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207 lines
4.7 KiB
207 lines
4.7 KiB
//+---------------------------------------------------------------------------
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//
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// Microsoft Windows
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// Copyright (C) Microsoft Corporation, 1995 - 1998
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//
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// File: PCache.hxx
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//
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// Contents: Protocol for HROW cache
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//
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// Classes: PMiniRowCache
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//
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// History: 05-Jun-95 KyleP Created
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//
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//----------------------------------------------------------------------------
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#pragma once
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//+---------------------------------------------------------------------------
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//
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// Class: PMiniRowCache
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//
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// Purpose: Protocol for HROW cache
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//
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// History: 05-Jun-95 KyleP Created.
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//
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// Notes: PMiniRowCache is responsible for caching behaviour.
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// Derived classes control movement within the rowset.
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// Unlike IRowset*, there is a notion of 'current position'
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// in PMiniRowCache.
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//
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// In addition to caching HROWs, a single binding can be
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// cached for the top row. This is used to assist in
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// sorting.
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//
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//----------------------------------------------------------------------------
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class PMiniRowCache
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{
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public:
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PMiniRowCache( int Index,
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IRowset * pRowset,
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unsigned cBindings,
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DBBINDING * pBindings,
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unsigned cbMaxLen );
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virtual ~PMiniRowCache();
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//
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// Iteration
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//
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enum ENext
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{
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Ok,
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NotNow,
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EndOfRows
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};
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virtual ENext Next( int iDir = 1 ) = 0;
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inline BOOL IsAtEnd() const;
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virtual void FlushCache();
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//
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// Member data access
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//
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inline HROW GetHROW();
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inline int Index() const;
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inline BYTE * GetData() const;
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inline ULONG DataLength() const;
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//
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// Cache control
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//
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inline ULONG CacheSize() const;
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void SetCacheSize( DBCOUNTITEM cNewRows );
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protected:
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void LoadData();
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//
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// Bookeeping.
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//
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int const _Index;
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IRowset * _pRowset;
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HACCESSOR _hacc;
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//
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// Cached rows
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//
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XArray<HROW> _ahrow;
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DBCOUNTITEM _chrow;
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DBCOUNTITEM _ihrow;
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//
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// Cached data for top row.
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//
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ULONG _cbRow;
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BYTE * _pbRow;
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};
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//+---------------------------------------------------------------------------
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//
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// Member: PMiniRowCache::IsAtEnd, public
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//
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// Returns: TRUE if there are no more rows in cache.
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//
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// History: 05-Jun-95 KyleP Created.
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//
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//----------------------------------------------------------------------------
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inline BOOL PMiniRowCache::IsAtEnd() const
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{
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return( _ihrow >= _chrow );
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}
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//+---------------------------------------------------------------------------
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//
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// Member: PMiniRowCache::CacheSize, public
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//
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// Returns: Size of cache.
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//
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// History: 05-Jun-95 KyleP Created.
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//
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//----------------------------------------------------------------------------
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inline ULONG PMiniRowCache::CacheSize() const
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{
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return _ahrow.Count();
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}
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//+---------------------------------------------------------------------------
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//
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// Member: PMiniRowCache::GetHROW, public
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//
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// Returns: HROW of top row.
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//
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// History: 05-Jun-95 KyleP Created.
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//
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//----------------------------------------------------------------------------
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inline HROW PMiniRowCache::GetHROW()
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{
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Win4Assert( !IsAtEnd() );
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return _ahrow[(unsigned) _ihrow];
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}
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//+---------------------------------------------------------------------------
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//
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// Member: PMiniRowCache::Index, public
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//
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// Returns: Index of this cache (usually position in array of rowsets).
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//
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// History: 05-Jun-95 KyleP Created.
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//
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//----------------------------------------------------------------------------
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inline int PMiniRowCache::Index() const
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{
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return _Index;
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}
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//+---------------------------------------------------------------------------
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//
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// Member: PMiniRowCache::GetData, public
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//
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// Returns: Prefetched data for top row.
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//
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// History: 05-Jun-95 KyleP Created.
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//
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//----------------------------------------------------------------------------
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inline BYTE * PMiniRowCache::GetData() const
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{
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Win4Assert( !IsAtEnd() );
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return _pbRow;
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}
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//+---------------------------------------------------------------------------
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//
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// Member: PMiniRowCache::DataLength, public
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// k
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// Returns: Size of prefetched data.
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//
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// History: 05-Jun-95 KyleP Created.
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//
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//----------------------------------------------------------------------------
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inline ULONG PMiniRowCache::DataLength() const
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{
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return _cbRow;
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}
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