The class template istreambuf_iterator defines an input iterator ([input.iterators]) that reads successive characters from the streambuf for which it was constructed. operator* provides access to the current input character, if any. [ Note: operator-> may return a proxy. — end note ] Each time operator++ is evaluated, the iterator advances to the next input character. If the end of stream is reached (streambuf_type::sgetc() returns traits::eof()), the iterator becomes equal to the end-of-stream iterator value. The default constructor istreambuf_iterator() and the constructor istreambuf_iterator(0) both construct an end-of-stream iterator object suitable for use as an end-of-range. All specializations of istreambuf_iterator shall have a trivial copy constructor, a constexpr default constructor, and a trivial destructor.
The result of operator*() on an end-of-stream iterator is undefined. For any other iterator value a char_type value is returned. It is impossible to assign a character via an input iterator.
namespace std {
template<class charT, class traits = char_traits<charT> >
class istreambuf_iterator
: public iterator<input_iterator_tag, charT,
typename traits::off_type, unspecified, charT> {
public:
typedef charT char_type;
typedef traits traits_type;
typedef typename traits::int_type int_type;
typedef basic_streambuf<charT,traits> streambuf_type;
typedef basic_istream<charT,traits> istream_type;
class proxy;
constexpr istreambuf_iterator() noexcept;
istreambuf_iterator(const istreambuf_iterator&) noexcept = default;
~istreambuf_iterator() = default;
istreambuf_iterator(istream_type& s) noexcept;
istreambuf_iterator(streambuf_type* s) noexcept;
istreambuf_iterator(const proxy& p) noexcept;
charT operator*() const;
pointer operator->() const;
istreambuf_iterator<charT,traits>& operator++();
proxy operator++(int);
bool equal(const istreambuf_iterator& b) const;
private:
streambuf_type* sbuf_; };
template <class charT, class traits>
bool operator==(const istreambuf_iterator<charT,traits>& a,
const istreambuf_iterator<charT,traits>& b);
template <class charT, class traits>
bool operator!=(const istreambuf_iterator<charT,traits>& a,
const istreambuf_iterator<charT,traits>& b);
}
24.6.3.1 Class template istreambuf_iterator::proxy [istreambuf.iterator::proxy]
namespace std {
template <class charT, class traits = char_traits<charT> >
class istreambuf_iterator<charT, traits>::proxy { charT keep_;
basic_streambuf<charT,traits>* sbuf_;
proxy(charT c, basic_streambuf<charT,traits>* sbuf)
: keep_(c), sbuf_(sbuf) { }
public:
charT operator*() { return keep_; }
};
}
Class istreambuf_iterator<charT,traits>::proxy is for exposition only. An implementation is permitted to provide equivalent functionality without providing a class with this name. Class istreambuf_iterator<charT, traits>::proxy provides a temporary placeholder as the return value of the post-increment operator (operator++). It keeps the character pointed to by the previous value of the iterator for some possible future access to get the character.
24.6.3.2 istreambuf_iterator constructors [istreambuf.iterator.cons] constexpr istreambuf_iterator() noexcept;
Effects: Constructs the end-of-stream iterator.
istreambuf_iterator(basic_istream<charT,traits>& s) noexcept; istreambuf_iterator(basic_streambuf<charT,traits>* s) noexcept;
Effects: Constructs an istreambuf_iterator<> that uses the basic_streambuf<> object *(s.rdbuf()), or *s, respectively. Constructs an end-of-stream iterator if s.rdbuf() is null.
istreambuf_iterator(const proxy& p) noexcept;
Effects: Constructs a istreambuf_iterator<> that uses the basic_streambuf<> object pointed to by the proxy object's constructor argument p.
24.6.3.4 istreambuf_iterator::operator++ [istreambuf.iterator::op++] istreambuf_iterator<charT,traits>& istreambuf_iterator<charT,traits>::operator++();
Effects: sbuf_->sbumpc().
proxy istreambuf_iterator<charT,traits>::operator++(int);
Returns: proxy(sbuf_->sbumpc(), sbuf_).
24.6.3.5 istreambuf_iterator::equal [istreambuf.iterator::equal] bool equal(const istreambuf_iterator<charT,traits>& b) const;
Returns: true if and only if both iterators are at end-of-stream, or neither is at end-of-stream, regardless of what streambuf object they use.
24.6.3.6 operator== [istreambuf.iterator::op==] template <class charT, class traits> bool operator==(const istreambuf_iterator<charT,traits>& a, const istreambuf_iterator<charT,traits>& b);
template <class charT, class traits> bool operator!=(const istreambuf_iterator<charT,traits>& a, const istreambuf_iterator<charT,traits>& b);
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