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 /***********************************************************************************\
 * (c) Copyright 1998-2024 CERN for the benefit of the LHCb and ATLAS collaborations *
 *                                                                                   *
 * This software is distributed under the terms of the Apache version 2 licence,     *
 * copied verbatim in the file "LICENSE".                                            *
 *                                                                                   *
 * In applying this licence, CERN does not waive the privileges and immunities       *
 * granted to it by virtue of its status as an Intergovernmental Organization        *
 * or submit itself to any jurisdiction.                                             *
 \***********************************************************************************/
 #ifndef GAUDIKERNEL_GAUDIHANDLE_H
 #define GAUDIKERNEL_GAUDIHANDLE_H
 
 // Includes
 #include <Gaudi/Property.h>
 #include <GaudiKernel/GaudiException.h>
 #include <GaudiKernel/IInterface.h>
 #include <GaudiKernel/System.h>
 
 #include <algorithm>
 #include <iostream>
 #include <stdexcept>
 #include <string>
 #include <type_traits>
 #include <vector>
 
 namespace details {
   /// Cast a pointer to a non const type
   template <class T>
   std::remove_const_t<T>* nonConst( T* p ) {
     return const_cast<std::remove_const_t<T>*>( p );
   }
 } // namespace details
 
 class GAUDI_API GaudiHandleInfo {
 protected:
   /** Some basic information and helper functions shared between various handles/arrays.
    @param myComponentType: string indicating what type of component the handle is pointing to.
                         For example: "PublicTool", "PrivateTool", "Service".
                         This is used for printout and on the python side for type checking.
                         On the python side there are classes with these names with "Handle" appended:
                         PublicToolHandle,PrivateToolHandle,ServiceHandle
    @param myParentName: Name of the parent that has this handle as a member. Used in printout.
   */
   GaudiHandleInfo( std::string myComponentType, std::string myParentName )
       : m_componentType( std::move( myComponentType ) ), m_parentName( std::move( myParentName ) ) {}
 
 public:
   /** virtual destructor so that derived class destructor is called. */
   // Don't use =default here.  Otherwise, in c++20 mode, clang will
   // instantiate the handle virtual functions early, breaking the case
   // where handles are used with a forward-declared class.
   virtual ~GaudiHandleInfo() {}
   //
   // Public member functions
   //
   const std::string& componentType() const { return m_componentType; }
 
   /** name as used in declareProperty(name,gaudiHandle) */
   const std::string& propertyName() const { return m_propertyName; }
 
   /** set name as used in declareProperty(name,gaudiHandle). Used in printout. */
   void setPropertyName( std::string propName ) { m_propertyName = std::move( propName ); }
 
   /** The name of the parent */
   const std::string& parentName() const { return m_parentName; }
 
   /** The python class name for the property in the genconf-generated configurables.
       The python class is defined in GaudiPython/python/GaudiHandles.py.
       To be implemented in derived class. */
   virtual std::string pythonPropertyClassName() const = 0;
 
   /** Python representation of handle, i.e. python class name and argument.
       Can be used in the genconf-generated configurables.
       The corresponding python classes are defined in GaudiPython/GaudiHandles.py.
       To be implemented in derived class. */
   virtual std::string pythonRepr() const = 0;
 
   // Easy printing out of Handles and HandleArrays
   // It prints <propertyName> = <HandleType>( <HandleType(s)AndName(s)> )
   friend std::ostream& operator<<( std::ostream& os, const GaudiHandleInfo& handle );
 
 protected:
   /** The component type */
   void setComponentType( std::string componentType ) { m_componentType = std::move( componentType ); }
 
   /** The name of the parent */
   void setParentName( std::string parent ) { m_parentName = std::move( parent ); }
 
 private:
   //
   // Data members
   //
   std::string m_componentType; // e.g.: "PublicTool","PrivateTool","Service"
   std::string m_propertyName;  // name as used in declareProperty(name,gaudiHandle)
   std::string m_parentName;    // name of the parent having this handle as a member
 };
 
 /** @class GaudiHandleBase GaudiHandle.h GaudiKernel/GaudiHandle.h
 
     Base class to handles to be used in lieu of naked pointers to various Gaudi components.
     This allows better control through the framework of component loading, configuration and usage.
     This base class implements common features.
     @author Martin.Woudstra@cern.ch
 */
 class GAUDI_API GaudiHandleBase : public GaudiHandleInfo {
   //
   // Ctors etc
   //
 protected:
   /** Create a handle ('smart pointer') to a gaudi component
    @param myTypeAndName: "MyType/MyName" ("MyType" is short for "MyType/MyType")
                        'MyType' is the name of the concrete class of the component
                        'MyName' is to distinguish several instances of the same concrete class
    @param myComponentType: string indicating what type of component the handle is pointing to.
                         For example: "PublicTool", "PrivateTool", "Service".
                         This is used for printout and on the python side for type checking.
                         On the python side there are classes with these names with "Handle" appended:
                         PublicToolHandle,PrivateToolHandle,ServiceHandle
    @param myParentName: Name of the parent that has this handle as a member. Used in printout.
   */
   GaudiHandleBase( std::string myTypeAndName, std::string myComponentType, std::string myParentName )
       : GaudiHandleInfo( std::move( myComponentType ), std::move( myParentName ) ) {
     setTypeAndName( std::move( myTypeAndName ) );
   }
 
 public:
   //
   // Public member functions
   //
   /** The full type and name: "type/name" */
   std::string typeAndName() const { return m_typeAndName; }
 
   /** The concrete component class name: the part before the '/' */
   std::string type() const;
 
   /** The instance name: the part after the '/' */
   std::string name() const;
 
   /** Check if the handle has been set to empty string (i.e. typeAndName string is empty). */
   bool empty() const { return m_typeAndName.empty(); }
 
   /** The component "type/name" string */
   void setTypeAndName( std::string myTypeAndName );
 
   /** Set the instance name (part after the '/') without changing the class type */
   void setName( std::string_view myName );
 
   /** Name of the componentType with "Handle" appended. Used as the python class name
       for the property in the genconf-generated configurables.
       The python class is defined in GaudiPython/python/GaudiHandles.py. */
   std::string pythonPropertyClassName() const override;
 
   /** name used for printing messages */
   std::string messageName() const;
 
   /** Python representation of handle, i.e. python class name and argument.
       Can be used in the genconf-generated configurables.
       The corresponding python classes are defined in GaudiPython/GaudiHandles.py */
   std::string pythonRepr() const override;
 
   using PropertyType = GaudiHandleProperty;
 
 private:
   //
   // Data member
   //
   std::string m_typeAndName; // the full type and name: "type/name"
 };
 
 /** @class GaudiHandle GaudiHandle.h GaudiKernel/GaudiHandle.h
 
     Handle to be used in lieu of naked pointers to gaudis. This allows
     better control through the framework of gaudi loading and usage.
     T is the type of the component interface (or concrete class).
 
     @author Martin.Woudstra@cern.ch
 */
 template <class T>
 class GAUDI_API GaudiHandle : public GaudiHandleBase {
   //
   // Constructors etc.
   //
 protected:
   GaudiHandle( std::string myTypeAndName, std::string myComponentType, std::string myParentName )
       : GaudiHandleBase( std::move( myTypeAndName ), std::move( myComponentType ), std::move( myParentName ) ) {}
 
 public:
   /** Copy constructor needed for correct ref-counting */
   template <typename CT = T, typename NCT = std::remove_const_t<T>>
   GaudiHandle( const GaudiHandle<NCT>& other,
                std::enable_if_t<std::is_const_v<CT> && !std::is_same_v<CT, NCT>>* = nullptr )
       : GaudiHandleBase( other ) {
     m_pObject = other.get();
     if ( m_pObject ) ::details::nonConst( m_pObject.load() )->addRef();
   }
 
   /** Copy constructor needed for correct ref-counting */
   GaudiHandle( const GaudiHandle& other ) : GaudiHandleBase( other ) {
     m_pObject = other.m_pObject.load();
     if ( m_pObject ) ::details::nonConst( m_pObject.load() )->addRef();
   }
 
   /** Assignment operator for correct ref-counting */
   template <typename CT = T, typename NCT = std::remove_const_t<T>>
   std::enable_if_t<std::is_const_v<CT> && !std::is_same_v<CT, NCT>, GaudiHandle&>
   operator=( const GaudiHandle<NCT>& other ) {
     GaudiHandleBase::operator=( other );
     // release any current tool
     release().ignore();
     m_pObject = other.get();
     // update ref-counting
     if ( m_pObject ) ::details::nonConst( m_pObject.load() )->addRef();
     return *this;
   }
 
   /** Assignment operator for correct ref-counting */
   GaudiHandle& operator=( const GaudiHandle& other ) {
     GaudiHandleBase::operator=( other );
     // release any current tool
     release().ignore();
     m_pObject = other.m_pObject.load();
     // update ref-counting
     if ( m_pObject ) ::details::nonConst( m_pObject.load() )->addRef();
     return *this;
   }
 
   /** Retrieve the component. Release existing component if needed. */
   StatusCode retrieve() const {
     // not really const, because it updates m_pObject
     // Do the lookup into a temporary pointer.
     T* p = nullptr;
     if ( retrieve( p ).isFailure() ) { return StatusCode::FAILURE; }
 
     // If m_pObject is null, then copy p to m_pObject.
     // Otherwise, release p.
     T* old = nullptr;
     if ( m_pObject.compare_exchange_strong( old, p ) ) { return StatusCode::SUCCESS; }
     return release( p );
   }
 
   /** Release the component. */
   StatusCode release() const {
     // not really const, because it updates m_pObject
     StatusCode sc = StatusCode::SUCCESS;
     if ( m_pObject ) {
       sc        = release( m_pObject );
       m_pObject = nullptr;
     }
     return sc;
   }
 
   /// Check if the handle is valid (try to retrive the object is not done yet).
   bool isValid() const {
     // not really const, because it may update m_pObject
     return m_pObject || retrieve().isSuccess();
   }
 
   /** For testing if handle has component. Does retrieve() if needed.
       If this returns false, the component could not be retrieved. */
   operator bool() const {
     // not really const, because it may update m_pObject
     return isValid();
   }
 
   /// Return the wrapped pointer, not calling retrieve() if null.
   T* get() { return m_pObject; }
 
   /// Return the wrapped pointer, not calling retrieve() if null.
   std::add_const_t<T>* get() const { return m_pObject; }
 
   /// True if the wrapped pointer is not null.
   bool isSet() const { return get(); }
 
   T& operator*() {
     assertObject();
     return *m_pObject;
   }
 
   T* operator->() {
     assertObject();
     return m_pObject;
   }
 
   std::add_const_t<T>& operator*() const {
     // not really const, because it may update m_pObject
     assertObject();
     return *m_pObject;
   }
 
   std::add_const_t<T>* operator->() const {
     // not really const, because it may update m_pObject
     assertObject();
     return m_pObject;
   }
 
   /** Helper function to get default type string from the class type */
   std::string getDefaultType() { return System::typeinfoName( typeid( T ) ); }
 
   std::string getDefaultName() {
     const auto defName = GaudiHandleBase::type();
     return ( defName.empty() ? getDefaultType() : defName );
   }
 
 protected:
   /** Retrieve the component. To be implemented by the derived class. It will pass the pointer */
   virtual StatusCode retrieve( T*& ) const = 0; // not really const, because it updates m_pObject
 
   /** Release the component. Default implementation calls release() on the component.
       Can be overridden by the derived class if something else is needed. */
   virtual StatusCode release( T* comp ) const { // not really const, because it updates m_pObject
     // const cast to support T being a const type
     ::details::nonConst( comp )->release();
     return StatusCode::SUCCESS;
   }
 
 private:
   /** Helper function to set default name and type */
   void setDefaultTypeAndName() {
     const std::string& myType = getDefaultType();
     GaudiHandleBase::setTypeAndName( myType + '/' + myType );
   }
 
   /** Helper function to set default type from the class type T */
   void setDefaultType() { GaudiHandleBase::setTypeAndName( getDefaultType() ); }
 
   /** Load the pointer to the component. Do a retrieve if needed. Throw an exception if
       retrieval fails. */
   void assertObject() const { // not really const, because it may update m_pObject
     if ( !isValid() ) {
       throw GaudiException( "Failed to retrieve " + componentType() + ": " + typeAndName(),
                             componentType() + " retrieve", StatusCode::FAILURE );
     }
   }
 
 private:
   //
   // Data members
   //
   mutable std::atomic<T*> m_pObject = nullptr;
 };
 
 /**
    Base class of array's of various gaudihandles. Used in communication with
    GaudiHandleArrayProperty. For that purpose is has some pure virtual functions.
    This is a non-templated class to one Property can handle all kinds of concrete handles.
 */
 
 class GAUDI_API GaudiHandleArrayBase : public GaudiHandleInfo {
 protected:
   GaudiHandleArrayBase( std::string myComponentType, std::string myParentName )
       : GaudiHandleInfo( std::move( myComponentType ), std::move( myParentName ) ) {}
 
 public:
   using PropertyType = GaudiHandleArrayProperty;
   typedef std::vector<GaudiHandleBase*>       BaseHandleArray;
   typedef std::vector<const GaudiHandleBase*> ConstBaseHandleArray;
 
   /** Set the array of handles from list of "type/name" strings in
       &lt;myTypesAndNamesList&gt;. Return whether set was successful or not */
   bool setTypesAndNames( const std::vector<std::string>& myTypesAndNamesList );
 
   /** Return a vector with "type/name" strings of all handles in the array.
       Inverse of setTypesAndNames() */
   const std::vector<std::string> typesAndNames() const;
 
   /** Return a vector with "type" strings of all handles in the array. */
   const std::vector<std::string> types() const;
 
   /** Return a vector with "type/name" strings of all handles in the array. */
   const std::vector<std::string> names() const;
 
   /** Helper function to get a vector of strings filled with the return value
       of each tool of a member function if GaudiHandleBase */
   const std::vector<std::string> getBaseInfos( std::string ( GaudiHandleBase::*pMemFunc )() const ) const;
 
   /** Name of the componentType with "HandleArray" appended. Used as the python class name
       for the property in the genconf-generated configurables.
       The python class is defined in GaudiPython/python/GaudiHandles.py. */
   std::string pythonPropertyClassName() const override;
 
   /** Python representation of array of handles, i.e. list of python handles.
       Can be used in the genconf-generated configurables.
       The corresponding python classes are defined in GaudiPython/GaudiHandles.py */
   std::string pythonRepr() const override;
 
   /** Add a handle to the array with "type/name" given in &lt;myHandleTypeAndName&gt;.
       Return whether addition was successful or not.
       Must be implemented by derived class with concrete handle category. */
   virtual bool push_back( const std::string& myHandleTypeAndName ) = 0;
 
   /** Clear the list of handles. Implemented in GaudiHandleArray */
   virtual void clear() = 0;
 
   /** Return whether the list of tools is empty. */
   virtual bool empty() const = 0;
 
   /** Get a read-only vector of const GaudiHandleBase* pointing to the real handles.
       Implemented in GaudiHandleArray. */
   virtual ConstBaseHandleArray getBaseArray() const = 0;
 
   /** Get a read-write vector of GaudiHandleBase* pointing to the real handles.
       Implemented in GaudiHandleArray. */
   virtual BaseHandleArray getBaseArray() = 0;
 
   /** To be able to tell if Array was ever retreived **/
   virtual bool retrieved() const = 0;
 };
 
 /** T is the concrete handle type, e.g. ToolHandle<IMyTool> */
 template <class T>
 class GAUDI_API GaudiHandleArray : public GaudiHandleArrayBase {
 public:
   //
   // public nested types
   //
   typedef std::vector<T>                                HandleVector;
   typedef typename HandleVector::value_type             value_type;
   typedef typename HandleVector::size_type              size_type;
   typedef typename HandleVector::reference              reference;
   typedef typename HandleVector::const_reference        const_reference;
   typedef typename HandleVector::iterator               iterator;
   typedef typename HandleVector::const_iterator         const_iterator;
   typedef typename HandleVector::reverse_iterator       reverse_iterator;
   typedef typename HandleVector::const_reverse_iterator const_reverse_iterator;
 
 protected:
   //
   // Constructors
   //
   /** Generic constructor. Probably not very useful...
       @param typesAndNamesList : a vector of strings with the concrete "type/name" strings
                                  for the list of tools
  */
   GaudiHandleArray( const std::vector<std::string>& myTypesAndNamesList, std::string myComponentType,
                     std::string myParentName )
       : GaudiHandleArrayBase( std::move( myComponentType ), std::move( myParentName ) ) {
     setTypesAndNames( myTypesAndNamesList );
   }
 
   /** Constructor creating an empty array.
       @param typesAndNamesList : a vector of strings with the concrete "type/name" strings
                                  for the list of tools
  */
   GaudiHandleArray( const std::string& myComponentType, const std::string& myParentName )
       : GaudiHandleArrayBase( myComponentType, myParentName ) {}
 
 public:
   /**Set the array of GaudiHandles from typeAndNames given in vector of strings. */
   GaudiHandleArray& operator=( const std::vector<std::string>& myTypesAndNamesList ) {
     setTypesAndNames( myTypesAndNamesList );
     return *this;
   }
 
   GaudiHandleArrayBase::BaseHandleArray getBaseArray() override {
     GaudiHandleArrayBase::BaseHandleArray baseArray;
     for ( auto& h : m_handleArray ) baseArray.push_back( &h );
     return baseArray;
   }
 
   GaudiHandleArrayBase::ConstBaseHandleArray getBaseArray() const override {
     GaudiHandleArrayBase::ConstBaseHandleArray baseArray;
     for ( auto& h : m_handleArray ) baseArray.push_back( &h );
     return baseArray;
   }
 
   //
   // Simulate (part of) an std::vector
   //
   iterator begin() { return m_handleArray.begin(); }
 
   iterator end() { return m_handleArray.end(); }
 
   const_iterator begin() const { return m_handleArray.begin(); }
 
   const_iterator end() const { return m_handleArray.end(); }
 
   const_iterator rbegin() const { return m_handleArray.rbegin(); }
 
   const_iterator rend() const { return m_handleArray.rend(); }
 
   size_type size() const { return m_handleArray.size(); }
 
   void clear() override { m_handleArray.clear(); }
 
   bool empty() const override { return m_handleArray.empty(); }
 
   T& operator[]( int index ) { return m_handleArray[index]; }
 
   const T& operator[]( int index ) const { return m_handleArray[index]; }
 
   /** Get pointer (!) to ToolHandle by instance name. Returns zero pointer if not found */
   T* operator[]( std::string_view name ) {
     auto it = std::find_if( begin(), end(), [&]( const_reference r ) { return r.name() == name; } );
     return it != end() ? &*it : nullptr;
   }
 
   /** Get const pointer (!) to ToolHandle by instance name. Returns zero pointer if not found */
   const T* operator[]( std::string_view name ) const {
     auto it = std::find_if( begin(), end(), [&]( const_reference r ) { return r.name() == name; } );
     return it != end() ? &*it : nullptr;
   }
 
   /** Add a handle with given type and name. Can be overridden in derived class.
       Return whether addition was successful or not. */
   using GaudiHandleArrayBase::push_back; // avoid compiler warning
   virtual bool push_back( const T& myHandle ) {
     m_handleArray.push_back( myHandle );
     return true;
   }
 
   /** Retrieve all tools */
   StatusCode retrieve() {
     StatusCode sc = StatusCode::SUCCESS;
     for ( auto& i : *this ) {
       // stop at first failure
       if ( i.retrieve().isFailure() ) {
         sc = StatusCode::FAILURE;
         break;
       }
     }
     if ( sc ) { m_retrieved = true; }
     return sc;
   }
 
   /** Release all tools */
   StatusCode release() {
     StatusCode sc = StatusCode::SUCCESS;
     for ( auto& i : *this ) {
       // continue trying to release other tools even if we fail...
       if ( i.release().isFailure() ) sc = StatusCode::FAILURE;
     }
     return sc;
   }
 
   /** has Array been retreived? **/
   virtual bool retrieved() const override { return m_retrieved; }
 
 private:
   //
   // Private data members
   //
   HandleVector m_handleArray;
   bool         m_retrieved{ false };
 };
 
 #endif // ! GAUDIKERNEL_GAUDIHANDLE_H

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