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