AssociationVector.h

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#ifndef DataFormats_Common_AssociationVector_h
#define DataFormats_Common_AssociationVector_h
/* class edm::AssociationVector<CKey, CVal>
 *
 * adds to a std::vector<CVal> a edm::RefProd<CKey>, in such a way
 * that, assuming that the CVal and CKey collections have the same
 * size and are properly ordered, the two collections can be
 * in one-to-one correspondance
 *
 * \author Luca Lista, INFN
 *
 */

#include "DataFormats/Common/interface/CMS_CLASS_VERSION.h"
#include "DataFormats/Common/interface/CommonExceptions.h"
#include "DataFormats/Common/interface/FillView.h"
#include "DataFormats/Common/interface/Ref.h"
#include "DataFormats/Common/interface/RefProd.h"
#include "DataFormats/Common/interface/RefToBase.h"
#include "DataFormats/Common/interface/RefToBaseProd.h"
#include "DataFormats/Common/interface/traits.h"
#include "DataFormats/Provenance/interface/ProductID.h"
#include "FWCore/Utilities/interface/EDMException.h"

#include <atomic>
#include <type_traits>
#include <memory>

namespace edm {
  template <class T>
  class Ptr;

  namespace helper {

    struct AssociationIdenticalKeyReference {
      template <typename T>
      static T const& get(T const& t, ProductID) {
        return t;
      }
    };

    template <typename T>
    struct AssociationKeyReferenceTrait {
      typedef AssociationIdenticalKeyReference type;
    };

    template <typename REFPROD>
    struct RefFromRefProdTrait {};

    template <typename C>
    struct RefFromRefProdTrait<RefProd<C> > {
      typedef Ref<typename RefProd<C>::product_type> ref_type;
    };

    template <typename T>
    struct RefFromRefProdTrait<RefToBaseProd<T> > {
      typedef RefToBase<T> ref_type;
    };
  }  // namespace helper

  template <typename KeyRefProd,
            typename CVal,
            typename KeyRef = typename helper::RefFromRefProdTrait<KeyRefProd>::ref_type,
            typename SizeType =
                unsigned int,  //the type used here can not change when go from 32bit to 64bit or across platforms
            typename KeyReferenceHelper = typename helper::AssociationKeyReferenceTrait<KeyRef>::type>
  class AssociationVector {
    static_assert(std::is_convertible<SizeType, typename CVal::size_type>::value,
                  "Can not convert container size_type to unsigned int.");
    typedef AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper> self;

  public:
    typedef KeyRefProd refprod_type;
    typedef typename KeyRefProd::product_type CKey;
    typedef SizeType size_type;
    typedef typename KeyRef::value_type key_type;
    typedef typename std::pair<KeyRef, typename CVal::value_type> value_type;
    typedef std::vector<value_type> transient_vector_type;
    typedef value_type const& const_reference;
    AssociationVector();
    AssociationVector(KeyRefProd const& ref, CKey const* = nullptr);
    AssociationVector(AssociationVector const&);
    ~AssociationVector();

    size_type size() const;
    bool empty() const;
    const_reference operator[](size_type n) const;
    typename CVal::const_reference operator[](KeyRef const& k) const;
    typename CVal::reference operator[](KeyRef const& k);

    template <typename K>
    typename CVal::const_reference operator[](edm::Ptr<K> const& k) const;
    template <typename K>
    typename CVal::const_reference operator[](edm::RefToBase<K> const& k) const;

    self& operator=(self const&);

    void clear();
    void swap(self& other);
    KeyRefProd const& keyProduct() const { return ref_; }
    KeyRef key(size_type i) const { return KeyRef(ref_, i); }
    typename CVal::value_type const value(size_type i) const { return data_[i]; }
    void setValue(size_type i, typename CVal::value_type const& val);
    void fillView(ProductID const& id, std::vector<void const*>& pointers, FillViewHelperVector& helpers) const;

    typedef typename transient_vector_type::const_iterator const_iterator;

    const_iterator begin() const { return transientVector().begin(); }
    const_iterator end() const { return transientVector().end(); }

    //Used by ROOT storage
    CMS_CLASS_VERSION(11)

  private:
    enum CacheState { kUnset, kFilling, kSet };
    CVal data_;
    KeyRefProd ref_;
    mutable std::atomic<transient_vector_type*> transientVector_;

    transient_vector_type const& transientVector() const;
    void fixup() const;
  };

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline
      typename AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::transient_vector_type const&
      AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::transientVector() const {
    fixup();
    return *(transientVector_.load(std::memory_order_acquire));
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::AssociationVector()
      : data_(), ref_(), transientVector_(nullptr) {}

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::AssociationVector(
      KeyRefProd const& ref, CKey const* coll)
      : data_(coll == nullptr ? ref->size() : coll->size()),
        ref_(ref),
        transientVector_(new transient_vector_type(coll == nullptr ? ref->size() : coll->size())) {}

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::AssociationVector(
      AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper> const& o)
      : data_(o.data_), ref_(o.ref_), transientVector_() {
    auto t = o.transientVector_.load(std::memory_order_acquire);
    if (t) {
      transientVector_.store(new transient_vector_type(*t), std::memory_order_release);
    }
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::~AssociationVector() {
    delete transientVector_.load(std::memory_order_acquire);
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline typename AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::const_reference
  AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::operator[](size_type n) const {
    return transientVector()[n];
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline typename CVal::const_reference
  AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::operator[](KeyRef const& k) const {
    KeyRef keyRef = KeyReferenceHelper::get(k, ref_.id());
    checkForWrongProduct(keyRef.id(), ref_.id());
    return data_[keyRef.key()];
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  template <typename K>
  inline typename CVal::const_reference
  AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::operator[](edm::Ptr<K> const& k) const {
    static_assert(std::is_base_of<K, key_type>::value,
                  "edm::Ptr's key type is not a base class of AssociationVector's item type");
    checkForWrongProduct(k.id(), ref_.id());
    return data_[k.key()];
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  template <typename K>
  typename CVal::const_reference AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::operator[](
      edm::RefToBase<K> const& k) const {
    static_assert(std::is_base_of<K, key_type>::value,
                  "edm::RefToBase's key type is not a base class of AssociationVector's item type");
    checkForWrongProduct(k.id(), ref_.id());
    return data_[k.key()];
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline typename CVal::reference AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::operator[](
      KeyRef const& k) {
    KeyRef keyRef = KeyReferenceHelper::get(k, ref_.id());
    auto t = transientVector_.exchange(nullptr, std::memory_order_acq_rel);
    delete t;
    checkForWrongProduct(keyRef.id(), ref_.id());
    return data_[keyRef.key()];
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>&
  AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::operator=(self const& o) {
    if (this == &o) {
      return *this;
    }
    data_ = o.data_;
    ref_ = o.ref_;
    auto t = transientVector_.exchange(nullptr, std::memory_order_acq_rel);
    delete t;
    return *this;
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline void AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::setValue(
      size_type i, typename CVal::value_type const& val) {
    data_[i] = val;
    KeyRef ref(ref_, i);
    auto t = transientVector_.load(std::memory_order_acquire);
    (*t)[i].first = ref;
    (*t)[i].second = data_[i];
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline typename AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::size_type
  AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::size() const {
    return data_.size();
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline bool AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::empty() const {
    return data_.empty();
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline void AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::clear() {
    data_.clear();
    auto t = transientVector_.load(std::memory_order_acquire);
    if (t)
      t->clear();
    ref_ = KeyRefProd();
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline void AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::swap(self& other) {
    data_.swap(other.data_);
    other.transientVector_.store(
        transientVector_.exchange(other.transientVector_.load(std::memory_order_acquire), std::memory_order_acq_rel),
        std::memory_order_release);
    ref_.swap(other.ref_);
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline void AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::fixup() const {
    if (nullptr == transientVector_.load(std::memory_order_acquire)) {
      std::unique_ptr<transient_vector_type> newT{new transient_vector_type(size())};
      for (size_type i = 0; i != size(); ++i) {
        (*newT)[i] = std::make_pair(KeyRef(ref_, i), data_[i]);
      }
      transient_vector_type* expected = nullptr;
      if (transientVector_.compare_exchange_strong(expected, newT.get())) {
        newT.release();
      }
    }
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  void AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>::fillView(
      ProductID const& id, std::vector<void const*>& pointers, FillViewHelperVector& helpers) const {
    detail::reallyFillView(*this, id, pointers, helpers);
    //     pointers.reserve(this->size());
    //     for(typename CVal::const_iterator i=data_.begin(), e=data_.end(); i!=e; ++i)
    //       pointers.push_back(&(*i));
    //     // helpers is not yet filled in.
    //     //Exception::throwThis(errors::UnimplementedFeature, "AssociationVector<T>::fillView(...)");
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline void swap(AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>& a,
                   AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper>& b) {
    a.swap(b);
  }

  //----------------------------------------------------------------------
  //
  // Free function template to support creation of Views.

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  inline void fillView(AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper> const& obj,
                       ProductID const& id,
                       std::vector<void const*>& pointers,
                       FillViewHelperVector& helpers) {
    obj.fillView(id, pointers, helpers);
  }

  template <typename KeyRefProd, typename CVal, typename KeyRef, typename SizeType, typename KeyReferenceHelper>
  struct has_fillView<AssociationVector<KeyRefProd, CVal, KeyRef, SizeType, KeyReferenceHelper> > {
    static bool const value = true;
  };

}  // namespace edm

#endif