146 lines
4.1 KiB
C++
146 lines
4.1 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 - 1994
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//
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// File: KeyHash.cxx
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//
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// Contents: Key hash
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//
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// History: 17-Feb-1994 KyleP Created
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// 29-May-1994 DwightKr Changed hash table to store bit
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// offset of first key on page, rather
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// than just the page number.
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//
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//--------------------------------------------------------------------------
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#include <pch.cxx>
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#pragma hdrstop
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#include "keyhash.hxx"
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//+-------------------------------------------------------------------------
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//
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// Method: CKeyHash::CKeyHash
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//
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// Synopsis: Construct keyhash
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//
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// Arguments: [cDirEntry] -- Number of leaf directory nodes
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//
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// History: 17-Feb-1994 KyleP Created
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//
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//--------------------------------------------------------------------------
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CKeyHash::CKeyHash( unsigned cDirEntry )
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: _cBitsPerEntry( Size(cDirEntry) )
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{
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}
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//+-------------------------------------------------------------------------
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//
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// Method: CRKeyHash::CRKeyHash
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//
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// Synopsis: Construct keyhash
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//
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// Arguments: [physHash] -- On disk stream
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// [cDirEntry] -- Number of leaf directory nodes
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//
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// History: 17-Feb-1994 KyleP Created
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//
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//--------------------------------------------------------------------------
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CRKeyHash::CRKeyHash( CPhysHash & physHash, unsigned cDirEntry )
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: CKeyHash(cDirEntry),
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_bitstm( physHash )
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{
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}
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//+-------------------------------------------------------------------------
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//
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// Method: CRKeyHash::Find
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//
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// Synopsis: Lookup value for key in hash
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//
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// Arguments: [kid] -- Key id
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//
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// Returns: Bitoffset for [kid]
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//
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// History: 17-Feb-1994 KyleP Created
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//
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//--------------------------------------------------------------------------
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void CRKeyHash::Find( KEYID kid, BitOffset & resultOffset )
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{
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BitOffset off = KidToOff(kid);
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_bitstm.Seek( off );
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ULONG ulResult = _bitstm.GetBits( BitsPerEntry() );
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resultOffset.Init( ulResult >> BITS_IN_CI_PAGE_SIZE,
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ulResult & CI_PAGE_MASK);
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ciDebugOut(( DEB_KEYLIST, "KeyHash: kid %u --> page,off 0x%x,0x%x\n",
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kid, resultOffset.Page(), resultOffset.Offset() ));
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}
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//+-------------------------------------------------------------------------
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//
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// Method: CWKeyHash::CWKeyHash
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//
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// Synopsis: Construct keyhash
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//
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// Arguments: [physHash] -- On disk stream
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// [cDirEntry] -- Number of leaf directory nodes
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// [kidMax] -- Number of keys to be stored
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//
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// History: 17-Feb-1994 KyleP Created
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//
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//--------------------------------------------------------------------------
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CWKeyHash::CWKeyHash( CPhysHash & physHash, unsigned cDirEntry, KEYID kidMax )
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: CKeyHash(cDirEntry),
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_bitstm( physHash )
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{
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//
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// Zero all pages by touching them.
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//
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BitOffset off = KidToOff(kidMax+1);
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ciDebugOut(( DEB_KEYLIST, "KeyHash: Zeroing %d pages\n", off.Page() ));
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for ( ULONG i = 0; i <= off.Page(); i++ )
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{
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physHash.BorrowNewBuffer( i );
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physHash.ReturnBuffer( i );
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}
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}
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//+-------------------------------------------------------------------------
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//
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// Method: CWKeyHash::Add
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//
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// Synopsis: Add mapping for new key
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//
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// Arguments: [kid] -- Key id
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// [bitOff] -- Directory entry corresponding to [kid]
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//
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// History: 17-Feb-1994 KyleP Created
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//
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//--------------------------------------------------------------------------
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void CWKeyHash::Add( KEYID kid, BitOffset & bitOff )
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{
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BitOffset off = KidToOff(kid);
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_bitstm.Seek( off );
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Win4Assert(bitOff.Page() < 0x100000); // Fits into a 20-bit number
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ULONG ulDirEntry = (bitOff.Page() << BITS_IN_CI_PAGE_SIZE ) | bitOff.Offset();
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_bitstm.OverwriteBits( ulDirEntry, BitsPerEntry() );
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ciDebugOut(( DEB_KEYLIST, "KeyHash: WRITE kid %u = page,offset 0x%x,0x%x\n",
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kid, bitOff.Page(), bitOff.Offset() ));
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}
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