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 #ifndef PODIO_FRAME_H
 #define PODIO_FRAME_H
 
 #include "podio/CollectionBase.h"
 #include "podio/CollectionIDTable.h"
 #include "podio/FrameCategories.h" // mainly for convenience
 #include "podio/GenericParameters.h"
 #include "podio/ICollectionProvider.h"
 #include "podio/SchemaEvolution.h"
 #include "podio/utilities/TypeHelpers.h"
 
 #include <concepts>
 #include <initializer_list>
 #include <memory>
 #include <mutex>
 #include <optional>
 #include <set>
 #include <stdexcept>
 #include <string>
 #include <type_traits>
 #include <unordered_map>
 #include <vector>
 
 namespace podio {
 
 /// Concept for enabling overloads for r-values
 template <typename T>
 concept RValueType = !std::is_lvalue_reference_v<T>;
 
 /// Concept for enabling overloads only for Collection r-values
 template <typename T>
 concept CollectionRValueType = CollectionType<T> && RValueType<T>;
 
 /// Concept encoding the minimal interface a type has to provide to usable as
 /// raw data from which a Frame can be constructed.
 ///
 /// Since the Frame either locks on raw data access, or is guaranteed to only
 /// run on a single thread when doing so (e.g. constructors) none of these have
 /// to be thread-safe either, even though implementations might be able to
 /// provide reasonable guarantees anyway.
 template <typename T>
 concept FrameDataType = requires(T t) {
   { t.getIDTable() } -> std::same_as<podio::CollectionIDTable>;
   { t.getCollectionBuffers(std::string{}) } -> std::same_as<std::optional<podio::CollectionReadBuffers>>;
   { t.getAvailableCollections() } -> std::same_as<std::vector<std::string>>;
   { t.getParameters() } -> std::same_as<std::unique_ptr<podio::GenericParameters>>;
 };
 
 template <typename T>
 concept RValueFrameDataType = FrameDataType<T> && RValueType<T>;
 
 namespace detail {
   /// The minimal interface for raw data types
   struct EmptyFrameData {
     podio::CollectionIDTable getIDTable() const {
       return {};
     }
 
     /// Try to get the buffers for a collection
     std::optional<podio::CollectionReadBuffers> getCollectionBuffers(const std::string&) {
       return std::nullopt;
     }
 
     /// Get the **still available**, i.e. yet unpacked, collections from the raw data
     std::vector<std::string> getAvailableCollections() const {
       return {};
     }
 
     /// Get the parameters that are stored in the raw data
     std::unique_ptr<podio::GenericParameters> getParameters() {
       return std::make_unique<podio::GenericParameters>();
     }
   };
   static_assert(FrameDataType<EmptyFrameData>, "EmptyFrameData should match FrameDataType concept");
 } // namespace detail
 
 template <FrameDataType FrameData>
 std::optional<podio::CollectionReadBuffers> unpack(FrameData* data, const std::string& name) {
   return data->getCollectionBuffers(name);
 }
 
 /// The Frame is a generalized (event) data container that aggregates all
 /// relevant data.
 ///
 /// It is possible to store collections as well as parameters / meta data in a
 /// Frame and all I/O facilities of podio operate on Frames.
 class Frame {
   /// Internal abstract interface for the type-erased implementation of the
   /// Frame class
   struct FrameConcept {
     virtual ~FrameConcept() = default;
     virtual const podio::CollectionBase* get(const std::string& name) const = 0;
     virtual const podio::CollectionBase* put(std::unique_ptr<podio::CollectionBase> coll, const std::string& name) = 0;
     virtual podio::GenericParameters& parameters() = 0;
     virtual const podio::GenericParameters& parameters() const = 0;
 
     virtual std::vector<std::string> availableCollections() const = 0;
 
     // Writing interface. Need this to be able to store all necessary information
     // TODO: Figure out whether this can be "hidden" somehow
     virtual podio::CollectionIDTable getIDTable() const = 0;
   };
 
   /// The interface implementation of the abstract FrameConcept that is
   /// necessary for a type-erased implementation of the Frame class
   template <typename FrameDataT>
   struct FrameModel final : FrameConcept, public ICollectionProvider {
 
     FrameModel(std::unique_ptr<FrameDataT> data);
     ~FrameModel() override = default;
     FrameModel(const FrameModel&) = delete;
     FrameModel& operator=(const FrameModel&) = delete;
     FrameModel(FrameModel&&) = default;
     FrameModel& operator=(FrameModel&&) = default;
 
     /// Try and get the collection from the internal storage and return a
     /// pointer to it if found. Otherwise return a nullptr
     const podio::CollectionBase* get(const std::string& name) const final;
 
     /// Try and place the collection into the internal storage and return a
     /// pointer to it. If a collection already exists or insertion fails, return
     /// a nullptr
     const podio::CollectionBase* put(std::unique_ptr<CollectionBase> coll, const std::string& name) final;
 
     /// Get a reference to the internally used GenericParameters
     podio::GenericParameters& parameters() override {
       return *m_parameters;
     }
     /// Get a const reference to the internally used GenericParameters
     const podio::GenericParameters& parameters() const override {
       return *m_parameters;
     }
 
     bool get(uint32_t collectionID, podio::CollectionBase*& collection) const override;
 
     podio::CollectionIDTable getIDTable() const override {
       // Make a copy
       return {m_idTable.ids(), m_idTable.names()};
     }
 
     std::vector<std::string> availableCollections() const override;
 
   private:
     podio::CollectionBase* doGet(const std::string& name, bool setReferences = true) const;
 
     using CollectionMapT = std::unordered_map<std::string, std::unique_ptr<podio::CollectionBase>>;
 
     mutable CollectionMapT m_collections{};                 ///< The internal map for storing unpacked collections
     mutable std::unique_ptr<std::mutex> m_mapMtx{nullptr};  ///< The mutex for guarding the internal collection map
     std::unique_ptr<FrameDataT> m_data{nullptr};            ///< The raw data read from file
     mutable std::unique_ptr<std::mutex> m_dataMtx{nullptr}; ///< The mutex for guarding the raw data
     podio::CollectionIDTable m_idTable{};                   ///< The collection ID table
     std::unique_ptr<podio::GenericParameters> m_parameters{nullptr}; ///< The generic parameter store for this frame
     mutable std::set<uint32_t> m_retrievedIDs{}; ///< The IDs of the collections that we have already read (but not yet
                                                  ///< put into the map)
   };
 
   std::unique_ptr<FrameConcept> m_self; ///< The internal concept pointer through which all the work is done
 
 public:
   /// Empty Frame constructor
   Frame();
 
   /// Frame constructor from (almost) arbitrary raw data.
   ///
   /// @tparam FrameData Arbitrary data container that provides access to the
   ///                   collection buffers as well as the metadata, when
   ///                   requested by the Frame. The unique_ptr has to be checked
   ///                   for validity before calling this constructor.
   ///
   /// @throws std::invalid_argument if the passed pointer is a nullptr.
   template <FrameDataType FrameData>
   Frame(std::unique_ptr<FrameData>);
 
 #ifdef PODIO_ROOT_OLDER_6_36
   /// Frame constructor from (almost) arbitrary raw data.
   ///
   /// This r-value overload is mainly present for enabling the python bindings,
   /// where cppyy seems to strip the std::unique_ptr somewhere in the process
   ///
   /// @tparam FrameData Arbitrary data container that provides access to the
   ///                   collection buffers as well as the metadata, when
   ///                   requested by the Frame.
   template <RValueFrameDataType FrameData>
   Frame(FrameData&&);
 #endif
 
   /// A Frame is move-only
   Frame(const Frame&) = delete;
   /// A Frame is move-only
   Frame& operator=(const Frame&) = delete;
 
   /// Frame move constructor
   Frame(Frame&&) = default;
 
   /// Frame move assignment operator
   Frame& operator=(Frame&&) = default;
 
   /// Frame destructor
   ///
   /// @note Since the Frame owns all the collections that have been put into it,
   /// or that can be obtained from it, this invalidates all references to these
   /// collections.
   ~Frame() = default;
 
   /// Get a collection from the Frame by name.
   ///
   /// @tparam CollT The type of the desired collection
   /// @param  name  The name of the collection
   ///
   /// @returns      A const reference to the collection if it is available or to
   ///               an empty (static) collection
   template <CollectionType CollT>
   const CollT& get(const std::string& name) const;
 
   /// Get a collection pointer from the Frame by name.
   ///
   /// This is a type-erased version that is also used by the python bindings.
   ///
   /// @returns A const pointer to a collection if it is available or a nullptr
   ///          if it is not
   const podio::CollectionBase* get(const std::string& name) const;
 
   /// (Destructively) move a collection into the Frame and get a reference to
   /// the inserted collection back for further use.
   ///
   /// The collection that is passed into the Frame has to be moved into it
   /// explicitly and the moved-from collection will be in the typical *valid but
   /// undefined state* in c++.
   ///
   /// @tparam CollT The type of the collection
   /// @param  coll  An rvalue reference to the collection to put into the Frame.
   /// @param  name  The name under which this collection should be stored in the
   ///               Frame
   ///
   /// @returns      A const reference to the collection that has just been
   ///               inserted
   ///
   /// @throws std::invalid_argument in case a collection already exists with the
   ///               same name
   template <CollectionRValueType CollT>
   const CollT& put(CollT&& coll, const std::string& name);
 
   /// (Destructively) move a collection into the Frame.
   ///
   /// @param coll The collection that should be moved into the Frame
   /// @param name The name under which this collection should be stored in the
   ///             Frame
   ///
   /// @throws std::invalid_argument in case a collection already exists with the
   ///               same name
   void put(std::unique_ptr<podio::CollectionBase> coll, const std::string& name);
 
   /// Add a value to the parameters of the Frame (if the type is supported).
   ///
   /// @tparam T    The type of the parameter. Has to be one of the types that
   ///              is supported by GenericParameters
   /// @param key   The name under which this parameter should be stored
   /// @param value The value of the parameter. A copy will be put into the Frame
   template <ValidGenericDataType T>
   inline void putParameter(const std::string& key, T value) {
     m_self->parameters().set(key, std::move(value));
   }
 
   /// Add a string value to the parameters of the Frame.
   ///
   /// This is a dedicated overload for enabling on-the-fly conversion from
   /// string literals.
   ///
   /// @param key   The name under which this parameter should be stored
   /// @param value The value of the parameter. A copy will be put into the Frame
   inline void putParameter(const std::string& key, std::string value) {
     putParameter<std::string>(key, std::move(value));
   }
 
   /// Add a vector of strings value the parameters of the Frame.
   ///
   /// This is a dedicated overload for enabling on-the-fly conversion from
   /// an initializer_list of string literals
   ///
   /// @param key    The name under which this parameter should be stored
   /// @param values The values of the parameter. A copy will be put into the Frame
   inline void putParameter(const std::string& key, std::vector<std::string> values) {
     putParameter<std::vector<std::string>>(key, std::move(values));
   }
 
   /// Add a vector of values to the parameters of the Frame (if the type is
   /// supported).
   ///
   /// This is a dedicated overload for enabling on-the-fly conversions of
   /// initializer_list of values
   ///
   /// @tparam T    The type of the parameter. Has to be one of the types that
   ///              is supported by GenericParameters
   /// @param key    The name under which this parameter should be stored
   /// @param values The values of the parameter. A copy will be put into the Frame
   template <ValidGenericDataType T>
   inline void putParameter(const std::string& key, std::initializer_list<T>&& values) {
     putParameter<std::vector<T>>(key, std::move(values));
   }
 
   /// Retrieve parameters via key from the internal store.
   ///
   /// @tparam T  The desired type of the parameter (can also be std::vector<T>)
   /// @param key The key under which the value is stored
   ///
   /// @returns   An optional holding the value if it is present
   template <ValidGenericDataType T>
   inline auto getParameter(const std::string& key) const {
     return m_self->parameters().get<T>(key);
   }
 
   /// Retrieve all parameters stored in this Frame.
   ///
   /// This is mainly intended for I/O purposes and we encourage to use the Frame
   /// functionality of getParameter or getParameterKeys in general.
   ///
   /// @returns The internally used GenericParameters
   inline const podio::GenericParameters& getParameters() const {
     return m_self->parameters();
   }
 
   /// Get the keys of all stored parameters for a given type
   ///
   /// @tparam T The desired parameter type
   ///
   /// @returns  A vector of keys for this parameter type
   template <ValidGenericDataType T>
   inline std::vector<std::string> getParameterKeys() const {
     return m_self->parameters().getKeys<T>();
   }
 
   /// Get all **currently** available collection names.
   ///
   /// @returns The names of all collections, including those that might still
   ///          need unpacking from the internal FrameData
   std::vector<std::string> getAvailableCollections() const {
     return m_self->availableCollections();
   }
 
   /// Get the name of the passed collection
   ///
   /// @param coll The collection for which the name should be obtained
   ///
   /// @returns The name of the collection or an empty optional if this
   ///          collection is not known to the Frame
   inline std::optional<std::string> getName(const podio::CollectionBase& coll) const {
     return getName(coll.getID());
   }
 
   /// Get the name for the passed collectionID
   ///
   /// @param collectionID The collection ID of the collection for which the name
   ///                     should be obtained
   /// @returns The name of the collection or an empty optional if this
   ///          collectionID is not known to the Frame
   inline std::optional<std::string> getName(const uint32_t collectionID) const {
     return m_self->getIDTable().name(collectionID);
   }
 
   // Interfaces for writing below
 
   /// Get a collection for writing.
   ///
   /// @note This method is intended for I/O purposes only and should not be used
   /// in other code.
   ///
   /// @returns The collection pointer in a prepared and "ready-to-write" state
   const podio::CollectionBase* getCollectionForWrite(const std::string& name) const {
     const auto* coll = m_self->get(name);
     if (coll) {
       coll->prepareForWrite();
     }
 
     return coll;
   }
 
   /// Get the internal CollectionIDTable for writing.
   ///
   /// @note This method is intended for I/O purposes only and should not be used
   /// in other code.
   ///
   /// @returns A copy of the internal collection id table
   podio::CollectionIDTable getCollectionIDTableForWrite() const {
     return m_self->getIDTable();
   }
 };
 
 // implementations below
 
 inline Frame::Frame() : Frame(std::make_unique<detail::EmptyFrameData>()) {
 }
 
 template <FrameDataType FrameData>
 Frame::Frame(std::unique_ptr<FrameData> data) : m_self(std::make_unique<FrameModel<FrameData>>(std::move(data))) {
 }
 
 #ifdef PODIO_ROOT_OLDER_6_36
 template <RValueFrameDataType FrameData>
 Frame::Frame(FrameData&& data) : Frame(std::make_unique<FrameData>(std::move(data))) {
 }
 #endif
 
 template <CollectionType CollT>
 const CollT& Frame::get(const std::string& name) const {
   if (const auto* coll = dynamic_cast<const CollT*>(m_self->get(name))) {
     return *coll;
   }
   throw std::runtime_error("Cannot retrieve collection " + name + " of type " + std::string(CollT::typeName));
 }
 
 inline const podio::CollectionBase* Frame::get(const std::string& name) const {
   return m_self->get(name);
 }
 
 inline void Frame::put(std::unique_ptr<podio::CollectionBase> coll, const std::string& name) {
   m_self->put(std::move(coll), name);
 }
 
 template <CollectionRValueType CollT>
 const CollT& Frame::put(CollT&& coll, const std::string& name) {
   return *static_cast<const CollT*>(m_self->put(std::make_unique<CollT>(std::move(coll)), name));
 }
 
 template <typename FrameDataT>
 Frame::FrameModel<FrameDataT>::FrameModel(std::unique_ptr<FrameDataT> data) :
     m_mapMtx(std::make_unique<std::mutex>()), m_dataMtx(std::make_unique<std::mutex>()) {
   if (!data) {
     throw std::invalid_argument(
         "FrameData is a nullptr. If you are reading from a file it may be corrupted or you may reading beyond the end "
         "of the file, please check the validity of the data before creating a Frame.");
   }
   m_data = std::move(data);
   m_idTable = std::move(m_data->getIDTable());
   m_parameters = std::move(m_data->getParameters());
 }
 
 template <typename FrameDataT>
 const podio::CollectionBase* Frame::FrameModel<FrameDataT>::get(const std::string& name) const {
   return doGet(name);
 }
 
 template <typename FrameDataT>
 podio::CollectionBase* Frame::FrameModel<FrameDataT>::doGet(const std::string& name, bool setReferences) const {
   {
     // First check whether the collection is in the map already
     //
     // Collections only land here if they are fully unpacked, i.e.
     // prepareAfterRead has been called or it has been put into the Frame
     std::lock_guard lock{*m_mapMtx};
     if (const auto it = m_collections.find(name); it != m_collections.end()) {
       return it->second.get();
     }
   }
 
   podio::CollectionBase* retColl = nullptr;
 
   // Now try to get it from the raw data if we have the possibility
   if (m_data) {
     // Have the buffers in the outer scope here to hold the raw data lock as
     // briefly as possible
     std::optional<podio::CollectionReadBuffers> buffers;
     {
       std::lock_guard lock{*m_dataMtx};
       buffers = unpack(m_data.get(), name);
     }
     if (buffers) {
       std::unique_ptr<podio::CollectionBase> coll{nullptr};
       // Subset collections do not need schema evolution (by definition)
       if (buffers->data == nullptr) {
         coll = buffers->createCollection(buffers.value(), true);
       } else {
         auto evolvedBuffers = podio::SchemaEvolution::instance().evolveBuffers(buffers.value(), buffers->schemaVersion,
                                                                                std::string(buffers->type));
         coll = evolvedBuffers.createCollection(evolvedBuffers, false);
       }
 
       coll->prepareAfterRead();
       coll->setID(m_idTable.collectionID(name).value());
       {
         std::lock_guard mapLock{*m_mapMtx};
         auto [it, success] = m_collections.emplace(name, std::move(coll));
         // TODO: Check success? Or simply assume that everything is fine at this point?
         // TODO: Collision handling?
         retColl = it->second.get();
       }
 
       if (setReferences) {
         retColl->setReferences(this);
       }
     }
   }
 
   return retColl;
 }
 
 template <typename FrameDataT>
 bool Frame::FrameModel<FrameDataT>::get(uint32_t collectionID, CollectionBase*& collection) const {
   const auto name = m_idTable.name(collectionID);
   if (!name) {
     return false;
   }
   const auto& [_, inserted] = m_retrievedIDs.insert(collectionID);
 
   if (inserted) {
     auto coll = doGet(name.value());
     if (coll) {
       collection = coll;
       return true;
     }
   } else {
     auto coll = doGet(name.value(), false);
     if (coll) {
       collection = coll;
       return true;
     }
   }
 
   return false;
 }
 
 template <typename FrameDataT>
 const podio::CollectionBase* Frame::FrameModel<FrameDataT>::put(std::unique_ptr<podio::CollectionBase> coll,
                                                                 const std::string& name) {
   {
     std::lock_guard lock{*m_mapMtx};
     auto [it, success] = m_collections.try_emplace(name, std::move(coll));
     if (success) {
       // TODO: Check whether this collection is already known to the idTable
       // -> What to do on collision?
       // -> Check before we emplace it into the internal map to prevent possible
       //    collisions from collections that are potentially present from rawdata?
       it->second->setID(m_idTable.add(name));
       return it->second.get();
     } else {
       throw std::invalid_argument("An object with key " + name + " already exists in the frame");
     }
   }
 
   return nullptr;
 }
 
 template <typename FrameDataT>
 std::vector<std::string> Frame::FrameModel<FrameDataT>::availableCollections() const {
   // TODO: Check if there is a more efficient way to do this. Currently this is
   // done very conservatively, but in a way that should always work, regardless
   // of assumptions. It might be possible to simply return what is in the
   // idTable here, because that should in principle encompass everything that is
   // in the raw data as well as things that have been put into the frame
 
   // Lock both the internal map and the rawdata for this
   std::scoped_lock lock{*m_mapMtx, *m_dataMtx};
 
   auto collections = m_data->getAvailableCollections();
   collections.reserve(collections.size() + m_collections.size());
 
   for (const auto& [name, _] : m_collections) {
     collections.push_back(name);
   }
 
   return collections;
 }
 
 } // namespace podio
 
 #endif // PODIO_FRAME_H

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