Re: [boost] Dynamic_bitset and access to underlying storage

Subject: Re: [boost] Dynamic_bitset and access to underlying storage
From: Sylvester-Bradley, Gareth (Gareth.Sylvester-Bradley_at_[hidden])
Date: 2010-06-29 05:50:24

Stefan Strasser wrote:
> all of these problems could be solved if dynamic_bitset was changed  
> into a container adapter similar to std::stack and leave the  
> underlying container to the user.

That seems like a neat idea.

In the meantime, [1] GotW #76 warns us not to do this...

#include <boost/dynamic_bitset.hpp>

typedef unsigned long block_t;

namespace { struct weasel { block_t* ptr; }; }

namespace boost {
  template <> template <>
  void dynamic_bitset< block_t >::append( weasel* first, weasel* last )
  {
    first->ptr = &m_bits[0];
    last->ptr = &m_bits[0] + m_bits.size();
  }
}

#include <iostream>

int main( int argc, char* const argv[] )
{
  boost::dynamic_bitset< block_t > db;
  db.append( 42 );
  weasel first = {0}, last = {0};
  db.append( &first, &last );
  std::cout << "size: " << last.ptr - first.ptr;
  std::cout << " first element: " << *first.ptr << std::endl;
  return 0;
}

;-)

Gareth

[1] http://www.gotw.ca/gotw/076.htm

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