[Boost-users] multi index sidx.relocate(sidx.end(), si) performance, legality

From: bert hubert (bert.hubert_at_[hidden])
Date: 2006-04-03 08:19:26

Hi People,

Does anybody know if the code below, which relocates an interator to the
end() of an index, is legal? I tried delving into the multi_index code but
it is over my head. 

I ask this because begin() is typically valid as an iterator, but end()
never is. The code does appear to work.

Also, would it be expensive? I think relocating in a sequenced index is
about as expensive as swapping pointers, but I'm not sure.

The code: 

  typedef multi_index_container<
    CacheEntry,
    indexed_by <
                ordered_unique<
                      composite_key< 
                        CacheEntry,
                        member<CacheEntry,string,&CacheEntry::d_qname>,
                        member<CacheEntry,uint16_t,&CacheEntry::d_qtype>
                      >
                >, 
               ordered_non_unique<const_mem_fun<CacheEntry,uint32_t,&CacheEntry::getTTD> >,
               sequenced<>
               >
  > cache_t;
  cache_t d_cache;

// i is given and a valid iterator to the composite key

typedef cache_t::nth_index<2>::type sequence_t;
sequence_t& sidx=d_cache.get<2>();

sequence_t::iterator si=d_cache.project<2>(i); 

sidx.relocate(sidx.end(), si); // does this work?

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