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                       Standard C++ Library
             Copyright 1998, Rogue Wave Software, Inc.


NAME
     istreambuf_iterator

      - Reads successive characters from the  stream  buffer  for
     which it was constructed.



SYNOPSIS
     #include <streambuf>
     template<class charT, class traits = char_traits<charT> >
     class istreambuf_iterator
     : public input_iterator



DESCRIPTION
     The  template  class_istreambuf_iterator  reads   successive
     characters  from  the  stream  buffer  for which it was con-
     structed. operator* gives access to the current input  char-
     acter,  if  any,  and  operator++ advances to the next input
     character. If the end of stream  is  reached,  the  iterator
     becomes  equal to the end of stream iterator value, which is
     constructed      by      the      default       constructor,
     istreambuf_iterator().  An istreambuf_iterator object can be
     used only for one-pass-algorithms.



INTERFACE
     template<class charT, class traits = char_traits<charT> >
     class istreambuf_iterator
     : public input_iterator {

     public:

      typedef charT                          char_type;
      typedef typename traits::int_type      int_type;
      typedef traits                         traits_type;
      typedef basic_streambuf<charT, traits> streambuf_type;
      typedef basic_istream<charT, traits>   istream_type;

      class proxy;

      istreambuf_iterator() throw();
      istreambuf_iterator(istream_type& s)  throw();
      istreambuf_iterator(streambuf_type *s) throw();
      istreambuf_iterator(const proxy& p) throw();

      char_type operator*();
      istreambuf_iterator<charT, traits>& operator++();
      proxy operator++(int);
      bool equal(istreambuf_iterator<charT, traits>& b);

     };



     template<class charT, class traits>
     bool operator==(istreambuf_iterator<charT, traits>& a,
                    istreambuf_iterator<charT, traits>& b);

     template<class charT, class traits>
     bool operator !=(istreambuf_iterator<charT, traits>& a,
                    istreambuf_iterator<charT, traits>& b);



TYPES
     char_type


        The type char_type is a synonym for the template  parame-
        ter charT.



     int_type


        The type int_type is a synonym of type traits::in_type.



     istream_type


        The  type  istream_type  is  an  instantiation  of  class
        basic_istream on types charT and traits:

        typedef basic_istream<charT, traits>   istream_type;



     streambuf_type

        The type streambuf_type  is  an  instantiation  of  class
        basic_streambuf on types charT and traits:

        typedef basic_streambuf<charT, traits> streambuf_type;



     traits_type


        The type traits_type is a synonym for the template param-
        eter traits.



NESTED CLASS PROXY
     Class  istreambuf_iterator<charT,traits>::proxy_is  a   tem-
     porary  placeholder  for  the  return  value  of  the  post-
     increment operator. It keeps the character pointed to by the
     previous  value  of  the  iterator  for some possible future
     access.



CONSTRUCTORS
     istreambuf_iterator()
      throw();


        Constructs the end of stream iterator.



     istreambuf_iterator(istream_type& s)
      throw();


        Constructs an istreambuf_iterator that inputs  characters
        using the basic_streambuf object pointed to by s.rdbuf().
        If s.rdbuf() is a null pointer,  the  istreambuf_iterator
        is the end-of-stream iterator.



     istreambuf_iterator(streambuf_type *s)
      throw();


        Constructs an istreambuf_iterator that inputs  characters
        using the basic_streambuf object pointed to by s. If s is
        a null pointer, the istreambuf_iterator  is  the  end-of-
        stream iterator.



     istreambuf_iterator(const proxy& p)
      throw();


        Constructs   an   istreambuf_iterator   that   uses   the
        basic_streambuf object embedded in the proxy object.



MEMBER OPERATORS
     char_type
     operator*();


        Returns the character pointed to by the input sequence of
        the attached stream buffer. If no character is available,
        the iterator becomes equal to the end-of-stream iterator.



     istreambuf_iterator<charT, traits>&
     operator++();


        Increments the input  sequence  of  the  attached  stream
        buffer  to  point  to  the next character. If the current
        character is the last one, the iterator becomes equal  to
        the end-of-stream iterator.



     proxy
     operator++(int);


        Increments the input  sequence  of  the  attached  stream
        buffer  to  point  to  the next character. If the current
        character is the last one, the iterator becomes equal  to
        the  end-of-stream  iterator.  The  proxy object returned
        contains the character pointed to before carrying out the
        post-increment operator.



PUBLIC MEMBER FUNCTIONS
     bool
     equal(istreambuf_iterator<charT, traits>& b);


        Returns true if and only if both iterators are at end  of
        stream,  or  neither  is  at end of stream, regardless of
        what stream buffer object they are using.



NON-MEMBER FUNCTIONS
     template<class charT, class traits>
     bool
     operator==(istreambuf_iterator<charT, traits>& a,
                    istreambuf_iterator<charT, traits>& b);


        Returns a.equal(b).



     template<class charT, class traits>
     bool
     operator==(istreambuf_iterator<charT, traits>& a,
                    istreambuf_iterator<charT, traits>& b);


        Returns !(a.equal(b)).



EXAMPLE
     //
     // stdlib/examples/manual/istreambuf_iterator.cpp
     //
     #include<iostream>
     #include<fstream>

     void main ( )
     {
      using namespace std;

       // open the file is_iter.out for reading and writing
      ofstream out("is_iter.out",
                    ios_base::out | ios_base::in );

       // output the example sentence into the file

      out << "Ceci est un simple example pour demontrer le"
           << endl;
      out << "fonctionement de istreambuf_iterator";

       // seek to the beginning of the file
      out.seekp(0);

       // construct an istreambuf_iterator pointing to
       // the ofstream object underlying stream buffer
      istreambuf_iterator<char> iter(out.rdbuf());

       // construct an end of stream iterator
      istreambuf_iterator<char> end_of_stream_iterator;

      cout << endl;

       // output the content of the file
      while( !iter.equal(end_of_stream_iterator) )

       // use both operator++ and operator*
      cout << *iter++;

      cout << endl;

     }



SEE ALSO
     basic_streambuf(3C++),                  basic_istream(3C++),
     ostreambuf_iterator(3C++)

     Working Paper for Draft Proposed International Standard  for
     Information   Systems--Programming   Language  C++,  Section
     24.5.3



STANDARDS CONFORMANCE
     ANSI X3J16/ISO WG21 Joint C++ Committee

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