std::istreambuf_iterator

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
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 functions

constructs a new istreambuf_iterator
(public member function)
(destructor)
(implicitly declared)
 destructs an istreambuf_iterator
(public member function)
(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)
advances the iterator
(public member function)
tests if both istreambuf_iterators are end-of-stream or if both are valid
(public member function)

Non-member functions

compares two istreambuf_iterators
(function template)

Member types

Member type Definition
value_type CharT
difference_type Traits::off_type
pointer /* unspecified, usually CharT* */
reference CharT
iterator_category std::input_iterator_tag

These member types 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)

Example

#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::vector<char> v( (std::istreambuf_iterator<char>(in)),
                          std::istreambuf_iterator<char>() );
    std::cout << "v has " << v.size() << " bytes. ";
    v.push_back('\0');
    std::cout << "it holds \"" << &v[0] << "\"\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:

v 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

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

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