1 /* |
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2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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3 * |
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4 * This code is free software; you can redistribute it and/or modify it |
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5 * under the terms of the GNU General Public License version 2 only, as |
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6 * published by the Free Software Foundation. Oracle designates this |
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7 * particular file as subject to the "Classpath" exception as provided |
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8 * by Oracle in the LICENSE file that accompanied this code. |
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9 * |
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10 * This code is distributed in the hope that it will be useful, but WITHOUT |
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11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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13 * version 2 for more details (a copy is included in the LICENSE file that |
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14 * accompanied this code). |
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15 * |
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16 * You should have received a copy of the GNU General Public License version |
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17 * 2 along with this work; if not, write to the Free Software Foundation, |
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18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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19 * |
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20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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21 * or visit www.oracle.com if you need additional information or have any |
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22 * questions. |
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23 */ |
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24 |
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25 /* inftrees.c -- generate Huffman trees for efficient decoding |
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26 * Copyright (C) 1995-2013 Mark Adler |
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27 * For conditions of distribution and use, see copyright notice in zlib.h |
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28 */ |
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29 |
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30 #include "zutil.h" |
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31 #include "inftrees.h" |
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32 |
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33 #define MAXBITS 15 |
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34 |
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35 const char inflate_copyright[] = |
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36 " inflate 1.2.8 Copyright 1995-2013 Mark Adler "; |
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37 /* |
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38 If you use the zlib library in a product, an acknowledgment is welcome |
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39 in the documentation of your product. If for some reason you cannot |
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40 include such an acknowledgment, I would appreciate that you keep this |
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41 copyright string in the executable of your product. |
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42 */ |
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43 |
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44 /* |
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45 Build a set of tables to decode the provided canonical Huffman code. |
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46 The code lengths are lens[0..codes-1]. The result starts at *table, |
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47 whose indices are 0..2^bits-1. work is a writable array of at least |
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48 lens shorts, which is used as a work area. type is the type of code |
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49 to be generated, CODES, LENS, or DISTS. On return, zero is success, |
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50 -1 is an invalid code, and +1 means that ENOUGH isn't enough. table |
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51 on return points to the next available entry's address. bits is the |
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52 requested root table index bits, and on return it is the actual root |
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53 table index bits. It will differ if the request is greater than the |
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54 longest code or if it is less than the shortest code. |
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55 */ |
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56 int ZLIB_INTERNAL inflate_table(type, lens, codes, table, bits, work) |
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57 codetype type; |
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58 unsigned short FAR *lens; |
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59 unsigned codes; |
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60 code FAR * FAR *table; |
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61 unsigned FAR *bits; |
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62 unsigned short FAR *work; |
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63 { |
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64 unsigned len; /* a code's length in bits */ |
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65 unsigned sym; /* index of code symbols */ |
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66 unsigned min, max; /* minimum and maximum code lengths */ |
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67 unsigned root; /* number of index bits for root table */ |
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68 unsigned curr; /* number of index bits for current table */ |
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69 unsigned drop; /* code bits to drop for sub-table */ |
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70 int left; /* number of prefix codes available */ |
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71 unsigned used; /* code entries in table used */ |
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72 unsigned huff; /* Huffman code */ |
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73 unsigned incr; /* for incrementing code, index */ |
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74 unsigned fill; /* index for replicating entries */ |
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75 unsigned low; /* low bits for current root entry */ |
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76 unsigned mask; /* mask for low root bits */ |
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77 code here; /* table entry for duplication */ |
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78 code FAR *next; /* next available space in table */ |
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79 const unsigned short FAR *base; /* base value table to use */ |
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80 const unsigned short FAR *extra; /* extra bits table to use */ |
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81 int end; /* use base and extra for symbol > end */ |
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82 unsigned short count[MAXBITS+1]; /* number of codes of each length */ |
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83 unsigned short offs[MAXBITS+1]; /* offsets in table for each length */ |
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84 static const unsigned short lbase[31] = { /* Length codes 257..285 base */ |
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85 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, |
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86 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; |
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87 static const unsigned short lext[31] = { /* Length codes 257..285 extra */ |
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88 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, |
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89 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 72, 78}; |
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90 static const unsigned short dbase[32] = { /* Distance codes 0..29 base */ |
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91 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, |
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92 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, |
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93 8193, 12289, 16385, 24577, 0, 0}; |
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94 static const unsigned short dext[32] = { /* Distance codes 0..29 extra */ |
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95 16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, |
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96 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, |
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97 28, 28, 29, 29, 64, 64}; |
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98 |
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99 /* |
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100 Process a set of code lengths to create a canonical Huffman code. The |
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101 code lengths are lens[0..codes-1]. Each length corresponds to the |
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102 symbols 0..codes-1. The Huffman code is generated by first sorting the |
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103 symbols by length from short to long, and retaining the symbol order |
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104 for codes with equal lengths. Then the code starts with all zero bits |
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105 for the first code of the shortest length, and the codes are integer |
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106 increments for the same length, and zeros are appended as the length |
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107 increases. For the deflate format, these bits are stored backwards |
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108 from their more natural integer increment ordering, and so when the |
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109 decoding tables are built in the large loop below, the integer codes |
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110 are incremented backwards. |
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111 |
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112 This routine assumes, but does not check, that all of the entries in |
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113 lens[] are in the range 0..MAXBITS. The caller must assure this. |
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114 1..MAXBITS is interpreted as that code length. zero means that that |
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115 symbol does not occur in this code. |
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116 |
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117 The codes are sorted by computing a count of codes for each length, |
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118 creating from that a table of starting indices for each length in the |
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119 sorted table, and then entering the symbols in order in the sorted |
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120 table. The sorted table is work[], with that space being provided by |
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121 the caller. |
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122 |
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123 The length counts are used for other purposes as well, i.e. finding |
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124 the minimum and maximum length codes, determining if there are any |
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125 codes at all, checking for a valid set of lengths, and looking ahead |
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126 at length counts to determine sub-table sizes when building the |
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127 decoding tables. |
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128 */ |
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129 |
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130 /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */ |
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131 for (len = 0; len <= MAXBITS; len++) |
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132 count[len] = 0; |
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133 for (sym = 0; sym < codes; sym++) |
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134 count[lens[sym]]++; |
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135 |
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136 /* bound code lengths, force root to be within code lengths */ |
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137 root = *bits; |
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138 for (max = MAXBITS; max >= 1; max--) |
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139 if (count[max] != 0) break; |
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140 if (root > max) root = max; |
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141 if (max == 0) { /* no symbols to code at all */ |
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142 here.op = (unsigned char)64; /* invalid code marker */ |
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143 here.bits = (unsigned char)1; |
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144 here.val = (unsigned short)0; |
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145 *(*table)++ = here; /* make a table to force an error */ |
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146 *(*table)++ = here; |
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147 *bits = 1; |
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148 return 0; /* no symbols, but wait for decoding to report error */ |
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149 } |
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150 for (min = 1; min < max; min++) |
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151 if (count[min] != 0) break; |
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152 if (root < min) root = min; |
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153 |
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154 /* check for an over-subscribed or incomplete set of lengths */ |
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155 left = 1; |
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156 for (len = 1; len <= MAXBITS; len++) { |
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157 left <<= 1; |
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158 left -= count[len]; |
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159 if (left < 0) return -1; /* over-subscribed */ |
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160 } |
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161 if (left > 0 && (type == CODES || max != 1)) |
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162 return -1; /* incomplete set */ |
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163 |
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164 /* generate offsets into symbol table for each length for sorting */ |
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165 offs[1] = 0; |
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166 for (len = 1; len < MAXBITS; len++) |
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167 offs[len + 1] = offs[len] + count[len]; |
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168 |
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169 /* sort symbols by length, by symbol order within each length */ |
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170 for (sym = 0; sym < codes; sym++) |
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171 if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym; |
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172 |
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173 /* |
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174 Create and fill in decoding tables. In this loop, the table being |
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175 filled is at next and has curr index bits. The code being used is huff |
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176 with length len. That code is converted to an index by dropping drop |
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177 bits off of the bottom. For codes where len is less than drop + curr, |
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178 those top drop + curr - len bits are incremented through all values to |
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179 fill the table with replicated entries. |
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180 |
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181 root is the number of index bits for the root table. When len exceeds |
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182 root, sub-tables are created pointed to by the root entry with an index |
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183 of the low root bits of huff. This is saved in low to check for when a |
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184 new sub-table should be started. drop is zero when the root table is |
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185 being filled, and drop is root when sub-tables are being filled. |
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186 |
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187 When a new sub-table is needed, it is necessary to look ahead in the |
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188 code lengths to determine what size sub-table is needed. The length |
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189 counts are used for this, and so count[] is decremented as codes are |
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190 entered in the tables. |
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191 |
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192 used keeps track of how many table entries have been allocated from the |
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193 provided *table space. It is checked for LENS and DIST tables against |
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194 the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in |
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195 the initial root table size constants. See the comments in inftrees.h |
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196 for more information. |
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197 |
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198 sym increments through all symbols, and the loop terminates when |
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199 all codes of length max, i.e. all codes, have been processed. This |
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200 routine permits incomplete codes, so another loop after this one fills |
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201 in the rest of the decoding tables with invalid code markers. |
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202 */ |
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203 |
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204 /* set up for code type */ |
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205 switch (type) { |
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206 case CODES: |
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207 base = extra = work; /* dummy value--not used */ |
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208 end = 19; |
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209 break; |
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210 case LENS: |
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211 base = lbase; |
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212 base -= 257; |
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213 extra = lext; |
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214 extra -= 257; |
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215 end = 256; |
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216 break; |
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217 default: /* DISTS */ |
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218 base = dbase; |
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219 extra = dext; |
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220 end = -1; |
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221 } |
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222 |
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223 /* initialize state for loop */ |
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224 huff = 0; /* starting code */ |
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225 sym = 0; /* starting code symbol */ |
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226 len = min; /* starting code length */ |
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227 next = *table; /* current table to fill in */ |
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228 curr = root; /* current table index bits */ |
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229 drop = 0; /* current bits to drop from code for index */ |
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230 low = (unsigned)(-1); /* trigger new sub-table when len > root */ |
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231 used = 1U << root; /* use root table entries */ |
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232 mask = used - 1; /* mask for comparing low */ |
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233 |
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234 /* check available table space */ |
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235 if ((type == LENS && used > ENOUGH_LENS) || |
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236 (type == DISTS && used > ENOUGH_DISTS)) |
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237 return 1; |
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238 |
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239 /* process all codes and make table entries */ |
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240 for (;;) { |
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241 /* create table entry */ |
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242 here.bits = (unsigned char)(len - drop); |
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243 if ((int)(work[sym]) < end) { |
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244 here.op = (unsigned char)0; |
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245 here.val = work[sym]; |
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246 } |
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247 else if ((int)(work[sym]) > end) { |
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248 here.op = (unsigned char)(extra[work[sym]]); |
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249 here.val = base[work[sym]]; |
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250 } |
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251 else { |
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252 here.op = (unsigned char)(32 + 64); /* end of block */ |
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253 here.val = 0; |
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254 } |
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255 |
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256 /* replicate for those indices with low len bits equal to huff */ |
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257 incr = 1U << (len - drop); |
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258 fill = 1U << curr; |
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259 min = fill; /* save offset to next table */ |
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260 do { |
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261 fill -= incr; |
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262 next[(huff >> drop) + fill] = here; |
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263 } while (fill != 0); |
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264 |
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265 /* backwards increment the len-bit code huff */ |
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266 incr = 1U << (len - 1); |
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267 while (huff & incr) |
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268 incr >>= 1; |
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269 if (incr != 0) { |
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270 huff &= incr - 1; |
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271 huff += incr; |
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272 } |
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273 else |
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274 huff = 0; |
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275 |
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276 /* go to next symbol, update count, len */ |
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277 sym++; |
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278 if (--(count[len]) == 0) { |
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279 if (len == max) break; |
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280 len = lens[work[sym]]; |
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281 } |
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282 |
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283 /* create new sub-table if needed */ |
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284 if (len > root && (huff & mask) != low) { |
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285 /* if first time, transition to sub-tables */ |
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286 if (drop == 0) |
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287 drop = root; |
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288 |
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289 /* increment past last table */ |
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290 next += min; /* here min is 1 << curr */ |
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291 |
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292 /* determine length of next table */ |
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293 curr = len - drop; |
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294 left = (int)(1 << curr); |
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295 while (curr + drop < max) { |
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296 left -= count[curr + drop]; |
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297 if (left <= 0) break; |
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298 curr++; |
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299 left <<= 1; |
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300 } |
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301 |
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302 /* check for enough space */ |
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303 used += 1U << curr; |
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304 if ((type == LENS && used > ENOUGH_LENS) || |
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305 (type == DISTS && used > ENOUGH_DISTS)) |
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306 return 1; |
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307 |
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308 /* point entry in root table to sub-table */ |
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309 low = huff & mask; |
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310 (*table)[low].op = (unsigned char)curr; |
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311 (*table)[low].bits = (unsigned char)root; |
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312 (*table)[low].val = (unsigned short)(next - *table); |
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313 } |
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314 } |
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315 |
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316 /* fill in remaining table entry if code is incomplete (guaranteed to have |
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317 at most one remaining entry, since if the code is incomplete, the |
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318 maximum code length that was allowed to get this far is one bit) */ |
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319 if (huff != 0) { |
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320 here.op = (unsigned char)64; /* invalid code marker */ |
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321 here.bits = (unsigned char)(len - drop); |
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322 here.val = (unsigned short)0; |
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323 next[huff] = here; |
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324 } |
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325 |
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326 /* set return parameters */ |
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327 *table += used; |
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328 *bits = root; |
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329 return 0; |
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330 } |
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