michael@0: /* inftrees.h -- header to use inftrees.c
michael@0:  * Copyright (C) 1995-2005, 2010 Mark Adler
michael@0:  * For conditions of distribution and use, see copyright notice in zlib.h
michael@0:  */
michael@0: 
michael@0: /* WARNING: this file should *not* be used by applications. It is
michael@0:    part of the implementation of the compression library and is
michael@0:    subject to change. Applications should only use zlib.h.
michael@0:  */
michael@0: 
michael@0: /* Structure for decoding tables.  Each entry provides either the
michael@0:    information needed to do the operation requested by the code that
michael@0:    indexed that table entry, or it provides a pointer to another
michael@0:    table that indexes more bits of the code.  op indicates whether
michael@0:    the entry is a pointer to another table, a literal, a length or
michael@0:    distance, an end-of-block, or an invalid code.  For a table
michael@0:    pointer, the low four bits of op is the number of index bits of
michael@0:    that table.  For a length or distance, the low four bits of op
michael@0:    is the number of extra bits to get after the code.  bits is
michael@0:    the number of bits in this code or part of the code to drop off
michael@0:    of the bit buffer.  val is the actual byte to output in the case
michael@0:    of a literal, the base length or distance, or the offset from
michael@0:    the current table to the next table.  Each entry is four bytes. */
michael@0: typedef struct {
michael@0:     unsigned char op;           /* operation, extra bits, table bits */
michael@0:     unsigned char bits;         /* bits in this part of the code */
michael@0:     unsigned short val;         /* offset in table or code value */
michael@0: } code;
michael@0: 
michael@0: /* op values as set by inflate_table():
michael@0:     00000000 - literal
michael@0:     0000tttt - table link, tttt != 0 is the number of table index bits
michael@0:     0001eeee - length or distance, eeee is the number of extra bits
michael@0:     01100000 - end of block
michael@0:     01000000 - invalid code
michael@0:  */
michael@0: 
michael@0: /* Maximum size of the dynamic table.  The maximum number of code structures is
michael@0:    1444, which is the sum of 852 for literal/length codes and 592 for distance
michael@0:    codes.  These values were found by exhaustive searches using the program
michael@0:    examples/enough.c found in the zlib distribtution.  The arguments to that
michael@0:    program are the number of symbols, the initial root table size, and the
michael@0:    maximum bit length of a code.  "enough 286 9 15" for literal/length codes
michael@0:    returns returns 852, and "enough 30 6 15" for distance codes returns 592.
michael@0:    The initial root table size (9 or 6) is found in the fifth argument of the
michael@0:    inflate_table() calls in inflate.c and infback.c.  If the root table size is
michael@0:    changed, then these maximum sizes would be need to be recalculated and
michael@0:    updated. */
michael@0: #define ENOUGH_LENS 852
michael@0: #define ENOUGH_DISTS 592
michael@0: #define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS)
michael@0: 
michael@0: /* Type of code to build for inflate_table() */
michael@0: typedef enum {
michael@0:     CODES,
michael@0:     LENS,
michael@0:     DISTS
michael@0: } codetype;
michael@0: 
michael@0: int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens,
michael@0:                              unsigned codes, code FAR * FAR *table,
michael@0:                              unsigned FAR *bits, unsigned short FAR *work));