80 lines
2.5 KiB
C
80 lines
2.5 KiB
C
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/*
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** header.h - Common information used in compressed file header manipulation.
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**
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** Author: DavidDi
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*/
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// Constants
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/////////////
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// compressed file signature: "SZDD<44><44>'3"
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#define COMP_SIG "SZDD\x88\xf0\x27\x33"
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#define COMP_SIG_LEN 8 // length of signature (bytes)
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// (no '\0' terminator)
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#define ALG_FIRST ((BYTE) 'A') // first version algorithm label for
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// Lempel-Ziv
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#define ALG_LZ ((BYTE) 'B') // new Lempel-Ziv algorithm label
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#define ALG_LZA ((BYTE) 'C') // Lempel-Ziv with arithmetic encoding
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// algorithm label
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// length of entire compressed file header (used as offset to start of
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// compressed data)
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#define HEADER_LEN 14
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// (14 == cbCompSigLength + algorithm + extension character
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// + uncompressed length)
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#define BYTE_MASK 0xff // mask used to isolate low-order byte
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// Types
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/////////
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// Declare compressed file header information structure. N.b., the
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// compressed file header does not contain the file size of the compressed
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// file since this is readily obtainable through filelength() or lseek().
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// The file info structure, however, does contain the compressed file size,
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// which is used when expanding the file.
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typedef struct tagFH
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{
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BYTE rgbyteMagic[COMP_SIG_LEN]; // array of compressed file signature
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// (magic bytes)
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BYTE byteAlgorithm; // algorithm label
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BYTE byteExtensionChar; // last extension character
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// (always 0 for ALG_FIRST)
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// The file sizes are unsigned longs instead of signed longs for backward
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// compatibilty with version 1.00.
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DWORD cbulUncompSize; // uncompressed file size
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DWORD cbulCompSize; // compressed file size (not stored in
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// header)
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} FH;
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typedef struct tagFH *PFH;
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// Macros
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//////////
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#if 0
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#define RecognizeCompAlg(chAlg) ((chAlg) == ALG_FIRST || \
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(chAlg) == ALG_LZ || \
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(chAlg) == ALG_LZA)
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#else
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#define RecognizeCompAlg(chAlg) ((chAlg) == ALG_FIRST)
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#endif
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// Prototypes
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//////////////
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// header.c
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extern INT WriteHdr(PFH pFH, INT doshDest, PLZINFO pLZI);
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extern INT GetHdr(PFH pFH, INT doshSource, LONG * pcblInSize);
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extern BOOL IsCompressed(PFH pFHIn);
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extern VOID MakeHeader(PFH pFHBlank, BYTE byteAlgorithm, BYTE byteExtensionChar,
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PLZINFO pLZI);
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