substream abstract method

Stream<List<T>> substream(int size)

Returns a sub-Stream with the next size elements.

A sub-Stream is a Stream consisting of the next size elements in the same order they occur in the stream used to create this iterator.

If read is called before the sub-Stream is fully read, a StateError will be thrown.

final s = ChunkedStreamIterator(_chunkedStream([
  ['a', 'b', 'c'],
  ['1', '2'],
]));
expect(await s.read(1), equals(['a']));

// creates a substream from the chunks holding the
// next three elements (['b', 'c'], ['1'])
final i = StreamIterator(s.substream(3));
expect(await i.moveNext(), isTrue);
expect(await i.current, equals(['b', 'c']));
expect(await i.moveNext(), isTrue);
expect(await i.current, equals(['1']));

// Since the substream has been read till the end, we can continue reading
// from the initial stream.
expect(await s.read(1), equals(['2']));

The resulting stream may contain less than size elements if the underlying stream has less than size elements before the end of stream.

When the substream is cancelled, the remaining elements in the substream are drained.

Implementation

Stream<List<T>> substream(int size);