Fix for write failures and incorrect free space on FAT32 volume with missing info sector

Author: ultibohub

source/rtl/ultibo/core/fatfs.pas

@@ -548,6 +548,7 @@ TFATFileSystem = class(TFileSystem)
  function SetVolumeFlags(AFlags:LongWord):Boolean;
 
  {Sector Methods}
+ function CheckInfoSector(ALock:Boolean;var ABuffer):Boolean;
  function UpdateInfoSector:Boolean;
 
  {Cluster Methods}
@@ -2772,6 +2773,70 @@ function TFATFileSystem.SetVolumeFlags(AFlags:LongWord):Boolean;
 
 {==============================================================================}
 
+function TFATFileSystem.CheckInfoSector(ALock:Boolean;var ABuffer):Boolean;
+{Check the FAT32 Info Sector for valid values}
+{Note: Caller must hold any required lock on buffer}
+var
+ Buffer:Pointer;
+begin
+ {}
+ Result:=False;
+
+ {Check Type}
+ case FFATType of
+ ftFAT12,ftFAT16:begin
+ Result:=True;
+ end;
+ ftFAT32:begin
+ {Get Buffer}
+ Buffer:=@ABuffer;
+
+ {Check Buffer}
+ if (PFATInfoSector(Buffer).LeadSignature <> fat32LeadSignature) or
+ (PFATInfoSector(Buffer).StructureSignature <> fat32StructSignature) or
+ (PFATInfoSector(Buffer).TrailSignature <> fat32TrailSignature) then
+ begin
+ if ALock and not(InfoLock) then Exit;
+ try
+ {$IFDEF FAT_DEBUG}
+ if FILESYS_LOG_ENABLED then FileSysLogDebug('TFATFileSystem.CheckInfoSector - Initializing Info Sector');
+ {$ENDIF}
+
+ {Initialize Info Sector}
+ PFATInfoSector(Buffer).LeadSignature:=fat32LeadSignature;
+ {PFATInfoSector(Buffer).Reserved1}
+ PFATInfoSector(Buffer).StructureSignature:=fat32StructSignature;
+ PFATInfoSector(Buffer).FreeClusterCount:=fatUnknownCluster;
+ PFATInfoSector(Buffer).LastFreeCluster:=fatUnknownCluster;
+ {PFATInfoSector(Buffer).Reserved2}
+ PFATInfoSector(Buffer).TrailSignature:=fat32TrailSignature;
+
+ {Check ReadOnly}
+ if not FReadOnly then
+ begin
+ {$IFDEF FAT_DEBUG}
+ if FILESYS_LOG_ENABLED then FileSysLogDebug('TFATFileSystem.CheckInfoSector - Writing Info Sector');
+ {$ENDIF}
+
+ {Write Info Sector}
+ if not WriteSectors(FInfoSector,1,Buffer^) then Exit;
+ end;
+
+ {$IFDEF FAT_DEBUG}
+ if FILESYS_LOG_ENABLED then FileSysLogDebug('TFATFileSystem.CheckInfoSector - Info Sector Initialized');
+ {$ENDIF}
+ finally
+ if ALock then InfoUnlock;
+ end;
+ end;
+
+ Result:=True;
+ end;
+ end;
+end;
+
+{==============================================================================}
+
 function TFATFileSystem.UpdateInfoSector:Boolean;
 {Update the FAT32 Info Sector with current values}
 begin
@@ -2803,6 +2868,9 @@ function TFATFileSystem.UpdateInfoSector:Boolean;
 
  {Read Info Sector}
  if not ReadSectors(FInfoSector,1,FInfoBuffer^) then Exit;
+
+ {Check Info Sector}
+ if not CheckInfoSector(False,FInfoBuffer^) then Exit;
  end;
 
  {Check Enable}
@@ -2973,9 +3041,11 @@ function TFATFileSystem.GetNextFreeCluster:LongWord;
 
  {Get Info Sector}
  if not ReadSectors(FInfoSector,1,FSectorBuffer^) then Exit;
- if PFATInfoSector(FSectorBuffer).LeadSignature <> fat32LeadSignature then Exit;
- if PFATInfoSector(FSectorBuffer).StructureSignature <> fat32StructSignature then Exit;
- if PFATInfoSector(FSectorBuffer).TrailSignature <> fat32TrailSignature then Exit;
+
+ {Check Info Sector}
+ if not CheckInfoSector(True,FSectorBuffer^) then Exit;
+
+ {Check Last Free Cluster}
  if PFATInfoSector(FSectorBuffer).LastFreeCluster <> fatUnknownCluster then
  begin
  {Get Last Free Cluster}
@@ -3105,7 +3175,7 @@ function TFATFileSystem.GetFreeClusterCount:LongWord;
  DiskBlock:TFATDiskBlock;
 begin
  {}
- Result:=0;
+ Result:=fatUnknownCluster;
 
  if FDriver = nil then Exit;
  if FTotalClusterCount = 0 then Exit;
@@ -3129,9 +3199,11 @@ function TFATFileSystem.GetFreeClusterCount:LongWord;
 
  {Get Info Sector}
  if not ReadSectors(FInfoSector,1,FSectorBuffer^) then Exit;
- if PFATInfoSector(FSectorBuffer).LeadSignature <> fat32LeadSignature then Exit;
- if PFATInfoSector(FSectorBuffer).StructureSignature <> fat32StructSignature then Exit;
- if PFATInfoSector(FSectorBuffer).TrailSignature <> fat32TrailSignature then Exit;
+
+ {Check Info Sector}
+ if not CheckInfoSector(True,FSectorBuffer^) then Exit;
+
+ {Check Free Cluster Count}
  if PFATInfoSector(FSectorBuffer).FreeClusterCount <> fatUnknownCluster then
  begin
  {Get Free Cluster Count}
@@ -3260,9 +3332,9 @@ function TFATFileSystem.SetNextFreeCluster(ACluster:LongWord):Boolean;
 
  {Get Info Sector}
  if not ReadSectors(FInfoSector,1,FSectorBuffer^) then Exit;
- if PFATInfoSector(FSectorBuffer).LeadSignature <> fat32LeadSignature then Exit;
- if PFATInfoSector(FSectorBuffer).StructureSignature <> fat32StructSignature then Exit;
- if PFATInfoSector(FSectorBuffer).TrailSignature <> fat32TrailSignature then Exit;
+
+ {Check Info Sector}
+ if not CheckInfoSector(True,FSectorBuffer^) then Exit;
 
  {Set Last Free Cluster}
  PFATInfoSector(FSectorBuffer).LastFreeCluster:=ACluster;
@@ -3301,9 +3373,9 @@ function TFATFileSystem.SetFreeClusterCount(ACount:LongWord):Boolean;
 
  {Get Info Sector}
  if not ReadSectors(FInfoSector,1,FSectorBuffer^) then Exit;
- if PFATInfoSector(FSectorBuffer).LeadSignature <> fat32LeadSignature then Exit;
- if PFATInfoSector(FSectorBuffer).StructureSignature <> fat32StructSignature then Exit;
- if PFATInfoSector(FSectorBuffer).TrailSignature <> fat32TrailSignature then Exit;
+
+ {Check Info Sector}
+ if not CheckInfoSector(True,FSectorBuffer^) then Exit;
 
  {Set Free Cluster Count}
  PFATInfoSector(FSectorBuffer).FreeClusterCount:=ACount;