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| Rev | Author | Line No. | Line |
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| 1 | daniel-mar | 1 | unit ZMExtrLZ7719; |
| 2 | |||
| 3 | (* |
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| 4 | ZMExtrLZ7719.pas - LZ77 stream expander |
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| 5 | Copyright (C) 2009, 2010 by Russell J. Peters, Roger Aelbrecht, |
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| 6 | Eric W. Engler and Chris Vleghert. |
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| 7 | |||
| 8 | This file is part of TZipMaster Version 1.9. |
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| 9 | |||
| 10 | TZipMaster is free software: you can redistribute it and/or modify |
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| 11 | it under the terms of the GNU Lesser General Public License as published by |
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| 12 | the Free Software Foundation, either version 3 of the License, or |
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| 13 | (at your option) any later version. |
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| 14 | |||
| 15 | TZipMaster is distributed in the hope that it will be useful, |
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| 16 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 18 | GNU Lesser General Public License for more details. |
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| 19 | |||
| 20 | You should have received a copy of the GNU Lesser General Public License |
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| 21 | along with TZipMaster. If not, see <http://www.gnu.org/licenses/>. |
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| 22 | |||
| 23 | contact: problems@delphizip.org (include ZipMaster in the subject). |
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| 24 | updates: http://www.delphizip.org |
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| 25 | DelphiZip maillist subscribe at http://www.freelists.org/list/delphizip |
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| 26 | |||
| 27 | modified 2007-11-05 |
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| 28 | ---------------------------------------------------------------------------*) |
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| 29 | |||
| 30 | interface |
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| 31 | |||
| 32 | uses |
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| 33 | Classes; |
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| 34 | |||
| 35 | // expects src at orig_size (integer), data (bytes) |
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| 36 | function LZ77Extract(dst, src: TStream; size: integer): integer; |
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| 37 | |||
| 38 | implementation |
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| 39 | |||
| 40 | const |
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| 41 | N = 4096; |
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| 42 | NMask = $FFF; //(N-1) |
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| 43 | F = 16; |
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| 44 | |||
| 45 | function GetByte(var bytes: Integer; Src: TStream): Integer; |
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| 46 | var |
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| 47 | cb: Byte; |
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| 48 | begin |
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| 49 | Result := -1; |
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| 50 | if (bytes > 4) and (Src.Size > Src.Position) then |
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| 51 | begin |
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| 52 | dec(bytes); |
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| 53 | if Src.Read(cb, 1) = 1 then |
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| 54 | Result := Integer(cb) |
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| 55 | else |
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| 56 | bytes := 0; |
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| 57 | end; |
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| 58 | end; |
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| 59 | |||
| 60 | function LZ77Extract(dst, src: TStream; size: integer): integer; |
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| 61 | var |
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| 62 | bits: Integer; |
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| 63 | Buffer: array of Byte; |
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| 64 | bytes: integer; |
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| 65 | ch: Integer; |
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| 66 | File_Size: integer; |
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| 67 | i: Integer; |
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| 68 | j: Integer; |
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| 69 | len: Integer; |
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| 70 | mask: Integer; |
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| 71 | written: integer; |
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| 72 | begin |
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| 73 | bytes := size; |
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| 74 | if bytes < 0 then |
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| 75 | bytes := HIGH(Integer); |
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| 76 | src.ReadBuffer(File_Size, sizeof(integer)); |
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| 77 | written := 0; |
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| 78 | |||
| 79 | SetLength(Buffer, N); |
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| 80 | i := N - F; |
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| 81 | while True do |
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| 82 | begin |
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| 83 | bits := GetByte(bytes, src); |
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| 84 | if (bits < 0) then |
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| 85 | break; |
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| 86 | |||
| 87 | mask := 1; |
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| 88 | while mask < 256 do |
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| 89 | begin |
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| 90 | if (bits and mask) = 0 then |
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| 91 | begin |
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| 92 | j := GetByte(bytes, src); |
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| 93 | if j < 0 then |
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| 94 | break; |
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| 95 | len := GetByte(bytes, src); |
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| 96 | inc(j, (len and $F0) shl 4); |
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| 97 | len := (len and 15) + 3; |
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| 98 | while len > 0 do |
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| 99 | begin |
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| 100 | Buffer[i] := Buffer[j]; |
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| 101 | dst.WriteBuffer(Buffer[i], 1); |
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| 102 | inc(written); |
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| 103 | j := succ(j) and NMask; |
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| 104 | i := succ(i) and NMask; |
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| 105 | dec(len); |
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| 106 | end; |
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| 107 | end |
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| 108 | else |
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| 109 | begin |
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| 110 | ch := GetByte(bytes, src); |
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| 111 | if ch < 0 then |
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| 112 | break; |
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| 113 | Buffer[i] := Byte(ch {and 255}); |
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| 114 | dst.WriteBuffer(ch, 1); |
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| 115 | inc(written); |
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| 116 | i := succ(i) and NMask; |
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| 117 | end; |
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| 118 | inc(mask, mask); |
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| 119 | end; |
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| 120 | end; |
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| 121 | if (File_Size = written) and (bytes = 4) then |
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| 122 | Result := 0 // good |
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| 123 | else |
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| 124 | if bytes = 4 then |
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| 125 | Result := -2 // wrong length |
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| 126 | else |
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| 127 | Result := -1; // invalid data |
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| 128 | Buffer := nil; |
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| 129 | end; |
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| 130 | |||
| 131 | end. |