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/* inftrees.c -- generate Huffman trees for efficient decoding |
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* Copyright (C) 1995-2013 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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#include "zutil.h" |
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#include "inftrees.h" |
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#define MAXBITS 15 |
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const char inflate_copyright[] = |
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" inflate 1.2.8 Copyright 1995-2013 Mark Adler "; |
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/* |
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If you use the zlib library in a product, an acknowledgment is welcome |
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in the documentation of your product. If for some reason you cannot |
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include such an acknowledgment, I would appreciate that you keep this |
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copyright string in the executable of your product. |
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*/ |
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20
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/* |
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Build a set of tables to decode the provided canonical Huffman code. |
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The code lengths are lens[0..codes-1]. The result starts at *table, |
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whose indices are 0..2^bits-1. work is a writable array of at least |
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lens shorts, which is used as a work area. type is the type of code |
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to be generated, CODES, LENS, or DISTS. On return, zero is success, |
26
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-1 is an invalid code, and +1 means that ENOUGH isn't enough. table |
27
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on return points to the next available entry's address. bits is the |
28
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requested root table index bits, and on return it is the actual root |
29
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table index bits. It will differ if the request is greater than the |
30
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longest code or if it is less than the shortest code. |
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*/ |
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36660
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int ZLIB_INTERNAL inflate_table( |
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codetype type, |
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unsigned short FAR *lens, |
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unsigned codes, |
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code FAR * FAR *table, |
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unsigned FAR *bits, |
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unsigned short FAR *work) |
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{ |
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unsigned len; /* a code's length in bits */ |
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unsigned sym; /* index of code symbols */ |
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unsigned min, max; /* minimum and maximum code lengths */ |
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unsigned root; /* number of index bits for root table */ |
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unsigned curr; /* number of index bits for current table */ |
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unsigned drop; /* code bits to drop for sub-table */ |
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int left; /* number of prefix codes available */ |
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unsigned used; /* code entries in table used */ |
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unsigned huff; /* Huffman code */ |
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unsigned incr; /* for incrementing code, index */ |
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unsigned fill; /* index for replicating entries */ |
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unsigned low; /* low bits for current root entry */ |
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unsigned mask; /* mask for low root bits */ |
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code here; /* table entry for duplication */ |
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code FAR *next; /* next available space in table */ |
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const unsigned short FAR *base; /* base value table to use */ |
56
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const unsigned short FAR *extra; /* extra bits table to use */ |
57
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int end; /* use base and extra for symbol > end */ |
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unsigned short count[MAXBITS+1]; /* number of codes of each length */ |
59
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unsigned short offs[MAXBITS+1]; /* offsets in table for each length */ |
60
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static const unsigned short lbase[31] = { /* Length codes 257..285 base */ |
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3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, |
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35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; |
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static const unsigned short lext[31] = { /* Length codes 257..285 extra */ |
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16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, |
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19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 72, 78}; |
66
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static const unsigned short dbase[32] = { /* Distance codes 0..29 base */ |
67
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1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, |
68
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257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, |
69
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8193, 12289, 16385, 24577, 0, 0}; |
70
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static const unsigned short dext[32] = { /* Distance codes 0..29 extra */ |
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16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, |
72
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23, 23, 24, 24, 25, 25, 26, 26, 27, 27, |
73
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28, 28, 29, 29, 64, 64}; |
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75
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/* |
76
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Process a set of code lengths to create a canonical Huffman code. The |
77
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code lengths are lens[0..codes-1]. Each length corresponds to the |
78
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symbols 0..codes-1. The Huffman code is generated by first sorting the |
79
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symbols by length from short to long, and retaining the symbol order |
80
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for codes with equal lengths. Then the code starts with all zero bits |
81
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for the first code of the shortest length, and the codes are integer |
82
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increments for the same length, and zeros are appended as the length |
83
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increases. For the deflate format, these bits are stored backwards |
84
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from their more natural integer increment ordering, and so when the |
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decoding tables are built in the large loop below, the integer codes |
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are incremented backwards. |
87
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88
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This routine assumes, but does not check, that all of the entries in |
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lens[] are in the range 0..MAXBITS. The caller must assure this. |
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1..MAXBITS is interpreted as that code length. zero means that that |
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symbol does not occur in this code. |
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93
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The codes are sorted by computing a count of codes for each length, |
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creating from that a table of starting indices for each length in the |
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sorted table, and then entering the symbols in order in the sorted |
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table. The sorted table is work[], with that space being provided by |
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the caller. |
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99
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The length counts are used for other purposes as well, i.e. finding |
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the minimum and maximum length codes, determining if there are any |
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codes at all, checking for a valid set of lengths, and looking ahead |
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at length counts to determine sub-table sizes when building the |
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decoding tables. |
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*/ |
105
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106
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/* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */ |
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623220
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for (len = 0; len <= MAXBITS; len++) |
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586560
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count[len] = 0; |
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3479996
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for (sym = 0; sym < codes; sym++) |
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3479996
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count[lens[sym]]++; |
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112
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/* bound code lengths, force root to be within code lengths */ |
113
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36660
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root = *bits; |
114
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436704
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for (max = MAXBITS; max >= 1; max--) |
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436704
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if (count[max] != 0) break; |
116
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36660
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if (root > max) root = max; |
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36660
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if (max == 0) { /* no symbols to code at all */ |
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0
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here.op = (unsigned char)64; /* invalid code marker */ |
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0
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here.bits = (unsigned char)1; |
120
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0
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here.val = (unsigned short)0; |
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0
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*(*table)++ = here; /* make a table to force an error */ |
122
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0
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*(*table)++ = here; |
123
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0
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*bits = 1; |
124
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0
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return 0; /* no symbols, but wait for decoding to report error */ |
125
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} |
126
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36562
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for (min = 1; min < max; min++) |
127
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61704
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if (count[min] != 0) break; |
128
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36660
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if (root < min) root = min; |
129
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130
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/* check for an over-subscribed or incomplete set of lengths */ |
131
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left = 1; |
132
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586560
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for (len = 1; len <= MAXBITS; len++) { |
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549900
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left <<= 1; |
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549900
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left -= count[len]; |
135
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549900
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if (left < 0) return -1; /* over-subscribed */ |
136
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} |
137
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36660
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if (left > 0 && (type == CODES || max != 1)) |
138
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return -1; /* incomplete set */ |
139
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140
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/* generate offsets into symbol table for each length for sorting */ |
141
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36622
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offs[1] = 0; |
142
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549330
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for (len = 1; len < MAXBITS; len++) |
143
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512708
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offs[len + 1] = offs[len] + count[len]; |
144
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145
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/* sort symbols by length, by symbol order within each length */ |
146
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3479274
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for (sym = 0; sym < codes; sym++) |
147
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3479274
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if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym; |
148
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149
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/* |
150
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Create and fill in decoding tables. In this loop, the table being |
151
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filled is at next and has curr index bits. The code being used is huff |
152
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with length len. That code is converted to an index by dropping drop |
153
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bits off of the bottom. For codes where len is less than drop + curr, |
154
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those top drop + curr - len bits are incremented through all values to |
155
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fill the table with replicated entries. |
156
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157
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root is the number of index bits for the root table. When len exceeds |
158
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root, sub-tables are created pointed to by the root entry with an index |
159
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of the low root bits of huff. This is saved in low to check for when a |
160
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new sub-table should be started. drop is zero when the root table is |
161
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being filled, and drop is root when sub-tables are being filled. |
162
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163
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When a new sub-table is needed, it is necessary to look ahead in the |
164
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code lengths to determine what size sub-table is needed. The length |
165
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counts are used for this, and so count[] is decremented as codes are |
166
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entered in the tables. |
167
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168
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used keeps track of how many table entries have been allocated from the |
169
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provided *table space. It is checked for LENS and DIST tables against |
170
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the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in |
171
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the initial root table size constants. See the comments in inftrees.h |
172
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for more information. |
173
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174
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sym increments through all symbols, and the loop terminates when |
175
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all codes of length max, i.e. all codes, have been processed. This |
176
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routine permits incomplete codes, so another loop after this one fills |
177
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in the rest of the decoding tables with invalid code markers. |
178
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*/ |
179
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180
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/* set up for code type */ |
181
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36622
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switch (type) { |
182
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case CODES: |
183
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base = extra = work; /* dummy value--not used */ |
184
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end = 19; |
185
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12866
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break; |
186
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case LENS: |
187
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base = lbase; |
188
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base -= 257; |
189
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extra = lext; |
190
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extra -= 257; |
191
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end = 256; |
192
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break; |
193
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default: /* DISTS */ |
194
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base = dbase; |
195
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extra = dext; |
196
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end = -1; |
197
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} |
198
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199
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/* initialize state for loop */ |
200
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huff = 0; /* starting code */ |
201
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sym = 0; /* starting code symbol */ |
202
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len = min; /* starting code length */ |
203
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36622
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next = *table; /* current table to fill in */ |
204
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curr = root; /* current table index bits */ |
205
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drop = 0; /* current bits to drop from code for index */ |
206
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low = (unsigned)(-1); /* trigger new sub-table when len > root */ |
207
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36622
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used = 1U << root; /* use root table entries */ |
208
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36622
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mask = used - 1; /* mask for comparing low */ |
209
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210
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/* check available table space */ |
211
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73244
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if ((type == LENS && used > ENOUGH_LENS) || |
212
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36622
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(type == DISTS && used > ENOUGH_DISTS)) |
213
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return 1; |
214
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215
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/* process all codes and make table entries */ |
216
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for (;;) { |
217
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/* create table entry */ |
218
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405650
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here.bits = (unsigned char)(len - drop); |
219
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405650
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if ((int)(work[sym]) < end) { |
220
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339052
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here.op = (unsigned char)0; |
221
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339052
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here.val = work[sym]; |
222
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} |
223
|
66598
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else if ((int)(work[sym]) > end) { |
224
|
54720
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here.op = (unsigned char)(extra[work[sym]]); |
225
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54720
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here.val = base[work[sym]]; |
226
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|
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} |
227
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|
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else { |
228
|
11878
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here.op = (unsigned char)(32 + 64); /* end of block */ |
229
|
11878
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here.val = 0; |
230
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} |
231
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232
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/* replicate for those indices with low len bits equal to huff */ |
233
|
405650
|
|
|
|
|
incr = 1U << (len - drop); |
234
|
405650
|
|
|
|
|
fill = 1U << curr; |
235
|
|
|
|
|
|
min = fill; /* save offset to next table */ |
236
|
|
|
|
|
|
do { |
237
|
1270086
|
|
|
|
|
fill -= incr; |
238
|
1270086
|
|
|
|
|
next[(huff >> drop) + fill] = here; |
239
|
1270086
|
|
|
|
|
} while (fill != 0); |
240
|
|
|
|
|
|
|
241
|
|
|
|
|
|
/* backwards increment the len-bit code huff */ |
242
|
405650
|
|
|
|
|
incr = 1U << (len - 1); |
243
|
1180328
|
|
|
|
|
while (huff & incr) |
244
|
369028
|
|
|
|
|
incr >>= 1; |
245
|
405650
|
|
|
|
|
if (incr != 0) { |
246
|
369028
|
|
|
|
|
huff &= incr - 1; |
247
|
369028
|
|
|
|
|
huff += incr; |
248
|
|
|
|
|
|
} |
249
|
|
|
|
|
|
else |
250
|
|
|
|
|
|
huff = 0; |
251
|
|
|
|
|
|
|
252
|
|
|
|
|
|
/* go to next symbol, update count, len */ |
253
|
405650
|
|
|
|
|
sym++; |
254
|
405650
|
|
|
|
|
if (--(count[len]) == 0) { |
255
|
112564
|
|
|
|
|
if (len == max) break; |
256
|
75942
|
|
|
|
|
len = lens[work[sym]]; |
257
|
|
|
|
|
|
} |
258
|
|
|
|
|
|
|
259
|
|
|
|
|
|
/* create new sub-table if needed */ |
260
|
369028
|
|
|
|
|
if (len > root && (huff & mask) != low) { |
261
|
|
|
|
|
|
/* if first time, transition to sub-tables */ |
262
|
1830
|
|
|
|
|
if (drop == 0) |
263
|
|
|
|
|
|
drop = root; |
264
|
|
|
|
|
|
|
265
|
|
|
|
|
|
/* increment past last table */ |
266
|
1830
|
|
|
|
|
next += min; /* here min is 1 << curr */ |
267
|
|
|
|
|
|
|
268
|
|
|
|
|
|
/* determine length of next table */ |
269
|
1830
|
|
|
|
|
curr = len - drop; |
270
|
1830
|
|
|
|
|
left = (int)(1 << curr); |
271
|
4352
|
|
|
|
|
while (curr + drop < max) { |
272
|
2272
|
|
|
|
|
left -= count[curr + drop]; |
273
|
2272
|
|
|
|
|
if (left <= 0) break; |
274
|
692
|
|
|
|
|
curr++; |
275
|
692
|
|
|
|
|
left <<= 1; |
276
|
|
|
|
|
|
} |
277
|
|
|
|
|
|
|
278
|
|
|
|
|
|
/* check for enough space */ |
279
|
1830
|
|
|
|
|
used += 1U << curr; |
280
|
3660
|
|
|
|
|
if ((type == LENS && used > ENOUGH_LENS) || |
281
|
1830
|
|
|
|
|
(type == DISTS && used > ENOUGH_DISTS)) |
282
|
|
|
|
|
|
return 1; |
283
|
|
|
|
|
|
|
284
|
|
|
|
|
|
/* point entry in root table to sub-table */ |
285
|
1830
|
|
|
|
|
low = huff & mask; |
286
|
1830
|
|
|
|
|
(*table)[low].op = (unsigned char)curr; |
287
|
1830
|
|
|
|
|
(*table)[low].bits = (unsigned char)root; |
288
|
1830
|
|
|
|
|
(*table)[low].val = (unsigned short)(next - *table); |
289
|
|
|
|
|
|
} |
290
|
|
|
|
|
|
} |
291
|
|
|
|
|
|
|
292
|
|
|
|
|
|
/* fill in remaining table entry if code is incomplete (guaranteed to have |
293
|
|
|
|
|
|
at most one remaining entry, since if the code is incomplete, the |
294
|
|
|
|
|
|
maximum code length that was allowed to get this far is one bit) */ |
295
|
36622
|
|
|
|
|
if (huff != 0) { |
296
|
0
|
|
|
|
|
here.op = (unsigned char)64; /* invalid code marker */ |
297
|
0
|
|
|
|
|
here.bits = (unsigned char)(len - drop); |
298
|
0
|
|
|
|
|
here.val = (unsigned short)0; |
299
|
0
|
|
|
|
|
next[huff] = here; |
300
|
|
|
|
|
|
} |
301
|
|
|
|
|
|
|
302
|
|
|
|
|
|
/* set return parameters */ |
303
|
36622
|
|
|
|
|
*table += used; |
304
|
36622
|
|
|
|
|
*bits = root; |
305
|
36622
|
|
|
|
|
return 0; |
306
|
|
|
|
|
|
} |