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 /// \file ROOT/REntry.hxx
 /// \ingroup NTuple
 /// \author Jakob Blomer <jblomer@cern.ch>
 /// \date 2018-07-19
 
 /*************************************************************************
  * Copyright (C) 1995-2019, Rene Brun and Fons Rademakers.               *
  * All rights reserved.                                                  *
  *                                                                       *
  * For the licensing terms see $ROOTSYS/LICENSE.                         *
  * For the list of contributors see $ROOTSYS/README/CREDITS.             *
  *************************************************************************/
 
 #ifndef ROOT_REntry
 #define ROOT_REntry
 
 #include <ROOT/RError.hxx>
 #include <ROOT/RField.hxx>
 #include <ROOT/RFieldToken.hxx>
 #include <string_view>
 
 #include <TError.h>
 
 #include <algorithm>
 #include <iterator>
 #include <memory>
 #include <type_traits>
 #include <utility>
 #include <vector>
 #include <unordered_map>
 
 namespace ROOT {
 
 class RNTupleFillContext;
 class RNTupleReader;
 
 namespace Experimental {
 class RNTupleAttrSetReader;
 
 namespace Internal {
 struct RNTupleAttrEntry;
 }
 } // namespace Experimental
 
 // clang-format off
 /**
 \class ROOT::REntry
 \ingroup NTuple
 \brief The REntry is a collection of values in an RNTuple corresponding to a complete row in the data set.
 
 The entry provides a memory-managed binder for a set of values read from fields in an RNTuple. The memory locations that are associated
 with values are managed through shared pointers.
 */
 // clang-format on
 class REntry {
    friend class RNTupleFillContext;
    friend class RNTupleModel;
    friend class RNTupleReader;
    friend class Experimental::RNTupleAttrSetReader;
    friend struct Experimental::Internal::RNTupleAttrEntry;
 
 private:
    /// The entry must be linked to a specific model, identified by a model ID
    std::uint64_t fModelId = 0;
    /// The entry and its tokens are also linked to a specific schema, identified by a schema ID
    std::uint64_t fSchemaId = 0;
    /// Corresponds to the fields of the linked model
    std::vector<ROOT::RFieldBase::RValue> fValues;
    /// For fast lookup of token IDs given a (sub)field name present in the entry
    std::unordered_map<std::string, std::size_t> fFieldName2Token;
    /// To ensure that the entry is standalone, a copy of all field types
    std::vector<std::string> fFieldTypes;
 
    /// Creation of entries can be done by the RNTupleModel, the RNTupleReader, or the RNTupleWriter.
    REntry() = default;
    explicit REntry(std::uint64_t modelId, std::uint64_t schemaId) : fModelId(modelId), fSchemaId(schemaId) {}
 
    void AddValue(ROOT::RFieldBase::RValue &&value)
    {
       fFieldName2Token[value.GetField().GetQualifiedFieldName()] = fValues.size();
       fFieldTypes.push_back(value.GetField().GetTypeName());
       fValues.emplace_back(std::move(value));
    }
 
    /// While building the entry, adds a new value for the field and returns the value's shared pointer
    template <typename T>
    std::shared_ptr<T> AddValue(ROOT::RField<T> &field)
    {
       fFieldName2Token[field.GetQualifiedFieldName()] = fValues.size();
       fFieldTypes.push_back(field.GetTypeName());
       auto value = field.CreateValue();
       fValues.emplace_back(value);
       // We know that the created RValue has the right type, skip the unnecessary check.
       return std::static_pointer_cast<T>(value.template GetPtr<void>());
    }
 
    void Read(ROOT::NTupleSize_t index)
    {
       for (auto &v : fValues) {
          v.Read(index);
       }
    }
 
    std::size_t Append()
    {
       std::size_t bytesWritten = 0;
       for (auto &v : fValues) {
          bytesWritten += v.Append();
       }
       return bytesWritten;
    }
 
    void EnsureMatchingModel(ROOT::RFieldToken token) const
    {
       if (fSchemaId != token.fSchemaId) {
          throw RException(R__FAIL("invalid token for this entry, "
                                   "make sure to use a token from a model with the same schema as this entry."));
       }
    }
 
    /// This function has linear complexity, only use it for more helpful error messages!
    const std::string &FindFieldName(ROOT::RFieldToken token) const
    {
       for (const auto &[fieldName, index] : fFieldName2Token) {
          if (index == token.fIndex) {
             return fieldName;
          }
       }
       // Should never happen, but avoid compiler warning about "returning reference to local temporary object".
       static const std::string empty = "";
       return empty;
    }
 
    template <typename T>
    void EnsureMatchingType(ROOT::RFieldToken token [[maybe_unused]]) const
    {
       if constexpr (!std::is_void_v<T>) {
          if (!Internal::IsMatchingFieldType<T>(fFieldTypes[token.fIndex])) {
             throw RException(R__FAIL("type mismatch for field " + FindFieldName(token) + ": " +
                                      fFieldTypes[token.fIndex] + " vs. " + ROOT::RField<T>::TypeName()));
          }
       }
    }
 
 public:
    using ConstIterator_t = decltype(fValues)::const_iterator;
 
    REntry(const REntry &other) = delete;
    REntry &operator=(const REntry &other) = delete;
    REntry(REntry &&other) = default;
    REntry &operator=(REntry &&other) = default;
    ~REntry() = default;
 
    /// The ordinal of the (sub)field fieldName; can be used in other methods to address the corresponding value
    ROOT::RFieldToken GetToken(std::string_view fieldName) const
    {
       auto it = fFieldName2Token.find(std::string(fieldName));
       if (it == fFieldName2Token.end()) {
          throw RException(R__FAIL("invalid field name: " + std::string(fieldName)));
       }
       return ROOT::RFieldToken(it->second, fSchemaId);
    }
 
    /// Create a new value for the field referenced by `token`.
    void EmplaceNewValue(ROOT::RFieldToken token)
    {
       EnsureMatchingModel(token);
       fValues[token.fIndex].EmplaceNew();
    }
 
    /// Create a new value for the field referenced by its name.
    void EmplaceNewValue(std::string_view fieldName) { EmplaceNewValue(GetToken(fieldName)); }
 
    /// Bind the value for the field, referenced by `token`, to `objPtr`.
    ///
    /// \sa BindValue(std::string_view, std::shared_ptr<T>)
    template <typename T>
    void BindValue(ROOT::RFieldToken token, std::shared_ptr<T> objPtr)
    {
       EnsureMatchingModel(token);
       EnsureMatchingType<T>(token);
       fValues[token.fIndex].Bind(objPtr);
    }
 
    /// Bind the value for the field, referenced by its name, to `objPtr`.
    ///
    /// Ownership is shared with the caller and the object will be kept alive until it is replaced (by a call to
    /// EmplaceNewValue, BindValue, or BindRawPtr) or the entry is destructed.
    ///
    /// **Note**: if `T = void`, type checks are disabled. It is the caller's responsibility to match the field and
    /// object types.
    template <typename T>
    void BindValue(std::string_view fieldName, std::shared_ptr<T> objPtr)
    {
       BindValue<T>(GetToken(fieldName), objPtr);
    }
 
    /// Bind the value for the field, referenced by `token`, to `rawPtr`.
    ///
    /// \sa BindRawPtr(std::string_view, T *)
    template <typename T>
    void BindRawPtr(ROOT::RFieldToken token, T *rawPtr)
    {
       EnsureMatchingModel(token);
       EnsureMatchingType<T>(token);
       fValues[token.fIndex].BindRawPtr(rawPtr);
    }
 
    /// Bind the value for the field, referenced by its name, to `rawPtr`.
    ///
    /// The caller retains ownership of the object and must ensure it is kept alive when reading or writing using the
    /// entry.
    ///
    /// **Note**: if `T = void`, type checks are disabled. It is the caller's responsibility to match the field and
    /// object types.
    template <typename T>
    void BindRawPtr(std::string_view fieldName, T *rawPtr)
    {
       BindRawPtr<T>(GetToken(fieldName), rawPtr);
    }
 
    /// Get the (typed) pointer to the value for the field referenced by `token`.
    ///
    /// \sa GetPtr(std::string_view)
    template <typename T>
    std::shared_ptr<T> GetPtr(ROOT::RFieldToken token) const
    {
       EnsureMatchingModel(token);
       EnsureMatchingType<T>(token);
       return std::static_pointer_cast<T>(fValues[token.fIndex].GetPtr<void>());
    }
 
    /// Get the (typed) pointer to the value for the field referenced by `token`.
    ///
    /// Ownership is shared and the caller can continue to use the object after the entry is destructed.
    ///
    /// **Note**: if `T = void`, type checks are disabled. It is the caller's responsibility to use the returned pointer
    /// according to the field type.
    template <typename T>
    std::shared_ptr<T> GetPtr(std::string_view fieldName) const
    {
       return GetPtr<T>(GetToken(fieldName));
    }
 
    const std::string &GetTypeName(ROOT::RFieldToken token) const
    {
       EnsureMatchingModel(token);
       return fFieldTypes[token.fIndex];
    }
 
    const std::string &GetTypeName(std::string_view fieldName) const { return GetTypeName(GetToken(fieldName)); }
 
    bool HasField(std::string_view fieldName) const { return fFieldName2Token.count(std::string(fieldName)) > 0; }
 
    std::uint64_t GetModelId() const { return fModelId; }
    std::uint64_t GetSchemaId() const { return fSchemaId; }
 
    ConstIterator_t begin() const { return fValues.cbegin(); }
    ConstIterator_t end() const { return fValues.cend(); }
 };
 
 } // namespace ROOT
 
 #endif

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