22 Iterators library [iterators]

22.6 Stream iterators [stream.iterators]

22.6.3 Class template istreambuf_­iterator [istreambuf.iterator]

22.6.3.2 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;
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_­.