262 lines
8.1 KiB
C++
262 lines
8.1 KiB
C++
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//+-------------------------------------------------------------------------
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//
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// Microsoft Windows
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// Copyright (C) Microsoft Corporation, 1992 - 1995.
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//
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// File: StrHash.hxx
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//
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// Contents: String column compressor definitions
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//
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// Classes: CCompressedColHashString
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// CStringBuffer
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//
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// History: 03 Mar 1995 Alanw Created
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//
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//--------------------------------------------------------------------------
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#pragma once
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#include <tblalloc.hxx>
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#include "colcompr.hxx"
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const DWORD stridInvalid = 0xffffffff;
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//+-------------------------------------------------------------------------
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//
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// Class: CStringBuffer
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//
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// Purpose: A smart string buffer used for the GetData methods
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// of CCompressedColHashString and CCompressedColPath.
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//
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// Interface:
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//
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// Notes:
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//
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// History: 03 Mar 1995 Alanw Created
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//
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//--------------------------------------------------------------------------
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class CStringBuffer
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{
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public:
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CStringBuffer() :
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_cchPathBuffer(0),
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_pwchPathBuffer(0),
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_fPathBufferInUse(FALSE) {
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}
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~CStringBuffer() {
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delete [] _pwchPathBuffer;
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}
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BOOL InUse() { return _fPathBufferInUse; }
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PWSTR Alloc( unsigned cchString );
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BOOL FreeConditionally( PWSTR pwszBuf )
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{
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if (_fPathBufferInUse && pwszBuf == _pwchPathBuffer) {
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_fPathBufferInUse = FALSE;
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return TRUE;
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}
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return FALSE;
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}
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private:
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//
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// Full path buffer used by GetData. At most one GetData can be
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// outstanding at any one time.
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//
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unsigned _cchPathBuffer; // size of _pwchPathBuffer
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PWSTR _pwchPathBuffer; // temp. buffer for path
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BOOL _fPathBufferInUse; // TRUE if _pwchPathBuffer in use
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};
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//+-------------------------------------------------------------------------
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//
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// Method: CStringBuffer::Alloc, public inline
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//
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// Synopsis: Return a pointer to a buffer large enough to
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// accomodate an the requested number of characters.
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//
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// Arguments: [cchPath] - number of characters needed, including
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// null terminator
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//
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// Returns: PWSTR - pointer to buffer
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//
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// Notes: At most one active GetData can ask for the path
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// at a time. GetData can be a performance hot spot,
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// so we don't want to do an allocation every time.
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//
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//--------------------------------------------------------------------------
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inline PWSTR CStringBuffer::Alloc( unsigned cchPath )
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{
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Win4Assert( _fPathBufferInUse == FALSE );
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if (cchPath > _cchPathBuffer)
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{
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delete [] _pwchPathBuffer;
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_pwchPathBuffer = new WCHAR[ cchPath ];
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_cchPathBuffer = cchPath;
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}
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_fPathBufferInUse = TRUE;
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return _pwchPathBuffer;
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}
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//+-------------------------------------------------------------------------
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//
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// Class: CCompressedColHashString
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//
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// Purpose: A compressed column which uses a hash table for
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// redundant value elimination. Specific to storing
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// string (VT_LPWSTR and VT_LPSTR) values.
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//
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// Interface: CCompressedCol
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//
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// Notes: To save storage space, strings are compressed to
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// ANSI strings whenever possible (only the ASCII
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// subset is tested for compression). Also, at most
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// MAX_HASHKEY distinct strings will be stored.
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//
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// Entries are only added to the table, never removed.
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// This reduces storage requirements since reference
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// counts do not need to be stored.
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//
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// History: 03 May 1994 Alanw Created
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//
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//--------------------------------------------------------------------------
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class CCompressedColHashString: public CCompressedCol
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{
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friend class CCompressedColPath; // needs access to _pAlloc, _AddData
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// and _GetStringBuffer.
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friend class CStringStore;
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struct HashEntry
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{
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HASHKEY ulHashChain; // hash chain (must be first!)
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TBL_OFF ulStringKey; // key to string value in variable data
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USHORT usSizeFmt; // size and format(ascii/wchar) of the string
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};
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public:
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CCompressedColHashString( BOOL fOptimizeAscii = TRUE ):
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CCompressedCol(
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VT_LPWSTR, // vtData,
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sizeof (HASHKEY), // cbKey,
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VarHash // ComprType
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),
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_cHashEntries( 0 ),
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_cDataItems( 0 ),
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_pAlloc( NULL ),
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_fOptimizeAscii( fOptimizeAscii ),
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_cbDataWidth( sizeof (HashEntry) ),
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_Buf1(),
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_Buf2() { }
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~CCompressedColHashString() {
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delete _pAlloc;
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}
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ULONG HashString( BYTE *pbData,
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USHORT cbData,
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VARTYPE vtType,
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BOOL fNullTerminated );
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ULONG HashWSTR( WCHAR const * pwszStr, USHORT nChar );
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ULONG HashSTR ( CHAR const * pszStr, USHORT nChar );
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void AddData(PROPVARIANT const * const pvarnt,
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ULONG * pKey,
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GetValueResult& reIndicator);
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void AddData( const WCHAR * pwszStr,
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ULONG & key,
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GetValueResult& reIndicator );
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void AddCountedWStr( const WCHAR * pwszStr,
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ULONG cwcStr,
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ULONG & key,
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GetValueResult& reIndicator );
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ULONG FindCountedWStr( const WCHAR * pwszStr,
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ULONG cwcStr );
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GetValueResult GetData( ULONG key, WCHAR * pwszStr, ULONG & cwcStr);
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GetValueResult GetData( PROPVARIANT * pvarnt,
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VARTYPE PreferredType,
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ULONG key = 0,
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PROPID prop = 0);
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const WCHAR * GetCountedWStr( ULONG key , ULONG & cwcStr );
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void FreeVariant(PROPVARIANT * pvarnt);
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ULONG MemUsed(void) {
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return _pAlloc ? _pAlloc->MemUsed() : 0;
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}
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USHORT DataLength(ULONG key);
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private:
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PWSTR _GetStringBuffer( unsigned cchPath );
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VOID _AddData( BYTE *pbData, USHORT cbDataSize,
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VARTYPE vt, ULONG* pKey,
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BOOL fNullTerminated );
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ULONG _FindData( BYTE * pbData,
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USHORT cbDataSize,
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VARTYPE vt,
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BOOL fNullTerminated );
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VOID _GrowHashTable( void );
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HashEntry* _IndexHashkey( HASHKEY iKey );
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USHORT _cHashEntries; // size of hash table
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const USHORT _cbDataWidth; // width of each data item
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ULONG _cDataItems; // number of entries in pDataItems
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CFixedVarAllocator *_pAlloc; // Data allocator
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BOOL _fOptimizeAscii;
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//
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// Name buffers used by GetData. There are two because sorted
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// insertion operations in the table can require two buffers.
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//
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CStringBuffer _Buf1;
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CStringBuffer _Buf2;
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};
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//+-------------------------------------------------------------------------
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//
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// Method: CCompressedColHashString::_IndexHashkey, private inline
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//
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// Synopsis: Index a hash key and return a pointer to the corresponding
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// data entry.
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//
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// Arguments: [iKey] - lookup key value
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//
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// Returns: HashEntry*, pointer to the indexed item
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//
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// Notes:
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//
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//--------------------------------------------------------------------------
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inline
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CCompressedColHashString::HashEntry* CCompressedColHashString::_IndexHashkey(
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HASHKEY iKey
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) {
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Win4Assert(iKey > 0 && iKey <= _cDataItems);
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return ((HashEntry*) _pAlloc->FirstRow()) + iKey - 1;
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}
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