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1057 lines
32 KiB
1057 lines
32 KiB
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// Copyright (c) 1996-1999 Microsoft Corporation
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//+-------------------------------------------------------------------------
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//
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// Microsoft Windows
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//
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// File: log.cxx
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//
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// Contents: Implementation of Tracking (Workstation) Service log of moves.
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//
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// Classes: CLog
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//
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// Functions:
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//
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// Notes: The log is composed of a header and a linked-list of move
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// notification entries. This structure is provided by the
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// CLogFile class.
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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 "trkwks.hxx"
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//+----------------------------------------------------------------------------
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//
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// Method: Initialize
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//
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// Synopsis: Initialize a CLog object.
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//
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// Arguments: [pLogCallback] (in)
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// A PLogCallback object, which we'll call when we have new
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// data.
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// [pcTrkWksConfiguration] (in)
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// Configuration parameters for the log.
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// [pcLogFile] (in)
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// The object representing the log file.
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//
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// Returns: None
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//
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//+----------------------------------------------------------------------------
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void
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CLog::Initialize( PLogCallback *pLogCallback,
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const CTrkWksConfiguration *pcTrkWksConfiguration,
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CLogFile *pcLogFile )
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{
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LogInfo loginfo;
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// Save the inputs
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TrkAssert( NULL != pcLogFile || NULL != _pcLogFile );
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if( NULL != pcLogFile )
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_pcLogFile = pcLogFile;
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TrkAssert( NULL != pcTrkWksConfiguration || NULL != _pcTrkWksConfiguration );
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if( NULL != pcTrkWksConfiguration )
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_pcTrkWksConfiguration = pcTrkWksConfiguration;
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TrkAssert( NULL != pLogCallback || NULL != _pLogCallback );
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if( NULL != pLogCallback )
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_pLogCallback = pLogCallback;
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// Read the log info from the log header.
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_pcLogFile->ReadExtendedHeader( CLOG_LOGINFO_START, &loginfo, CLOG_LOGINFO_LENGTH );
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// If the log hadn't been shut down properly, it's been fixed by now, but
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// we can't trust the loginfo we just read from the header. We also
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// can't trust it if it doesn't make sense. So if for some reason we
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// can't trust it, we'll recalculate it (this can be slow, though).
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if( !_pcLogFile->IsShutdown() || loginfo.ilogStart == loginfo.ilogEnd )
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{
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_fDirty = TRUE;
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loginfo = QueryLogInfo();
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}
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// Save the now-good information.
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_loginfo = loginfo;
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} // CLog::Initialize()
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//+----------------------------------------------------------------------------
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//
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// Method: QueryLogInfo
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//
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// Synopsis: Read the log entries and determine the indices and sequence
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// numbers.
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//
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// Arguments: None
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//
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// Returns: A LogInfo structure
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//
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//+----------------------------------------------------------------------------
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LogInfo
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CLog::QueryLogInfo()
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{
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SequenceNumber seqMin, seqMax;
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ULONG cEntries;
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LogIndex ilogMin, ilogMax, ilogEntry;
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LogInfo loginfo;
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LogMoveNotification lmn;
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BOOL fLogEmpty = TRUE;
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LogEntryHeader entryheader;
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TrkLog(( TRKDBG_LOG, TEXT("Reading log to determine correct indices") ));
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// ------------
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// Scan the log
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// ------------
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seqMin = 0;
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seqMax = 0;
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cEntries = _pcLogFile->NumEntriesInFile();
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ilogMin = 0;
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ilogMax = cEntries - 1;
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// Scan the log and look at the sequence numbers to find
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// the start and end indices.
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for( ilogEntry = 0; ilogEntry < cEntries; ilogEntry++ )
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{
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_pcLogFile->ReadMoveNotification( ilogEntry, &lmn );
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if( LE_TYPE_MOVE == lmn.type )
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{
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SequenceNumber seq = lmn.seq;
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// If this is the first move notification that we've
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// found, then it is currently both the min and the max.
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if( fLogEmpty )
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{
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fLogEmpty = FALSE;
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seqMin = seqMax = seq;
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ilogMin = ilogMax = seq;
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}
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// If this isn't the first entry we've found, then see
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// if it is a new min or max.
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else
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{
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if( seq <= seqMin )
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{
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seqMin = seq;
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ilogMin = ilogEntry;
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}
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else if( seq >= seqMax )
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{
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seqMax = seq;
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ilogMax = ilogEntry;
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}
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}
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} // if( LE_TYPE_MOVE == _pcLogFile->ReadMoveNotification( ilogEntry )->type )
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} // for( ilogEntry = 0; ilogEntry < cEntries; ilogEntry++ )
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// -------------------------------
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// Determine the log indices, etc.
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// -------------------------------
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// Were there any entries in the log?
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if( fLogEmpty )
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{
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// No, the log is empty.
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loginfo.ilogStart = loginfo.ilogWrite = 0;
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loginfo.ilogLast = loginfo.ilogEnd = cEntries - 1;
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}
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else
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{
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// Yes, the log is non-empty.
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// Point the start index to the oldest move in the log.
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loginfo.ilogStart = ilogMin;
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// Point the last index to the oldest move in the log,
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// and point the write index to the entry after that
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// (which is the first available entry).
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loginfo.ilogLast = loginfo.ilogWrite = ilogMax;
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_pcLogFile->AdjustLogIndex( &loginfo.ilogWrite, 1 );
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// The write & start indices should only be the same
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// in an empty log. We know we're not empty at this point,
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// so if they're the same, then the start index must have
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// actually advanced (otherwise, the write index wouldn't be
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// allowed to be here). So we advance the start index.
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if( loginfo.ilogWrite == loginfo.ilogStart )
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{
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_pcLogFile->AdjustLogIndex( &loginfo.ilogStart, 1 );
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}
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} // if( fLogEmpty ) ... else
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// The end if the log is just before the start in the circular list.
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loginfo.ilogEnd = loginfo.ilogStart;
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_pcLogFile->AdjustLogIndex( &loginfo.ilogEnd, -1 );
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// The read index and next available
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// sequence number are stored in the last entry header.
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entryheader = _pcLogFile->ReadEntryHeader( loginfo.ilogLast );
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loginfo.ilogRead = entryheader.ilogRead;
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loginfo.seqNext = entryheader.seq;
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// The sequence number of the entry last read is one below the sequence number
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// of the entry currently at the read pointer. If everything is read
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// (the read pointer is beyond the last entry) or if the entry at the
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// read pointer is invalid, then we'll assume that the last read seq
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// number is seqNext-1.
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_pcLogFile->ReadMoveNotification( loginfo.ilogRead, &lmn );
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loginfo.seqLastRead = ( loginfo.ilogWrite != loginfo.ilogRead && LE_TYPE_MOVE == lmn.type )
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? lmn.seq - 1 : loginfo.seqNext-1;
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TrkAssert( seqMax + 1 == loginfo.seqNext || 0 == loginfo.seqNext );
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TrkAssert( loginfo.seqLastRead < loginfo.seqNext );
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return( loginfo );
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} // CLog::QueryLogInfo()
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//+----------------------------------------------------------------------------
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//
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// Method: GenerateDefaultLogInfo
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//
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// Synopsis: Calculates the default _loginfo structure, based only on
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// the last index. This requires no calls to CLogFile.
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//
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// Arguments: [ilogEnd] (in)
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// The index of the last entry in the logfile.
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//
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// Returns: None
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//
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//+----------------------------------------------------------------------------
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void
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CLog::GenerateDefaultLogInfo( LogIndex ilogEnd )
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{
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SetDirty( TRUE ); // Must be called before changing _loginfo
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_loginfo.ilogStart = _loginfo.ilogWrite = _loginfo.ilogRead = 0;
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_loginfo.ilogLast = _loginfo.ilogEnd = ilogEnd;
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_loginfo.seqNext = 0;
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_loginfo.seqLastRead = _loginfo.seqNext - 1;
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}
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//+----------------------------------------------------------------------------
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//
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// Method: Flush
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//
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// Synopsis: Write the _loginfo structure to the CLogFile.
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//
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// Arguments: None
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//
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// Returns: None
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//
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//+----------------------------------------------------------------------------
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void
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CLog::Flush( )
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{
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if( _fDirty )
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_pcLogFile->WriteExtendedHeader( CLOG_LOGINFO_START, &_loginfo, CLOG_LOGINFO_LENGTH );
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SetDirty( FALSE );
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}
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//+----------------------------------------------------------------------------
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//
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// Method: ExpandLog
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//
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// Synopsis: Grow the log file, initialize the new entries, and update
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// our indices. We determine how much to grow based on
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// configuration parameters in CTrkWksConfiguration.
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//
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// Arguments: None.
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//
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// Returns: None.
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//
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//+----------------------------------------------------------------------------
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void
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CLog::ExpandLog()
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{
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TrkAssert( !_pcLogFile->IsMaxSize() );
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TrkAssert( IsFull() );
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SetDirty( TRUE ); // Must be called before changing _loginfo
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// Grow the file, initialize the new log entries, and link the new
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// entries into the existing linked list. We only need to tell
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// the CLogFile where the start of the circular linked-list is.
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_pcLogFile->Expand( _loginfo.ilogStart );
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// Update the end pointer.
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_loginfo.ilogEnd = _loginfo.ilogStart;
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_pcLogFile->AdjustLogIndex( &_loginfo.ilogEnd, -1 );
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} // CLog::Expand
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//+----------------------------------------------------------------------------
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//
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// Method: Read
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//
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// Synopsis: Read zero or more entries from the log, starting at the
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// Read index. Read until we reach the end of the data in
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// the log, or until we've read as many as the caller
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// requested.
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//
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// Note that we don't update the read index after this read,
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// the caller must call Seek to accomplish this. This was done
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// so that if the caller encountered an error after the Read,
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// the log would still be unchanged for a retry.
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//
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// Arguments: [pNotifications] (in/out)
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// Receives the move notification records.
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// [pseqFirst] (out)
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// The sequence number of the first notification returned.
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// [pcRead] (in/out)
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// (in) the number of notifications desired
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// (out) the number of notifications actually read
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// If the number read is less than the number requested,
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// the caller may assume that there are no more entries
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// to read.
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//
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// Returns: None
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//
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//+----------------------------------------------------------------------------
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void
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CLog::Read(CObjId rgobjidCurrent[],
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CDomainRelativeObjId rgdroidBirth[],
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CDomainRelativeObjId rgdroidNew[],
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SequenceNumber *pseqFirst,
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IN OUT ULONG *pcRead)
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{
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// --------------
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// Initialization
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// --------------
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LogIndex ilogEntry;
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ULONG cRead = 0;
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ULONG iRead = 0;
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SequenceNumber seqExpected = 0;
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ilogEntry = _loginfo.ilogRead;
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// ----------------
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// Read the entries
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// ----------------
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// We can NOOP if the call request no entries, or if there
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// are no entries in the log, or if all the entries have
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// been read already.
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if( *pcRead != 0 && !IsEmpty() && !IsRead() )
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{
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LogMoveNotification lmn;
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// There are entries which we can read.
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// Save the sequence number of the first entry that
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// we'll return to the caller.
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_pcLogFile->ReadMoveNotification( ilogEntry, &lmn );
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*pseqFirst = lmn.seq;
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seqExpected = lmn.seq;
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// Read the entries from the log in order, validating
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// the sequence numbers as we go.
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do
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{
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// Copy the move information into the caller's buffer.
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// ReadMoveNotification doesn't make the CLogFile dirty.
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_pcLogFile->ReadMoveNotification( ilogEntry, &lmn );
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TrkAssert( seqExpected == lmn.seq );
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if( seqExpected != lmn.seq )
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{
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TrkLog(( TRKDBG_ERROR, TEXT("Invalid sequence numbers reading log (%d, %d)"),
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seqExpected, lmn.seq ));
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TrkRaiseException( TRK_E_CORRUPT_LOG );
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}
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seqExpected++;
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rgobjidCurrent[iRead] = lmn.objidCurrent;
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rgdroidNew[iRead] = lmn.droidNew;
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rgdroidBirth[iRead] = lmn.droidBirth;
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cRead++;
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iRead++;
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// Move on to the next entry.
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_pcLogFile->AdjustLogIndex( &ilogEntry, 1 );
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// Continue as long as there's still room in the caller's buffer
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// and we haven't reached the last entry.
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} while ( cRead < *pcRead && ilogEntry != _loginfo.ilogWrite );
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}
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*pcRead = cRead;
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} // CLog:Read()
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//+----------------------------------------------------------------------------
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//
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// CLog::DoSearch
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//
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// This is a private worker method that searches the log, either for a
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// sequence number, or an object ID (which to use is determined by the
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// fSearchUsingSeq parameter).
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//
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// The log entry data and index are returned.
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//
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//+----------------------------------------------------------------------------
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// NOTE! *piFound is not modified if Search returns FALSE
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BOOL
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CLog::DoSearch( BOOL fSearchUsingSeq,
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SequenceNumber seqSearch, // Use this if fSearchUsingSeq
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const CObjId &objidCurrent, // Use this if !fSearchUsingSeq
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ULONG *piFound,
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CDomainRelativeObjId *pdroidNew,
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CMachineId *pmcidNew,
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CDomainRelativeObjId *pdroidBirth )
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{
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BOOL fFound = FALSE;
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BOOL fFirstPass = TRUE;
|
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SequenceNumber seqPrevious = 0;
|
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|
|
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#if DBG
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LONG l = GetTickCount();
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#endif
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// Only bother to look if there's entries in the log.
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|
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if (!IsEmpty())
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{
|
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// Determine the max entries in the log so that we can
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// detect if we're in an infinite loop.
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|
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ULONG cEntriesMax = _pcLogFile->NumEntriesInFile();
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ULONG cEntryCurrent = 0;
|
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|
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LogIndex ilogSearch = _loginfo.ilogWrite;
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|
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// Search from the end, until we find what we're looking for,
|
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// or we reach the beginning of the log.
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|
|
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// It's important that we search backwards because of tunneling.
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// Here's the scenario ... An object is moved from machine A to
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// B, quickly back to A, and then to C. Since it reappeared on A
|
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// quickly after it first disappeared, tunneling will give it the
|
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// same Object ID that it had before. So when it moves to C,
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// we end up with two entries in the log for the object. We want
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// to search backwards so that we see the move to C, not the move
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// to B.
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|
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while( !fFound && ilogSearch != _loginfo.ilogStart )
|
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{
|
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// Check to see if we're in an infinite loop.
|
|
|
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if( ++cEntryCurrent > cEntriesMax )
|
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{
|
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TrkLog((TRKDBG_ERROR, TEXT("Corrupt log file: cycle found during search")));
|
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TrkRaiseException( TRK_E_CORRUPT_LOG );
|
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}
|
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|
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// Read the previous entry.
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|
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_pcLogFile->AdjustLogIndex( &ilogSearch, -1 );
|
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LogMoveNotification lmnSearch;
|
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_pcLogFile->ReadMoveNotification( ilogSearch, &lmnSearch );
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|
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// If this isn't a move entry, then there's nothing left to search.
|
|
if( LE_TYPE_MOVE != lmnSearch.type )
|
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goto Exit;
|
|
|
|
// Or, if this isn't the first pass, ensure that the sequence numbers
|
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// are consequtive.
|
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else if( !fFirstPass )
|
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{
|
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fFirstPass = FALSE;
|
|
|
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TrkAssert( seqPrevious - 1 == lmnSearch.seq );
|
|
|
|
if( seqPrevious - 1 != lmnSearch.seq )
|
|
{
|
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TrkLog(( TRKDBG_ERROR, TEXT("Corrupt log file: non-consequtive sequence numbers (%d %d)"),
|
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seqPrevious, lmnSearch.seq ));
|
|
TrkRaiseException( TRK_E_CORRUPT_LOG );
|
|
}
|
|
|
|
}
|
|
|
|
// Is this the entry we're looking for?
|
|
|
|
if( fSearchUsingSeq && seqSearch == lmnSearch.seq
|
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||
|
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!fSearchUsingSeq && objidCurrent == lmnSearch.objidCurrent )
|
|
{
|
|
if( NULL != piFound )
|
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*piFound = ilogSearch;
|
|
|
|
if( NULL != pdroidNew )
|
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{
|
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*pdroidNew = lmnSearch.droidNew;
|
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*pmcidNew = lmnSearch.mcidNew;
|
|
*pdroidBirth = lmnSearch.droidBirth;
|
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}
|
|
|
|
fFound = TRUE;
|
|
}
|
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} // while( !fFound && ilogSearch != _loginfo.ilogStart )
|
|
} // if (!IsEmpty())
|
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|
|
|
|
Exit:
|
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|
|
return( fFound );
|
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|
|
} // CLog::DoSearch
|
|
|
|
|
|
|
|
//+----------------------------------------------------------------------------
|
|
//
|
|
// Method: Search
|
|
//
|
|
// Synopsis: Search the log for an Object ID. Once found, return that
|
|
// entry's LinkData and BirthID.
|
|
//
|
|
// Arguments: [droidCurrent] (in)
|
|
// The ObjectID for which to search.
|
|
// [pdroidNew] (out)
|
|
// The entry's LinkData
|
|
// [pdroidBirth] (out)
|
|
// The entry's Birth ID.
|
|
//
|
|
// Returns: None
|
|
//
|
|
//+----------------------------------------------------------------------------
|
|
|
|
|
|
BOOL
|
|
CLog::Search( const CObjId &objidCurrent,
|
|
CDomainRelativeObjId *pdroidNew,
|
|
CMachineId *pmcidNew,
|
|
CDomainRelativeObjId *pdroidBirth )
|
|
{
|
|
ULONG iFound;
|
|
return DoSearch( FALSE, // => Use objidCurrent
|
|
0, // Therefore, we don't need a seq number
|
|
objidCurrent,
|
|
&iFound,
|
|
pdroidNew,
|
|
pmcidNew,
|
|
pdroidBirth );
|
|
|
|
} // CLog::Search( CDomainRelativeObjId& ...
|
|
|
|
|
|
//+----------------------------------------------------------------------------
|
|
//
|
|
// Method: CLog::Search
|
|
//
|
|
// Synopsis: Search the log for the entry with a particular sequence
|
|
// number.
|
|
//
|
|
// Arguments: [seqSearch] (in)
|
|
// The sequence number for which to search.
|
|
// [piFound] (out)
|
|
// The index with this sequence number (if found).
|
|
//
|
|
// Returns: [BOOL]
|
|
// TRUE if found, FALSE otherwise.
|
|
//
|
|
//+----------------------------------------------------------------------------
|
|
|
|
BOOL
|
|
CLog::Search( SequenceNumber seqSearch, ULONG *piFound )
|
|
{
|
|
CObjId oidNull;
|
|
return DoSearch( TRUE, // => Use seqSearch
|
|
seqSearch,
|
|
oidNull, // We don't need to pass an objid
|
|
piFound,
|
|
// And we don't need out-droids & mcid.
|
|
NULL, NULL, NULL );
|
|
|
|
} // CLog::Search( SequenceNumber ...
|
|
|
|
|
|
|
|
|
|
//+----------------------------------------------------------------------------
|
|
//
|
|
// Method: Append
|
|
//
|
|
// Synopsis: Add a move notification to the log. If the log is full,
|
|
// either overwrite an old entry, or grow the log.
|
|
//
|
|
// Arguments: [droidCurrent] (in)
|
|
// The link information of the file which was moved.
|
|
// [droidNew] (in)
|
|
// The link information of the new file.
|
|
// [droidBirth] (in)
|
|
// The Birth ID of the file.
|
|
//
|
|
// Returns: None
|
|
//
|
|
//+----------------------------------------------------------------------------
|
|
|
|
// Perf optimization: Tell the caller if the log is now full. The service can then lazily
|
|
// expand it, hopefully before the next move occurs.
|
|
|
|
void
|
|
CLog::Append(const CVolumeId &volidCurrent,
|
|
const CObjId &objidCurrent,
|
|
const CDomainRelativeObjId &droidNew,
|
|
const CMachineId &mcidNew,
|
|
const CDomainRelativeObjId &droidBirth)
|
|
{
|
|
LogMoveNotification lmnWrite;
|
|
|
|
CFILETIME cftNow; // Defaults to current UTC
|
|
BOOL fAdvanceStart = FALSE;
|
|
LogEntryHeader entryheader;
|
|
LogInfo loginfoZero;
|
|
|
|
// -----------------
|
|
// Handle a Full Log
|
|
// -----------------
|
|
|
|
if( IsFull() )
|
|
{
|
|
// Is the log already maxed? If so, we wrap.
|
|
|
|
if( _pcLogFile->IsMaxSize() )
|
|
{
|
|
fAdvanceStart = TRUE;
|
|
TrkLog(( TRKDBG_VOLUME, TEXT("Wrapping log") ));
|
|
}
|
|
|
|
// Otherwise, we'll handle it by growing the log file.
|
|
|
|
else
|
|
ExpandLog();
|
|
}
|
|
|
|
// -------------------------
|
|
// Write the data to the log
|
|
// -------------------------
|
|
|
|
// Before anything else, we must mark ourselves dirty. If the logfile is
|
|
// currently in the ProperShutdown state, this SetDirty call will take it
|
|
// out of that state and do a flush.
|
|
|
|
SetDirty( TRUE );
|
|
|
|
// Mark our loginfo cache in the header as invalid,
|
|
// in case we get pre-empted.
|
|
|
|
memset( &loginfoZero, 0, sizeof(loginfoZero) );
|
|
_pcLogFile->WriteExtendedHeader( CLOG_LOGINFO_START, &loginfoZero, CLOG_LOGINFO_LENGTH );
|
|
|
|
// Collect the move-notification information
|
|
|
|
memset( &lmnWrite, 0, sizeof(lmnWrite) );
|
|
lmnWrite.seq = _loginfo.seqNext;
|
|
lmnWrite.type = LE_TYPE_MOVE;
|
|
|
|
lmnWrite.objidCurrent = objidCurrent;
|
|
lmnWrite.droidNew = droidNew;
|
|
lmnWrite.mcidNew = mcidNew;
|
|
lmnWrite.droidBirth = droidBirth;
|
|
lmnWrite.DateWritten = TrkTimeUnits( cftNow );
|
|
|
|
// Collect the entry header information
|
|
|
|
memset( &entryheader, 0, sizeof(entryheader) );
|
|
entryheader.ilogRead = _loginfo.ilogRead;
|
|
entryheader.seq = _loginfo.seqNext + 1; // Reflect that we'll increment after the write
|
|
|
|
// Write everything to the log (this will do a flush). If this fails, it will raise.
|
|
|
|
_pcLogFile->WriteMoveNotification( _loginfo.ilogWrite, lmnWrite, entryheader );
|
|
|
|
// Update the sequence number and last & write indices now that we
|
|
// know the write was successful (all the way to the disk).
|
|
|
|
_loginfo.seqNext++;
|
|
_loginfo.ilogLast = _loginfo.ilogWrite;
|
|
_pcLogFile->AdjustLogIndex( &_loginfo.ilogWrite, 1 );
|
|
|
|
// Do we need to advance the start pointer?
|
|
// We save this for the end, because it may cause us to access
|
|
// the disk.
|
|
|
|
if( fAdvanceStart )
|
|
{
|
|
// We're about to advance the start index, and thus effectively
|
|
// lose an entry. If the read index points to the same place,
|
|
// then we should advance it as well.
|
|
|
|
if( _loginfo.ilogStart == _loginfo.ilogRead )
|
|
_pcLogFile->AdjustLogIndex( &_loginfo.ilogRead, 1 );
|
|
|
|
// Advance the start/end indices.
|
|
|
|
_pcLogFile->AdjustLogIndex( &_loginfo.ilogEnd, 1 );
|
|
_pcLogFile->AdjustLogIndex( &_loginfo.ilogStart, 1 );
|
|
}
|
|
|
|
TrkLog(( TRKDBG_VOLUME, TEXT("Appended %s to log (seq=%d)"),
|
|
(const TCHAR*)CDebugString(objidCurrent), lmnWrite.seq ));
|
|
|
|
// Notify the callback object that there is data available.
|
|
// Note: This must be the last operation of this method.
|
|
|
|
_pLogCallback->OnEntriesAvailable();
|
|
|
|
}
|
|
|
|
|
|
//+----------------------------------------------------------------------------
|
|
//
|
|
// Method: Seek( SequenceNumber ...
|
|
//
|
|
// Synopsis: Moves the Read index to a the log entry with the specified
|
|
// sequence number. If the seq number doesn't exist, we back
|
|
// up to the start of the log.
|
|
//
|
|
// If this seek causes us to back up the Read index, we notify
|
|
// the PLogCallback object, since we now have data available
|
|
// to read.
|
|
//
|
|
// Arguments: [seqSeek] (in)
|
|
// The sequence number to which to seek.
|
|
//
|
|
// Returns: [BOOL]
|
|
// TRUE if the sequence number was found, FALSE otherwise.
|
|
//
|
|
//+----------------------------------------------------------------------------
|
|
|
|
BOOL
|
|
CLog::Seek( const SequenceNumber &seqSeek )
|
|
{
|
|
BOOL fFound = FALSE;
|
|
SequenceNumber seqReadOriginal, seqReadNew;
|
|
LogMoveNotification lmn;
|
|
|
|
LogIndex ilogSearch = 0;
|
|
|
|
// Are we seeking to the end of the log?
|
|
|
|
if( seqSeek == _loginfo.seqNext )
|
|
{
|
|
// We found what we're looking for.
|
|
fFound = TRUE;
|
|
|
|
// Are we already at seqNext?
|
|
if( !IsRead() )
|
|
{
|
|
// No, update the read index.
|
|
SetDirty( TRUE );
|
|
_loginfo.ilogRead = _loginfo.ilogWrite;
|
|
}
|
|
|
|
goto Exit;
|
|
}
|
|
|
|
// If the log is empty, then there's nothing we need do.
|
|
|
|
if( IsEmpty() )
|
|
goto Exit;
|
|
|
|
// Or, if the caller wishes to seek beyond the end of our log, then
|
|
// again there's nothing to do. This could be the case, for example,
|
|
// if the log has been restored.
|
|
|
|
if( seqSeek >= _loginfo.seqNext )
|
|
goto Exit;
|
|
|
|
// Keep track of the current seq number at the read pointer, so that
|
|
// we can later tell if it's necessary to notify the client that
|
|
// there is "new" data.
|
|
|
|
if( IsRead() )
|
|
{
|
|
seqReadOriginal = _loginfo.seqNext;
|
|
}
|
|
else
|
|
{
|
|
_pcLogFile->ReadMoveNotification( _loginfo.ilogRead, &lmn );
|
|
seqReadOriginal = lmn.seq;
|
|
}
|
|
|
|
// If this seq number is in the log, set the Read index
|
|
// to it. Otherwise set it to the oldest entry in the
|
|
// log (that's the best we can do).
|
|
|
|
SetDirty( TRUE ); // Must be called before changing _loginfo
|
|
|
|
if( fFound = Search( seqSeek, &ilogSearch ))
|
|
_loginfo.ilogRead = ilogSearch;
|
|
else
|
|
_loginfo.ilogRead = _loginfo.ilogStart;
|
|
|
|
// Calculate the sequence number of the entry now at the read pointer, and
|
|
// use it to cache the seq number of the last-read entry (recall that
|
|
// the read pointer points to the next entry to be read, not the
|
|
// last entry read).
|
|
|
|
if( IsRead() )
|
|
{
|
|
seqReadNew = _loginfo.seqNext;
|
|
}
|
|
else
|
|
{
|
|
_pcLogFile->ReadMoveNotification( _loginfo.ilogRead, &lmn );
|
|
seqReadNew = lmn.seq;
|
|
}
|
|
|
|
_loginfo.seqLastRead = seqReadNew - 1; // We already set _fDirty
|
|
|
|
// Update the entry headers with the new read pointer.
|
|
WriteEntryHeader();
|
|
|
|
// If we've backed up the read pointer, notify the registered callback.
|
|
|
|
if ( seqReadOriginal > seqReadNew )
|
|
{
|
|
// Note: This must be the last operation of this method.
|
|
_pLogCallback->OnEntriesAvailable();
|
|
}
|
|
|
|
// ----
|
|
// Exit
|
|
// ----
|
|
|
|
Exit:
|
|
|
|
return( fFound );
|
|
|
|
} // CLog::Seek( SequenceNumber ...
|
|
|
|
|
|
|
|
//+----------------------------------------------------------------------------
|
|
//
|
|
// Method: Seek( origin ...
|
|
//
|
|
// Synopsis: Move the read pointer relative to an origin (begin, current, end).
|
|
//
|
|
// There are two differences between a CLog seek and a file seek:
|
|
// - If you seek from the beginning (SEEK_SET), and seek beyond the
|
|
// end of the log, the pointer is wrapped, rather than growing
|
|
// the log.
|
|
// - If you seek from the current location (SEEK_CUR), and seek
|
|
// beyond the end of the log, the log is not grown, and there
|
|
// is no wrap, the index simply stops there (either at _loginfo.ilogWrite
|
|
// or _loginfo.ilogStart).
|
|
//
|
|
// Arguments: [origin]
|
|
// Must be either SEEK_SET or SEEK_CUR (there is currently no
|
|
// support for SEEK_END).
|
|
// [iSeek]
|
|
// The amount to move relative to the origin.
|
|
//
|
|
// Returns: None
|
|
//
|
|
//+----------------------------------------------------------------------------
|
|
|
|
void
|
|
CLog::Seek( int origin, int iSeek )
|
|
{
|
|
|
|
SequenceNumber seqReadOriginal = 0, seqReadNew = 0;
|
|
|
|
LogMoveNotification lmn;
|
|
|
|
// Early exit if there's nothing to do
|
|
|
|
if( IsEmpty() )
|
|
goto Exit;
|
|
|
|
// Keep track of where we are now, so that we can determine if
|
|
// we've gone overall backwards or forwards.
|
|
|
|
if( IsRead() )
|
|
{
|
|
seqReadOriginal = _loginfo.seqNext;
|
|
}
|
|
else
|
|
{
|
|
_pcLogFile->ReadMoveNotification( _loginfo.ilogRead, &lmn );
|
|
seqReadOriginal = lmn.seq;
|
|
}
|
|
|
|
// Seek based on the origin.
|
|
|
|
switch( origin )
|
|
{
|
|
case SEEK_SET:
|
|
{
|
|
// Advance from the start index.
|
|
|
|
LogIndex ilogRead = _loginfo.ilogStart;
|
|
|
|
_pcLogFile->AdjustLogIndex( &ilogRead, iSeek );
|
|
|
|
SetDirty( TRUE ); // Must be called before changing _loginfo
|
|
_loginfo.ilogRead = ilogRead;
|
|
}
|
|
break;
|
|
|
|
case SEEK_CUR:
|
|
{
|
|
// Advance or retreat from the current read index.
|
|
|
|
LogIndex ilogRead = _loginfo.ilogRead;
|
|
|
|
_pcLogFile->AdjustLogIndex( &ilogRead, iSeek, CLogFile::ADJUST_WITHIN_LIMIT,
|
|
iSeek >= 0 ? _loginfo.ilogWrite : _loginfo.ilogStart );
|
|
|
|
SetDirty( TRUE ); // Must be called before changing _loginfo
|
|
_loginfo.ilogRead = ilogRead;
|
|
}
|
|
break;
|
|
|
|
default:
|
|
|
|
TrkAssert( FALSE && TEXT("Unexpected origin in CLog::Seek") );
|
|
break;
|
|
}
|
|
|
|
// Calculate the sequence number of the entry at the read pointer, and
|
|
// use it to store the seq number of the last-read entry (recall that
|
|
// the read pointer points to the next entry to be read, not the
|
|
// last entry read).
|
|
|
|
if( IsRead() )
|
|
{
|
|
seqReadNew = _loginfo.seqNext;
|
|
}
|
|
else
|
|
{
|
|
_pcLogFile->ReadMoveNotification( _loginfo.ilogRead, &lmn );
|
|
seqReadNew = lmn.seq;
|
|
}
|
|
|
|
SetDirty( TRUE ); // Must be called before changing _loginfo
|
|
_loginfo.seqLastRead = seqReadNew - 1;
|
|
|
|
// Update the entry headers with the new read pointer.
|
|
WriteEntryHeader();
|
|
|
|
|
|
// If we've backed up the read pointer, notify the registered callback.
|
|
|
|
if ( seqReadOriginal > seqReadNew )
|
|
{
|
|
// Note: This must be the last operation of this method.
|
|
_pLogCallback->OnEntriesAvailable();
|
|
}
|
|
|
|
// ----
|
|
// Exit
|
|
// ----
|
|
|
|
Exit:
|
|
|
|
return;
|
|
|
|
} // CLog::Seek( origin ...
|
|
|
|
|
|
|
|
//+----------------------------------------------------------------------------
|
|
//
|
|
// Method: CLog::IsRead( LogIndex ) (private)
|
|
//
|
|
// Synopsis: Determine if the specified entry has been read. See also
|
|
// the IsRead(void) overload, which checks to see if the whole
|
|
// log has been read.
|
|
//
|
|
// Inputs: [ilog] (in)
|
|
// The index in the log to be checked. It is assumed
|
|
// that this index points to a valid move notification
|
|
// entry.
|
|
//
|
|
// Outputs: [BOOL]
|
|
// True if and only if the entry has been marked as read.
|
|
//
|
|
//+----------------------------------------------------------------------------
|
|
|
|
BOOL
|
|
CLog::IsRead( LogIndex ilog )
|
|
{
|
|
LogMoveNotification lmn;
|
|
|
|
// Has the whole log been read?
|
|
|
|
if( IsRead() )
|
|
return( TRUE );
|
|
|
|
// Or, has this entry been read?
|
|
|
|
_pcLogFile->ReadMoveNotification( ilog, &lmn );
|
|
|
|
if( _loginfo.seqLastRead >= lmn.seq )
|
|
return( TRUE );
|
|
|
|
// Otherwise, we know the entry hasn't been read.
|
|
|
|
else
|
|
return( FALSE );
|
|
|
|
} // CLog::IsRead( LogIndex )
|