Scott McMurray skrev:
On 2009-03-15, Thorsten Ottosen <thorsten.ottosen@dezide.com> wrote:
Scott McMurray skrev:
Is there really a cost to allowing it, though? I'd assume it would have a vector-like operator= that'd be something like this:
copy(other.begin(), other.begin() + size(), begin()); if (size() > other.size()) erase(begin()+other.size(), end()); else insert(end(), other.begin()+size(), other.end()); That is not quite how I implemented it, but for operator= the extra check is not that important, so I can add it,
I agree that self-assignment is uncommon enough for an explicit check to be a pessimization, though. Is the algorithm you have ( the attachment to the first post in this thread doesn't have operator= ) really more efficient than one that doesn't need the explicit check?
Here's the current version. I guess I would have to do some test to make 100% sure it's faster. -Thorsten auto_buffer& operator=( const auto_buffer& r ) // basic { BOOST_ASSERT( this != &r ); difference_type diff = size_ - r.size_; if( diff >= 0 ) { pop_back_n( static_cast<size_type>(diff) ); assign_impl( r.begin(), r.end(), begin() ); } else { if( capacity_ >= r.size() ) { unchecked_push_back_n( static_cast<size_type>(-diff) ); assign_impl( r.begin(), r.end(), begin() ); } else { pointer new_buffer = allocate( r.size() ); (*this).~auto_buffer(); buffer_ = new_buffer; capacity_ = r.size(); copy_impl( r.begin(), r.end(), buffer_ ); size_ = capacity_; } } BOOST_ASSERT( size() == r.size() ); BOOST_ASSERT( is_valid() ); return *this; }