std::istreambuf_iterator

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Iterator library

Iterator concepts
indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) input_or_output_iterator (C++20) sentinel_for (C++20) sized_sentinel_for (C++20)	input_iterator (C++20) output_iterator (C++20) forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
Iterator primitives
iterator_traits input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20) iterator (deprecated in C++17)	incrementable_traits (C++20) indirectly_readable_traits (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)
Algorithm concepts and utilities
Indirect callable concepts
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)
Common algorithm requirements
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)
Utilities
indirect_result_t (C++20)	projected (C++20)
Iterator adaptors
reverse_iterator move_iterator (C++11) 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) back_insert_iterator front_insert_iterator insert_iterator	make_reverse_iterator (C++14) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20) make_const_iterator (C++23) make_const_sentinel (C++23) back_inserter front_inserter inserter
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) endcend (C++11)(C++14) sizessize (C++17)(C++20)	rbegincrbegin (C++14)(C++14) rendcrend (C++14)(C++14) empty (C++17) data (C++17)

 

std::istreambuf_iterator

Member functions

istreambuf_iterator::istreambuf_iterator

istreambuf_iterator::operator*istreambuf_iterator::operator-> (C++11)(until C++17)

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.

(since C++11)

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*operator-> (since C++11)(until C++17)	obtains a copy of the current character accesses a member of the current character, if CharT has members (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 <string>
#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;
    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 'b'
after incrementing i2, but not i1
i1 returns 'c'
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)