HashMap::iterator::operator* returns new pair

[Paul J. Lucas]

This function returns a brand new std::pair as its return value. It has to copy-construct both T and V every time you call operator*.

If HashEntry had the key/value declared like this:

 std::pair<KeyHolder,ValueHolder>

then operator* could simply return a reference to a reinterpret_cast to that:

 return *reinterpret_cast<std::pair<T,V>*>( &entry );

assuming you move theIsFree to be after the pair in the HashEntry struct layout.

[Markos Zaharioudakis (markos-za)]

This is a good suggestion, but notice that the iterator also provides getKey() and getValue() methods, which do not copy. So, if you have a situation where performance may suffer due to the copying done by oprator*, you can use getKey() and getValue() in the mean time.