Utilities/interface/TypeIDBase.h

0001 #ifndef FWCore_Utilities_TypeIDBase_h
0002 #define FWCore_Utilities_TypeIDBase_h
0003 // -*- C++ -*-
0004 //
0005 // Package:     Utilities
0006 // Class  :     TypeIDBase
0007 //
0008 /**\class TypeIDBase TypeIDBase.h FWCore/Utilities/interface/TypeIDBase.h
0009
0010  Description: Base class for classes used to compare C++ types
0011
0012  Usage:
0013     This class is not meant to be used polymorphically (which is why there is no virtual destructor).
0014  Instead it is used to hold a common methods needed by all type comparing classes.
0015
0016 */
0017 //
0018 // Original Author:  Chris Jones
0019 //         Created:  Thu Nov 10 14:59:35 EST 2005
0020 //
0021
0022 // system include files
0023 #include <typeinfo>
0024
0025 // user include files
0026
0027 // forward declarations
0028 namespace edm {
0029   class TypeIDBase {
0030   public:
0031     struct Def {};
0032
0033     constexpr TypeIDBase() noexcept : t_(&(typeid(Def))) {}
0034
0035     constexpr explicit TypeIDBase(const std::type_info& t) noexcept : t_(&t) {}
0036
0037     constexpr explicit TypeIDBase(const std::type_info* t) noexcept : t_(t == nullptr ? &(typeid(Def)) : t) {}
0038
0039     // ---------- const member functions ---------------------
0040
0041     /** Returned C-style string owned by system; do not delete[] it.
0042          This is the (horrible, mangled, platform-dependent) name of
0043          the type. */
0044     const char* name() const { return t_->name(); }
0045
0046     bool operator<(const TypeIDBase& b) const { return t_->before(*(b.t_)); }
0047     bool operator==(const TypeIDBase& b) const { return (*t_) == *(b.t_); }
0048
0049   protected:
0050     constexpr const std::type_info& typeInfo() const { return *t_; }
0051
0052   private:
0053     //const TypeIDBase& operator=(const TypeIDBase&); // stop default
0054
0055     // ---------- member data --------------------------------
0056     //NOTE: since the compiler generates the type_info's and they have a lifetime
0057     //  good for the entire application, we do not have to delete it
0058     //  We also are using a pointer rather than a reference so that operator= will work
0059     const std::type_info* t_;
0060   };
0061
0062   inline bool operator>(const TypeIDBase& a, const TypeIDBase& b) { return b < a; }
0063
0064   inline bool operator!=(const TypeIDBase& a, const TypeIDBase& b) { return !(a == b); }
0065
0066 }  // namespace edm
0067
0068 #endif