IdentContIndexingPolicy.icc

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
/**
 * @file AthLinks/tools/IdentContIndexingPolicy.icc
 * @author scott snyder <snyder@bnl.gov>
 * @date Apr, 2014
 * @brief Indexing policy for an IdentifiableContainer.
 */
 
 
#include <algorithm>
 
 
namespace SG { 
 
 
/**
 * @brief Test to see if an index is valid.
 * @param index The index to test.
 */
template <class CONT>
inline
bool IdentContIndexingPolicy<CONT>::isValid (stored_index_type index)
{
  return IdentContIndex(index).isValid();
}
 
 
/**
 * @brief Convert from stored to external index types.
 * @param index The stored index.
 */
template <class CONT>
inline
typename IdentContIndexingPolicy<CONT>::index_type
IdentContIndexingPolicy<CONT>::storedToExternal (stored_index_type index)
{
  return index;
}
 
 
/**
 * @brief Make an index invalid.
 * @param index[out] The index to reset.
 */
template <class CONT>
inline
void IdentContIndexingPolicy<CONT>::reset (stored_index_type& index)
{
  index = IdentContIndex().hashAndIndex();
}
    
 
/**
 * @brief Retrieve from a container the element corresponding to an index.
 * @param index The index to fetch.
 * @param data The container.
 *
 * Will throw SG::ExcInvalidIndex if the index is invalid and
 * SG::ExcIndexNotFound if the index is not in the container.
 */
template <class CONT>
typename IdentContIndexingPolicy<CONT>::ElementType
IdentContIndexingPolicy<CONT>::lookup (index_type index, const CONT& data)
{ 
  if (!isValid(index))
    SG::throwExcInvalidIndex ("IdentContIndexingPolicy");
 
  // Find object with hash and index in collection
  IdentContIndex compIndex(index);
  typename CONT::const_iterator it = data.indexFind (compIndex.collHash());
  if (it != data.end()) {
    // Found collection
    // Check if objIndex was correctly set
    if (compIndex.objIndex() < (*it)->size()) {
      return ((**it)[compIndex.objIndex()]);
    }
  }
  // No object found!
  SG::throwExcIndexNotFound ("IdentContIndexingPolicy");
}
 
 
/**
 * @brief Find the index of the (first) instance of ELEMENT in DATA.
 * @param data The container to search.
 * @param element The element to find.
 * @param index[out] The index in the container of @c element.
 *
 * Throws SG::ExcElementNotFound if the element is not in the container.
 */
template <class CONT>
void
IdentContIndexingPolicy<CONT>::reverseLookup(const CONT& data, 
                                             ElementConstReference element,
                                             index_type& index)
{
  // compiler checks we can compare elements
  static_assert (std::equality_comparable<ElementType>);
 
  // The hash and possibly the object index may already have
  // been set by the user. We verify that the index does
  // correspond to the object, and otherwise we recalculate the
  // index
  IdentContIndex compIndex(index);
  typename CONT::const_iterator it = data.indexFind (compIndex.collHash());
  if (it != data.end()) {
    // Found collection
    // Check if objIndex was correctly set
    if (compIndex.objIndex() < (*it)->size()) {
      if ((**it)[compIndex.objIndex()] == element) {
        return;
      }
    }
    // objIndex was not correctly set, look for object
    for (unsigned int i = 0; i < (*it)->size(); ++i) {
      if ((**it)[i] == element) {
        // Save index in collection to object
        compIndex.setObjIndex(i);
        index = compIndex.hashAndIndex();
        return;
      }
    }
    // Correct collection, but object not found
    SG::throwExcElementNotFound ("IdentContIndexingPolicy: reverseLookup");
    return; // Not reached
  }
 
  // Neither hash, nor object index set, must find both - THIS
  // IS SLOW!!
  for (typename CONT::const_iterator it = data.begin();
       it != data.end();
       ++it) {
    const coll_type* coll = *it;
    if (coll) {
      typename coll_type::const_iterator objIt = 
        std::find (coll->begin(), coll->end(),
                   element);
      if (objIt != coll->end()) {
        // Save collection hash and index to object in collection
        compIndex.setCollHash(coll->identifyHash());
        compIndex.setObjIndex(std::distance (coll->begin(), objIt));
        index = compIndex.hashAndIndex();
        return;
      }    
    }
  }
  SG::throwExcElementNotFound ("IdentContIndexingPolicy: reverseLookup");
}
 
 
} // namespace SG