1 /* inftrees.c -- generate Huffman trees for efficient decoding |
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2 * Copyright (C) 1995-2002 Mark Adler |
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3 * For conditions of distribution and use, see copyright notice in zlib.h |
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4 */ |
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5 |
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6 #include "zutil.h" |
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7 #include "inftrees.h" |
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8 |
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9 #if !defined(BUILDFIXED) && !defined(STDC) |
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10 # define BUILDFIXED /* non ANSI compilers may not accept inffixed.h */ |
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11 #endif |
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12 |
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13 |
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14 #if 0 |
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15 local const char inflate_copyright[] = |
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16 " inflate 1.1.4 Copyright 1995-2002 Mark Adler "; |
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17 #endif |
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18 /* |
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19 If you use the zlib library in a product, an acknowledgment is welcome |
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20 in the documentation of your product. If for some reason you cannot |
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21 include such an acknowledgment, I would appreciate that you keep this |
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22 copyright string in the executable of your product. |
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23 */ |
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24 |
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25 /* simplify the use of the inflate_huft type with some defines */ |
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26 #define exop word.what.Exop |
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27 #define bits word.what.Bits |
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28 |
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29 |
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30 local int huft_build OF(( |
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31 uIntf *, /* code lengths in bits */ |
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32 uInt, /* number of codes */ |
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33 uInt, /* number of "simple" codes */ |
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34 const uIntf *, /* list of base values for non-simple codes */ |
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35 const uIntf *, /* list of extra bits for non-simple codes */ |
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36 inflate_huft * FAR*,/* result: starting table */ |
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37 uIntf *, /* maximum lookup bits (returns actual) */ |
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38 inflate_huft *, /* space for trees */ |
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39 uInt *, /* hufts used in space */ |
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40 uIntf * )); /* space for values */ |
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41 |
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42 /* Tables for deflate from PKZIP's appnote.txt. */ |
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43 local const uInt cplens[31] = { /* Copy lengths for literal codes 257..285 */ |
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44 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, |
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45 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; |
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46 /* see note #13 above about 258 */ |
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47 local const uInt cplext[31] = { /* Extra bits for literal codes 257..285 */ |
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48 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, |
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49 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 112, 112}; /* 112==invalid */ |
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50 local const uInt cpdist[30] = { /* Copy offsets for distance codes 0..29 */ |
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51 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, |
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52 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, |
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53 8193, 12289, 16385, 24577}; |
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54 local const uInt cpdext[30] = { /* Extra bits for distance codes */ |
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55 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, |
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56 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, |
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57 12, 12, 13, 13}; |
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58 |
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59 /* |
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60 Huffman code decoding is performed using a multi-level table lookup. |
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61 The fastest way to decode is to simply build a lookup table whose |
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62 size is determined by the longest code. However, the time it takes |
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63 to build this table can also be a factor if the data being decoded |
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64 is not very long. The most common codes are necessarily the |
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65 shortest codes, so those codes dominate the decoding time, and hence |
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66 the speed. The idea is you can have a shorter table that decodes the |
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67 shorter, more probable codes, and then point to subsidiary tables for |
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68 the longer codes. The time it costs to decode the longer codes is |
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69 then traded against the time it takes to make longer tables. |
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70 |
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71 This results of this trade are in the variables lbits and dbits |
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72 below. lbits is the number of bits the first level table for literal/ |
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73 length codes can decode in one step, and dbits is the same thing for |
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74 the distance codes. Subsequent tables are also less than or equal to |
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75 those sizes. These values may be adjusted either when all of the |
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76 codes are shorter than that, in which case the longest code length in |
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77 bits is used, or when the shortest code is *longer* than the requested |
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78 table size, in which case the length of the shortest code in bits is |
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79 used. |
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80 |
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81 There are two different values for the two tables, since they code a |
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82 different number of possibilities each. The literal/length table |
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83 codes 286 possible values, or in a flat code, a little over eight |
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84 bits. The distance table codes 30 possible values, or a little less |
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85 than five bits, flat. The optimum values for speed end up being |
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86 about one bit more than those, so lbits is 8+1 and dbits is 5+1. |
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87 The optimum values may differ though from machine to machine, and |
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88 possibly even between compilers. Your mileage may vary. |
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89 */ |
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90 |
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91 |
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92 /* If BMAX needs to be larger than 16, then h and x[] should be uLong. */ |
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93 #define BMAX 15 /* maximum bit length of any code */ |
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94 |
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95 local int huft_build( /* b, n, s, d, e, t, m, hp, hn, v) */ |
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96 uIntf *b, /* code lengths in bits (all assumed <= BMAX) */ |
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97 uInt n, /* number of codes (assumed <= 288) */ |
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98 uInt s, /* number of simple-valued codes (0..s-1) */ |
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99 const uIntf *d, /* list of base values for non-simple codes */ |
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100 const uIntf *e, /* list of extra bits for non-simple codes */ |
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101 inflate_huft * FAR *t, /* result: starting table */ |
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102 uIntf *m, /* maximum lookup bits, returns actual */ |
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103 inflate_huft *hp, /* space for trees */ |
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104 uInt *hn, /* hufts used in space */ |
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105 uIntf *v /* working area: values in order of bit length */ |
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106 /* Given a list of code lengths and a maximum table size, make a set of |
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107 tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR |
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108 if the given code set is incomplete (the tables are still built in this |
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109 case), or Z_DATA_ERROR if the input is invalid. */ |
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110 ) |
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111 { |
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112 |
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113 uInt a; /* counter for codes of length k */ |
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114 uInt c[BMAX+1]; /* bit length count table */ |
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115 uInt f; /* i repeats in table every f entries */ |
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116 int g; /* maximum code length */ |
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117 int h; /* table level */ |
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118 register uInt i; /* counter, current code */ |
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119 register uInt j; /* counter */ |
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120 register int k; /* number of bits in current code */ |
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121 int l; /* bits per table (returned in m) */ |
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122 uInt mask; /* (1 << w) - 1, to avoid cc -O bug on HP */ |
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123 register uIntf *p; /* pointer into c[], b[], or v[] */ |
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124 inflate_huft *q; /* points to current table */ |
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125 struct inflate_huft_s r; /* table entry for structure assignment */ |
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126 inflate_huft *u[BMAX]; /* table stack */ |
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127 register int w; /* bits before this table == (l * h) */ |
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128 uInt x[BMAX+1]; /* bit offsets, then code stack */ |
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129 uIntf *xp; /* pointer into x */ |
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130 int y; /* number of dummy codes added */ |
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131 uInt z; /* number of entries in current table */ |
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132 |
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133 |
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134 /* Make compiler happy */ |
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135 r.base = 0; |
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136 |
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137 /* Generate counts for each bit length */ |
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138 p = c; |
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139 #define C0 *p++ = 0; |
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140 #define C2 C0 C0 C0 C0 |
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141 #define C4 C2 C2 C2 C2 |
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142 C4 /* clear c[]--assume BMAX+1 is 16 */ |
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143 p = b; i = n; |
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144 do { |
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145 c[*p++]++; /* assume all entries <= BMAX */ |
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146 } while (--i); |
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147 if (c[0] == n) /* null input--all zero length codes */ |
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148 { |
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149 *t = (inflate_huft *)Z_NULL; |
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150 *m = 0; |
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151 return Z_OK; |
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152 } |
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153 |
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154 |
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155 /* Find minimum and maximum length, bound *m by those */ |
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156 l = *m; |
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157 for (j = 1; j <= BMAX; j++) |
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158 if (c[j]) |
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159 break; |
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160 k = j; /* minimum code length */ |
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161 if ((uInt)l < j) |
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162 l = j; |
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163 for (i = BMAX; i; i--) |
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164 if (c[i]) |
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165 break; |
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166 g = i; /* maximum code length */ |
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167 if ((uInt)l > i) |
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168 l = i; |
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169 *m = l; |
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170 |
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171 |
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172 /* Adjust last length count to fill out codes, if needed */ |
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173 for (y = 1 << j; j < i; j++, y <<= 1) |
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174 if ((y -= c[j]) < 0) |
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175 return Z_DATA_ERROR; |
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176 if ((y -= c[i]) < 0) |
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177 return Z_DATA_ERROR; |
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178 c[i] += y; |
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179 |
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180 |
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181 /* Generate starting offsets into the value table for each length */ |
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182 x[1] = j = 0; |
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183 p = c + 1; xp = x + 2; |
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184 while (--i) { /* note that i == g from above */ |
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185 *xp++ = (j += *p++); |
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186 } |
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187 |
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188 |
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189 /* Make a table of values in order of bit lengths */ |
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190 p = b; i = 0; |
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191 do { |
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192 if ((j = *p++) != 0) |
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193 v[x[j]++] = i; |
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194 } while (++i < n); |
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195 n = x[g]; /* set n to length of v */ |
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196 |
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197 |
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198 /* Generate the Huffman codes and for each, make the table entries */ |
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199 x[0] = i = 0; /* first Huffman code is zero */ |
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200 p = v; /* grab values in bit order */ |
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201 h = -1; /* no tables yet--level -1 */ |
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202 w = -l; /* bits decoded == (l * h) */ |
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203 u[0] = (inflate_huft *)Z_NULL; /* just to keep compilers happy */ |
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204 q = (inflate_huft *)Z_NULL; /* ditto */ |
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205 z = 0; /* ditto */ |
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206 |
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207 /* go through the bit lengths (k already is bits in shortest code) */ |
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208 for (; k <= g; k++) |
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209 { |
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210 a = c[k]; |
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211 while (a--) |
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212 { |
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213 /* here i is the Huffman code of length k bits for value *p */ |
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214 /* make tables up to required level */ |
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215 while (k > w + l) |
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216 { |
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217 h++; |
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218 w += l; /* previous table always l bits */ |
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219 |
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220 /* compute minimum size table less than or equal to l bits */ |
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221 z = g - w; |
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222 z = z > (uInt)l ? (uInt)l : z; /* table size upper limit */ |
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223 if ((f = 1 << (j = k - w)) > a + 1) /* try a k-w bit table */ |
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224 { /* too few codes for k-w bit table */ |
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225 f -= a + 1; /* deduct codes from patterns left */ |
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226 xp = c + k; |
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227 if (j < z) |
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228 while (++j < z) /* try smaller tables up to z bits */ |
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229 { |
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230 if ((f <<= 1) <= *++xp) |
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231 break; /* enough codes to use up j bits */ |
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232 f -= *xp; /* else deduct codes from patterns */ |
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233 } |
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234 } |
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235 z = 1 << j; /* table entries for j-bit table */ |
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236 |
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237 /* allocate new table */ |
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238 if (*hn + z > MANY) /* (note: doesn't matter for fixed) */ |
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239 return Z_DATA_ERROR; /* overflow of MANY */ |
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240 u[h] = q = hp + *hn; |
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241 *hn += z; |
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242 |
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243 /* connect to last table, if there is one */ |
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244 if (h) |
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245 { |
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246 x[h] = i; /* save pattern for backing up */ |
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247 r.bits = (Byte)l; /* bits to dump before this table */ |
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248 r.exop = (Byte)j; /* bits in this table */ |
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249 j = i >> (w - l); |
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250 r.base = (uInt)(q - u[h-1] - j); /* offset to this table */ |
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251 u[h-1][j] = r; /* connect to last table */ |
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252 } |
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253 else |
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254 *t = q; /* first table is returned result */ |
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255 } |
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256 |
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257 /* set up table entry in r */ |
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258 r.bits = (Byte)(k - w); |
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259 if (p >= v + n) |
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260 r.exop = 128 + 64; /* out of values--invalid code */ |
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261 else if (*p < s) |
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262 { |
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263 r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */ |
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264 r.base = *p++; /* simple code is just the value */ |
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265 } |
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266 else |
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267 { |
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268 r.exop = (Byte)(e[*p - s] + 16 + 64);/* non-simple--look up in lists */ |
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269 r.base = d[*p++ - s]; |
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270 } |
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271 |
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272 /* fill code-like entries with r */ |
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273 f = 1 << (k - w); |
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274 for (j = i >> w; j < z; j += f) |
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275 q[j] = r; |
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276 |
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277 /* backwards increment the k-bit code i */ |
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278 for (j = 1 << (k - 1); i & j; j >>= 1) |
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279 i ^= j; |
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280 i ^= j; |
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281 |
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282 /* backup over finished tables */ |
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283 mask = (1 << w) - 1; /* needed on HP, cc -O bug */ |
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284 while ((i & mask) != x[h]) |
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285 { |
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286 h--; /* don't need to update q */ |
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287 w -= l; |
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288 mask = (1 << w) - 1; |
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289 } |
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290 } |
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291 } |
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292 |
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293 |
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294 /* Return Z_BUF_ERROR if we were given an incomplete table */ |
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295 return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK; |
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296 } |
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297 |
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298 |
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299 local int inflate_trees_bits( /* c, bb, tb, hp, z) */ |
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300 uIntf *c, /* 19 code lengths */ |
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301 uIntf *bb, /* bits tree desired/actual depth */ |
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302 inflate_huft * FAR *tb, /* bits tree result */ |
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303 inflate_huft *hp, /* space for trees */ |
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304 z_streamp z /* for messages */ |
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305 ) |
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306 { |
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307 int r; |
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308 uInt hn = 0; /* hufts used in space */ |
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309 uIntf *v; /* work area for huft_build */ |
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310 |
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311 if ((v = (uIntf*)ZALLOC(z, 19, sizeof(uInt))) == Z_NULL) |
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312 return Z_MEM_ERROR; |
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313 r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL, |
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314 tb, bb, hp, &hn, v); |
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315 if (r == Z_DATA_ERROR) |
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316 z->msg = (char*)"oversubscribed dynamic bit lengths tree"; |
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317 else if (r == Z_BUF_ERROR || *bb == 0) |
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318 { |
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319 z->msg = (char*)"incomplete dynamic bit lengths tree"; |
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320 r = Z_DATA_ERROR; |
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321 } |
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322 ZFREE(z, v); |
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323 return r; |
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324 } |
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325 |
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326 |
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327 local int inflate_trees_dynamic( /* nl, nd, c, bl, bd, tl, td, hp, z) */ |
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328 uInt nl, /* number of literal/length codes */ |
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329 uInt nd, /* number of distance codes */ |
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330 uIntf *c, /* that many (total) code lengths */ |
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331 uIntf *bl, /* literal desired/actual bit depth */ |
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332 uIntf *bd, /* distance desired/actual bit depth */ |
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333 inflate_huft * FAR *tl, /* literal/length tree result */ |
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334 inflate_huft * FAR *td, /* distance tree result */ |
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335 inflate_huft *hp, /* space for trees */ |
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336 z_streamp z /* for messages */ |
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337 ) |
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338 { |
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339 int r; |
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340 uInt hn = 0; /* hufts used in space */ |
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341 uIntf *v; /* work area for huft_build */ |
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342 |
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343 /* allocate work area */ |
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344 if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) |
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345 return Z_MEM_ERROR; |
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346 |
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347 /* build literal/length tree */ |
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348 r = huft_build(c, nl, 257, cplens, cplext, tl, bl, hp, &hn, v); |
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349 if (r != Z_OK || *bl == 0) |
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350 { |
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351 if (r == Z_DATA_ERROR) |
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352 z->msg = (char*)"oversubscribed literal/length tree"; |
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353 else if (r != Z_MEM_ERROR) |
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354 { |
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355 z->msg = (char*)"incomplete literal/length tree"; |
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356 r = Z_DATA_ERROR; |
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357 } |
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358 ZFREE(z, v); |
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359 return r; |
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360 } |
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361 |
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362 /* build distance tree */ |
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363 r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, hp, &hn, v); |
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364 if (r != Z_OK || (*bd == 0 && nl > 257)) |
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365 { |
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366 if (r == Z_DATA_ERROR) |
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367 z->msg = (char*)"oversubscribed distance tree"; |
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368 else if (r == Z_BUF_ERROR) { |
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369 #if 0 |
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370 { |
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371 #endif |
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372 #ifdef PKZIP_BUG_WORKAROUND |
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373 r = Z_OK; |
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374 } |
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375 #else |
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376 z->msg = (char*)"incomplete distance tree"; |
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377 r = Z_DATA_ERROR; |
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378 } |
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379 else if (r != Z_MEM_ERROR) |
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380 { |
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381 z->msg = (char*)"empty distance tree with lengths"; |
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382 r = Z_DATA_ERROR; |
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383 } |
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384 ZFREE(z, v); |
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385 return r; |
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386 #endif |
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387 } |
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388 |
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389 /* done */ |
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390 ZFREE(z, v); |
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391 return Z_OK; |
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392 } |
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393 |
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394 |
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395 /* build fixed tables only once--keep them here */ |
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396 #ifdef BUILDFIXED |
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397 local int fixed_built = 0; |
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398 #define FIXEDH 544 /* number of hufts used by fixed tables */ |
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399 local inflate_huft fixed_mem[FIXEDH]; |
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400 local uInt fixed_bl; |
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401 local uInt fixed_bd; |
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402 local inflate_huft *fixed_tl; |
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403 local inflate_huft *fixed_td; |
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404 #else |
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405 #include "inffixed.h" |
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406 #endif |
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407 |
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408 |
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409 local int inflate_trees_fixed( /* bl, bd, tl, td, z) */ |
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410 uIntf *bl, /* literal desired/actual bit depth */ |
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411 uIntf *bd, /* distance desired/actual bit depth */ |
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412 const inflate_huft * FAR *tl, /* literal/length tree result */ |
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413 const inflate_huft * FAR *td, /* distance tree result */ |
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414 z_streamp z /* for memory allocation */ |
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415 ) |
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416 { |
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417 #ifdef BUILDFIXED |
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418 /* build fixed tables if not already */ |
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419 if (!fixed_built) |
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420 { |
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421 int k; /* temporary variable */ |
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422 uInt f = 0; /* number of hufts used in fixed_mem */ |
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423 uIntf *c; /* length list for huft_build */ |
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424 uIntf *v; /* work area for huft_build */ |
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425 |
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426 /* allocate memory */ |
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427 if ((c = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) |
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428 return Z_MEM_ERROR; |
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429 if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) |
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430 { |
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431 ZFREE(z, c); |
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432 return Z_MEM_ERROR; |
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433 } |
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434 |
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435 /* literal table */ |
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436 for (k = 0; k < 144; k++) |
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437 c[k] = 8; |
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438 for (; k < 256; k++) |
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439 c[k] = 9; |
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440 for (; k < 280; k++) |
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441 c[k] = 7; |
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442 for (; k < 288; k++) |
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443 c[k] = 8; |
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444 fixed_bl = 9; |
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445 huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl, |
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446 fixed_mem, &f, v); |
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447 |
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448 /* distance table */ |
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449 for (k = 0; k < 30; k++) |
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450 c[k] = 5; |
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451 fixed_bd = 5; |
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452 huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd, |
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453 fixed_mem, &f, v); |
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454 |
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455 /* done */ |
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456 ZFREE(z, v); |
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457 ZFREE(z, c); |
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458 fixed_built = 1; |
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459 } |
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460 #else |
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461 FT_UNUSED(z); |
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462 #endif |
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463 *bl = fixed_bl; |
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464 *bd = fixed_bd; |
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465 *tl = fixed_tl; |
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466 *td = fixed_td; |
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467 return Z_OK; |
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468 } |
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