378 lines
9.4 KiB
C
378 lines
9.4 KiB
C
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//
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// General Data Compression
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//
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#ifndef _H_GDC
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#define _H_GDC
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//
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//
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// CONSTANTS
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//
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//
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//
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// Scratch buffer mutex
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//
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#define GDC_MUTEX_NAME "GDCMutex"
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//
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// Compression Types (bit flags)
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//
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#define GCT_NOCOMPRESSION 0x0000
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#define GCT_PKZIP 0x0001
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#define GCT_PERSIST_PKZIP 0x0002
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#define GCT_DEFAULT (GCT_PKZIP | GCT_PERSIST_PKZIP)
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//
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// Compression Options for GCT_PKZIP
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//
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#define GDCCO_MAXSPEED 0
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#define GDCCO_MAXCOMPRESSION 1
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//
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// Data sizes used to determine the saved dictionary space in our work
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// buffer.
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//
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#define GDC_DATA_SMALL 1024
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#define GDC_DATA_MEDIUM 2048
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#define GDC_DATA_MAX 4096
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//
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// Persistent Dictionaries used for compression/decompression
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//
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enum
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{
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GDC_DICT_UPDATES = 0,
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GDC_DICT_MISC,
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GDC_DICT_INPUT,
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GDC_DICT_COUNT
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};
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typedef struct tagGDC_DICTIONARY
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{
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UINT cbUsed; // Amount of saved data
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BYTE pData[GDC_DATA_MAX]; // Saved uncompressed data
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} GDC_DICTIONARY;
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typedef GDC_DICTIONARY * PGDC_DICTIONARY;
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//
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// Byte runs that can be replaced with smaller bit sequences
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//
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#define GDC_MINREP 2
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#define GDC_MAXREP (GDC_MINREP+(8*1)+2+4+8+16+32+64+128+256-4)
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// GDC_MAXREP is 516, 129*4
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//
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// Holds uncompressed data for both compression/decompression
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//
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#define GDC_UNCOMPRESSED (GDC_MAXREP + 2*GDC_DATA_MAX)
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//
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// We don't need to double-buffer compressed data--we just read it out
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// of the caller's source or write it into the caller's dest directly.
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//
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// NOTE: With real PKZIP, which mostly reads from/writes to files,
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// they don't have memory pointers containing raw data already. That's
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// whe original code we got used Read/Write routine callbacks. This is
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// no longer necessary.
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//
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//
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// Random, little understood PKZIP table values, codes
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//
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#define KMP_THRESHOLD 10
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#define GDC_LIT_SIZE (256 + GDC_MAXREP + 2)
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// GDC_LIT_SIZE is 774
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// EOF is last index of Lit array
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#define EOF_CODE (GDC_LIT_SIZE-1)
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#define ABORT_CODE (EOF_CODE+1)
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//
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// EXT_DIST_BITS is the # of bits needed to store an index into a GDC_DIST_SIZE
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// array. That's defined to be 64, which is 2^6, hence 6 bits. Smaller
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// dictionary compressions use fewer bits and hence not all of the DIST
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// items. The mask
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// is used to pull the 6-bit sized index out of a byte.
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//
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#define GDC_DIST_SIZE 64
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#define EXT_DIST_BITS_MIN 4
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#define EXT_DIST_BITS_MEDIUM 5
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#define EXT_DIST_BITS_MAC 6
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#define GDC_LEN_SIZE 16
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#define GDC_DECODED_SIZE 256
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//
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// The hash function has 4*256+5*256 different values, which means
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// we need that many entries in our hash array.
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//
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#define GDC_HASHFN(x) (4*(x)[0] + 5*(x)[1])
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#define GDC_HASH_SIZE (4*256 + 5*256)
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//
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// Structure: GDC_IMPLODE
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//
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// Workspace for compressing our data. We have simplified and shrunk this
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// structure a fair amount, by having constant code/bit tables and not
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// double-buffering the compressed result. PKZIP's implode calculates the
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// LitBits & LitCodes every time through (rather than storing 2 774 byte
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// arrays in data--which would be a pain to declare anyway!), and makes a
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// private copy of the DistBits & DistCodes.
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//
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typedef struct tagGDC_IMPLODE
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{
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//
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// NO SOURCE INFO--we copy source chunks and maybe dictionary into
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// RawData. Then at the end we copy RawData back into the dictionary
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// if there is one.
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//
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//
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// Destination info
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//
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LPBYTE pDst; // Current Dest ptr (advances as we write)
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UINT cbDst; // Amount of Dest left (shrinks as we write)
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UINT iDstBit; // Current bit pos in Current Dest ptr byte
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//
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// Compression info
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//
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UINT cbDictSize;
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UINT cbDictUsed;
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UINT ExtDistBits;
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UINT ExtDistMask;
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//
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// Working info
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//
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UINT Distance;
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UINT ibRawData;
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// NOTE: GDC_UNCOMPRESSED is a multiple of 4
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BYTE RawData[GDC_UNCOMPRESSED];
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// NOTE: This is DWORD aligned (GDC_MAXREP is a multiple of 4
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// and the extra 2 WORDS == 1 DWORD
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short Next[2 + GDC_MAXREP];
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// NOTE: GDC_UNCOMPRESED is a multiple of 4
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WORD SortArray[GDC_UNCOMPRESSED];
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// NOTE: This is DWORD aligned since GDC_HASH_SIZE is a multiple of 4
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WORD HashArray[GDC_HASH_SIZE];
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} GDC_IMPLODE, * PGDC_IMPLODE;
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//
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// GDC_EXPLODE
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// Workspace for uncompressing our data. We have vastly simplified and
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// shrunk this structure as per the comments for GDC_IMPLODE.
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//
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typedef struct tagGDC_EXPLODE
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{
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//
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// Source info
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//
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LPBYTE pSrc; // Current Src ptr (advances as we read)
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UINT cbSrc; // Amount of Src left (shrinks as we read)
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UINT SrcByte; // Look ahead byte in source
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UINT SrcBits; // Remainded src bits
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//
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// NO DEST INFO--we copy maybe dictionary into RawData at the beginning.
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// Then at the end we maybe copy RawData back into the dictionary.
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//
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//
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// Compression info
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//
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UINT ExtDistBits;
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UINT ExtDistMask;
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UINT cbDictUsed;
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UINT Distance;
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UINT iRawData; // Current index into RawData
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BYTE RawData[GDC_UNCOMPRESSED];
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} GDC_EXPLODE, *PGDC_EXPLODE;
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#define GDC_WORKBUF_SIZE max(sizeof(GDC_IMPLODE), sizeof(GDC_EXPLODE))
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//
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// EXTERNAL FUNCTIONS
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//
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//
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// API FUNCTION: GDC_Init()
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//
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// DESCRIPTION:
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//
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// Initialises the General Data Compressor.
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// Must be called before any other GDC functions.
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//
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// PARAMETERS:
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//
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//
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//
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void GDC_Init(void);
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//
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// FUNCTION: GDC_Compress(..)
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//
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// DESCRIPTION:
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//
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// Compresses source data into a destination buffer.
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//
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//
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// PARAMETERS:
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//
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// pDictionary - NULL if old PKZIP, valid ptr if persistent
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//
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// Options - specifies whether speed of compression or
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// size of the compressed data is the most important factor. This
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// basically affects the amount of previous data saved for looking
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// backwards. MAXSPEED means smaller dictionary. MAXCOMPRESSION
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// means a bigger one. The dictionary size is basically the amount
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// of overlap in the source data used when calculating the hash
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// index.
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//
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// GDCCO_MAXSPEED - compress the data as quickly as possible, at
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// the expense of increased compressed data size
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//
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// GDCCO_MAXCOMPRESSION - compress the data as much as possible, at the
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// expense of increased compression time.
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// With a persistent dictionary, only GDCCO_MAXCOMPRESSION is meaningful.
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//
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// pSrc - pointer to the source (uncompressed) data.
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//
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// cbSrcSize - the number of bytes of source.
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//
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// pDst - pointer to the destination, where the
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// compressed result will go.
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//
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// pcbDstSize - pointer to the maximum amount the destina-
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// tion can hold. If the compressed result ends
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// up being bigger than this amount, we bail
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// out and don't compress the source at all.
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// Otherwise the resulting size is written back.
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//
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// RETURNS:
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//
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// TRUE if success, FALSE if failure.
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//
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//
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BOOL GDC_Compress
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(
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PGDC_DICTIONARY pDictionary,
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UINT Options,
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LPBYTE pWorkBuf,
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LPBYTE pSrc,
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UINT cbSrcSize,
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LPBYTE pDst,
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UINT * pcbDstSize
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);
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//
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// API FUNCTION: GDC_Decompress(..)
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//
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// DESCRIPTION:
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//
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// Decompresses source data into a destination buffer.
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//
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//
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// PARAMETERS:
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//
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// pDictionary - NULL if old PKZIP, ptr to saved data if
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// persistent.
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//
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// pSrc - pointer to the source (compressed) data.
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//
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// cbSrcSize - the number of bytes of source.
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//
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// pDst - pointer to the destination, where the
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// uncompressed result will go.
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//
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// pcbDstSize - pointer to the maximum amount the desina-
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// tion can hold. If the uncompressed result
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// ends up being bigger than this amount, we
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// bail out since we can't decompress it.
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// Otherwise the resulting size is written back.
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//
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// RETURNS:
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//
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// TRUE if success, FALSE if failure.
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//
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BOOL GDC_Decompress
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(
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PGDC_DICTIONARY pDictionary,
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LPBYTE pWorkBuf,
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LPBYTE pSrc,
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UINT cbSrcSize,
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LPBYTE pDst,
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UINT * pcbDstSize
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);
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//
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// INTERNAL FUNCTIONS
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//
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void GDCCalcDecode(const BYTE * pBits, const BYTE * pCodes, UINT size, LPBYTE pDecode);
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LPBYTE GDCGetWorkBuf(void);
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void GDCReleaseWorkBuf(LPBYTE);
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UINT GDCFindRep(PGDC_IMPLODE pgdcImp, LPBYTE Start);
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void GDCSortBuffer(PGDC_IMPLODE pgdcImp, LPBYTE low, LPBYTE hi);
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BOOL GDCOutputBits(PGDC_IMPLODE pgdcImp, WORD Cnt, WORD Code);
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UINT GDCDecodeLit(PGDC_EXPLODE);
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UINT GDCDecodeDist(PGDC_EXPLODE pgdcExp, UINT Len);
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BOOL GDCWasteBits(PGDC_EXPLODE pgdcExp, UINT Bits);
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#endif // _H_GDC
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