int readIntoSync(List<int> buffer, [ int start = 0, int end ])

Synchronously reads into an existing List<int> from the file. If start is present, the bytes will be filled into buffer from at index start, otherwise index 0. If end is present, the end - start bytes will be read into buffer, otherwise up to buffer.length. If end == start nothing happens.

Throws a FileSystemException if the operation fails.

Source 

int readIntoSync(List<int> buffer, [int start = 0, int end]);