add volume size

stepmania/src/arch/MemoryCard/MemoryCardDriver.h

@@ -22,6 +22,7 @@ struct UsbStorageDevice
 		sVendor = "";
 		sProduct = "";
 		sVolumeLabel = "";
+		iVolumeSizeMB = 0;
 	};
 	int iBus;
 	int iPort;
@@ -60,6 +61,7 @@ struct UsbStorageDevice
 	CString sVendor;
 	CString sProduct;
 	CString sVolumeLabel;
+	int iVolumeSizeMB;
 
 	bool IsBlank() const { return m_State == STATE_NONE; }
 	void SetOsMountDir( const CString &s );

stepmania/src/arch/MemoryCard/MemoryCardDriverThreaded_Windows.cpp

@@ -101,6 +101,21 @@ bool MemoryCardDriverThreaded_Windows::DoOneUpdate( bool bMount, vector<UsbStora
 			else
 				usbd.SetError( "MountFailed" );
 
+			// find volume size
+			DWORD dwSectorsPerCluster;
+			DWORD dwBytesPerSector;
+			DWORD dwNumberOfFreeClusters;
+			DWORD dwTotalNumberOfClusters;
+			if( GetDiskFreeSpace(
+					sDrive,
+					&dwSectorsPerCluster,
+					&dwBytesPerSector,
+					&dwNumberOfFreeClusters,
+					&dwTotalNumberOfClusters ) )
+			{
+				usbd.iVolumeSizeMB = (int)roundf( dwTotalNumberOfClusters * (float)dwSectorsPerCluster * dwBytesPerSector / (1024*1024) );
+			}
+
 			// read name
 			this->Mount( &usbd );
 			FILEMAN->Mount( "dir", usbd.sOsMountDir, TEMP_MOUNT_POINT_INTERNAL );