subset abstract method
Return a InputStream to read a subset of this stream. It does not
move the read position of this stream. position is specified relative
to the start of the buffer. If position is not specified, the current
read position is used. If length is not specified, the remainder of this
stream is used.
If bufferSize is provided, and this is an InputFileStream, the
returned InputStream will get its own FileBuffer with the given
bufferSize, otherwise it will share the FileBuffer of this
InputFileStream.
Implementation
InputStream subset({int? position, int? length, int? bufferSize});