Chris@4: /* inftrees.h -- header to use inftrees.c
Chris@4:  * Copyright (C) 1995-2005, 2010 Mark Adler
Chris@4:  * For conditions of distribution and use, see copyright notice in zlib.h
Chris@4:  */
Chris@4: 
Chris@4: /* WARNING: this file should *not* be used by applications. It is
Chris@4:    part of the implementation of the compression library and is
Chris@4:    subject to change. Applications should only use zlib.h.
Chris@4:  */
Chris@4: 
Chris@4: /* Structure for decoding tables.  Each entry provides either the
Chris@4:    information needed to do the operation requested by the code that
Chris@4:    indexed that table entry, or it provides a pointer to another
Chris@4:    table that indexes more bits of the code.  op indicates whether
Chris@4:    the entry is a pointer to another table, a literal, a length or
Chris@4:    distance, an end-of-block, or an invalid code.  For a table
Chris@4:    pointer, the low four bits of op is the number of index bits of
Chris@4:    that table.  For a length or distance, the low four bits of op
Chris@4:    is the number of extra bits to get after the code.  bits is
Chris@4:    the number of bits in this code or part of the code to drop off
Chris@4:    of the bit buffer.  val is the actual byte to output in the case
Chris@4:    of a literal, the base length or distance, or the offset from
Chris@4:    the current table to the next table.  Each entry is four bytes. */
Chris@4: typedef struct {
Chris@4:     unsigned char op;           /* operation, extra bits, table bits */
Chris@4:     unsigned char bits;         /* bits in this part of the code */
Chris@4:     unsigned short val;         /* offset in table or code value */
Chris@4: } code;
Chris@4: 
Chris@4: /* op values as set by inflate_table():
Chris@4:     00000000 - literal
Chris@4:     0000tttt - table link, tttt != 0 is the number of table index bits
Chris@4:     0001eeee - length or distance, eeee is the number of extra bits
Chris@4:     01100000 - end of block
Chris@4:     01000000 - invalid code
Chris@4:  */
Chris@4: 
Chris@4: /* Maximum size of the dynamic table.  The maximum number of code structures is
Chris@4:    1444, which is the sum of 852 for literal/length codes and 592 for distance
Chris@4:    codes.  These values were found by exhaustive searches using the program
Chris@4:    examples/enough.c found in the zlib distribtution.  The arguments to that
Chris@4:    program are the number of symbols, the initial root table size, and the
Chris@4:    maximum bit length of a code.  "enough 286 9 15" for literal/length codes
Chris@4:    returns returns 852, and "enough 30 6 15" for distance codes returns 592.
Chris@4:    The initial root table size (9 or 6) is found in the fifth argument of the
Chris@4:    inflate_table() calls in inflate.c and infback.c.  If the root table size is
Chris@4:    changed, then these maximum sizes would be need to be recalculated and
Chris@4:    updated. */
Chris@4: #define ENOUGH_LENS 852
Chris@4: #define ENOUGH_DISTS 592
Chris@4: #define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS)
Chris@4: 
Chris@4: /* Type of code to build for inflate_table() */
Chris@4: typedef enum {
Chris@4:     CODES,
Chris@4:     LENS,
Chris@4:     DISTS
Chris@4: } codetype;
Chris@4: 
Chris@4: int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens,
Chris@4:                              unsigned codes, code FAR * FAR *table,
Chris@4:                              unsigned FAR *bits, unsigned short FAR *work));