zlib/inftrees.h

   1 /* inftrees.h -- header to use inftrees.c
   2  * Copyright (C) 1995-2003 Mark Adler
   3  * For conditions of distribution and use, see copyright notice in zlib.h
   4  */
   5
   6 /* WARNING: this file should *not* be used by applications. It is
   7    part of the implementation of the compression library and is
   8    subject to change. Applications should only use zlib.h.
   9  */
  10
  11 /* Structure for decoding tables.  Each entry provides either the
  12    information needed to do the operation requested by the code that
  13    indexed that table entry, or it provides a pointer to another
  14    table that indexes more bits of the code.  op indicates whether
  15    the entry is a pointer to another table, a literal, a length or
  16    distance, an end-of-block, or an invalid code.  For a table
  17    pointer, the low four bits of op is the number of index bits of
  18    that table.  For a length or distance, the low four bits of op
  19    is the number of extra bits to get after the code.  bits is
  20    the number of bits in this code or part of the code to drop off
  21    of the bit buffer.  val is the actual byte to output in the case
  22    of a literal, the base length or distance, or the offset from
  23    the current table to the next table.  Each entry is four bytes. */
  24 typedef struct {
  25     unsigned char op;           /* operation, extra bits, table bits */
  26     unsigned char bits;         /* bits in this part of the code */
  27     unsigned short val;         /* offset in table or code value */
  28 } code;
  29
  30 /* op values as set by inflate_table():
  31     00000000 - literal
  32     0000tttt - table link, tttt != 0 is the number of table index bits
  33     0001eeee - length or distance, eeee is the number of extra bits
  34     01100000 - end of block
  35     01000000 - invalid code
  36  */
  37
  38 /* Maximum size of dynamic tree.  The maximum found in a long but non-
  39    exhaustive search was 1004 code structures (850 for length/literals
  40    and 154 for distances, the latter actually the result of an
  41    exhaustive search).  The true maximum is not known, but the value
  42    below is more than safe. */
  43 #define ENOUGH 1440
  44 #define MAXD 154
  45
  46 /* Type of code to build for inftable() */
  47 typedef enum {
  48     CODES,
  49     LENS,
  50     DISTS
  51 } codetype;
  52
  53 extern int inflate_table OF((codetype type, unsigned short FAR *lens,
  54                              unsigned codes, code FAR * FAR *table,
  55                              unsigned FAR *bits, unsigned short FAR *work));