--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/userlibandfileserver/fileserver/sfat/sl_scan.cpp Mon Oct 19 15:55:17 2009 +0100
@@ -0,0 +1,688 @@
+// Copyright (c) 1998-2009 Nokia Corporation and/or its subsidiary(-ies).
+// All rights reserved.
+// This component and the accompanying materials are made available
+// under the terms of the License "Eclipse Public License v1.0"
+// which accompanies this distribution, and is available
+// at the URL "http://www.eclipse.org/legal/epl-v10.html".
+//
+// Initial Contributors:
+// Nokia Corporation - initial contribution.
+//
+// Contributors:
+//
+// Description:
+// f32\sfat\sl_scan.cpp
+// ScanDrive code, specific for EFAT.FSY
+//
+//
+
+/**
+ @file
+ @internalTechnology
+*/
+
+
+//#define DEBUG_SCANDRIVE
+
+#include "sl_std.h"
+#include "sl_scandrv.h"
+
+const TInt KEndOfDirectory = 0xFFFF; ///< End of directory marker
+const TInt KMaxScanDepth = 20; ///< Maximum scan depth of to avoid stack over flow
+const TInt KClusterListGranularity = 8; ///< Granularity of cluster list used for storage of clusters when KMaxScanDepth is reached
+
+/**
+Creates a CScanDrive
+
+@param aMount The owning mount
+*/
+CScanDrive* CScanDrive::NewL(CFatMountCB* aMount)
+ {
+ if(aMount==NULL)
+ User::Leave(KErrArgument);
+ CScanDrive* self=new (ELeave) CScanDrive();
+ CleanupStack::PushL(self);
+ self->ConstructL(aMount);
+ CleanupStack::Pop();
+ return self;
+ }
+
+
+CScanDrive::CScanDrive()
+//
+// Constructor
+//
+ {
+ }
+
+
+CScanDrive::~CScanDrive()
+//
+// Destructor
+//
+ {
+ delete iNewFat;
+ for(TInt i=0;i<KMaxArrayDepth && iClusterListArray[i]!=NULL;++i)
+ {
+ iClusterListArray[i]->Close();
+ delete iClusterListArray[i];
+ }
+ }
+
+
+void CScanDrive::ConstructL(CFatMountCB* aMount)
+//
+// Create the new fat and initalise
+//
+ {
+ iMount=aMount;
+ iNewFat=CCheckFatTable::NewL(aMount);
+ iNewFat->InitializeL();
+ }
+
+
+TBool CScanDrive::AlreadyExistsL(TInt aCluster)const
+//
+// Return ETrue if aCluster in the new fat contains a non-zero entry
+//
+ {
+ return(iNewFat->ReadL(aCluster)!=0);
+ }
+
+
+TBool CScanDrive::IsEndOfRootDir(const TEntryPos& aPos)const
+//
+// Return ETrue if aPos is the last entry in the root directory
+//
+ {
+ return(iMount->IsRootDir(aPos)&&(iMount->StartOfRootDirInBytes()+aPos.iPos==(iMount->RootDirEnd()-KSizeOfFatDirEntry)));
+ }
+
+/**
+@param aVal Value of the cluster to be tested
+@return ETrue if aVal is the end of cluster marker
+*/
+TBool CScanDrive::IsEofF(TInt aVal)const
+ {
+ return iMount->IsEndOfClusterCh(aVal);
+ }
+
+/**
+@return True if a directory error has been found
+*/
+TBool CScanDrive::IsDirError()const
+ {
+ return(iDirError!=0);
+ }
+
+
+
+/**
+ After StartL() and finishing allows us to know if there were any problems at all.
+ The client may wish to remount the filesystem if there were errors.
+
+ @return EFalse if there were no problems in FS.
+*/
+TBool CScanDrive::ProblemsDiscovered() const
+{
+ return IsDirError() || iFoundProblems;
+}
+
+/**
+ Sets the flag indicating than there are errors in filesystem structure
+ See ProblemsDiscovered()
+*/
+void CScanDrive::IndicateErrorsFound()
+{
+ iFoundProblems = ETrue;
+}
+
+
+
+/**
+Start point for scan drive also fixes up errors
+
+@return The result of the scan
+@leave
+*/
+TInt CScanDrive::StartL()
+ {
+ __PRINT(_L("CScanDrive::StartL"));
+ // check directory structure
+ CheckDirStructureL();
+#if defined(DEBUG_SCANDRIVE)
+ CompareFatsL();
+#endif
+ // fix error in directory structure
+ if(IsDirError())
+ FixupDirErrorL();
+ // flush new fat
+ WriteNewFatsL();
+#if defined(DEBUG_SCANDRIVE)
+ PrintErrors();
+#endif
+ return KErrNone;
+ }
+
+/**
+Fix errors detected by the drive scan
+
+@leave System wide error code
+*/
+void CScanDrive::FixupDirErrorL()
+ {
+ if(!IsDirError())
+ return;
+ if(iDirError==EScanMatchingEntry)
+ {
+ FindSameStartClusterL();
+ FixMatchingEntryL();
+ }
+ else
+ {
+ FixPartEntryL();
+ }
+
+ IndicateErrorsFound(); //-- indicate that we have found errors
+ }
+
+/**
+Find positions of entries with same start cluster for error correction, searches
+the whole volume. Starts at the root directory.
+
+@leave System wide error code
+*/
+void CScanDrive::FindSameStartClusterL()
+ {
+ TInt err=FindStartClusterL(0);
+ if(err==KErrNone)
+ return;
+ for(TInt i=0;i<KMaxArrayDepth && iClusterListArray[i]!=NULL;++i)
+ {
+ RArray<TInt>* clusterList=iClusterListArray[i];
+ for(TInt j=0;j<clusterList->Count();++j)
+ {
+ iRecursiveDepth=0;
+ err=FindStartClusterL((*clusterList)[j]);
+ if(err==KErrNone)
+ return;
+ }
+ }
+ __ASSERT_ALWAYS(err==KErrNone,User::Leave(KErrNotFound));
+ }
+/**
+Scan through directory structure looking for start cluster found in iMatching
+
+@param aDirCluster Start cluster for scan to start
+@return System wide error value
+@leave
+*/
+TInt CScanDrive::FindStartClusterL(TInt aDirCluster)
+ {
+ __PRINT1(_L("CScanDrive::FindStartCluster dirCluster=%d"),aDirCluster);
+ __ASSERT_ALWAYS(aDirCluster>=0,User::Leave(KErrCorrupt));
+ if(++iRecursiveDepth==KMaxScanDepth)
+ {
+ --iRecursiveDepth;
+ return(KErrNotFound);
+ }
+ TEntryPos entryPos(aDirCluster,0);
+ TInt dirEntries=0;
+ FOREVER
+ {
+ TFatDirEntry entry;
+ iMount->ReadDirEntryL(entryPos,entry);
+ if(entry.IsParentDirectory()||entry.IsCurrentDirectory()||entry.IsErased())
+ {
+ if(IsEndOfRootDir(entryPos))
+ break;
+ iMount->MoveToNextEntryL(entryPos);
+ continue;
+ }
+ if(entry.IsEndOfDirectory())
+ break;
+ TBool isComplete;
+ TEntryPos vfatPos=entryPos;
+ isComplete=MoveToVFatEndL(entryPos,entry,dirEntries);
+ __ASSERT_ALWAYS(isComplete,User::Leave(KErrBadName));
+ TInt err=CheckEntryClusterL(entry,vfatPos);
+ if(err==KErrNone)
+ {
+ --iRecursiveDepth;
+ return(err);
+ }
+ if(IsEndOfRootDir(entryPos))
+ break;
+ iMount->MoveToNextEntryL(entryPos);
+ }
+ --iRecursiveDepth;
+ return(KErrNotFound);
+ }
+
+/**
+Procces aEntry to find matching start cluster
+
+@param aEntry Directory entry to check
+@param aEntryPos Position of directory to check
+@return System wide error value
+@leave
+*/
+TInt CScanDrive::CheckEntryClusterL(const TFatDirEntry& aEntry, const TEntryPos& aEntryPos)
+ {
+ __PRINT(_L("CScanDrive::CheckEntryClusterL"));
+ if(iMount->StartCluster(aEntry)==iMatching.iStartCluster)
+ {
+ TBool complete=AddMatchingEntryL(aEntryPos);
+ if(complete)
+ return(KErrNone);
+ }
+ else if(aEntry.Attributes()&KEntryAttDir)
+ return(FindStartClusterL(iMount->StartCluster(aEntry)));
+ return(KErrNotFound);
+ }
+
+/**
+Checks directory strucutre for errors, can be considered the start point of the scan.
+Handles recursion depth to avoid stack overflow.
+
+@leave System wide error code
+*/
+void CScanDrive::CheckDirStructureL()
+ {
+ CheckDirL(iMount->RootIndicator());
+ // Due to recursive nature of CheckDirL when a depth of
+ // KMaxScanDepth is reached clusters are stored in a list
+ // and passed into CheckDirL afresh
+ for(TInt i=0;i<KMaxArrayDepth && iClusterListArray[i]!=NULL;++i)
+ {
+ RArray<TInt>* clusterList=iClusterListArray[i];
+ ++iListArrayIndex;
+ for(TInt j=0;j<clusterList->Count();++j)
+ {
+ iRecursiveDepth=0;
+ CheckDirL((*clusterList)[j]);
+ }
+ }
+ }
+/**
+Function is called recursively with Process entry untill the whole volume has been scanned.
+Each directory entry is scanned for errors, these are recorded for later fixing.
+
+@param aCluster Directory cluster to start checking
+@leave System wide error codes
+*/
+void CScanDrive::CheckDirL(TInt aCluster)
+ {
+ __PRINT1(_L("CScanDrive::CheckDirL aCluster=%d"),aCluster);
+ __ASSERT_ALWAYS(aCluster>=0,User::Leave(KErrCorrupt));
+ // check depth of recursion
+ if(++iRecursiveDepth==KMaxScanDepth)
+ {
+ AddToClusterListL(aCluster);
+ --iRecursiveDepth;
+ return;
+ }
+#if defined(DEBUG_SCANDRIVE)
+ ++iDirsChecked;
+#endif
+ TEntryPos entryPos(aCluster,0);
+ TInt dirEntries=0;
+ FOREVER
+ {
+ TFatDirEntry entry;
+ iMount->ReadDirEntryL(entryPos,entry);
+ if(!iMount->IsEndOfClusterCh(entryPos.iCluster))
+ ++dirEntries;
+ if(entry.IsParentDirectory()||entry.IsCurrentDirectory()||entry.IsErased())
+ {
+ if(IsEndOfRootDir(entryPos))
+ break;
+ iMount->MoveToNextEntryL(entryPos);
+ continue;
+ }
+ if(entry.IsEndOfDirectory())
+ {
+ if(aCluster)
+ WriteClusterChainL(aCluster,dirEntries<<KSizeOfFatDirEntryLog2);
+ break;
+ }
+ TEntryPos origPos=entryPos;
+ TFatDirEntry origEntry=entry;
+ TInt origDirEntries=dirEntries;
+ TBool isComplete;
+ isComplete=MoveToVFatEndL(entryPos,entry,dirEntries);
+ // Only assume that this is a corrupted VFAT entry if the VFAT attributes are set;
+ // assuming a non-VFAT corrupted entry is a VFAT entry is dangerous as we then assume that the
+ // first byte is a count of entries to skip, thus completely invalidating the next <n> directories.
+ if (!isComplete && origEntry.IsVFatEntry())
+ {
+ AddPartialVFatL(origPos,origEntry);
+ if(entryPos.iCluster!=KEndOfDirectory)
+ {
+ TInt toMove=origEntry.NumFollowing()-(dirEntries-origDirEntries);
+ if(toMove)
+ MovePastEntriesL(entryPos,entry,toMove,dirEntries);
+ }
+ else
+ {
+ // we fell off the end of the directory file, so just strip this
+ // incomplete long file name entry
+ dirEntries = origDirEntries;
+ }
+ }
+ else
+ ProcessEntryL(entry);
+ if(IsEndOfRootDir(entryPos))
+ break;
+ iMount->MoveToNextEntryL(entryPos);
+ }
+ --iRecursiveDepth;
+ }
+
+/**
+Process non trivial entries, such as files, if they are correct by filling out their
+cluster allocation in the bit packed Fat table. If it comes accross a directory
+CheckDirL will be called.
+
+@param aEntry Directory entry to check
+@leave System wide error code
+*/
+void CScanDrive::ProcessEntryL(const TFatDirEntry& aEntry)
+ {
+ __PRINT(_L("CScanDrive::ProcessEntryL"));
+ TInt entryAtt=aEntry.Attributes();
+ __ASSERT_ALWAYS(!(entryAtt&~KEntryAttMaskSupported)&&!aEntry.IsErased(),User::Leave(KErrCorrupt));
+ if(!(entryAtt&(KEntryAttDir|KEntryAttVolume)) && iMount->StartCluster(aEntry)>0)
+ WriteClusterChainL(iMount->StartCluster(aEntry),aEntry.Size());
+ else if(entryAtt&KEntryAttDir)
+ CheckDirL(iMount->StartCluster(aEntry));
+ }
+
+/**
+Writes out the cluster chain for a correct file or directory, checks that the cluster
+has not already been used and that the correct number of clusters are allocated for the
+size of file. Registers cluster as used if correct
+
+@param aCluster Cluster chain start point
+@param aSizeInBytes Size of the file or directory in bytes
+@leave System wide error values
+*/
+void CScanDrive::WriteClusterChainL(TInt aCluster,TInt aSizeInBytes)
+//
+// Mark off in the new fat the clusters used by entry with start cluster of aCluster
+//
+ {
+
+ IndicateErrorsFound(); //-- indicate that we have found errors
+
+ __PRINT1(_L("CScanDrive::WriteClusterChainL starting at %d"),aCluster);
+ __ASSERT_ALWAYS(aCluster>0 && aSizeInBytes>=0,User::Leave(KErrCorrupt));
+ TInt clusterCount;
+ if(aSizeInBytes==0)
+ clusterCount=1;
+ else
+ clusterCount=(aSizeInBytes+(1<<iMount->ClusterSizeLog2())-1)>>iMount->ClusterSizeLog2();
+ TInt startCluster=aCluster;
+ while(clusterCount)
+ {
+ if(AlreadyExistsL(aCluster))
+ {
+ __ASSERT_ALWAYS(!IsDirError()&&iMatching.iStartCluster==0&&aCluster==startCluster,User::Leave(KErrCorrupt));
+ iMatching.iStartCluster=aCluster;
+ iDirError=EScanMatchingEntry;
+ return;
+ }
+ if(clusterCount==1)
+ {
+ iNewFat->WriteFatEntryEofFL(aCluster);
+ return;
+ }
+ else
+ {
+ TInt clusterVal;
+ clusterVal=iMount->FAT().ReadL(aCluster);
+ __ASSERT_ALWAYS(!IsEofF(clusterVal) && clusterVal!=0,User::Leave(KErrCorrupt));
+ iNewFat->WriteL(aCluster,clusterVal);
+ aCluster=clusterVal;
+ --clusterCount;
+ }
+ }
+ }
+
+/**
+Move to dos entry, checking all vfat entry ID numbers are in sequence.
+Assumes aEntry is not erased
+
+@param aPos Position of the entry to move from, returns with new position
+@param aEntry The Dos entry after the Vfat entries on return
+@param aDirLength Running total of the length of the directory in entries
+@leave System wide error codes
+@return EFalse if not valid vfat entries or dos entry, else returns ETrue
+*/
+TBool CScanDrive::MoveToVFatEndL(TEntryPos& aPos,TFatDirEntry& aEntry,TInt& aDirLength)
+ {
+ __PRINT2(_L("CScanDrive::MoveToVFatEndL cluster=%d,pos=%d"),aPos.iCluster,aPos.iPos);
+ if(!aEntry.IsVFatEntry())
+ return IsDosEntry(aEntry);
+ TInt toFollow=aEntry.NumFollowing();
+ __ASSERT_ALWAYS(toFollow>0&&!aEntry.IsErased(),User::Leave(KErrCorrupt));
+ FOREVER
+ {
+ iMount->MoveToNextEntryL(aPos);
+ iMount->ReadDirEntryL(aPos,aEntry);
+ ++aDirLength;
+ --toFollow;
+ if(!toFollow)
+ break;
+ if(!IsValidVFatEntry(aEntry,toFollow))
+ return(EFalse);
+ }
+ return(IsDosEntry(aEntry));
+ }
+
+/**
+Check if an entry is valid VFat
+
+@param aEntry Entry to check
+@param aPrevNum Number into VFat entries for a dos entry to ensure in correct position
+@return ETrue if aEntry is a valid vfat entry
+*/
+TBool CScanDrive::IsValidVFatEntry(const TFatDirEntry& aEntry, TInt aPrevNum)const
+ {
+ if(aEntry.IsErased()||!aEntry.IsVFatEntry())
+ return(EFalse);
+ return(aEntry.NumFollowing()==aPrevNum);
+ }
+
+/**
+Check if an entry is a Dos entry
+
+@param aEntry Entry to check
+@return ETrue if aEntry is a dos entry
+*/
+TBool CScanDrive::IsDosEntry(const TFatDirEntry& aEntry)const
+ {
+ TBool res = !(aEntry.Attributes()&~KEntryAttMaskSupported) && !aEntry.IsErased() && !aEntry.IsVFatEntry() && !aEntry.IsEndOfDirectory();
+ return res;
+ }
+
+/**
+Add partial entry to iPartEntry under the error condition of not all Vfat entries
+being present
+
+@param aStartPos Position of the Dos entry associated with the VFat entries
+@param aEntry Directory Entry of the Dos entry associated with the VFat entries
+@leave KErrCorrupt Occurs if the entry is not valid
+*/
+void CScanDrive::AddPartialVFatL(const TEntryPos& aStartPos, const TFatDirEntry& aEntry)
+ {
+ __PRINT2(_L("CScanDrive::AddPartialVFatL cluster=%d pos=%d"),aStartPos.iCluster,aStartPos.iPos);
+ __ASSERT_ALWAYS(!IsDirError(),User::Leave(KErrCorrupt));
+ iPartEntry.iEntryPos=aStartPos;
+ iPartEntry.iEntry=aEntry;
+ iDirError=EScanPartEntry;
+ }
+
+/**
+Add entry position to iMatching
+
+@param aEntryPos Position of the entry with the matching entry
+@leave KErrCorrupt if the start cluster is 0 or more that two matching entries occurs
+@return
+*/
+TBool CScanDrive::AddMatchingEntryL(const TEntryPos& aEntryPos)
+ {
+ __PRINT2(_L("CScanDrive::AddMatchingEntryL cluster=%d pos=%d"),aEntryPos.iCluster,aEntryPos.iPos);
+ __ASSERT_ALWAYS(iMatching.iStartCluster>0 && iMatching.iCount<KMaxMatchingEntries,User::Leave(KErrCorrupt));
+ iMatching.iEntries[iMatching.iCount++]=aEntryPos;
+ return iMatching.iCount==KMaxMatchingEntries;
+ }
+
+
+/**
+Scan for differnces in the new and old FAT table writing them to media if discovered
+
+@leave System wide error codes
+*/
+void CScanDrive::WriteNewFatsL()
+//
+// Write the new fat table to disk
+//
+ {
+ if(iNewFat->FlushL())
+ IndicateErrorsFound(); //-- indicate that we have found errors
+ }
+
+TInt CScanDrive::GetReservedidL(TEntryPos aVFatPos)
+//
+// Return the id found in reserved2 field of dos entry
+//
+ {
+ __PRINT(_L("CScanDrive::GetReservedidL"));
+ TFatDirEntry entry;
+ iMount->ReadDirEntryL(aVFatPos,entry);
+ if(!IsDosEntry(entry))
+ {
+ TInt toMove=entry.NumFollowing();
+ while(toMove--)
+ iMount->MoveToNextEntryL(aVFatPos);
+ iMount->ReadDirEntryL(aVFatPos,entry);
+ }
+ return(entry.RuggedFatEntryId());
+ }
+
+/**
+Erase part entry found in iPartEntry
+
+@leave System wide error code
+*/
+void CScanDrive::FixPartEntryL()
+ {
+ __PRINT2(_L("CScanDrive::FixPartEntryL cluster=%d,pos=%d"),iPartEntry.iEntryPos.iCluster,iPartEntry.iEntryPos.iPos);
+ iMount->EraseDirEntryL(iPartEntry.iEntryPos,iPartEntry.iEntry);
+ IndicateErrorsFound(); //-- indicate that we have found errors
+ }
+
+/**
+Delete entry with largest value in the reserved2 section(bytes 20 and 21) of dos entry
+
+@leave System wide error code
+*/
+void CScanDrive::FixMatchingEntryL()
+ {
+ __PRINT1(_L("CScanDrive::FixMatchingEntryL() start cluster=%d"),iMatching.iStartCluster);
+ __ASSERT_ALWAYS(iMatching.iCount==KMaxMatchingEntries,User::Leave(KErrCorrupt));
+ TInt idOne=GetReservedidL(iMatching.iEntries[0]);
+ TInt idTwo=GetReservedidL(iMatching.iEntries[1]);
+ TFatDirEntry entry;
+ TInt num=idOne>idTwo?0:1;
+ iMount->ReadDirEntryL(iMatching.iEntries[num],entry);
+ iMount->EraseDirEntryL(iMatching.iEntries[num],entry);
+ IndicateErrorsFound(); //-- indicate that we have found errors
+ }
+/**
+Move past specified number of entries
+
+@param aEntryPos Start position to move from, updated as move takes place
+@param aEntry Directory entry moved to
+@param aToMove Number of entries to move through
+@param aDirEntries Number of entries moved, updated as move takes place
+@leave System wide error code
+*/
+void CScanDrive::MovePastEntriesL(TEntryPos& aEntryPos,TFatDirEntry& aEntry,TInt aToMove,TInt& aDirEntries)
+ {
+ while(aToMove-- && aEntryPos.iCluster!=KEndOfDirectory)
+ {
+ iMount->MoveToNextEntryL(aEntryPos);
+ ++aDirEntries;
+ }
+ iMount->ReadDirEntryL(aEntryPos,aEntry);
+ }
+
+/**
+Adds aCluster to cluster list array so that it may be revisited later, avoids stack
+over flow
+
+@param aCluster Directory cluster number to add to the list
+@leave KErrNoMemory If allocation fails
+*/
+void CScanDrive::AddToClusterListL(TInt aCluster)
+ {
+ if(iListArrayIndex>=KMaxArrayDepth)
+ return;
+ if(iClusterListArray[iListArrayIndex]==NULL)
+ iClusterListArray[iListArrayIndex]=new(ELeave) RArray<TInt>(KClusterListGranularity);
+ iClusterListArray[iListArrayIndex]->Append(aCluster);
+ }
+
+
+#if defined(DEBUG_SCANDRIVE)
+void CScanDrive::CompareFatsL()
+//
+// Compare new fat and first fat table
+//
+ {
+ __PRINT(_L("CScanDrive::CompareFatsL()"));
+ TInt maxClusters;
+ maxClusters=iMount->UsableClusters();
+ for(TInt i=KFatFirstSearchCluster; i<maxClusters; ++i)
+ {
+ TInt realFat=iMount->FAT().ReadL(i);
+ TInt newFat=iNewFat->ReadL(i);
+ if(realFat!=newFat)
+ {
+ if(realFat!=0 && newFat==0)
+ __PRINT1(_L("Lost cluster=%d\n"),i)
+ else if((realFat>0 && !IsEofF(realFat)) && IsEofF(newFat))
+ __PRINT1(_L("Hanging cluster = %d\n"),i)
+ else if(realFat==0 && newFat>0)
+ __PRINT1(_L("Unflushed cluster = %d\n"),i)
+ else
+ User::Leave(KErrCorrupt);
+ }
+ }
+ }
+
+
+/**
+For debug purposes, print errors found as debug output
+
+*/
+void CScanDrive::PrintErrors()
+ {
+ __PRINT1(_L("Directories visisted = %d\n"),iDirsChecked);
+ if(iDirError==EScanPartEntry)
+ __PRINT2(_L("Part entry-dir cluster=%d,dir pos=%d,\n"),iPartEntry.iEntryPos.iCluster,iPartEntry.iEntryPos.iPos)
+ else if(iDirError==EScanMatchingEntry)
+ {
+ __PRINT1(_L("Matching cluster - cluster no=%d\n"),iMatching.iStartCluster);
+ __PRINT2(_L("\tcluster 1 - dir cluster=%d,dir pos=%d\n"),iMatching.iEntries[0].iCluster,iMatching.iEntries[0].iPos);
+ __PRINT2(_L("\tcluster 2 - dir cluster=%d,dir pos=%d\n"),iMatching.iEntries[1].iCluster,iMatching.iEntries[1].iPos);
+ }
+ }
+
+#endif
+
+
+
+