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

Synchronously reads into an existing List 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 happends.

Throws a FileSystemException if the operation fails.

Source 

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