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