Re: circular iterators

From:

"Greg Herlihy" <greghe@pacbell.net>

Newsgroups:

comp.std.c++

Date:

Fri, 28 Jul 2006 00:20:58 CST

Message-ID:

<1154045806.438849.159700@p79g2000cwp.googlegroups.com>

werasm wrote:

Hi all,

I recently had a problem where I found that writing an iterator adaptor
that would wrap (to the beginning) when incremented to the end, would
make my solution more efficient (instead of rotating) and copying into
a new sequence. Something like this:

CircularIter& operator++()
{ // preincrement
  myIter_.operator++(); //Call underlying preincrement

  if( myIter_ == mySeq_.end() )
  {
    myIter_ = mySeq.begin();
  }
  return (*this);
}

- Are there C++ containers modelling this concept (of not having an end
- circular)?

- Are they considering this kind of concept for standards to come? If
not, why not etc. :-)

It sounds very much like you are describing a circular buffer - a type
of buffer that tends to minimize copying operations when reading and
writing large amounts of data. See
http://en.wikipedia.org/wiki/Circular_buffer.

There is indeed a C++ implementation of a STL-compliant circular buffer
that appears to be ready for a formal boost review. See
http://boost.cvs.sourceforge.net/*checkout*/boost-sandbox/boost-sandbox/libs/circular_buffer/doc/circular_buffer.html.

Greg

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