modules/zlib/src/inftrees.h@b8a032363ba2 (annotated)
modules/zlib/src/inftrees.h
Thu, 22 Jan 2015 13:21:57 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Thu, 22 Jan 2015 13:21:57 +0100
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
- permissions
- -rw-r--r--
Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6
| michael@0 | 1 | /* inftrees.h -- header to use inftrees.c |
| michael@0 | 2 | * Copyright (C) 1995-2005, 2010 Mark Adler |
| michael@0 | 3 | * For conditions of distribution and use, see copyright notice in zlib.h |
| michael@0 | 4 | */ |
| michael@0 | 5 | |
| michael@0 | 6 | /* WARNING: this file should *not* be used by applications. It is |
| michael@0 | 7 | part of the implementation of the compression library and is |
| michael@0 | 8 | subject to change. Applications should only use zlib.h. |
| michael@0 | 9 | */ |
| michael@0 | 10 | |
| michael@0 | 11 | /* Structure for decoding tables. Each entry provides either the |
| michael@0 | 12 | information needed to do the operation requested by the code that |
| michael@0 | 13 | indexed that table entry, or it provides a pointer to another |
| michael@0 | 14 | table that indexes more bits of the code. op indicates whether |
| michael@0 | 15 | the entry is a pointer to another table, a literal, a length or |
| michael@0 | 16 | distance, an end-of-block, or an invalid code. For a table |
| michael@0 | 17 | pointer, the low four bits of op is the number of index bits of |
| michael@0 | 18 | that table. For a length or distance, the low four bits of op |
| michael@0 | 19 | is the number of extra bits to get after the code. bits is |
| michael@0 | 20 | the number of bits in this code or part of the code to drop off |
| michael@0 | 21 | of the bit buffer. val is the actual byte to output in the case |
| michael@0 | 22 | of a literal, the base length or distance, or the offset from |
| michael@0 | 23 | the current table to the next table. Each entry is four bytes. */ |
| michael@0 | 24 | typedef struct { |
| michael@0 | 25 | unsigned char op; /* operation, extra bits, table bits */ |
| michael@0 | 26 | unsigned char bits; /* bits in this part of the code */ |
| michael@0 | 27 | unsigned short val; /* offset in table or code value */ |
| michael@0 | 28 | } code; |
| michael@0 | 29 | |
| michael@0 | 30 | /* op values as set by inflate_table(): |
| michael@0 | 31 | 00000000 - literal |
| michael@0 | 32 | 0000tttt - table link, tttt != 0 is the number of table index bits |
| michael@0 | 33 | 0001eeee - length or distance, eeee is the number of extra bits |
| michael@0 | 34 | 01100000 - end of block |
| michael@0 | 35 | 01000000 - invalid code |
| michael@0 | 36 | */ |
| michael@0 | 37 | |
| michael@0 | 38 | /* Maximum size of the dynamic table. The maximum number of code structures is |
| michael@0 | 39 | 1444, which is the sum of 852 for literal/length codes and 592 for distance |
| michael@0 | 40 | codes. These values were found by exhaustive searches using the program |
| michael@0 | 41 | examples/enough.c found in the zlib distribtution. The arguments to that |
| michael@0 | 42 | program are the number of symbols, the initial root table size, and the |
| michael@0 | 43 | maximum bit length of a code. "enough 286 9 15" for literal/length codes |
| michael@0 | 44 | returns returns 852, and "enough 30 6 15" for distance codes returns 592. |
| michael@0 | 45 | The initial root table size (9 or 6) is found in the fifth argument of the |
| michael@0 | 46 | inflate_table() calls in inflate.c and infback.c. If the root table size is |
| michael@0 | 47 | changed, then these maximum sizes would be need to be recalculated and |
| michael@0 | 48 | updated. */ |
| michael@0 | 49 | #define ENOUGH_LENS 852 |
| michael@0 | 50 | #define ENOUGH_DISTS 592 |
| michael@0 | 51 | #define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS) |
| michael@0 | 52 | |
| michael@0 | 53 | /* Type of code to build for inflate_table() */ |
| michael@0 | 54 | typedef enum { |
| michael@0 | 55 | CODES, |
| michael@0 | 56 | LENS, |
| michael@0 | 57 | DISTS |
| michael@0 | 58 | } codetype; |
| michael@0 | 59 | |
| michael@0 | 60 | int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens, |
| michael@0 | 61 | unsigned codes, code FAR * FAR *table, |
| michael@0 | 62 | unsigned FAR *bits, unsigned short FAR *work)); |
