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1 /* inffast.c -- process literals and length/distance pairs fast |
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2 * Copyright (C) 1995-1998 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 #include "infblock.h" |
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9 #include "infcodes.h" |
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10 #include "infutil.h" |
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11 #include "inffast.h" |
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12 |
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13 struct inflate_codes_state {int dummy;}; /* for buggy compilers */ |
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14 |
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15 /* simplify the use of the inflate_huft type with some defines */ |
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16 #define exop word.what.Exop |
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17 #define bits word.what.Bits |
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18 |
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19 /* macros for bit input with no checking and for returning unused bytes */ |
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20 #define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}} |
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21 #define UNGRAB {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;} |
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22 |
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23 /* Called with number of bytes left to write in window at least 258 |
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24 (the maximum string length) and number of input bytes available |
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25 at least ten. The ten bytes are six bytes for the longest length/ |
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26 distance pair plus four bytes for overloading the bit buffer. */ |
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27 |
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28 int inflate_fast(uInt bl, uInt bd, inflate_huft *tl, inflate_huft *td, inflate_blocks_statef *s, z_streamp z) |
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29 /* inflate_huft *td need separate declaration for Borland C++ */ |
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30 { |
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31 inflate_huft *t; /* temporary pointer */ |
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32 uInt e; /* extra bits or operation */ |
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33 uLong b; /* bit buffer */ |
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34 uInt k; /* bits in bit buffer */ |
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35 Bytef *p; /* input data pointer */ |
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36 uInt n; /* bytes available there */ |
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37 Bytef *q; /* output window write pointer */ |
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38 uInt m; /* bytes to end of window or read pointer */ |
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39 uInt ml; /* mask for literal/length tree */ |
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40 uInt md; /* mask for distance tree */ |
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41 uInt c; /* bytes to copy */ |
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42 uInt d; /* distance back to copy from */ |
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43 Bytef *r; /* copy source pointer */ |
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44 |
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45 /* load input, output, bit values */ |
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46 LOAD |
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47 |
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48 /* initialize masks */ |
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49 ml = inflate_mask[bl]; |
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50 md = inflate_mask[bd]; |
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51 |
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52 /* do until not enough input or output space for fast loop */ |
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53 do { /* assume called with m >= 258 && n >= 10 */ |
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54 /* get literal/length code */ |
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55 GRABBITS(20) /* max bits for literal/length code */ |
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56 if ((e = (t = tl + ((uInt)b & ml))->exop) == 0) |
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57 { |
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58 DUMPBITS(t->bits) |
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59 Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ? |
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60 "inflate: * literal '%c'\n" : |
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61 "inflate: * literal 0x%02x\n", t->base)); |
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62 *q++ = (Byte)t->base; |
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63 m--; |
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64 continue; |
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65 } |
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66 do { |
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67 DUMPBITS(t->bits) |
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68 if (e & 16) |
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69 { |
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70 /* get extra bits for length */ |
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71 e &= 15; |
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72 c = t->base + ((uInt)b & inflate_mask[e]); |
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73 DUMPBITS(e) |
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74 Tracevv((stderr, "inflate: * length %u\n", c)); |
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75 |
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76 /* decode distance base of block to copy */ |
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77 GRABBITS(15); /* max bits for distance code */ |
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78 e = (t = td + ((uInt)b & md))->exop; |
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79 do { |
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80 DUMPBITS(t->bits) |
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81 if (e & 16) |
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82 { |
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83 /* get extra bits to add to distance base */ |
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84 e &= 15; |
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85 GRABBITS(e) /* get extra bits (up to 13) */ |
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86 d = t->base + ((uInt)b & inflate_mask[e]); |
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87 DUMPBITS(e) |
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88 Tracevv((stderr, "inflate: * distance %u\n", d)); |
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89 |
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90 /* do the copy */ |
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91 m -= c; |
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92 if ((uInt)(q - s->window) >= d) /* offset before dest */ |
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93 { /* just copy */ |
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94 r = q - d; |
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95 *q++ = *r++; c--; /* minimum count is three, */ |
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96 *q++ = *r++; c--; /* so unroll loop a little */ |
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97 } |
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98 else /* else offset after destination */ |
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99 { |
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100 e = d - (uInt)(q - s->window); /* bytes from offset to end */ |
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101 r = s->end - e; /* pointer to offset */ |
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102 if (c > e) /* if source crosses, */ |
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103 { |
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104 c -= e; /* copy to end of window */ |
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105 do { |
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106 *q++ = *r++; |
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107 } while (--e); |
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108 r = s->window; /* copy rest from start of window */ |
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109 } |
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110 } |
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111 do { /* copy all or what's left */ |
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112 *q++ = *r++; |
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113 } while (--c); |
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114 break; |
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115 } |
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116 else if ((e & 64) == 0) |
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117 { |
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118 t += t->base; |
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119 e = (t += ((uInt)b & inflate_mask[e]))->exop; |
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120 } |
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121 else |
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122 { |
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123 z->msg = (char*)"invalid distance code"; |
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124 UNGRAB |
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125 UPDATE |
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126 return Z_DATA_ERROR; |
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127 } |
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128 } while (1); |
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129 break; |
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130 } |
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131 if ((e & 64) == 0) |
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132 { |
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133 t += t->base; |
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134 if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0) |
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135 { |
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136 DUMPBITS(t->bits) |
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137 Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ? |
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138 "inflate: * literal '%c'\n" : |
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139 "inflate: * literal 0x%02x\n", t->base)); |
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140 *q++ = (Byte)t->base; |
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141 m--; |
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142 break; |
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143 } |
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144 } |
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145 else if (e & 32) |
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146 { |
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147 Tracevv((stderr, "inflate: * end of block\n")); |
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148 UNGRAB |
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149 UPDATE |
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150 return Z_STREAM_END; |
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151 } |
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152 else |
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153 { |
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154 z->msg = (char*)"invalid literal/length code"; |
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155 UNGRAB |
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156 UPDATE |
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157 return Z_DATA_ERROR; |
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158 } |
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159 } while (1); |
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160 } while (m >= 258 && n >= 10); |
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161 |
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162 /* not enough input or output--restore pointers and return */ |
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163 UNGRAB |
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164 UPDATE |
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165 return Z_OK; |
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166 } |