd0b74Schristos of the bit buffer. val is the actual byte to output in the case 22*75fd0b74Schristos of a literal, the base length or distance, or the offset from 23*75fd0b74Schristos the current table to the next table. Each entry is four bytes. */ 24*75fd0b74Schristos typedef struct { 25*75fd0b74Schristos unsigned char op; /* operation, extra bits, table bits */ 26*75fd0b74Schristos unsigned char bits; /* bits in this part of the code */ 27*75fd0b74Schristos unsigned short val; /* offset in table or code value */ 28*75fd0b74Schristos } code; 29*75fd0b74Schristos 30*75fd0b74Schristos /* op values as set by inflate_table(): 31*75fd0b74Schristos 00000000 - literal 32*75fd0b74Schristos 0000tttt - table link, tttt != 0 is the number of table index bits 33*75fd0b74Schristos 0001eeee - length or distance, eeee is the number of extra bits 34*75fd0b74Schristos 01100000 - end of block 35*75fd0b74Schristos 01000000 - invalid code 36*75fd0b74Schristos */ 37*75fd0b74Schristos 38*75fd0b74Schristos /* Maximum size of the dynamic table. The maximum number of code structures is 39*75fd0b74Schristos 1444, which is the sum of 852 for literal/length codes and 592 for distance 40*75fd0b74Schristos codes. These values were found by exhaustive searches using the program 41*75fd0b74Schristos examples/enough.c found in the zlib distribtution. The arguments to that 42*75fd0b74Schristos program are the number of symbols, the initial root table size, and the 43*75fd0b74Schristos maximum bit length of a code. "enough 286 9 15" for literal/length codes 44*75fd0b74Schristos returns returns 852, and "enough 30 6 15" for distance codes returns 592. 45*75fd0b74Schristos The initial root table size (9 or 6) is found in the fifth argument of the 46*75fd0b74Schristos inflate_table() calls in inflate.c and infback.c. If the root table size is 47*75fd0b74Schristos changed, then these maximum sizes would be need to be recalculated and 48*75fd0b74Schristos updated. */ 49*75fd0b74Schristos #define ENOUGH_LENS 852 50*75fd0b74Schristos #define ENOUGH_DISTS 592 51*75fd0b74Schristos #define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS) 52*75fd0b74Schristos 53*75fd0b74Schristos /* Type of code to build for inflate_table() */ 54*75fd0b74Schristos typedef enum { 55*75fd0b74Schristos CODES, 56*75fd0b74Schristos LENS, 57*75fd0b74Schristos DISTS 58*75fd0b74Schristos } codetype; 59*75fd0b74Schristos 60*75fd0b74Schristos int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens, 61*75fd0b74Schristos unsigned codes, code FAR * FAR *table, 62*75fd0b74Schristos unsigned FAR *bits, unsigned short FAR *work)); 63