1  /* inftrees.h -- header to use inftrees.c
       2   * Copyright (C) 1995-2005, 2010 Mark Adler
       3   * For conditions of distribution and use, see copyright notice in zlib.h
       4   */
       5  
       6  #ifndef INFTREES_H
       7  #define INFTREES_H
       8  
       9  /* WARNING: this file should *not* be used by applications. It is
      10     part of the implementation of the compression library and is
      11     subject to change. Applications should only use zlib.h.
      12   */
      13  
      14  /* Structure for decoding tables.  Each entry provides either the
      15     information needed to do the operation requested by the code that
      16     indexed that table entry, or it provides a pointer to another
      17     table that indexes more bits of the code.  op indicates whether
      18     the entry is a pointer to another table, a literal, a length or
      19     distance, an end-of-block, or an invalid code.  For a table
      20     pointer, the low four bits of op is the number of index bits of
      21     that table.  For a length or distance, the low four bits of op
      22     is the number of extra bits to get after the code.  bits is
      23     the number of bits in this code or part of the code to drop off
      24     of the bit buffer.  val is the actual byte to output in the case
      25     of a literal, the base length or distance, or the offset from
      26     the current table to the next table.  Each entry is four bytes. */
      27  typedef struct {
      28      unsigned char op;           /* operation, extra bits, table bits */
      29      unsigned char bits;         /* bits in this part of the code */
      30      unsigned short val;         /* offset in table or code value */
      31  } code;
      32  
      33  /* op values as set by inflate_table():
      34      00000000 - literal
      35      0000tttt - table link, tttt != 0 is the number of table index bits
      36      0001eeee - length or distance, eeee is the number of extra bits
      37      01100000 - end of block
      38      01000000 - invalid code
      39   */
      40  
      41  /* Maximum size of the dynamic table.  The maximum number of code structures is
      42     1444, which is the sum of 852 for literal/length codes and 592 for distance
      43     codes.  These values were found by exhaustive searches using the program
      44     examples/enough.c found in the zlib distribution.  The arguments to that
      45     program are the number of symbols, the initial root table size, and the
      46     maximum bit length of a code.  "enough 286 9 15" for literal/length codes
      47     returns returns 852, and "enough 30 6 15" for distance codes returns 592.
      48     The initial root table size (9 or 6) is found in the fifth argument of the
      49     inflate_table() calls in inflate.c and infback.c.  If the root table size is
      50     changed, then these maximum sizes would be need to be recalculated and
      51     updated. */
      52  #define ENOUGH_LENS 852
      53  #define ENOUGH_DISTS 592
      54  #define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS)
      55  
      56  /* Type of code to build for inflate_table() */
      57  typedef enum {
      58      CODES,
      59      LENS,
      60      DISTS
      61  } codetype;
      62  
      63  static int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens,
      64                               unsigned codes, code FAR * FAR *table,
      65                               unsigned FAR *bits, unsigned short FAR *work));
      66  
      67  #endif  /* INFTREES_H_ */