Mercurial > cpython-lru_cache-weakref

annotate Modules/zlib/inftrees.c @ 54294:dba767bc3155 legacy-trunk

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
remove mention of old ctypes version
author Benjamin Peterson <benjamin@python.org>
date Sat, 23 May 2009 20:59:09 +0000
parents 81fa47d2d477
children 467019588fcc
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
36186
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
1 /* inftrees.c -- generate Huffman trees for efficient decoding
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
2 * Copyright (C) 1995-2005 Mark Adler
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
3 * For conditions of distribution and use, see copyright notice in zlib.h
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
4 */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
5
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
6 #include "zutil.h"
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
7 #include "inftrees.h"
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
8
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
9 #define MAXBITS 15
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
10
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
11 const char inflate_copyright[] =
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
12 " inflate 1.2.3 Copyright 1995-2005 Mark Adler ";
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
13 /*
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
14 If you use the zlib library in a product, an acknowledgment is welcome
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
15 in the documentation of your product. If for some reason you cannot
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
16 include such an acknowledgment, I would appreciate that you keep this
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
17 copyright string in the executable of your product.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
18 */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
19
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
20 /*
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
21 Build a set of tables to decode the provided canonical Huffman code.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
22 The code lengths are lens[0..codes-1]. The result starts at *table,
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
23 whose indices are 0..2^bits-1. work is a writable array of at least
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
24 lens shorts, which is used as a work area. type is the type of code
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
25 to be generated, CODES, LENS, or DISTS. On return, zero is success,
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
26 -1 is an invalid code, and +1 means that ENOUGH isn't enough. table
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
27 on return points to the next available entry's address. bits is the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
28 requested root table index bits, and on return it is the actual root
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
29 table index bits. It will differ if the request is greater than the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
30 longest code or if it is less than the shortest code.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
31 */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
32 int inflate_table(type, lens, codes, table, bits, work)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
33 codetype type;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
34 unsigned short FAR *lens;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
35 unsigned codes;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
36 code FAR * FAR *table;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
37 unsigned FAR *bits;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
38 unsigned short FAR *work;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
39 {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
40 unsigned len; /* a code's length in bits */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
41 unsigned sym; /* index of code symbols */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
42 unsigned min, max; /* minimum and maximum code lengths */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
43 unsigned root; /* number of index bits for root table */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
44 unsigned curr; /* number of index bits for current table */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
45 unsigned drop; /* code bits to drop for sub-table */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
46 int left; /* number of prefix codes available */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
47 unsigned used; /* code entries in table used */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
48 unsigned huff; /* Huffman code */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
49 unsigned incr; /* for incrementing code, index */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
50 unsigned fill; /* index for replicating entries */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
51 unsigned low; /* low bits for current root entry */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
52 unsigned mask; /* mask for low root bits */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
53 code this; /* table entry for duplication */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
54 code FAR *next; /* next available space in table */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
55 const unsigned short FAR *base; /* base value table to use */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
56 const unsigned short FAR *extra; /* extra bits table to use */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
57 int end; /* use base and extra for symbol > end */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
58 unsigned short count[MAXBITS+1]; /* number of codes of each length */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
59 unsigned short offs[MAXBITS+1]; /* offsets in table for each length */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
60 static const unsigned short lbase[31] = { /* Length codes 257..285 base */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
61 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
62 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
63 static const unsigned short lext[31] = { /* Length codes 257..285 extra */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
64 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
65 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 201, 196};
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
66 static const unsigned short dbase[32] = { /* Distance codes 0..29 base */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
67 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
68 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
69 8193, 12289, 16385, 24577, 0, 0};
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
70 static const unsigned short dext[32] = { /* Distance codes 0..29 extra */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
71 16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22,
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
72 23, 23, 24, 24, 25, 25, 26, 26, 27, 27,
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
73 28, 28, 29, 29, 64, 64};
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
74
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
75 /*
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
76 Process a set of code lengths to create a canonical Huffman code. The
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
77 code lengths are lens[0..codes-1]. Each length corresponds to the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
78 symbols 0..codes-1. The Huffman code is generated by first sorting the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
79 symbols by length from short to long, and retaining the symbol order
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
80 for codes with equal lengths. Then the code starts with all zero bits
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
81 for the first code of the shortest length, and the codes are integer
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
82 increments for the same length, and zeros are appended as the length
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
83 increases. For the deflate format, these bits are stored backwards
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
84 from their more natural integer increment ordering, and so when the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
85 decoding tables are built in the large loop below, the integer codes
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
86 are incremented backwards.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
87
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
88 This routine assumes, but does not check, that all of the entries in
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
89 lens[] are in the range 0..MAXBITS. The caller must assure this.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
90 1..MAXBITS is interpreted as that code length. zero means that that
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
91 symbol does not occur in this code.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
92
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
93 The codes are sorted by computing a count of codes for each length,
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
94 creating from that a table of starting indices for each length in the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
95 sorted table, and then entering the symbols in order in the sorted
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
96 table. The sorted table is work[], with that space being provided by
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
97 the caller.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
98
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
99 The length counts are used for other purposes as well, i.e. finding
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
100 the minimum and maximum length codes, determining if there are any
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
101 codes at all, checking for a valid set of lengths, and looking ahead
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
102 at length counts to determine sub-table sizes when building the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
103 decoding tables.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
104 */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
105
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
106 /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
107 for (len = 0; len <= MAXBITS; len++)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
108 count[len] = 0;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
109 for (sym = 0; sym < codes; sym++)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
110 count[lens[sym]]++;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
111
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
112 /* bound code lengths, force root to be within code lengths */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
113 root = *bits;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
114 for (max = MAXBITS; max >= 1; max--)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
115 if (count[max] != 0) break;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
116 if (root > max) root = max;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
117 if (max == 0) { /* no symbols to code at all */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
118 this.op = (unsigned char)64; /* invalid code marker */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
119 this.bits = (unsigned char)1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
120 this.val = (unsigned short)0;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
121 *(*table)++ = this; /* make a table to force an error */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
122 *(*table)++ = this;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
123 *bits = 1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
124 return 0; /* no symbols, but wait for decoding to report error */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
125 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
126 for (min = 1; min <= MAXBITS; min++)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
127 if (count[min] != 0) break;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
128 if (root < min) root = min;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
129
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
130 /* check for an over-subscribed or incomplete set of lengths */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
131 left = 1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
132 for (len = 1; len <= MAXBITS; len++) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
133 left <<= 1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
134 left -= count[len];
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
135 if (left < 0) return -1; /* over-subscribed */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
136 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
137 if (left > 0 && (type == CODES || max != 1))
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
138 return -1; /* incomplete set */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
139
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
140 /* generate offsets into symbol table for each length for sorting */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
141 offs[1] = 0;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
142 for (len = 1; len < MAXBITS; len++)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
143 offs[len + 1] = offs[len] + count[len];
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
144
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
145 /* sort symbols by length, by symbol order within each length */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
146 for (sym = 0; sym < codes; sym++)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
147 if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
148
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
149 /*
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
150 Create and fill in decoding tables. In this loop, the table being
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
151 filled is at next and has curr index bits. The code being used is huff
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
152 with length len. That code is converted to an index by dropping drop
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
153 bits off of the bottom. For codes where len is less than drop + curr,
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
154 those top drop + curr - len bits are incremented through all values to
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
155 fill the table with replicated entries.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
156
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
157 root is the number of index bits for the root table. When len exceeds
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
158 root, sub-tables are created pointed to by the root entry with an index
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
159 of the low root bits of huff. This is saved in low to check for when a
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
160 new sub-table should be started. drop is zero when the root table is
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
161 being filled, and drop is root when sub-tables are being filled.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
162
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
163 When a new sub-table is needed, it is necessary to look ahead in the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
164 code lengths to determine what size sub-table is needed. The length
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
165 counts are used for this, and so count[] is decremented as codes are
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
166 entered in the tables.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
167
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
168 used keeps track of how many table entries have been allocated from the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
169 provided *table space. It is checked when a LENS table is being made
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
170 against the space in *table, ENOUGH, minus the maximum space needed by
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
171 the worst case distance code, MAXD. This should never happen, but the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
172 sufficiency of ENOUGH has not been proven exhaustively, hence the check.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
173 This assumes that when type == LENS, bits == 9.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
174
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
175 sym increments through all symbols, and the loop terminates when
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
176 all codes of length max, i.e. all codes, have been processed. This
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
177 routine permits incomplete codes, so another loop after this one fills
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
178 in the rest of the decoding tables with invalid code markers.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
179 */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
180
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
181 /* set up for code type */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
182 switch (type) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
183 case CODES:
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
184 base = extra = work; /* dummy value--not used */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
185 end = 19;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
186 break;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
187 case LENS:
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
188 base = lbase;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
189 base -= 257;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
190 extra = lext;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
191 extra -= 257;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
192 end = 256;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
193 break;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
194 default: /* DISTS */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
195 base = dbase;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
196 extra = dext;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
197 end = -1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
198 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
199
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
200 /* initialize state for loop */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
201 huff = 0; /* starting code */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
202 sym = 0; /* starting code symbol */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
203 len = min; /* starting code length */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
204 next = *table; /* current table to fill in */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
205 curr = root; /* current table index bits */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
206 drop = 0; /* current bits to drop from code for index */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
207 low = (unsigned)(-1); /* trigger new sub-table when len > root */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
208 used = 1U << root; /* use root table entries */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
209 mask = used - 1; /* mask for comparing low */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
210
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
211 /* check available table space */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
212 if (type == LENS && used >= ENOUGH - MAXD)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
213 return 1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
214
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
215 /* process all codes and make table entries */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
216 for (;;) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
217 /* create table entry */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
218 this.bits = (unsigned char)(len - drop);
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
219 if ((int)(work[sym]) < end) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
220 this.op = (unsigned char)0;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
221 this.val = work[sym];
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
222 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
223 else if ((int)(work[sym]) > end) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
224 this.op = (unsigned char)(extra[work[sym]]);
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
225 this.val = base[work[sym]];
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
226 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
227 else {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
228 this.op = (unsigned char)(32 + 64); /* end of block */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
229 this.val = 0;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
230 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
231
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
232 /* replicate for those indices with low len bits equal to huff */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
233 incr = 1U << (len - drop);
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
234 fill = 1U << curr;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
235 min = fill; /* save offset to next table */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
236 do {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
237 fill -= incr;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
238 next[(huff >> drop) + fill] = this;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
239 } while (fill != 0);
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
240
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
241 /* backwards increment the len-bit code huff */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
242 incr = 1U << (len - 1);
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
243 while (huff & incr)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
244 incr >>= 1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
245 if (incr != 0) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
246 huff &= incr - 1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
247 huff += incr;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
248 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
249 else
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
250 huff = 0;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
251
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
252 /* go to next symbol, update count, len */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
253 sym++;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
254 if (--(count[len]) == 0) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
255 if (len == max) break;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
256 len = lens[work[sym]];
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
257 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
258
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
259 /* create new sub-table if needed */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
260 if (len > root && (huff & mask) != low) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
261 /* if first time, transition to sub-tables */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
262 if (drop == 0)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
263 drop = root;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
264
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
265 /* increment past last table */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
266 next += min; /* here min is 1 << curr */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
267
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
268 /* determine length of next table */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
269 curr = len - drop;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
270 left = (int)(1 << curr);
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
271 while (curr + drop < max) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
272 left -= count[curr + drop];
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
273 if (left <= 0) break;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
274 curr++;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
275 left <<= 1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
276 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
277
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
278 /* check for enough space */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
279 used += 1U << curr;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
280 if (type == LENS && used >= ENOUGH - MAXD)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
281 return 1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
282
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
283 /* point entry in root table to sub-table */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
284 low = huff & mask;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
285 (*table)[low].op = (unsigned char)curr;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
286 (*table)[low].bits = (unsigned char)root;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
287 (*table)[low].val = (unsigned short)(next - *table);
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
288 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
289 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
290
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
291 /*
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
292 Fill in rest of table for incomplete codes. This loop is similar to the
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
293 loop above in incrementing huff for table indices. It is assumed that
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
294 len is equal to curr + drop, so there is no loop needed to increment
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
295 through high index bits. When the current sub-table is filled, the loop
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
296 drops back to the root table to fill in any remaining entries there.
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
297 */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
298 this.op = (unsigned char)64; /* invalid code marker */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
299 this.bits = (unsigned char)(len - drop);
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
300 this.val = (unsigned short)0;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
301 while (huff != 0) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
302 /* when done with sub-table, drop back to root table */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
303 if (drop != 0 && (huff & mask) != low) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
304 drop = 0;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
305 len = root;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
306 next = *table;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
307 this.bits = (unsigned char)len;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
308 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
309
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
310 /* put invalid code marker in table */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
311 next[huff >> drop] = this;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
312
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
313 /* backwards increment the len-bit code huff */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
314 incr = 1U << (len - 1);
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
315 while (huff & incr)
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
316 incr >>= 1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
317 if (incr != 0) {
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
318 huff &= incr - 1;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
319 huff += incr;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
320 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
321 else
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
322 huff = 0;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
323 }
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
324
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
325 /* set return parameters */
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
326 *table += used;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
327 *bits = root;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
328 return 0;
81fa47d2d477 Import zlib into Python tree.
Martin v. Löwis <martin@v.loewis.de>
parents:
diff changeset
329 }