Synchronously reads into an existing List<int> from the file and returns the number of bytes read.
start is present, the bytes will be filled into
buffer from at
start, otherwise index 0. If
end is present, the
start bytes will be read into
buffer, otherwise up to
start nothing happens.
Throws a FileSystemException if the operation fails.
int readIntoSync(List<int> buffer, [int start = 0, int end]);