repo sync | baa3858 | 2013-07-26 17:53:31 -0700 | [diff] [blame] | 1 | 7z Format description (2.30 Beta 25)
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| 2 | -----------------------------------
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| 3 |
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| 4 | This file contains description of 7z archive format.
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| 5 | 7z archive can contain files compressed with any method.
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| 6 | See "Methods.txt" for description for defined compressing methods.
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| 7 |
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| 8 |
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| 9 | Format structure Overview
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| 10 | -------------------------
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| 11 |
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| 12 | Some fields can be optional.
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| 13 |
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| 14 | Archive structure
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| 15 | ~~~~~~~~~~~~~~~~~
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| 16 | SignatureHeader
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| 17 | [PackedStreams]
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| 18 | [PackedStreamsForHeaders]
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| 19 | [
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| 20 | Header
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| 21 | or
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| 22 | {
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| 23 | Packed Header
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| 24 | HeaderInfo
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| 25 | }
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| 26 | ]
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| 27 |
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| 28 |
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| 29 |
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| 30 | Header structure
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| 31 | ~~~~~~~~~~~~~~~~
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| 32 | {
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| 33 | ArchiveProperties
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| 34 | AdditionalStreams
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| 35 | {
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| 36 | PackInfo
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| 37 | {
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| 38 | PackPos
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| 39 | NumPackStreams
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| 40 | Sizes[NumPackStreams]
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| 41 | CRCs[NumPackStreams]
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| 42 | }
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| 43 | CodersInfo
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| 44 | {
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| 45 | NumFolders
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| 46 | Folders[NumFolders]
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| 47 | {
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| 48 | NumCoders
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| 49 | CodersInfo[NumCoders]
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| 50 | {
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| 51 | ID
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| 52 | NumInStreams;
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| 53 | NumOutStreams;
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| 54 | PropertiesSize
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| 55 | Properties[PropertiesSize]
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| 56 | }
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| 57 | NumBindPairs
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| 58 | BindPairsInfo[NumBindPairs]
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| 59 | {
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| 60 | InIndex;
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| 61 | OutIndex;
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| 62 | }
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| 63 | PackedIndices
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| 64 | }
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| 65 | UnPackSize[Folders][Folders.NumOutstreams]
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| 66 | CRCs[NumFolders]
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| 67 | }
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| 68 | SubStreamsInfo
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| 69 | {
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| 70 | NumUnPackStreamsInFolders[NumFolders];
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| 71 | UnPackSizes[]
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| 72 | CRCs[]
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| 73 | }
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| 74 | }
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| 75 | MainStreamsInfo
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| 76 | {
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| 77 | (Same as in AdditionalStreams)
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| 78 | }
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| 79 | FilesInfo
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| 80 | {
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| 81 | NumFiles
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| 82 | Properties[]
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| 83 | {
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| 84 | ID
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| 85 | Size
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| 86 | Data
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| 87 | }
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| 88 | }
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| 89 | }
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| 90 |
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| 91 | HeaderInfo structure
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| 92 | ~~~~~~~~~~~~~~~~~~~~
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| 93 | {
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| 94 | (Same as in AdditionalStreams)
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| 95 | }
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| 96 |
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| 97 |
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| 98 |
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| 99 | Notes about Notation and encoding
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| 100 | ---------------------------------
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| 101 |
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| 102 | 7z uses little endian encoding.
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| 103 |
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| 104 | 7z archive format has optional headers that are marked as
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| 105 | []
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| 106 | Header
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| 107 | []
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| 108 |
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| 109 | REAL_UINT64 means real UINT64.
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| 110 |
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| 111 | UINT64 means real UINT64 encoded with the following scheme:
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| 112 |
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| 113 | Size of encoding sequence depends from first byte:
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| 114 | First_Byte Extra_Bytes Value
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| 115 | (binary)
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| 116 | 0xxxxxxx : ( xxxxxxx )
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| 117 | 10xxxxxx BYTE y[1] : ( xxxxxx << (8 * 1)) + y
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| 118 | 110xxxxx BYTE y[2] : ( xxxxx << (8 * 2)) + y
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| 119 | ...
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| 120 | 1111110x BYTE y[6] : ( x << (8 * 6)) + y
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| 121 | 11111110 BYTE y[7] : y
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| 122 | 11111111 BYTE y[8] : y
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| 123 |
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| 124 |
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| 125 |
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| 126 | Property IDs
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| 127 | ------------
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| 128 |
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| 129 | 0x00 = kEnd,
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| 130 |
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| 131 | 0x01 = kHeader,
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| 132 |
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| 133 | 0x02 = kArchiveProperties,
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| 134 |
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| 135 | 0x03 = kAdditionalStreamsInfo,
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| 136 | 0x04 = kMainStreamsInfo,
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| 137 | 0x05 = kFilesInfo,
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| 138 |
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| 139 | 0x06 = kPackInfo,
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| 140 | 0x07 = kUnPackInfo,
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| 141 | 0x08 = kSubStreamsInfo,
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| 142 |
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| 143 | 0x09 = kSize,
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| 144 | 0x0A = kCRC,
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| 145 |
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| 146 | 0x0B = kFolder,
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| 147 |
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| 148 | 0x0C = kCodersUnPackSize,
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| 149 | 0x0D = kNumUnPackStream,
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| 150 |
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| 151 | 0x0E = kEmptyStream,
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| 152 | 0x0F = kEmptyFile,
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| 153 | 0x10 = kAnti,
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| 154 |
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| 155 | 0x11 = kName,
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| 156 | 0x12 = kCreationTime,
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| 157 | 0x13 = kLastAccessTime,
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| 158 | 0x14 = kLastWriteTime,
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| 159 | 0x15 = kWinAttributes,
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| 160 | 0x16 = kComment,
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| 161 |
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| 162 | 0x17 = kEncodedHeader,
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| 163 |
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| 164 |
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| 165 | 7z format headers
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| 166 | -----------------
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| 167 |
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| 168 | SignatureHeader
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| 169 | ~~~~~~~~~~~~~~~
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| 170 | BYTE kSignature[6] = {'7', 'z', 0xBC, 0xAF, 0x27, 0x1C};
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| 171 |
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| 172 | ArchiveVersion
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| 173 | {
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| 174 | BYTE Major; // now = 0
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| 175 | BYTE Minor; // now = 2
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| 176 | };
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| 177 |
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| 178 | UINT32 StartHeaderCRC;
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| 179 |
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| 180 | StartHeader
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| 181 | {
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| 182 | REAL_UINT64 NextHeaderOffset
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| 183 | REAL_UINT64 NextHeaderSize
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| 184 | UINT32 NextHeaderCRC
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| 185 | }
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| 186 |
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| 187 |
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| 188 | ...........................
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| 189 |
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| 190 |
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| 191 | ArchiveProperties
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| 192 | ~~~~~~~~~~~~~~~~~
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| 193 | BYTE NID::kArchiveProperties (0x02)
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| 194 | for (;;)
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| 195 | {
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| 196 | BYTE PropertyType;
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| 197 | if (aType == 0)
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| 198 | break;
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| 199 | UINT64 PropertySize;
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| 200 | BYTE PropertyData[PropertySize];
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| 201 | }
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| 202 |
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| 203 |
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| 204 | Digests (NumStreams)
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| 205 | ~~~~~~~~~~~~~~~~~~~~~
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| 206 | BYTE AllAreDefined
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| 207 | if (AllAreDefined == 0)
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| 208 | {
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| 209 | for(NumStreams)
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| 210 | BIT Defined
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| 211 | }
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| 212 | UINT32 CRCs[NumDefined]
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| 213 |
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| 214 |
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| 215 | PackInfo
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| 216 | ~~~~~~~~~~~~
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| 217 | BYTE NID::kPackInfo (0x06)
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| 218 | UINT64 PackPos
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| 219 | UINT64 NumPackStreams
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| 220 |
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| 221 | []
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| 222 | BYTE NID::kSize (0x09)
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| 223 | UINT64 PackSizes[NumPackStreams]
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| 224 | []
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| 225 |
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| 226 | []
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| 227 | BYTE NID::kCRC (0x0A)
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| 228 | PackStreamDigests[NumPackStreams]
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| 229 | []
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| 230 |
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| 231 | BYTE NID::kEnd
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| 232 |
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| 233 |
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| 234 | Folder
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| 235 | ~~~~~~
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| 236 | UINT64 NumCoders;
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| 237 | for (NumCoders)
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| 238 | {
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| 239 | BYTE
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| 240 | {
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| 241 | 0:3 DecompressionMethod.IDSize
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| 242 | 4:
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| 243 | 0 - IsSimple
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| 244 | 1 - Is not simple
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| 245 | 5:
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| 246 | 0 - No Attributes
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| 247 | 1 - There Are Attributes
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| 248 | 7:
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| 249 | 0 - Last Method in Alternative_Method_List
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| 250 | 1 - There are more alternative methods
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| 251 | }
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| 252 | BYTE DecompressionMethod.ID[DecompressionMethod.IDSize]
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| 253 | if (!IsSimple)
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| 254 | {
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| 255 | UINT64 NumInStreams;
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| 256 | UINT64 NumOutStreams;
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| 257 | }
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| 258 | if (DecompressionMethod[0] != 0)
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| 259 | {
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| 260 | UINT64 PropertiesSize
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| 261 | BYTE Properties[PropertiesSize]
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| 262 | }
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| 263 | }
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| 264 |
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| 265 | NumBindPairs = NumOutStreamsTotal - 1;
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| 266 |
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| 267 | for (NumBindPairs)
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| 268 | {
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| 269 | UINT64 InIndex;
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| 270 | UINT64 OutIndex;
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| 271 | }
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| 272 |
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| 273 | NumPackedStreams = NumInStreamsTotal - NumBindPairs;
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| 274 | if (NumPackedStreams > 1)
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| 275 | for(NumPackedStreams)
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| 276 | {
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| 277 | UINT64 Index;
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| 278 | };
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| 279 |
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| 280 |
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| 281 |
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| 282 |
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| 283 | Coders Info
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| 284 | ~~~~~~~~~~~
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| 285 |
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| 286 | BYTE NID::kUnPackInfo (0x07)
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| 287 |
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| 288 |
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| 289 | BYTE NID::kFolder (0x0B)
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| 290 | UINT64 NumFolders
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| 291 | BYTE External
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| 292 | switch(External)
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| 293 | {
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| 294 | case 0:
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| 295 | Folders[NumFolders]
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| 296 | case 1:
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| 297 | UINT64 DataStreamIndex
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| 298 | }
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| 299 |
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| 300 |
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| 301 | BYTE ID::kCodersUnPackSize (0x0C)
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| 302 | for(Folders)
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| 303 | for(Folder.NumOutStreams)
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| 304 | UINT64 UnPackSize;
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| 305 |
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| 306 |
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| 307 | []
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| 308 | BYTE NID::kCRC (0x0A)
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| 309 | UnPackDigests[NumFolders]
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| 310 | []
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| 311 |
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| 312 |
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| 313 |
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| 314 | BYTE NID::kEnd
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| 315 |
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| 316 |
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| 317 |
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| 318 | SubStreams Info
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| 319 | ~~~~~~~~~~~~~~
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| 320 | BYTE NID::kSubStreamsInfo; (0x08)
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| 321 |
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| 322 | []
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| 323 | BYTE NID::kNumUnPackStream; (0x0D)
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| 324 | UINT64 NumUnPackStreamsInFolders[NumFolders];
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| 325 | []
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| 326 |
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| 327 |
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| 328 | []
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| 329 | BYTE NID::kSize (0x09)
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| 330 | UINT64 UnPackSizes[]
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| 331 | []
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| 332 |
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| 333 |
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| 334 | []
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| 335 | BYTE NID::kCRC (0x0A)
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| 336 | Digests[Number of streams with unknown CRC]
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| 337 | []
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| 338 |
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| 339 |
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| 340 | BYTE NID::kEnd
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| 341 |
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| 342 |
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| 343 | Streams Info
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| 344 | ~~~~~~~~~~~~
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| 345 |
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| 346 | []
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| 347 | PackInfo
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| 348 | []
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| 349 |
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| 350 |
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| 351 | []
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| 352 | CodersInfo
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| 353 | []
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| 354 |
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| 355 |
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| 356 | []
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| 357 | SubStreamsInfo
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| 358 | []
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| 359 |
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| 360 | BYTE NID::kEnd
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| 361 |
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| 362 |
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| 363 | FilesInfo
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| 364 | ~~~~~~~~~
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| 365 | BYTE NID::kFilesInfo; (0x05)
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| 366 | UINT64 NumFiles
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| 367 |
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| 368 | for (;;)
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| 369 | {
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| 370 | BYTE PropertyType;
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| 371 | if (aType == 0)
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| 372 | break;
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| 373 |
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| 374 | UINT64 Size;
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| 375 |
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| 376 | switch(PropertyType)
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| 377 | {
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| 378 | kEmptyStream: (0x0E)
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| 379 | for(NumFiles)
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| 380 | BIT IsEmptyStream
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| 381 |
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| 382 | kEmptyFile: (0x0F)
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| 383 | for(EmptyStreams)
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| 384 | BIT IsEmptyFile
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| 385 |
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| 386 | kAnti: (0x10)
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| 387 | for(EmptyStreams)
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| 388 | BIT IsAntiFile
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| 389 |
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| 390 | case kCreationTime: (0x12)
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| 391 | case kLastAccessTime: (0x13)
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| 392 | case kLastWriteTime: (0x14)
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| 393 | BYTE AllAreDefined
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| 394 | if (AllAreDefined == 0)
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| 395 | {
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| 396 | for(NumFiles)
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| 397 | BIT TimeDefined
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| 398 | }
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| 399 | BYTE External;
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| 400 | if(External != 0)
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| 401 | UINT64 DataIndex
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| 402 | []
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| 403 | for(Definded Items)
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| 404 | UINT32 Time
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| 405 | []
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| 406 |
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| 407 | kNames: (0x11)
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| 408 | BYTE External;
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| 409 | if(External != 0)
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| 410 | UINT64 DataIndex
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| 411 | []
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| 412 | for(Files)
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| 413 | {
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| 414 | wchar_t Names[NameSize];
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| 415 | wchar_t 0;
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| 416 | }
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| 417 | []
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| 418 |
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| 419 | kAttributes: (0x15)
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| 420 | BYTE AllAreDefined
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| 421 | if (AllAreDefined == 0)
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| 422 | {
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| 423 | for(NumFiles)
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| 424 | BIT AttributesAreDefined
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| 425 | }
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| 426 | BYTE External;
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| 427 | if(External != 0)
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| 428 | UINT64 DataIndex
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| 429 | []
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| 430 | for(Definded Attributes)
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| 431 | UINT32 Attributes
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| 432 | []
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| 433 | }
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| 434 | }
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| 435 |
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| 436 |
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| 437 | Header
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| 438 | ~~~~~~
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| 439 | BYTE NID::kHeader (0x01)
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| 440 |
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| 441 | []
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| 442 | ArchiveProperties
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| 443 | []
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| 444 |
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| 445 | []
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| 446 | BYTE NID::kAdditionalStreamsInfo; (0x03)
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| 447 | StreamsInfo
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| 448 | []
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| 449 |
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| 450 | []
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| 451 | BYTE NID::kMainStreamsInfo; (0x04)
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| 452 | StreamsInfo
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| 453 | []
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| 454 |
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| 455 | []
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| 456 | FilesInfo
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| 457 | []
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| 458 |
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| 459 | BYTE NID::kEnd
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| 460 |
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| 461 |
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| 462 | HeaderInfo
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| 463 | ~~~~~~~~~~
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| 464 | []
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| 465 | BYTE NID::kEncodedHeader; (0x17)
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| 466 | StreamsInfo for Encoded Header
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| 467 | []
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| 468 |
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| 469 |
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| 470 | ---
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| 471 | End of document
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