ostreambuf_iterator

 

Overview

IOStream classes provides iterators for reading and writing from streams just like a containers. ostreambuf_iterator enables writing characters to the stream.

Details

ostream iterators are output iterators that write successive characters from an output stream (such as cout).

They are constructed from a basic_ostream object, to which they become associated, so that whenever an assignment operator (=) is used on the ostream_iterator (dereferenced or not) it inserts a new element into the stream.

Syntax

The syntax is as below. 

template< class CharT = char,
          class Traits = char_traits<CharT>
class ostreambuf_iterator;

Name	Description
charT	Character type of the associated istream object.
traits	Character traits of the associated istream object.

Members

 It defines following types.

member type	definition
iterator_category	output_iterator_tag
value_type	charT
difference_type	void
pointer	void
reference	void

Operation

An ostreambuf_iterator  as an output iterator supports operators *, ++, and =. 

ostreambuf_iterator  is a single-pass  output iterator that writes successive  characters  into the basic_ostream object for which it was constructed, using operator<<. Optional delimiter string is written to the output stream after every write operation. The write operation is performed when the iterator (whether dereferenced or not) is assigned to. Incrementing the ostreambuf_iterator   is a no-op.

In other words, unlike in a list or a vector, the iterator solely depends on the current position of the stream iterator of the stream object. 

A sentry object is not constructed and destructed once per character.

In a typical implementation, the only data members of ostreambuf_iterator   are a pointer to the associated basic_ostream object.

This can be clearly seen in the example below. 

wstring msg = L"Hello, Khri$ha!";
//same as wcout << msg;
copy (begin(msg), end(msg), ostreambuf_iterator<wchar_t>(wcout));

Functionality

Constructors

Name	Description
ostream_iterator( ostream_type& s) ostream_iterator( streambuf_type *buf);	Constructs from a stream Constructs from a streambuf; Example: //1 wstring msg = L"Hello, Khri$ha!"; //same as wcout << msg; copy (begin(msg), end(msg), ostreambuf_iterator<wchar_t>(wcout)); //2 wstringstream ss; //same as wstringstream ss(L"Hello, Khri$ha!") copy (begin(msg), end(msg), ostreambuf_iterator<wchar_t>(ss.rdbuf())); wcout << endl << ss.str();
ostreambuf_iterator (const ostreambuf_iterator& x)	copy constructor Constructs an ostreambuf iterator, with the same ostreambuf reference. Example: ostreambuf_iterator<char> it(cout), it2(it); //prints kr *it='k'; it2='r';

Overloaded operators

Name	Example
ostreambuf_iterator& operator*()	Does nothing.
ostreambuf_iterator& operator++() ostreambuf_iterator& operator++(int)	Does nothing.
ostreambuf_iterator& operator=(const T& value)	Writes to the stream. Example: ostreambuf_iterator<char> it(cout); //prints kr *it='k'; it2='r';