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std::istreambuf_iterator

From cppreference.com
< cpp‎ | iterator
 
 
Iterator library
Iterator concepts
Iterator primitives
Algorithm concepts and utilities
Indirect callable concepts
Common algorithm requirements
Utilities
Iterator adaptors
Stream iterators
istreambuf_iterator
Iterator customization points
Iterator operations
(C++11)
(C++11)
Range access
(C++11)(C++14)
(C++11)(C++14)
(C++17)(C++20)
(C++14)(C++14)
(C++14)(C++14)
(C++17)
(C++17)
 
 
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)

Contents

[edit] 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)

[edit] Member functions

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

[edit] Non-member functions

(removed in C++20)
compares two istreambuf_iterators
(function template) [edit]

[edit] Example

#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'

[edit] See also

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