@Override
	public long length() throws IOException {
		return getDataFile().length();
	}
Create a new local data file item.
@param fileSystem file system
@param propertyFile serialized data property file
@param istream data source input stream (should be a start of data and will be read to end of file).
The invoker of this constructor is responsible for closing istream.
@param contentType user content type
@param monitor progress monitor (used for cancel support, 
progress not used since length of input stream is unknown)
@throws IOException if an IO Error occurs
@throws CancelledException if monitor cancels operation
Ghidra/Framework/FileSystem/src/main/java/ghidra/framework/store/local/LocalDataFile.java