istreambuf_iterator Class

 

The latest version of this topic can be found at istreambuf_iterator Class.

The template class istreambuf_iterator describes an input iterator object that extracts character elements from an input stream buffer, which it accesses through an object it stores, of type pointer to basic_streambuf< CharType, Traits>.

Syntax

template <class CharType class Traits = char_traits <CharType>>  
class istreambuf_iterator : public iterator<input_iterator_tag, CharType, typename Traits ::off_type, CharType *, CharType &>

Parameters

CharType
The type that represents the character type for the istreambuf_iterator.

Traits
The type that represents the character type for the istreambuf_iterator. This argument is optional and the default value is char_traits< CharType>.

Remarks

The istreambuf_iterator class must satisfy the requirements for an input iterator.

After constructing or incrementing an object of class istreambuf_iterator with a non-null stored pointer, the object effectively attempts to extract and store an object of type CharType from the associated input stream. The extraction may be delayed, however, until the object is actually dereferenced or copied. If the extraction fails, the object effectively replaces the stored pointer with a null pointer, thus making an end-of-sequence indicator.

Constructors

istreambuf_iterator

Constructs an istreambuf_iterator that is initialized to read characters from the input stream.

Typedefs

char_type	A type that provides for the character type of the ostreambuf_iterator.
int_type	A type that provides an integer type for an istreambuf_iterator.
istream_type	A type that provides for the stream type of the istream_iterator.
streambuf_type	A type that provides for the stream type of the istreambuf_iterator.
traits_type	A type that provides for the character traits type of the istream_iterator.

Member Functions

equal

Tests for equality between two input stream buffer iterators.

Operators

operator*	The dereferencing operator returns the next character in the stream.
operator++	Either returns the next character from the input stream or copies the object before incrementing it and returns the copy.
operator->	Returns the value of a member, if any.

Requirements

Header: <iterator>

Namespace: std

istreambuf_iterator::char_type

A type that provides for the character type of the ostreambuf_iterator.

typedef CharType char_type;

Remarks

The type is a synonym for the template parameter CharType.

Example

// istreambuf_iterator_char_type.cpp  
// compile with: /EHsc  
#include <iterator>  
#include <vector>  
#include <iostream>  
#include <algorithm>  
  
int main( )  
{  
   using namespace std;  
  
   typedef istreambuf_iterator<char>::char_type CHT1;  
   typedef istreambuf_iterator<char>::traits_type CHTR1;  
  
   cout << "(Try the example: 'So many dots to be done'\n"  
        << " then an Enter key to insert into the output,\n"  
        << " & use a ctrl-Z Enter key combination to exit): ";  
  
   // istreambuf_iterator for input stream  
   istreambuf_iterator< CHT1, CHTR1> charInBuf ( cin );  
   ostreambuf_iterator<char> charOut ( cout );  
  
   // Used in conjunction with replace_copy algorithm  
   // to insert into output stream and replace spaces  
   // with dot-separators  
   replace_copy ( charInBuf , istreambuf_iterator<char>( ),  
        charOut , ' ' , '.' );  
}  

istreambuf_iterator::equal

Tests for equivalence between two input stream buffer iterators.

bool equal(
    const istreambuf_iterator<CharType, Traits>& right) const;

Parameters

right
The iterator for which to check for equality.

Return Value

true if both istreambuf_iterators are end-of-stream iterators or if neither is an end-of-stream iterator; otherwise false.

Remarks

A range is defined by the istreambuf_iterator to the current position and the end-of-stream iterator, but since all non-end-of stream iterators are equivalent under the equal member function, it is not possible to define any subranges using istreambuf_iterators. The == and != operators have the same semantics.

Example

// istreambuf_iterator_equal.cpp  
// compile with: /EHsc  
#include <iterator>  
#include <iostream>  
  
int main( )  
{  
   using namespace std;  
  
   cout << "(Try the example: 'Hello world!'\n"  
        << " then an Enter key to insert into the output,\n"  
        << " & use a ctrl-Z Enter key combination to exit): ";  
  
   istreambuf_iterator<char> charReadIn1 ( cin );  
   istreambuf_iterator<char> charReadIn2 ( cin );  
  
   bool b1 = charReadIn1.equal ( charReadIn2 );  
  
   if (b1)  
      cout << "The iterators are equal." << endl;  
   else  
      cout << "The iterators are not equal." << endl;  
}  

istreambuf_iterator::int_type

A type that provides an integer type for an istreambuf_iterator.

typedef typename traits_type::int_type int_type;

Remarks

The type is a synonym for Traits::int_type.

Example

// istreambuf_iterator_int_type.cpp  
// compile with: /EHsc  
#include <iterator>  
#include <iostream>  
  
int main( )  
{  
   using namespace std;  
   istreambuf_iterator<char>::int_type inttype1 = 100;  
   cout << "The inttype1 = " << inttype1 << "." << endl;  
}  
\* Output:   
The inttype1 = 100.  
*\  

istreambuf_iterator::istream_type

A type that provides for the stream type of the istreambuf_iterator.

typedef basic_istream<CharType, Traits> istream_type;

Remarks

The type is a synonym for basic_istream< CharType, Traits>.

Example

See istreambuf_iterator for an example of how to declare and use istream_type.

istreambuf_iterator::istreambuf_iterator

Constructs an istreambuf_iterator that is initialized to read characters from the input stream.

istreambuf_iterator(streambuf_type* strbuf = 0) throw();

istreambuf_iterator(istream_type& _Istr) throw();

Parameters

strbuf
The input stream buffer to which the istreambuf_iterator is being attached.

_Istr
The input stream to which the istreambuf_iterator is being attached.

Remarks

The first constructor initializes the input stream-buffer pointer with strbuf. The second constructor initializes the input stream-buffer pointer with _Istr. rdbuf, and then eventually attempts to extract and store an object of type CharType.

Example

// istreambuf_iterator_istreambuf_iterator.cpp  
// compile with: /EHsc  
#include <iterator>  
#include <vector>  
#include <algorithm>  
#include <iostream>  
  
int main( )  
{  
   using namespace std;  
  
   // Following declarations will not compile:  
   istreambuf_iterator<char>::istream_type &istrm = cin;  
   istreambuf_iterator<char>::streambuf_type *strmbf = cin.rdbuf( );  
  
   cout << "(Try the example: 'Oh what a world!'\n"  
      << " then an Enter key to insert into the output,\n"  
      << " & use a ctrl-Z Enter key combination to exit): ";  
   istreambuf_iterator<char> charReadIn ( cin );  
   ostreambuf_iterator<char> charOut ( cout );  
  
   // Used in conjunction with replace_copy algorithm  
   // to insert into output stream and replace spaces  
   // with hyphen-separators  
   replace_copy ( charReadIn , istreambuf_iterator<char>( ),  
      charOut , ' ' , '-' );  
}  

istreambuf_iterator::operator*

The dereferencing operator returns the next character in the stream.

CharType operator*() const;

Return Value

The next character in the stream.

Example

// istreambuf_iterator_operator_deref.cpp  
// compile with: /EHsc  
#include <iterator>  
#include <iostream>  
  
int main( )  
{  
   using namespace std;  
  
   cout << "Type string of characters & enter to output it,\n"  
      << " with stream buffer iterators,(try: 'I'll be back.')\n"  
      << " repeat as many times as desired,\n"   
      << " then keystroke ctrl-Z Enter to exit program: ";  
   istreambuf_iterator<char> inpos ( cin );  
   istreambuf_iterator<char> endpos;  
   ostreambuf_iterator<char> outpos ( cout );  
   while ( inpos != endpos )  
   {  
 *outpos = *inpos;   //Put value of outpos equal to inpos  
      ++inpos;  
      ++outpos;  
   }  
}  

istreambuf_iterator::operator++

Either returns the next character from the input stream or copies the object before incrementing it and returns the copy.

istreambuf_iterator<CharType, Traits>& operator++();

istreambuf_iterator<CharType, Traits> operator++(int);

Return Value

An istreambuf_iterator or a reference to an istreambuf_iterator.

Remarks

The first operator eventually attempts to extract and store an object of type CharType from the associated input stream. The second operator makes a copy of the object, increments the object, and then returns the copy.

Example

// istreambuf_iterator_operator_incr.cpp  
// compile with: /EHsc  
#include <iterator>  
#include <iostream>  
  
int main( )  
{  
   using namespace std;  
  
   cout << "Type string of characters & enter to output it,\n"  
      << " with stream buffer iterators,(try: 'I'll be back.')\n"  
      << " repeat as many times as desired,\n"   
      << " then keystroke ctrl-Z Enter to exit program: ";  
   istreambuf_iterator<char> inpos ( cin );  
   istreambuf_iterator<char> endpos;  
   ostreambuf_iterator<char> outpos ( cout );  
   while ( inpos != endpos )  
   {  
 *outpos = *inpos;  
      ++inpos;   //Increment istreambuf_iterator  
      ++outpos;  
   }  
}  

istreambuf_iterator::operator->

Returns the value of a member, if any.

const Elem* operator->() const;

Return Value

The operator returns &**this.

istreambuf_iterator::streambuf_type

A type that provides for the stream type of the istreambuf_iterator.

typedef basic_streambuf<CharType, Traits> streambuf_type;

Remarks

The type is a synonym for basic_streambuf< CharType, Traits>.

Example

See istreambuf_iterator for an example of how to declare and use istreambuf_type.

istreambuf_iterator::traits_type

A type that provides for the character traits type of the istream_iterator.

typedef Traits traits_type;

Remarks

The type is a synonym for the template parameter Traits.

Example

// istreambuf_iterator_traits_type.cpp  
// compile with: /EHsc  
#include <iterator>  
#include <vector>  
#include <iostream>  
#include <algorithm>  
  
int main( )  
{  
   using namespace std;  
  
   typedef istreambuf_iterator<char>::char_type CHT1;  
   typedef istreambuf_iterator<char>::traits_type CHTR1;  
  
   cout << "(Try the example: 'So many dots to be done'\n"  
        << " then an Enter key to insert into the output,\n"  
        << " & use a ctrl-Z Enter key combination to exit): ";  
  
   // istreambuf_iterator for input stream  
   istreambuf_iterator< CHT1, CHTR1> charInBuf ( cin );  
   ostreambuf_iterator<char> charOut ( cout );  
  
   // Used in conjunction with replace_copy algorithm  
   // to insert into output stream and replace spaces  
   // with dot-separators  
   replace_copy ( charInBuf , istreambuf_iterator<char>( ),  
        charOut , ' ' , '.' );  
}  

See Also

iterator Struct
<iterator>
Thread Safety in the C++ Standard Library
Standard Template Library