| 1 | /* |
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| 2 | lzw.h |
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| 3 | |
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| 4 | Original version: Ed McCreight: 19 Feb 90 |
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| 5 | Edit History: |
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| 6 | Ed McCreight: 23 Feb 90 |
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| 7 | End Edit History. |
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| 8 | |
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| 9 | Lempel-Ziv-Welch filters |
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| 10 | */ |
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| 11 | |
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| 12 | /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * |
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| 13 | * |
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| 14 | * The LZW compression method is said to be the subject of patents |
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| 15 | * owned by the Unisys Corporation. For further information, consult |
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| 16 | * the PostScript Language Reference Manual, second edition |
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| 17 | * (Addison Wesley, 1990, ISBN 0-201-18127-4). |
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| 18 | * |
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| 19 | * This source code is provided to you by Adobe on a non-exclusive, |
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| 20 | * royalty-free basis to facilitate your development of PostScript |
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| 21 | * language programs. You may incorporate it into your software as is |
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| 22 | * or modified, provided that you include the following copyright |
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| 23 | * notice with every copy of your software containing any portion of |
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| 24 | * this source code. |
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| 25 | * |
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| 26 | * Copyright 1990-91 Adobe Systems Incorporated. All Rights Reserved. |
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| 27 | * |
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| 28 | * Adobe does not warrant or guarantee that this source code will |
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| 29 | * perform in any manner. You alone assume any risks and |
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| 30 | * responsibilities associated with implementing, using or |
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| 31 | * incorporating this source code into your software. |
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| 32 | * |
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| 33 | * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ |
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| 34 | |
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| 35 | #ifndef LZW_H |
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| 36 | |
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| 37 | #define LZW_H |
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| 38 | |
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| 39 | #ifndef CHKSYNCH |
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| 40 | #define CHKSYNCH 0 /* for debugging */ |
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| 41 | #endif /* CHKSYNCH */ |
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| 42 | #define SYNCHPAT 0x0C |
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| 43 | #define SYNCHLEN 4 |
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| 44 | |
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| 45 | #define LZWMAXCODE 4096 /* codes */ |
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| 46 | #define LZWMINCODELEN 9 /* bits */ |
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| 47 | #define LZWMAXCODELEN 12 /* bits */ |
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| 48 | |
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| 49 | /* This LZW coding is intended to be identical to the TIFF 5.0 spec. |
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| 50 | |
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| 51 | Codes 0 - 255 represent their literal byte values |
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| 52 | Code 256 is the "Clear" code |
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| 53 | Code 257 is the "EOD" code |
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| 54 | Codes >=258 represent multi-byte sequences |
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| 55 | */ |
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| 56 | #define LZW_CLEAR 256 |
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| 57 | #define LZW_EOD 257 |
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| 58 | #define NLITCODES 258 |
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| 59 | |
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| 60 | typedef struct _t_LZWCodeRec |
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| 61 | { |
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| 62 | unsigned short prevCodeWord; |
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| 63 | unsigned char finalChar; |
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| 64 | unsigned char seqLen; |
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| 65 | /* 0 means undefined, |
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| 66 | 1 means special code (LZW_CLEAR, LZW_EOD), |
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| 67 | 2 means length 1, |
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| 68 | 3 means length 2, |
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| 69 | ..., |
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| 70 | 255 means length 254 or longer |
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| 71 | */ |
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| 72 | } |
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| 73 | LZWCodeRec, * LZWCode; |
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| 74 | |
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| 75 | #endif /* LZW_H */ |
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| 76 | |
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