IInterface.h

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/***********************************************************************************\
* (c) Copyright 1998-2025 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.                                             *
\***********************************************************************************/
#pragma once
 
#include <Gaudi/Concepts.h>
#include <GaudiKernel/Kernel.h>
#include <GaudiKernel/StatusCode.h>
#include <GaudiKernel/System.h>
#include <ostream>
#include <type_traits>
#include <typeinfo>

#define DeclareInterfaceID( iface, major, minor )                                                                      \
  static const InterfaceID& interfaceID() { return iid::interfaceID(); }                                               \
  using iid      = Gaudi::InterfaceId<iface, major, minor>;                                                            \
  using ext_iids = typename iid::iids

class GAUDI_API InterfaceID final {
public:
  constexpr InterfaceID( unsigned long id, unsigned long major, unsigned long minor = 0 )
      : m_id( id ), m_major_ver( major ), m_minor_ver( minor ) {}

  InterfaceID( const char* name, unsigned long major, unsigned long minor = 0 )
      : m_id( hash32( name ) ), m_major_ver( major ), m_minor_ver( minor ) {}

  constexpr unsigned long id() const { return m_id; }
  constexpr unsigned long majorVersion() const { return m_major_ver; }
  constexpr unsigned long minorVersion() const { return m_minor_ver; }
  constexpr bool versionMatch( const InterfaceID& iid ) const {
    return ( id() == iid.id() && majorVersion() == iid.majorVersion() && minorVersion() >= iid.minorVersion() );
  }

  constexpr bool fullMatch( const InterfaceID& iid ) const {
    return ( id() == iid.id() && majorVersion() == iid.majorVersion() && minorVersion() == iid.minorVersion() );
  }

  constexpr bool operator==( const InterfaceID& iid ) const { return fullMatch( iid ); }
  static unsigned int hash32( const char* key ) {
    unsigned int hash = 0;
    for ( const char* k = key; *k; ++k ) {
      hash += *k;
      hash += ( hash << 10 );
      hash ^= ( hash >> 6 );
    }
    hash += ( hash << 3 );
    hash ^= ( hash >> 11 );
    hash += ( hash << 15 );
    return hash;
  }

  friend std::ostream& operator<<( std::ostream& s, const InterfaceID& id ) {
    s << "IID_" << id.id();
    return s;
  }
 
private:
  unsigned long m_id;
  unsigned long m_major_ver;
  unsigned long m_minor_ver;
};
 
namespace Gaudi {
 
  template <typename... I>
  struct interface_list {};
 
  namespace meta {
    // identity T -> type = T; note that id_<T> is a complete type, even if T is not
    template <typename T>
    struct id_ {
      using type = T;
    };
 
    namespace detail {
      template <typename... Is>
      struct inherit_from : Is... {};
 
      template <typename List, typename I>
      struct append1 {};
 
      // interpose an id_<I> as id_<I> is a complete type, even if I is not... and we need complete
      // types to inherit from
      template <typename... Is, typename I>
      struct append1<interface_list<Is...>, I>
          : id_<std::conditional_t<std::is_base_of_v<id_<I>, inherit_from<id_<Is>...>>, interface_list<Is...>,
                                   interface_list<Is..., I>>> {};
 
      template <typename, typename>
      struct appendN {};
 
      template <typename State>
      struct appendN<interface_list<>, State> : id_<State> {};
 
      template <typename... Is, typename I, typename List>
      struct appendN<interface_list<I, Is...>, List> : appendN<interface_list<Is...>, typename append1<List, I>::type> {
      };
    } // namespace detail
 
    template <typename... Is>
    using unique_interface_list = detail::appendN<interface_list<Is...>, interface_list<>>;
  } // namespace meta
 
  // interface_list concatenation
  template <typename... I>
  struct interface_list_cat;
 
  // identity
  template <typename... I>
  struct interface_list_cat<interface_list<I...>> : meta::unique_interface_list<I...> {};
 
  // binary op
  template <typename... I1, typename... I2>
  struct interface_list_cat<interface_list<I1...>, interface_list<I2...>> : meta::unique_interface_list<I1..., I2...> {
  };
 
  // induction of binary op
  template <typename... I1, typename... I2, typename... Others>
  struct interface_list_cat<interface_list<I1...>, interface_list<I2...>, Others...>
      : interface_list_cat<interface_list<I1..., I2...>, Others...> {};
 
  // append is a special case of concatenation...
  template <typename... I>
  struct interface_list_append;
 
  template <typename... Is, typename I>
  struct interface_list_append<interface_list<Is...>, I>
      : interface_list_cat<interface_list<Is...>, interface_list<I>> {};
 
  template <typename... Is>
  std::vector<std::string> getInterfaceNames( Gaudi::interface_list<Is...> ) {
    return { Is::name()... };
  }
 
  template <typename... Is, typename P>
  void* iid_cast( const InterfaceID& tid, Gaudi::interface_list<Is...>, P* ptr ) {
    const void* target = nullptr;
    ( ( tid.versionMatch( Is::interfaceID() ) &&
        ( target = static_cast<typename Is::interface_type const*>( ptr ), true ) ) ||
      ... );
    return const_cast<void*>( target );
  }

  template <typename INTERFACE, unsigned long majVers, unsigned long minVers>
  struct InterfaceId final {
    using interface_type = INTERFACE;
    using iids = typename Gaudi::interface_list_append<typename interface_type::ext_iids, InterfaceId>::type;
 
    static inline std::string      name() { return System::typeinfoName( typeid( INTERFACE ) ); }
    static constexpr unsigned long majorVersion() { return majVers; }
    static constexpr unsigned long minorVersion() { return minVers; }
 
    static inline const std::type_info& TypeInfo() { return typeid( typename iids::type ); }
 
    static inline const InterfaceID& interfaceID() {
      static const InterfaceID s_iid( name().c_str(), majVers, minVers );
      return s_iid;
    }
  };
 
  constexpr struct fullMatch_t {
    template <typename IFACE1, typename IFACE2, unsigned long major1, unsigned long major2, unsigned long minor1,
              unsigned long minor2>
    constexpr bool operator()( InterfaceId<IFACE1, major1, minor1>, InterfaceId<IFACE2, major2, minor2> ) const {
      return false;
    }
    template <typename IFACE, unsigned long major, unsigned long minor>
    constexpr bool operator()( InterfaceId<IFACE, major, minor>, InterfaceId<IFACE, major, minor> ) const {
      return true;
    }
  } fullMatch{};
 
  constexpr struct majorMatch_t {
    template <typename IFACE1, typename IFACE2, unsigned long major1, unsigned long major2, unsigned long minor1,
              unsigned long minor2>
    constexpr bool operator()( InterfaceId<IFACE1, major1, minor1>, InterfaceId<IFACE2, major2, minor2> ) const {
      return false;
    }
    template <typename IFACE, unsigned long major, unsigned long minor1, unsigned long minor2>
    constexpr bool operator()( InterfaceId<IFACE, major, minor1>, InterfaceId<IFACE, major, minor2> ) const {
      return true;
    }
  } majorMatch{};
} // namespace Gaudi

class GAUDI_API IInterface {
public:
  using iid = Gaudi::InterfaceId<IInterface, 0, 0>;

  using ext_iids = Gaudi::interface_list<iid>;

  static inline const InterfaceID& interfaceID() { return iid::interfaceID(); }
 
  template <Gaudi::IsInterface TARGET>
  TARGET* cast() {
    if ( auto output = i_cast( TARGET::interfaceID() ) ) { return reinterpret_cast<TARGET*>( output ); }
    if constexpr ( Gaudi::IsInterface<TARGET> ) {
      void* tgt = nullptr;
      queryInterface( TARGET::interfaceID(), &tgt ).ignore();
      if ( tgt ) {
        // queryInterface bumps the reference count of the target object, but we should not
        auto* target = reinterpret_cast<TARGET*>( tgt );
        // we cannot use release() because we may be called with an object with initial reference count of 0 and that
        // would delete the object
        static_cast<const IInterface*>( target )->decRef();
        return target;
      }
    }
    return nullptr;
  }
 
  template <Gaudi::IsInterface TARGET>
  TARGET const* cast() const {
    if ( auto output = i_cast( TARGET::interfaceID() ) ) { return reinterpret_cast<TARGET const*>( output ); }
    if constexpr ( Gaudi::IsInterface<TARGET> ) {
      void* tgt = nullptr;
      const_cast<IInterface*>( this )->queryInterface( TARGET::interfaceID(), &tgt ).ignore();
      if ( tgt ) {
        // queryInterface bumps the reference count of the target object, but we should not
        auto* target = reinterpret_cast<const TARGET*>( tgt );
        // we cannot use release() because we may be called with an object with initial reference count of 0 and that
        // would delete the object
        static_cast<const IInterface*>( target )->decRef();
        return target;
      }
    }
    return nullptr;
  }
 
  template <typename TARGET>
    requires( !Gaudi::IsInterface<TARGET> )
  TARGET* cast() {
    return dynamic_cast<TARGET*>( this );
  }
 
  template <typename TARGET>
    requires( !Gaudi::IsInterface<TARGET> )
  TARGET const* cast() const {
    return dynamic_cast<TARGET const*>( this );
  }

  virtual std::vector<std::string> getInterfaceNames() const = 0;

  virtual unsigned long addRef() const = 0;

  virtual unsigned long release() const = 0;

  virtual unsigned long refCount() const = 0;

  virtual StatusCode queryInterface( const InterfaceID& ti, void** pp ) = 0;

  enum class Status : StatusCode::code_t {
    FAILURE = 0,
    SUCCESS = 1,
    NO_INTERFACE,
    VERSMISMATCH,
    LAST_ERROR
  };

  virtual ~IInterface() = default;
 
  // Note: these cannot be protected methods because they may be needed by specializations
  // that delegate to other instances (like queryInterface does).
  virtual void const* i_cast( const InterfaceID& ) const = 0;
 
  void* i_cast( const InterfaceID& iid ) {
    return const_cast<void*>( const_cast<const IInterface*>( this )->i_cast( iid ) );
  }
 
protected:
  virtual unsigned long decRef() const = 0;
};
 
STATUSCODE_ENUM_DECL( IInterface::Status )
 
namespace Gaudi {
  template <typename TARGET>
  TARGET* Cast( IInterface* i ) {
    return i ? i->cast<TARGET>() : nullptr;
  }
 
  template <typename TARGET>
  const TARGET* Cast( const IInterface* i ) {
    return i ? i->cast<const TARGET>() : nullptr;
  }
} // namespace Gaudi

template <class IFace>
bool isValidInterface( IFace* i ) {
  void* ii = nullptr;
  return i->queryInterface( IFace::interfaceID(), &ii ).isSuccess();
}

template <class DEST, class SRC>
inline DEST** pp_cast( SRC** ptr ) {
  return reinterpret_cast<DEST**>( ptr );
}
 
#include <GaudiKernel/extend_interfaces.h>
#include <GaudiKernel/extends.h>
#include <GaudiKernel/implements.h>