141 lines
3.4 KiB
C++
141 lines
3.4 KiB
C++
//+---------------------------------------------------------------------------
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//
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// Microsoft Windows
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// Copyright (C) Microsoft Corporation, 1992 - 1994.
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//
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// File: shardbuf.hxx
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//
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// Contents: A shared buffer used by the bigtable code to create temporary
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// variants. Rather than allocate memory each time, this will
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// facilitate usage of a single buffer.
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//
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// Classes: CSharedBuffer and XUseSharedBuffer
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//
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// Functions:
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//
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// History: 5-22-95 srikants Created
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//
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//----------------------------------------------------------------------------
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#pragma once
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#include <tableseg.hxx>
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//+---------------------------------------------------------------------------
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//
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// Class: CSharedBuffer
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//
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// Purpose: A Shared buffer used by the table to do temporary alloocations
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// for variant creation.
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//
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// History: 5-22-95 srikants Created
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//
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// Notes:
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//
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//----------------------------------------------------------------------------
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class CSharedBuffer
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{
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friend class XUseSharedBuffer;
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public:
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CSharedBuffer() : _fInUse(FALSE) {}
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BOOL IsInUse() const { return _fInUse; }
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private:
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BOOL _fInUse;
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// this is an array of LONGLONGs to force 8-byte alignment
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LONGLONG _abBuffer[ ( TBL_MAX_DATA + sizeof PROPVARIANT ) /
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sizeof LONGLONG ];
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BYTE * _GetBuffer()
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{
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Win4Assert( 0 == ( sizeof _abBuffer & ( sizeof(LONGLONG) - 1 ) ) );
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return (BYTE *) &_abBuffer;
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}
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void _SetInUse()
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{
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Win4Assert( !_fInUse );
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_fInUse = TRUE;
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}
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void _Release()
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{
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Win4Assert( _fInUse );
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_fInUse = FALSE;
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}
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};
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//+---------------------------------------------------------------------------
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//
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// Class: XUseSharedBuffer
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//
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// Purpose: Used to access the shared buffer and make sure that there
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// are no two simultaneous users of the shared buffer.
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//
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// History: 5-22-95 srikants Created
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//
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// Notes: It is assumed that the shared buffer is being accessed under
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// a larger lock like the bigtable lock.
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//
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//----------------------------------------------------------------------------
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class XUseSharedBuffer
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{
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public:
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XUseSharedBuffer( CSharedBuffer & sharedBuf,
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BOOL fAcquire = TRUE ) : _sharedBuf(sharedBuf),
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_fAcquired(FALSE)
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{
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if ( fAcquire )
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{
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Win4Assert( !_sharedBuf.IsInUse() );
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if ( _sharedBuf.IsInUse() )
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{
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THROW( CException( STATUS_CONFLICTING_ADDRESSES ) );
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}
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_sharedBuf._SetInUse();
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_fAcquired = TRUE;
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}
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}
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~XUseSharedBuffer()
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{
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if ( _fAcquired )
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{
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_sharedBuf._Release();
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}
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}
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void LokAcquire()
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{
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Win4Assert( !_fAcquired );
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_sharedBuf._SetInUse();
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_fAcquired = TRUE;
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}
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BYTE * LokGetBuffer()
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{
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Win4Assert( _fAcquired );
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return _sharedBuf._GetBuffer();
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}
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unsigned LokGetSize() const { return sizeof(_sharedBuf._abBuffer); }
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BOOL IsAcquired() const { return _fAcquired; }
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private:
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CSharedBuffer & _sharedBuf;
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BOOL _fAcquired;
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};
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