25 Iterators library [iterators]

25.6 Stream iterators [stream.iterators]

25.6.4 Class template istreambuf_iterator [istreambuf.iterator]

25.6.4.3 Constructors [istreambuf.iterator.cons]

For each istreambuf_iterator constructor in this subclause, an end-of-stream iterator is constructed if and only if the exposition-only member sbuf_ is initialized with a null pointer value.
constexpr istreambuf_iterator() noexcept; constexpr istreambuf_iterator(default_sentinel_t) noexcept;
Effects: Initializes sbuf_ with nullptr.
istreambuf_iterator(istream_type& s) noexcept;
Effects: Initializes sbuf_ with s.rdbuf().
istreambuf_iterator(streambuf_type* s) noexcept;
Effects: Initializes sbuf_ with s.
istreambuf_iterator(const proxy& p) noexcept;
Effects: Initializes sbuf_ with p.sbuf_.