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1455 lines
41 KiB
1455 lines
41 KiB
#include "precomp.h"
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//
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// GDC.CPP
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// General Data Compressor
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//
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// Copyright(c) Microsoft 1997-
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//
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#define MLZ_FILE_ZONE ZONE_NET
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//
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// Tables used by the compression / decompression algorithms
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//
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const BYTE s_gdcExLenBits[GDC_LEN_SIZE] =
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{
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0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8
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};
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const WORD s_gdcLenBase[GDC_LEN_SIZE] =
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{
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0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 14, 22, 38, 70, 134, 262
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};
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//
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// Dist: Bits, Coded, Decoded
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//
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const BYTE s_gdcDistBits[GDC_DIST_SIZE] =
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{
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2, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6,
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6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
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8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8
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};
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const BYTE s_gdcDistCode[GDC_DIST_SIZE] =
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{
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0x03, 0x0d, 0x05, 0x19, 0x09, 0x11, 0x01, 0x3e,
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0x1e, 0x2e, 0x0e, 0x36, 0x16, 0x26, 0x06, 0x3a,
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0x1a, 0x2a, 0x0a, 0x32, 0x12, 0x22, 0x42, 0x02,
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0x7c, 0x3c, 0x5c, 0x1c, 0x6c, 0x2c, 0x4c, 0x0c,
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0x74, 0x34, 0x54, 0x14, 0x64, 0x24, 0x44, 0x04,
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0x78, 0x38, 0x58, 0x18, 0x68, 0x28, 0x48, 0x08,
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0xf0, 0x70, 0xb0, 0x30, 0xd0, 0x50, 0x90, 0x10,
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0xe0, 0x60, 0xa0, 0x20, 0xc0, 0x40, 0x80, 0x00
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};
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//
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// Len: Bits, Coded, Decoded
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//
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const BYTE s_gdcLenBits[GDC_LEN_SIZE] =
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{
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3, 2, 3, 3, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 7, 7
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};
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const BYTE s_gdcLenCode[GDC_LEN_SIZE] =
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{
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0x05, 0x03, 0x01, 0x06, 0x0A, 0x02, 0x0C, 0x14,
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0x04, 0x18, 0x08, 0x30, 0x10, 0x20, 0x40, 0x00
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};
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//
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// GDC_Init()
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//
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// BOGUS LAURABU:
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// Having one global scratch compression buffer is lousy in multiple
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// conference situations. Maybe allocate it or use caching scheme in
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// future, then get rid of mutex.
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//
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void GDC_Init(void)
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{
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UINT i, j, k;
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DebugEntry(GDC_Init);
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//
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// Set up the binary data used for PDC compression. We 'calculate'
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// these since putting this in raw const data is too complicated!
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// The LitBits/LitCodes arrays have 774 entries each, and
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// the LenBits/DistBits arrays have 256 entries.
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//
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// Non-compressed chars take 9 bits in the compressed version: one
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// bit (zero) to indicate that what follows is not a distance/size
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// code, then the 8 bits of the char.
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//
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for (k = 0; k < GDC_DECODED_SIZE; k++)
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{
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s_gdcLitBits[k] = 9;
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s_gdcLitCode[k] = (WORD)(k << 1);
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}
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for (i = 0; i < GDC_LEN_SIZE; i++)
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{
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for (j = 0; j < (1U << s_gdcExLenBits[i]); j++, k++)
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{
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s_gdcLitBits[k] = (BYTE)(s_gdcLenBits[i] + s_gdcExLenBits[i] + 1);
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s_gdcLitCode[k] = (WORD)((j << (s_gdcLenBits[i] + 1)) |
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(s_gdcLenCode[i] << 1) | 1);
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}
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}
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GDCCalcDecode(s_gdcLenBits, s_gdcLenCode, GDC_LEN_SIZE, s_gdcLenDecode);
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GDCCalcDecode(s_gdcDistBits, s_gdcDistCode, GDC_DIST_SIZE, s_gdcDistDecode);
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DebugExitVOID(GDC_Init);
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}
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//
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// GDCCalcDecode()
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// This calculates 'const' arrays for s_gdcLenDecode and s_gdcDistDecode.
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//
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void GDCCalcDecode
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(
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const BYTE * pSrcBits,
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const BYTE * pSrcCodes,
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UINT cSrc,
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LPBYTE pDstDecodes
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)
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{
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UINT j;
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UINT Incr;
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int i;
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DebugEntry(GDC_CalcDecode);
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for (i = cSrc-1; i >= 0; i--)
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{
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Incr = 1 << pSrcBits[i];
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j = pSrcCodes[i];
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do
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{
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pDstDecodes[j] = (BYTE)i;
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j += Incr;
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}
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while (j < GDC_DECODED_SIZE);
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}
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DebugExitVOID(GDC_CalcDecode);
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}
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//
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// Optimize compilation for speed (not space)
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//
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#pragma optimize ("s", off)
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#pragma optimize ("t", on)
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//
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// GDC_Compress()
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// Compresses data based on different options.
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// This compresses data using PKZIP for both persistent and non-persistent
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// types. The differences between the algorithms are few:
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// * Persistent compression is never used for sources > 4096 bytes
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// * We copy in & update saved dictionary data before starting
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// * We copy back updated dictionary data after ending
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// * One byte of the used DistBits is used for PDC, 2 bytes for
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// plain PKZIP compression in the resulting compressed packet.
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//
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BOOL GDC_Compress
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(
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PGDC_DICTIONARY pDictionary, // NULL if not persistent
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UINT Options, // Not meaningful if 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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BOOL rc = FALSE;
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UINT Len;
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UINT cbRaw;
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UINT Passes;
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LPBYTE pCur;
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LPBYTE pMax;
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PGDC_IMPLODE pgdcImp;
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#ifdef _DEBUG
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UINT cbSrcOrg;
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#endif // _DEBUG
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DebugEntry(GDC_Compress);
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pgdcImp = (PGDC_IMPLODE)pWorkBuf;
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ASSERT(pgdcImp);
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#ifdef _DEBUG
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cbSrcOrg = cbSrcSize;
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#endif // _DEBUG
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//
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// Figure out what size dictionary to use.
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//
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if (pDictionary)
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pgdcImp->cbDictSize = GDC_DATA_MAX;
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else if (Options == GDCCO_MAXSPEED)
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{
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//
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// Use the smallest for max speed.
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//
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pgdcImp->cbDictSize = GDC_DATA_SMALL;
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}
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else
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{
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ASSERT(Options == GDCCO_MAXCOMPRESSION);
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//
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// Use the nearest dictionary size to the source size.
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//
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if (cbSrcSize <= GDC_DATA_SMALL)
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pgdcImp->cbDictSize = GDC_DATA_SMALL;
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else if (cbSrcSize <= GDC_DATA_MEDIUM)
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pgdcImp->cbDictSize = GDC_DATA_MEDIUM;
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else
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pgdcImp->cbDictSize = GDC_DATA_MAX;
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}
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//
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// How many bits of distance are needed to back the dictionary size
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// # of bytes?
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//
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switch (pgdcImp->cbDictSize)
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{
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case GDC_DATA_SMALL:
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pgdcImp->ExtDistBits = EXT_DIST_BITS_MIN;
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break;
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case GDC_DATA_MEDIUM:
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pgdcImp->ExtDistBits = EXT_DIST_BITS_MEDIUM;
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break;
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case GDC_DATA_MAX:
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pgdcImp->ExtDistBits = EXT_DIST_BITS_MAC;
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break;
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}
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pgdcImp->ExtDistMask = 0xFFFF >> (16 - pgdcImp->ExtDistBits);
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//
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// We need at least 4 bytes (2 max for ExtDistBits, 2 for EOF code).
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//
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ASSERT(*pcbDstSize > 4);
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//
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// Now save the destination info in our struct. That we we can just
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// pass a pointer to our GDC_IMPLODE routine around with everything
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// we need.
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//
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pgdcImp->pDst = pDst;
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pgdcImp->cbDst = *pcbDstSize;
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//
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// For non PDC compression, the first little-endian WORD is the ExtDistBits
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// used in decompression. For PDC compression, just the first BYTE is
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// the ExtDistBits.
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//
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if (!pDictionary)
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{
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*(pgdcImp->pDst)++ = 0;
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--(pgdcImp->cbDst);
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}
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*(pgdcImp->pDst)++ = (BYTE)pgdcImp->ExtDistBits;
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--(pgdcImp->cbDst);
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//
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// Since pDst could be huge, we don't zero it all out before using.
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// As the pointer into the destination advances, we zero out a byte
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// just before we start writing bits into it.
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//
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pgdcImp->iDstBit = 0;
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*(pgdcImp->pDst) = 0;
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//
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// Now, if we have a dictonary, restore the contents into our scratch
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// buffer.
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//
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if (pDictionary && pDictionary->cbUsed)
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{
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TRACE_OUT(("Restoring %u dictionary bytes before compression",
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pDictionary->cbUsed));
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//
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// NOTE: the data saved in pDictionary->pData is front aligned.
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// But the data in RawData is end aligned so that we can slide up
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// new data chunk by chunk when compressing. Therefore only copy
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// the part that is valid, but make it end at the back of the
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// space for the dictionary data.
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//
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ASSERT(pDictionary->cbUsed <= pgdcImp->cbDictSize);
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memcpy(pgdcImp->RawData + GDC_MAXREP + pgdcImp->cbDictSize - pDictionary->cbUsed,
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pDictionary->pData, pDictionary->cbUsed);
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pgdcImp->cbDictUsed = pDictionary->cbUsed;
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}
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else
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{
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pgdcImp->cbDictUsed = 0;
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}
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//
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// We only compress GDC_DATA_MAX bytes at a time. Therefore we have
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// this loop to grab at most that amount each time around. Since we
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// only persistently compress packets <= GDC_DATA_MAX, we should never
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// go through it more than once for that compression type. But normal
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// compression, you betcha since the max packet size is 32K.
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//
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Passes = 0;
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pCur = pgdcImp->RawData + GDC_MAXREP + pgdcImp->cbDictSize;
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do
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{
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//
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// cbRaw will either be GDC_DATA_MAX (if source has >= that to go)
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// or remainder. Copy that much uncompressed data into our
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// working RawData buffer in the 'new data' space.
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//
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ASSERT(cbSrcSize);
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cbRaw = min(cbSrcSize, GDC_DATA_MAX);
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memcpy(pgdcImp->RawData + GDC_MAXREP + pgdcImp->cbDictSize,
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pSrc, cbRaw);
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pSrc += cbRaw;
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cbSrcSize -= cbRaw;
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//
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// Now get a pointer just past the end of the data we read. Well,
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// almost. We fed in cbRaw bytes starting at GDC_MAXREP +
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// pgdcImp->cbDictSize. So unless this is the last chunk of raw
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// data to process, pMax is GDC_MAXREP before the end of the
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// new raw data.
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//
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// NOTE that in several of the functions that follow, we read
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// a byte or two past the end and the beginning of the valid new
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// raw data. THIS IS INTENTIONAL.
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//
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// Doing so is the only way to get the beginning and ending bytes
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// indexed, since the hash function uses TWO bytes. We won't
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// GPF because of padding in our RawData buffer.
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//
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pMax = pgdcImp->RawData + pgdcImp->cbDictSize + cbRaw;
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if (!cbSrcSize)
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{
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pMax += GDC_MAXREP;
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}
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else
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{
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//
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// This better NOT be persistent compression, since we don't
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// let you compress packets bigger than the chunk size we
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// process (GDC_DATA_MAX).
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//
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ASSERT(!pDictionary);
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}
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//
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// Generate the sort buffer, which orders the raw data according
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// to an index calculated using pairs of contiguous bytes that
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// occur within it. Without a dictionary yet, the first pass
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// only indexes the current chunk. With a dictionary (a second or
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// greater pass--or PERSISTENT COMPRESSION has saved enough data
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// from last time), we look back into the previous chunk (what we
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// call the dictionary).
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//
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// This takes longer since we go through more bytes, but produces
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// better results. Hence the dictionary size controls the speed/
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// resulting size.
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//
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switch (Passes)
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{
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case 0:
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{
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if (pgdcImp->cbDictUsed > GDC_MAXREP)
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{
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//
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// On the zeroth pass, cbDictUsed is always ZERO
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// for non-persistent PKZIP.
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//
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ASSERT(pDictionary);
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GDCSortBuffer(pgdcImp, pCur - pgdcImp->cbDictUsed + GDC_MAXREP,
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pMax + 1);
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}
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else
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{
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GDCSortBuffer(pgdcImp, pCur, pMax + 1);
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}
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++Passes;
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//
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// After completing a pass we slide the raw data up into
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// the dictionary slot, bumping out the older dictionary
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// data.
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//
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if (pgdcImp->cbDictSize != GDC_DATA_MAX)
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{
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ASSERT(pgdcImp->cbDictUsed == 0);
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ASSERT(!pDictionary);
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++Passes;
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}
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}
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break;
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case 1:
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{
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//
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// Start sorting GDC_MAXREP bytes after the start. NOTE
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// that this is exactly what PERSISTENT compression does
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// on the zeroth pass--it acts like we already have
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// dictionary data, using the bytes from the last time
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// we compressed something.
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//
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GDCSortBuffer(pgdcImp, pCur - pgdcImp->cbDictSize + GDC_MAXREP,
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pMax + 1);
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++Passes;
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}
|
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break;
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|
|
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default:
|
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{
|
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//
|
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// Start sort from the beginning of the dictionary.
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// This works because we copy raw data around before
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// starting the next pass.
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//
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GDCSortBuffer(pgdcImp, pCur - pgdcImp->cbDictSize, pMax + 1);
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}
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break;
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}
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|
|
|
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//
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// Now compress the raw data chunk we ar working on.
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//
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while (pCur < pMax)
|
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{
|
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Len = GDCFindRep(pgdcImp, pCur);
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SkipFindRep:
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if (!Len || (Len == GDC_MINREP && pgdcImp->Distance >= GDC_DECODED_SIZE))
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{
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if (!GDCOutputBits(pgdcImp, s_gdcLitBits[*pCur],
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s_gdcLitCode[*pCur]))
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DC_QUIT;
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|
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pCur++;
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continue;
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}
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|
|
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//
|
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// Only do this if we're on the last chunk
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//
|
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if (!cbSrcSize && (pCur + Len > pMax))
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{
|
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//
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// Peg run size so it doesn't go past end of raw data.
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//
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Len = (UINT)(pMax - pCur);
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if ((Len < GDC_MINREP) ||
|
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(Len == GDC_MINREP && pgdcImp->Distance >= GDC_DECODED_SIZE))
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{
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if (!GDCOutputBits(pgdcImp, s_gdcLitBits[*pCur],
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s_gdcLitCode[*pCur]))
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DC_QUIT;
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pCur++;
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continue;
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}
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}
|
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else if ((Len < 8) && (pCur + 1 < pMax))
|
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{
|
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UINT Save_Distance;
|
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UINT Save_Len;
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|
|
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//
|
|
// Make temp copies of Distance and Len so we can
|
|
// look ahead and see if a better compression run is
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// looming. If so, we won't bother starting it here,
|
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// we'll grab the better one next time around.
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//
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Save_Distance = pgdcImp->Distance;
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Save_Len = Len;
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|
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Len = GDCFindRep(pgdcImp, pCur + 1);
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if ((Len > Save_Len) &&
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((Len > Save_Len + 1) || (Save_Distance > (GDC_DECODED_SIZE/2))))
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{
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if (!GDCOutputBits(pgdcImp, s_gdcLitBits[*pCur],
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s_gdcLitCode[*pCur]))
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DC_QUIT;
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++pCur;
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goto SkipFindRep;
|
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}
|
|
|
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//
|
|
// Put back old Len and Distance, we'll take this one.
|
|
//
|
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Len = Save_Len;
|
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pgdcImp->Distance = Save_Distance;
|
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}
|
|
|
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if (!GDCOutputBits(pgdcImp, s_gdcLitBits[256 + Len - GDC_MINREP],
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s_gdcLitCode[256 + Len - GDC_MINREP]))
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DC_QUIT;
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|
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if (Len == GDC_MINREP)
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{
|
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//
|
|
// GDC_MINREP is 2, so we right shift Distance by 2
|
|
// (divide by 4). Then we mask out the last 2 bits
|
|
// of Distance.
|
|
//
|
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if (!GDCOutputBits(pgdcImp,
|
|
s_gdcDistBits[pgdcImp->Distance >> GDC_MINREP],
|
|
s_gdcDistCode[pgdcImp->Distance >> GDC_MINREP]))
|
|
DC_QUIT;
|
|
|
|
if (!GDCOutputBits(pgdcImp, GDC_MINREP, (WORD)(pgdcImp->Distance & 3)))
|
|
DC_QUIT;
|
|
}
|
|
else
|
|
{
|
|
if (!GDCOutputBits(pgdcImp,
|
|
s_gdcDistBits[pgdcImp->Distance >> pgdcImp->ExtDistBits],
|
|
s_gdcDistCode[pgdcImp->Distance >> pgdcImp->ExtDistBits]))
|
|
DC_QUIT;
|
|
|
|
if (!GDCOutputBits(pgdcImp, (WORD)pgdcImp->ExtDistBits,
|
|
(WORD)(pgdcImp->Distance & pgdcImp->ExtDistMask)))
|
|
DC_QUIT;
|
|
}
|
|
|
|
pCur += Len;
|
|
}
|
|
|
|
|
|
if (cbSrcSize)
|
|
{
|
|
//
|
|
// There's more data to process. Here's where we slide up the
|
|
// current raw data into the dictionary space. This is simply
|
|
// the final cbDictSize + GDC_MAXREP bytes of data. It
|
|
// begins GDC_DATA_MAX after the start of the bufer.
|
|
//
|
|
// For example, if the dict size is 1K, the current data goes
|
|
// from 1K to 5K, and we slide up the data from 4K to 5K.
|
|
//
|
|
memcpy(pgdcImp->RawData, pgdcImp->RawData + GDC_DATA_MAX,
|
|
pgdcImp->cbDictSize + GDC_MAXREP);
|
|
|
|
//
|
|
// Now move our raw data pointer back and update the
|
|
// dictonary used amount. Since we have GDC_DATA_MAX of data,
|
|
// we fill the dictionary completely.
|
|
//
|
|
pCur -= GDC_DATA_MAX;
|
|
pgdcImp->cbDictUsed = pgdcImp->cbDictSize;
|
|
}
|
|
}
|
|
while (cbSrcSize);
|
|
|
|
//
|
|
// Add the end code.
|
|
//
|
|
if (!GDCOutputBits(pgdcImp, s_gdcLitBits[EOF_CODE], s_gdcLitCode[EOF_CODE]))
|
|
DC_QUIT;
|
|
|
|
//
|
|
// Return the resulting compressed data size.
|
|
//
|
|
// NOTE that partial bits are already in the destination. But we
|
|
// need to account for any in the total size.
|
|
//
|
|
if (pgdcImp->iDstBit)
|
|
++(pgdcImp->pDst);
|
|
|
|
*pcbDstSize = (UINT)(pgdcImp->pDst - pDst);
|
|
|
|
//
|
|
// We're done. If we have a persistent dictionary, copy back our
|
|
// last block of raw data into it. We only copy as much as is actually
|
|
// valid however.
|
|
//
|
|
// We can only get here on successful compression. NOTE that we do not
|
|
// wipe out our dictionary on failure like we used to. This helps us
|
|
// by permitting better compression the next time. The receiver will
|
|
// be OK, since his receive dictionary won't be altered upon reception
|
|
// of a non-compressed packet.
|
|
//
|
|
if (pDictionary)
|
|
{
|
|
pDictionary->cbUsed = min(pgdcImp->cbDictSize, pgdcImp->cbDictUsed + cbRaw);
|
|
|
|
TRACE_OUT(("Copying back %u dictionary bytes after compression",
|
|
pDictionary->cbUsed));
|
|
|
|
memcpy(pDictionary->pData, pgdcImp->RawData + GDC_MAXREP +
|
|
pgdcImp->cbDictSize + cbRaw - pDictionary->cbUsed,
|
|
pDictionary->cbUsed);
|
|
|
|
}
|
|
|
|
TRACE_OUT(("%sCompressed %u bytes to %u",
|
|
(pDictionary ? "PDC " : ""), cbSrcOrg, *pcbDstSize));
|
|
|
|
rc = TRUE;
|
|
|
|
DC_EXIT_POINT:
|
|
if (!rc && !pgdcImp->cbDst)
|
|
{
|
|
TRACE_OUT(("GDC_Compress: compressed size is bigger than decompressed size %u.",
|
|
cbSrcOrg));
|
|
}
|
|
|
|
DebugExitBOOL(GDC_Compress, rc);
|
|
return(rc);
|
|
}
|
|
|
|
|
|
|
|
//
|
|
// GDCSortBuffer()
|
|
//
|
|
void GDCSortBuffer
|
|
(
|
|
PGDC_IMPLODE pgdcImp,
|
|
LPBYTE pStart,
|
|
LPBYTE pEnd
|
|
)
|
|
{
|
|
WORD Accum;
|
|
WORD * pHash;
|
|
LPBYTE pTmp;
|
|
|
|
DebugEntry(GDCSortBuffer);
|
|
|
|
ASSERT(pStart >= pgdcImp->RawData + pgdcImp->cbDictSize - pgdcImp->cbDictUsed);
|
|
//
|
|
// For each pair of bytes in the raw data, from pStart to pEnd,
|
|
// calculate the hash value for the pair . The hash value ranges from
|
|
// 0 to GDC_HASH_SIZE-1. Thus the HashArray structure is an array of
|
|
// GDC_HASH_SIZE WORDs. Keep a count of how many times a particular
|
|
// hash value occurs in the uncompressed data.
|
|
//
|
|
//
|
|
ZeroMemory(pgdcImp->HashArray, sizeof(pgdcImp->HashArray));
|
|
|
|
pTmp = pStart;
|
|
do
|
|
{
|
|
++(pgdcImp->HashArray[GDC_HASHFN(pTmp)]);
|
|
}
|
|
while (++pTmp < pEnd);
|
|
|
|
|
|
//
|
|
// Now go back and make each HashArray entry a cumulative total of the
|
|
// occurrences of the hash values up to and including itself. Kind
|
|
// of like the Fibonacci sequence actually.
|
|
//
|
|
Accum = 0;
|
|
pHash = pgdcImp->HashArray;
|
|
do
|
|
{
|
|
Accum += *pHash;
|
|
*pHash = Accum;
|
|
}
|
|
while (++pHash < pgdcImp->HashArray + GDC_HASH_SIZE);
|
|
|
|
|
|
//
|
|
// Find the entry in the HashArray containing the accumulated
|
|
// instance count for the current data WORD. Since these values are
|
|
// calculated from the data in the passed in range, we know that the
|
|
// value in any slot we get to by hashing some bytes in the range is
|
|
// at least 1.
|
|
//
|
|
// We start at the end and work towards the beginning so that we
|
|
// end up with the first instance of such an occurrence in the SortArray.
|
|
//
|
|
pTmp = pEnd - 1;
|
|
do
|
|
{
|
|
pHash = pgdcImp->HashArray + GDC_HASHFN(pTmp);
|
|
|
|
ASSERT(*pHash > 0);
|
|
|
|
//
|
|
// The count (*pHash) is to be used as an array index, so subtract
|
|
// one from it. If there was only one instance, put it in array
|
|
// element 0. If there is more than one instance of a particular
|
|
// hash, then next time we will start with a lower accumulated
|
|
// total. The array element will be one back, and so on.
|
|
//
|
|
--(*pHash);
|
|
|
|
//
|
|
// Store an offset from the beginning of the RawData buffer to
|
|
// each byte of data into the SortArray. This is inserted
|
|
// using the hash instance count as the index.
|
|
//
|
|
// In other words, the buffer is sorted in ascending order of hash
|
|
// for a particular piece of data. Where two bytes of data have
|
|
// the same hash, they are referenced in the SortBuffer in the
|
|
// same order as in the RawData since we are scanning backwards.
|
|
//
|
|
pgdcImp->SortArray[*pHash] = (WORD)(pTmp - pgdcImp->RawData);
|
|
}
|
|
while (--pTmp >= pStart);
|
|
|
|
|
|
//
|
|
// Now all entries in the HashArray index the first occurrence of a byte
|
|
// in the workspace which has a particular index, via the SortArray
|
|
// offset. That is, the above do-while loop decrements each HashArray
|
|
// entry until all data bytes for that entry are written to SortBuffer.
|
|
//
|
|
DebugExitVOID(GDCSortBuffer);
|
|
}
|
|
|
|
|
|
|
|
//
|
|
// GDCFindRep
|
|
//
|
|
// This looks for byte patterns in the uncompressed data that can be
|
|
// represented in the compressed data with smaller sequences. The biggest
|
|
// wins come from repeating byte sequences; later sequences can be
|
|
// compressed into a few bytes referring to an earlier sequence (how big,
|
|
// how many bytes back).
|
|
//
|
|
// This returns the length of the uncompressed data to be replaced.
|
|
//
|
|
UINT GDCFindRep
|
|
(
|
|
PGDC_IMPLODE pgdcImp,
|
|
LPBYTE pDataStart
|
|
)
|
|
{
|
|
UINT CurLen;
|
|
UINT Len;
|
|
LPBYTE pDataPat;
|
|
LPBYTE pData;
|
|
UINT iDataMin;
|
|
UINT SortIndex;
|
|
LPBYTE pDataMax;
|
|
UINT HashVal;
|
|
UINT i1;
|
|
short j1;
|
|
LPBYTE pBase;
|
|
|
|
DebugEntry(GDCFindRep);
|
|
|
|
//
|
|
// See GDCSortBuffer for a description of the contents of the
|
|
// Index array. GDC_HASHFN() returns a hash value for a byte
|
|
// using it and its successor in the uncompressed data stream.
|
|
//
|
|
|
|
HashVal = GDC_HASHFN(pDataStart);
|
|
ASSERT(HashVal < GDC_HASH_SIZE);
|
|
|
|
SortIndex = pgdcImp->HashArray[HashVal];
|
|
|
|
//
|
|
// Find the minimum sort buffer value. This is the offset of the
|
|
// first byte of data.
|
|
//
|
|
iDataMin = (UINT)(pDataStart - pgdcImp->cbDictSize + 1 - pgdcImp->RawData);
|
|
|
|
if (pgdcImp->SortArray[SortIndex] < iDataMin)
|
|
{
|
|
//
|
|
// The SortArray is referencing stale data, data that is no
|
|
// longer in the range we are processing. Move forward until
|
|
// we hit the first entry that's in the current chunk.
|
|
//
|
|
do
|
|
{
|
|
++SortIndex;
|
|
}
|
|
while (pgdcImp->SortArray[SortIndex] < iDataMin);
|
|
|
|
//
|
|
// Save this new sort value in the hash.
|
|
//
|
|
pgdcImp->HashArray[HashVal] = (WORD)SortIndex;
|
|
}
|
|
|
|
//
|
|
// Need more than 2 bytes with the same index before processing it.
|
|
//
|
|
pDataMax = pDataStart - 1;
|
|
|
|
//
|
|
// Get a Ptr to the first byte in the compression buffer referenced by
|
|
// the SortBuffer offset indexed by the SortIndex we just calculated.
|
|
// If this Ptr is not at least 2 bytes before pDataStart then return 0.
|
|
// This means that the byte pointed to by Start does not share the
|
|
// index with earlier bytes.
|
|
//
|
|
pData = pgdcImp->RawData + pgdcImp->SortArray[SortIndex];
|
|
if (pData >= pDataMax)
|
|
return 0;
|
|
|
|
//
|
|
// Now the current bytes have the same index as at least 2 other
|
|
// sequences. Ptr points to the first compress buffer byte with
|
|
// the same index as that pointed to by pDataStart.
|
|
//
|
|
pDataPat = pDataStart;
|
|
CurLen = 1;
|
|
|
|
do
|
|
{
|
|
if (*(pData + CurLen - 1) == *(pDataPat + CurLen - 1) &&
|
|
*(pData) == *(pDataPat))
|
|
{
|
|
//
|
|
// This processes a sequence of identical bytes, one starting
|
|
// at pDataPat, the other at pData.
|
|
//
|
|
++pData;
|
|
++pDataPat;
|
|
Len = 2;
|
|
|
|
// Skip past matching bytes, keeping a count.
|
|
while ((*++pData == *++pDataPat) && (++Len < GDC_MAXREP))
|
|
;
|
|
|
|
pDataPat = pDataStart;
|
|
if (Len >= CurLen)
|
|
{
|
|
pgdcImp->Distance = (UINT)(pDataPat - pData + Len - 1);
|
|
if ((CurLen = Len) > KMP_THRESHOLD)
|
|
{
|
|
if (Len == GDC_MAXREP)
|
|
{
|
|
--(pgdcImp->Distance);
|
|
return Len;
|
|
}
|
|
goto DoKMP;
|
|
}
|
|
}
|
|
}
|
|
|
|
//
|
|
// Get a pointer to the next compress buffer byte having the same
|
|
// hash. If this byte comes before pDataMax, go back around the
|
|
// loop and look for a matching sequence.
|
|
//
|
|
pData = pgdcImp->RawData + pgdcImp->SortArray[++SortIndex];
|
|
|
|
}
|
|
while (pData < pDataMax);
|
|
|
|
return (CurLen >= GDC_MINREP) ? CurLen : 0;
|
|
|
|
|
|
DoKMP:
|
|
if (pgdcImp->RawData + pgdcImp->SortArray[SortIndex+1] >= pDataMax)
|
|
return CurLen;
|
|
|
|
j1 = pgdcImp->Next[1] = 0;
|
|
pgdcImp->Next[0] = -1;
|
|
|
|
i1 = 1;
|
|
do
|
|
{
|
|
if ((pDataPat[i1] == pDataPat[j1]) || ((j1 = pgdcImp->Next[j1]) == -1))
|
|
pgdcImp->Next[++i1] = ++j1;
|
|
}
|
|
while (i1 < CurLen);
|
|
|
|
Len = CurLen;
|
|
pData = pgdcImp->RawData + pgdcImp->SortArray[SortIndex] + CurLen;
|
|
|
|
while (TRUE)
|
|
{
|
|
if ((Len = pgdcImp->Next[Len]) == -1)
|
|
Len = 0;
|
|
|
|
do
|
|
{
|
|
pBase = pgdcImp->RawData + pgdcImp->SortArray[++SortIndex];
|
|
if (pBase >= pDataMax)
|
|
return CurLen;
|
|
}
|
|
while (pBase + Len < pData);
|
|
|
|
if (*(pBase + CurLen - 2) != *(pDataPat + CurLen - 2))
|
|
{
|
|
do
|
|
{
|
|
pBase = pgdcImp->RawData + pgdcImp->SortArray[++SortIndex];
|
|
if (pBase >= pDataMax)
|
|
return CurLen;
|
|
}
|
|
while ((*(pBase + CurLen - 2) != *(pDataPat + CurLen - 2)) ||
|
|
(*(pBase) != *(pDataPat)));
|
|
|
|
Len = 2;
|
|
pData = pBase + Len;
|
|
}
|
|
else if (pBase + Len != pData)
|
|
{
|
|
Len = 0;
|
|
pData = pBase;
|
|
}
|
|
|
|
while ((*pData == pDataPat[Len]) && (++Len < GDC_MAXREP))
|
|
pData++;
|
|
|
|
if (Len >= CurLen)
|
|
{
|
|
ASSERT(pBase < pDataStart);
|
|
pgdcImp->Distance = (UINT)(pDataStart - pBase - 1);
|
|
|
|
if (Len > CurLen)
|
|
{
|
|
if (Len == GDC_MAXREP)
|
|
return Len;
|
|
|
|
CurLen = Len;
|
|
|
|
do
|
|
{
|
|
if ((pDataPat[i1] == pDataPat[j1]) ||
|
|
((j1 = pgdcImp->Next[j1]) == -1))
|
|
pgdcImp->Next[++i1] = ++j1;
|
|
}
|
|
while (i1 < CurLen);
|
|
}
|
|
}
|
|
}
|
|
|
|
DebugExitVOID(GDCFindRep);
|
|
}
|
|
|
|
|
|
//
|
|
// GDCOutputBits()
|
|
//
|
|
// This writes compressed output into our output buffer. If the total
|
|
// goes past the max compressed chunk we have workspace for, we flush
|
|
// our buffer into the apps'destination.
|
|
//
|
|
// It returns FALSE on failure, i.e. we would go past the end of the
|
|
// destination.
|
|
//
|
|
BOOL GDCOutputBits
|
|
(
|
|
PGDC_IMPLODE pgdcImp,
|
|
WORD Cnt,
|
|
WORD Code
|
|
)
|
|
{
|
|
UINT iDstBit;
|
|
BOOL rc = FALSE;
|
|
|
|
DebugEntry(GDCOutputBits);
|
|
|
|
//
|
|
// If we are writing more than a byte's worth of bits, call ourself
|
|
// recursively to write just 8. NOTE THAT WE NEVER OUTPUT MORE THAN
|
|
// A WORD'S WORTH, since Code is a WORD sized object.
|
|
//
|
|
if (Cnt > 8)
|
|
{
|
|
if (!GDCOutputBits(pgdcImp, 8, Code))
|
|
DC_QUIT;
|
|
|
|
Cnt -= 8;
|
|
Code >>= 8;
|
|
}
|
|
|
|
ASSERT(pgdcImp->cbDst > 0);
|
|
|
|
//
|
|
// OR on the bits of the Code (Cnt of them). Then advance our
|
|
// current bit pointer and current byte pointer in the output buffer.
|
|
//
|
|
iDstBit = pgdcImp->iDstBit;
|
|
ASSERT(iDstBit < 8);
|
|
|
|
//
|
|
// NOTE: This is why it is extremely important to have zeroed out
|
|
// the current destination byte when we advance. We OR on bit
|
|
// sequences to the current byte.
|
|
//
|
|
*(pgdcImp->pDst) |= (BYTE)(Code << iDstBit);
|
|
pgdcImp->iDstBit += Cnt;
|
|
|
|
if (pgdcImp->iDstBit >= 8)
|
|
{
|
|
//
|
|
// We've gone past a byte. Advance the destination ptr to the next
|
|
// one.
|
|
//
|
|
++(pgdcImp->pDst);
|
|
if (--(pgdcImp->cbDst) == 0)
|
|
{
|
|
//
|
|
// We just filled the last byte and are trying to move past
|
|
// the end of the destination. Bail out now
|
|
//
|
|
DC_QUIT;
|
|
}
|
|
|
|
//
|
|
// Phew, we have room left. Carry over the slop bits.
|
|
//
|
|
if (pgdcImp->iDstBit > 8)
|
|
{
|
|
//
|
|
// Carry over slop.
|
|
//
|
|
*(pgdcImp->pDst) = (BYTE)(Code >> (8 - iDstBit));
|
|
}
|
|
else
|
|
*(pgdcImp->pDst) = 0;
|
|
|
|
// Now the new byte is fullly initialized.
|
|
|
|
pgdcImp->iDstBit &= 7;
|
|
}
|
|
|
|
rc= TRUE;
|
|
|
|
DC_EXIT_POINT:
|
|
DebugExitBOOL(GDCOutputBits, rc);
|
|
return(rc);
|
|
}
|
|
|
|
|
|
|
|
|
|
//
|
|
// GDC_Decompress()
|
|
//
|
|
BOOL GDC_Decompress
|
|
(
|
|
PGDC_DICTIONARY pDictionary,
|
|
LPBYTE pWorkBuf,
|
|
LPBYTE pSrc,
|
|
UINT cbSrcSize,
|
|
LPBYTE pDst,
|
|
UINT * pcbDstSize
|
|
)
|
|
{
|
|
BOOL rc = FALSE;
|
|
UINT Len;
|
|
UINT Dist;
|
|
UINT i;
|
|
UINT cbDstSize;
|
|
LPBYTE pDstOrg;
|
|
LPBYTE pEarlier;
|
|
LPBYTE pNow;
|
|
PGDC_EXPLODE pgdcExp;
|
|
#ifdef _DEBUG
|
|
UINT cbSrcOrg;
|
|
#endif // _DEBUG
|
|
|
|
DebugEntry(GDC_Decompress);
|
|
|
|
pgdcExp = (PGDC_EXPLODE)pWorkBuf;
|
|
ASSERT(pgdcExp);
|
|
|
|
#ifdef _DEBUG
|
|
cbSrcOrg = cbSrcSize;
|
|
#endif // _DEBUG
|
|
|
|
//
|
|
// This shouldn't be possible--but since this compressed data
|
|
// comes from another machine, we want to make sure _we_ don't blow
|
|
// up if that machine flaked out.
|
|
//
|
|
if (cbSrcSize <= 4)
|
|
{
|
|
ERROR_OUT(("GDC_Decompress: bogus compressed data"));
|
|
DC_QUIT;
|
|
}
|
|
|
|
//
|
|
// Get the distance bits and calculate the mask needed for that many.
|
|
//
|
|
// NOTE: For PDC compression, the ExtDistBits are just in the first
|
|
// byte. For plain compression, the ExtDistBits are in the first
|
|
// little-endian word. Either way, we only allow from 4 to 6, so
|
|
// the high byte in the non-PDC case is not useful.
|
|
//
|
|
if (!pDictionary)
|
|
{
|
|
// First byte better be zero
|
|
if (*pSrc != 0)
|
|
{
|
|
ERROR_OUT(("GDC_Decompress: unrecognized distance bits"));
|
|
DC_QUIT;
|
|
}
|
|
|
|
++pSrc;
|
|
--cbSrcSize;
|
|
}
|
|
|
|
pgdcExp->ExtDistBits = *pSrc;
|
|
if ((pgdcExp->ExtDistBits < EXT_DIST_BITS_MIN) ||
|
|
(pgdcExp->ExtDistBits > EXT_DIST_BITS_MAC))
|
|
{
|
|
ERROR_OUT(("GDC_Decompress: unrecognized distance bits"));
|
|
DC_QUIT;
|
|
}
|
|
pgdcExp->ExtDistMask = 0xFFFF >> (16 - pgdcExp->ExtDistBits);
|
|
|
|
|
|
//
|
|
// Set up source data info (compressed goop). SrcByte is the current
|
|
// byte & bits we're reading from. pSrc is the pointer to the next
|
|
// byte.
|
|
//
|
|
pgdcExp->SrcByte = *(pSrc+1);
|
|
pgdcExp->SrcBits = 0;
|
|
pgdcExp->pSrc = pSrc + 2;
|
|
pgdcExp->cbSrc = cbSrcSize - 2;
|
|
|
|
//
|
|
// Save the beginning of the result buffer so we can calculate how
|
|
// many bytes we wrote into it afterwards.
|
|
//
|
|
pDstOrg = pDst;
|
|
cbDstSize = *pcbDstSize;
|
|
|
|
//
|
|
// If we have a dictionary, put its data into our work area--the
|
|
// compression might be referencing byte sequences in it (that's the
|
|
// whole point, you get better compression that way when you send
|
|
// packets with the same info over and over).
|
|
//
|
|
// We remember and update cbDictUsed to do the minimal dictionary
|
|
// byte copying back and forth.
|
|
//
|
|
if (pDictionary && pDictionary->cbUsed)
|
|
{
|
|
TRACE_OUT(("Restoring %u dictionary bytes before decompression",
|
|
pDictionary->cbUsed));
|
|
|
|
memcpy(pgdcExp->RawData + GDC_DATA_MAX - pDictionary->cbUsed,
|
|
pDictionary->pData, pDictionary->cbUsed);
|
|
pgdcExp->cbDictUsed = pDictionary->cbUsed;
|
|
}
|
|
else
|
|
{
|
|
pgdcExp->cbDictUsed = 0;
|
|
}
|
|
|
|
//
|
|
// The decompressed data starts filling in at GDC_DATA_MAX bytes into
|
|
// the RawData array. We have to double buffer the output (just
|
|
// like we double buffer the input during compression) because
|
|
// decompressing may require reaching backwards into the decompressed
|
|
// byte stream to pull out sequences.
|
|
//
|
|
pgdcExp->iRawData = GDC_DATA_MAX;
|
|
|
|
while ((Len = GDCDecodeLit(pgdcExp)) < EOF_CODE)
|
|
{
|
|
if (Len < 256)
|
|
{
|
|
pgdcExp->RawData[pgdcExp->iRawData++] = (BYTE)Len;
|
|
}
|
|
else
|
|
{
|
|
Len -= (256 - GDC_MINREP);
|
|
Dist = GDCDecodeDist(pgdcExp, Len);
|
|
if (!Dist)
|
|
DC_QUIT;
|
|
|
|
//
|
|
// Now we're reaching back, this may in fact spill into the
|
|
// dictionary data that preceded us.
|
|
//
|
|
pNow = pgdcExp->RawData + pgdcExp->iRawData;
|
|
pEarlier = pNow - Dist;
|
|
|
|
ASSERT(pEarlier >= pgdcExp->RawData + GDC_DATA_MAX - pgdcExp->cbDictUsed);
|
|
|
|
|
|
pgdcExp->iRawData += Len;
|
|
do
|
|
{
|
|
*pNow++ = *pEarlier++;
|
|
}
|
|
while (--Len > 0);
|
|
}
|
|
|
|
//
|
|
// We've gone past the end of our workspace, flush the decompressed
|
|
// data out. This is why RawData in GDC_EXPLODE has an extra pad of
|
|
// GDC_MAXREP at the end. This prevents us from spilling out of
|
|
// the RawData buffer, we will never go more than GDC_MAXREP beyond
|
|
// the last GDC_DATA_MAX chunk.
|
|
//
|
|
if (pgdcExp->iRawData >= 2*GDC_DATA_MAX)
|
|
{
|
|
//
|
|
// Do we have enough space left in the destination?
|
|
//
|
|
if (cbDstSize < GDC_DATA_MAX)
|
|
{
|
|
cbDstSize = 0;
|
|
DC_QUIT;
|
|
}
|
|
|
|
// Yup.
|
|
memcpy(pDst, pgdcExp->RawData + GDC_DATA_MAX, GDC_DATA_MAX);
|
|
|
|
pDst += GDC_DATA_MAX;
|
|
cbDstSize -= GDC_DATA_MAX;
|
|
|
|
//
|
|
// Slide decoded data up to be used for decoding the next
|
|
// chunk ofcompressed source. It's convenient that the
|
|
// dictionary size and flush size are the same.
|
|
//
|
|
pgdcExp->iRawData -= GDC_DATA_MAX;
|
|
memcpy(pgdcExp->RawData, pgdcExp->RawData + GDC_DATA_MAX,
|
|
pgdcExp->iRawData);
|
|
pgdcExp->cbDictUsed = GDC_DATA_MAX;
|
|
}
|
|
}
|
|
|
|
if (Len == ABORT_CODE)
|
|
DC_QUIT;
|
|
|
|
i = pgdcExp->iRawData - GDC_DATA_MAX;
|
|
|
|
if (i > 0)
|
|
{
|
|
//
|
|
// This is the remaining decompressed data--can we we right it
|
|
// out?
|
|
//
|
|
if (cbDstSize < i)
|
|
{
|
|
cbDstSize = 0;
|
|
DC_QUIT;
|
|
}
|
|
|
|
memcpy(pDst, pgdcExp->RawData + GDC_DATA_MAX, i);
|
|
|
|
//
|
|
// Advance pDst so that the delta between it and the original is
|
|
// the resulting uncompressed size.
|
|
//
|
|
pDst += i;
|
|
|
|
//
|
|
// And update the dictionary used size
|
|
//
|
|
pgdcExp->cbDictUsed = min(pgdcExp->cbDictUsed + i, GDC_DATA_MAX);
|
|
}
|
|
|
|
//
|
|
// If we make it to here, we've successfully decompressed the input.
|
|
// So fill in the resulting uncompressed size.
|
|
//
|
|
*pcbDstSize = (UINT)(pDst - pDstOrg);
|
|
|
|
//
|
|
// If a persistent dictionary was passed in, save the current contents
|
|
// back into the thing for next time.
|
|
//
|
|
if (pDictionary)
|
|
{
|
|
TRACE_OUT(("Copying back %u dictionary bytes after decompression",
|
|
pgdcExp->cbDictUsed));
|
|
|
|
memcpy(pDictionary->pData, pgdcExp->RawData + GDC_DATA_MAX +
|
|
i - pgdcExp->cbDictUsed, pgdcExp->cbDictUsed);
|
|
pDictionary->cbUsed = pgdcExp->cbDictUsed;
|
|
}
|
|
|
|
TRACE_OUT(("%sExploded %u bytes from %u",
|
|
(pDictionary ? "PDC " : ""), *pcbDstSize, cbSrcOrg));
|
|
|
|
rc = TRUE;
|
|
|
|
DC_EXIT_POINT:
|
|
if (!rc && !cbDstSize)
|
|
{
|
|
ERROR_OUT(("GDC_Decompress: decompressed data too big"));
|
|
}
|
|
|
|
DebugExitBOOL(GDC_Decompress, rc);
|
|
return(rc);
|
|
}
|
|
|
|
|
|
|
|
|
|
//
|
|
// GDCDecodeLit()
|
|
//
|
|
UINT GDCDecodeLit
|
|
(
|
|
PGDC_EXPLODE pgdcExp
|
|
)
|
|
{
|
|
UINT LitChar, i;
|
|
|
|
if (pgdcExp->SrcByte & 0x01)
|
|
{
|
|
// Length found
|
|
if (!GDCWasteBits(pgdcExp, 1))
|
|
return ABORT_CODE;
|
|
|
|
LitChar = s_gdcLenDecode[pgdcExp->SrcByte & 0xFF];
|
|
|
|
if (!GDCWasteBits(pgdcExp, s_gdcLenBits[LitChar]))
|
|
return ABORT_CODE;
|
|
|
|
if (s_gdcExLenBits[LitChar])
|
|
{
|
|
i = pgdcExp->SrcByte & ((1 << s_gdcExLenBits[LitChar]) - 1);
|
|
|
|
if (!GDCWasteBits(pgdcExp, s_gdcExLenBits[LitChar]))
|
|
{
|
|
// If this isn't EOF, something is wrong
|
|
if (LitChar + i != 15 + 255)
|
|
return ABORT_CODE;
|
|
}
|
|
|
|
LitChar = s_gdcLenBase[LitChar] + i;
|
|
}
|
|
|
|
LitChar += 256;
|
|
}
|
|
else
|
|
{
|
|
// Char found
|
|
if (!GDCWasteBits(pgdcExp, 1))
|
|
return ABORT_CODE;
|
|
|
|
LitChar = (pgdcExp->SrcByte & 0xFF);
|
|
|
|
if (!GDCWasteBits(pgdcExp, 8))
|
|
return ABORT_CODE;
|
|
}
|
|
|
|
return LitChar;
|
|
}
|
|
|
|
|
|
//
|
|
// GDCDecodeDist()
|
|
//
|
|
UINT GDCDecodeDist
|
|
(
|
|
PGDC_EXPLODE pgdcExp,
|
|
UINT Len
|
|
)
|
|
{
|
|
UINT Dist;
|
|
|
|
Dist = s_gdcDistDecode[pgdcExp->SrcByte & 0xFF];
|
|
|
|
if (!GDCWasteBits(pgdcExp, s_gdcDistBits[Dist]))
|
|
return 0;
|
|
|
|
if (Len == GDC_MINREP)
|
|
{
|
|
// GDC_MINREP is 2, hence we shift over by 2 then mask the low 2 bits
|
|
Dist <<= GDC_MINREP;
|
|
Dist |= (pgdcExp->SrcByte & 3);
|
|
if (!GDCWasteBits(pgdcExp, GDC_MINREP))
|
|
return 0;
|
|
}
|
|
else
|
|
{
|
|
Dist <<= pgdcExp->ExtDistBits;
|
|
Dist |=( pgdcExp->SrcByte & pgdcExp->ExtDistMask);
|
|
if (!GDCWasteBits(pgdcExp, pgdcExp->ExtDistBits))
|
|
return 0;
|
|
}
|
|
|
|
return Dist+1;
|
|
}
|
|
|
|
|
|
//
|
|
// GDCWasteBits()
|
|
//
|
|
BOOL GDCWasteBits
|
|
(
|
|
PGDC_EXPLODE pgdcExp,
|
|
UINT cBits
|
|
)
|
|
{
|
|
if (cBits <= pgdcExp->SrcBits)
|
|
{
|
|
pgdcExp->SrcByte >>= cBits;
|
|
pgdcExp->SrcBits -= cBits;
|
|
}
|
|
else
|
|
{
|
|
pgdcExp->SrcByte >>= pgdcExp->SrcBits;
|
|
|
|
//
|
|
// We need to advance to the next source byte. Can we, or have
|
|
// we reached the end already?
|
|
//
|
|
if (!pgdcExp->cbSrc)
|
|
return(FALSE);
|
|
|
|
pgdcExp->SrcByte |= (*pgdcExp->pSrc) << 8;
|
|
|
|
//
|
|
// Move these to the next byte in the compressed source
|
|
//
|
|
++(pgdcExp->pSrc);
|
|
--(pgdcExp->cbSrc);
|
|
|
|
pgdcExp->SrcByte >>= (cBits - pgdcExp->SrcBits);
|
|
pgdcExp->SrcBits = 8 - (cBits - pgdcExp->SrcBits);
|
|
}
|
|
|
|
return(TRUE);
|
|
}
|
|
|
|
|
|
|