std::istreambuf_iterator

 

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indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) is-integer-like is-signed-integer-like (C++20)(C++20)	sentinel_for (C++20) sized_sentinel_for (C++20) input_iterator (C++20) output_iterator (C++20) input_or_output_iterator (C++20)	forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
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input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20)	iter_value_titer_difference_titer_reference_titer_const_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++23)(C++20)(C++20)	iterator (deprecated in C++17) iterator_traits incrementable_traits (C++20) indirectly_readable_traits (C++20)
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indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20)	indirect_unary_predicate (C++20) indirect_binary_predicate (C++20)	indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
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indirectly_movable (C++20) indirectly_movable_storable (C++20) indirectly_copyable (C++20)	indirectly_copyable_storable (C++20)   indirectly_swappable (C++20) indirectly_comparable (C++20)	permutable (C++20) mergeable (C++20) sortable (C++20)
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indirect_result_t (C++20)	projected (C++20)	projected_value_t (C++26)
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reverse_iterator make_reverse_iterator (C++14) move_iterator (C++11) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20)	front_insert_iterator back_insert_iterator inserter insert_iterator front_inserter back_inserter move_sentinel (C++20)	common_iterator (C++20) counted_iterator (C++20) basic_const_iterator (C++23) const_iterator (C++23) const_sentinel (C++23) make_const_iterator (C++23) make_const_sentinel (C++23)
Stream iterators istream_iterator    ostream_iterator istreambuf_iterator ostreambuf_iterator	Iterator customization points ranges::iter_move (C++20) ranges::iter_swap (C++20)
Iterator operations advance distance prev (C++11)   next (C++11) ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)	Range access begincbegin (C++11)(C++14) rbegincrbegin (C++14)(C++14)   endcend (C++11)(C++14) rendcrend (C++14)(C++14)   sizessize (C++17)(C++20) empty (C++17) data (C++17)

 

std::istreambuf_iterator

Member functions

istreambuf_iterator::istreambuf_iterator

istreambuf_iterator::operator*

istreambuf_iterator::operator++istreambuf_iterator::operator++(int)

istreambuf_iterator::equal

Non-member functions

operator==operator!= (until C++20)

 

Defined in header <iterator>
template< class CharT, class Traits = std::char_traits<CharT> > class istreambuf_iterator : public std::iterator< std::input_iterator_tag,                                                   CharT,                                                   typename Traits::off_type,                                                   /* unspecified, usually CharT* */,                                                   CharT >		(until C++17)
template< class CharT, class Traits = std::char_traits<CharT> > class istreambuf_iterator;		(since C++17)

std::istreambuf_iterator is a single-pass input iterator that reads successive characters from the std::basic_streambuf object for which it was constructed.

The default-constructed std::istreambuf_iterator is known as the end-of-stream iterator. When a valid std::istreambuf_iterator reaches the end of the underlying stream, it becomes equal to the end-of-stream iterator. Dereferencing or incrementing it further invokes undefined behavior.

std::istreambuf_iterator has a trivial copy constructor, a constexpr default constructor, and a trivial destructor.

Member types

Member type	Definition
iterator_category	std::input_iterator_tag
value_type	CharT
difference_type	Traits::off_type
pointer	/* unspecified, usually CharT* */
reference	CharT
char_type	CharT
traits_type	Traits
int_type	typename traits::int_type
streambuf_type	std::basic_streambuf<CharT, Traits>
istream_type	std::basic_istream<CharT, Traits>
/* proxy */	Implementation defined class type. The name proxy is for exposition only. A proxy object holds a char_type character and a streambuf_type* pointer. Deferencing a proxy object with operator* yields the stored character.

Member types iterator_category, value_type, difference_type, pointer and reference are required to be obtained by inheriting from std::iterator<std::input_iterator_tag, CharT, Traits::off_type, /* unspecified, usually CharT* */, CharT>.

(until C++17)

Member functions

(constructor)	constructs a new istreambuf_iterator (public member function)
(destructor) (implicitly declared)	destructs an istreambuf_iterator (public member function)
operator*	obtains a copy of the current character (public member function)
operator++operator++(int)	advances the iterator (public member function)
equal	tests if both istreambuf_iterators are end-of-stream or if both are valid (public member function)

Non-member functions

operator==operator!= (removed in C++20)

compares two istreambuf_iterators (function template)

Example

Run this code

#include <vector>
#include <sstream>
#include <iostream>
#include <iterator>
 
int main()
{
    // typical use case: an input stream represented as a pair of iterators
    std::istringstream in("Hello, world");
    std::istreambuf_iterator<char> it(in), end;
    std::string ss(it, end);
    std::cout << "ss has " << ss.size() << " bytes. "
                 "it holds \"" << ss << "\"\n";
 
    // demonstration of the single-pass nature
    std::istringstream s("abc");
    std::istreambuf_iterator<char> i1(s), i2(s);
    std::cout << "i1 returns " << *i1 << '\n'
              << "i2 returns " << *i2 << '\n';
    ++i1;
    std::cout << "after incrementing i1, but not i2\n"
                 "i1 returns " << *i1 << '\n'
                 "i2 returns " << *i2 << '\n';
    ++i2; // this makes the apparent value of *i2 to jump from 'a' to 'c'
    std::cout << "after incrementing i2, but not i1\n"
                 "i1 returns " << *i1 << '\n'
                 "i2 returns " << *i2 << '\n';
 
}

Output:

ss has 12 bytes. it holds "Hello, world"
i1 returns a
i2 returns a
after incrementing i1, but not i2
i1 returns b
i2 returns a
after incrementing i2, but not i1
i1 returns b
i2 returns c

See also

ostreambuf_iterator	output iterator that writes to std::basic_streambuf (class template)
istream_iterator	input iterator that reads from std::basic_istream (class template)