diskcapacity.txt

show disk capacity for large drive in delphi

function GetDiskCapacity(Drv: Char; var dskSize,dskFree: Comp;
		var errMsg: string): Boolean;
var
	TmpDrv: string;
	SectorsPerCluster,
	BytesPerSector,
	NumberOfFreeClusters,
	TotalNumberOfClusters,
	ErrMode: DWord;
	EAX,EDX,ECX,EBX: Comp;
begin
	if Drv = #0 then
	raise TAPIException.Create('SetDiskCapacity FAILED!');
	ErrMode:= SetErrorMode(SEM_FAILCRITICALERRORS);
	TmpDrv:= Drv+':\';
	dskSize:= 0;
	dskFree:= 0;
	{$I-}
	result:= GetDiskFreeSpace(PChar(TmpDrv),SectorsPerCluster,BytesPerSector,
		NumberOfFreeClusters,TotalNumberOfClusters);
	{$I+}
	if result then
	begin
		EAX:= SectorsPerCluster;				// Convert DWord to Double so it can
		ECX:= BytesPerSector;           // hold larger disk capacity otherwise
		EBX:= NumberOfFreeClusters;     // capacity calculation will produce an
		EDX:= TotalNumberOfClusters;    // error ->> Invalid Math Operation.
	{
	Or if you do this you'll get Integer Overflow error.
	Try if you like!
	}
	// dskSize:= (SectorsPerCluster*BytesPerSector*TotalNumberOfClusters); ->> Integer Overflow
	// dskFree:= (SectorsPerCluster*NumberOfFreeClusters*BytesPerSector);  ->> Integer Overflow

		dskSize:= (EAX*ECX*EDX);
		dskFree:= (EAX*EBX*ECX);
	end else
	errMsg:= GetLastErrorMsg;
	SetErrorMode(ErrMode);
end;