move and rename directory: Reference->include/loki
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416
include/loki/MultiMethods.h
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416
include/loki/MultiMethods.h
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////////////////////////////////////////////////////////////////////////////////
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// The Loki Library
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// Copyright (c) 2001 by Andrei Alexandrescu
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// This code accompanies the book:
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// Alexandrescu, Andrei. "Modern C++ Design: Generic Programming and Design
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// Patterns Applied". Copyright (c) 2001. Addison-Wesley.
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// Permission to use, copy, modify, distribute and sell this software for any
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// purpose is hereby granted without fee, provided that the above copyright
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// notice appear in all copies and that both that copyright notice and this
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// permission notice appear in supporting documentation.
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// The author or Addison-Wesley Longman make no representations about the
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// suitability of this software for any purpose. It is provided "as is"
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// without express or implied warranty.
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////////////////////////////////////////////////////////////////////////////////
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#ifndef MULTIMETHODS_INC_
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#define MULTIMETHODS_INC_
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#include "Typelist.h"
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#include "LokiTypeInfo.h"
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#include "Functor.h"
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#include "AssocVector.h"
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////////////////////////////////////////////////////////////////////////////////
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// IMPORTANT NOTE:
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// The double dispatchers implemented below differ from the excerpts shown in
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// the book - they are simpler while respecting the same interface.
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////////////////////////////////////////////////////////////////////////////////
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namespace Loki
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{
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////////////////////////////////////////////////////////////////////////////////
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// class template InvocationTraits (helper)
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// Helps implementing optional symmetry
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////////////////////////////////////////////////////////////////////////////////
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namespace Private
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{
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template <class SomeLhs, class SomeRhs,
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class Executor, typename ResultType>
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struct InvocationTraits
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{
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static ResultType
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DoDispatch(SomeLhs& lhs, SomeRhs& rhs,
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Executor& exec, Int2Type<false>)
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{
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return exec.Fire(lhs, rhs);
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}
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static ResultType
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DoDispatch(SomeLhs& lhs, SomeRhs& rhs,
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Executor& exec, Int2Type<true>)
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{
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return exec.Fire(rhs, lhs);
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}
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};
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}
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////////////////////////////////////////////////////////////////////////////////
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// class template StaticDispatcher
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// Implements an automatic static double dispatcher based on two typelists
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////////////////////////////////////////////////////////////////////////////////
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template
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<
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class Executor,
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class BaseLhs,
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class TypesLhs,
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bool symmetric = true,
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class BaseRhs = BaseLhs,
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class TypesRhs = TypesLhs,
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typename ResultType = void
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>
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class StaticDispatcher
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{
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template <class SomeLhs>
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static ResultType DispatchRhs(SomeLhs& lhs, BaseRhs& rhs,
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Executor exec, NullType)
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{ return exec.OnError(lhs, rhs); }
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template <class Head, class Tail, class SomeLhs>
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static ResultType DispatchRhs(SomeLhs& lhs, BaseRhs& rhs,
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Executor exec, Typelist<Head, Tail>)
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{
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if (Head* p2 = dynamic_cast<Head*>(&rhs))
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{
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Int2Type<(symmetric &&
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int(TL::IndexOf<TypesRhs, Head>::value) <
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int(TL::IndexOf<TypesLhs, SomeLhs>::value))> i2t;
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typedef Private::InvocationTraits<
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SomeLhs, Head, Executor, ResultType> CallTraits;
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return CallTraits::DoDispatch(lhs, *p2, exec, i2t);
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}
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return DispatchRhs(lhs, rhs, exec, Tail());
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}
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static ResultType DispatchLhs(BaseLhs& lhs, BaseRhs& rhs,
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Executor exec, NullType)
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{ return exec.OnError(lhs, rhs); }
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template <class Head, class Tail>
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static ResultType DispatchLhs(BaseLhs& lhs, BaseRhs& rhs,
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Executor exec, Typelist<Head, Tail>)
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{
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if (Head* p1 = dynamic_cast<Head*>(&lhs))
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{
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return DispatchRhs(*p1, rhs, exec, TypesRhs());
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}
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return DispatchLhs(lhs, rhs, exec, Tail());
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}
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public:
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static ResultType Go(BaseLhs& lhs, BaseRhs& rhs,
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Executor exec)
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{ return DispatchLhs(lhs, rhs, exec, TypesLhs()); }
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};
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////////////////////////////////////////////////////////////////////////////////
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// class template BasicDispatcher
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// Implements a logarithmic double dispatcher for functors (or functions)
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// Doesn't offer automated casts or symmetry
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////////////////////////////////////////////////////////////////////////////////
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template
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<
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class BaseLhs,
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class BaseRhs = BaseLhs,
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typename ResultType = void,
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typename CallbackType = ResultType (*)(BaseLhs&, BaseRhs&)
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>
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class BasicDispatcher
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{
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typedef std::pair<TypeInfo,TypeInfo> KeyType;
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typedef CallbackType MappedType;
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typedef AssocVector<KeyType, MappedType> MapType;
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MapType callbackMap_;
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void DoAdd(TypeInfo lhs, TypeInfo rhs, CallbackType fun);
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bool DoRemove(TypeInfo lhs, TypeInfo rhs);
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public:
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template <class SomeLhs, class SomeRhs>
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void Add(CallbackType fun)
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{
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DoAdd(typeid(SomeLhs), typeid(SomeRhs), fun);
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}
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template <class SomeLhs, class SomeRhs>
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bool Remove()
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{
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return DoRemove(typeid(SomeLhs), typeid(SomeRhs));
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}
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ResultType Go(BaseLhs& lhs, BaseRhs& rhs);
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};
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// Non-inline to reduce compile time overhead...
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template <class BaseLhs, class BaseRhs,
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typename ResultType, typename CallbackType>
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void BasicDispatcher<BaseLhs,BaseRhs,ResultType,CallbackType>
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::DoAdd(TypeInfo lhs, TypeInfo rhs, CallbackType fun)
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{
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callbackMap_[KeyType(lhs, rhs)] = fun;
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}
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template <class BaseLhs, class BaseRhs,
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typename ResultType, typename CallbackType>
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bool BasicDispatcher<BaseLhs,BaseRhs,ResultType,CallbackType>
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::DoRemove(TypeInfo lhs, TypeInfo rhs)
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{
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return callbackMap_.erase(KeyType(lhs, rhs)) == 1;
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}
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template <class BaseLhs, class BaseRhs,
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typename ResultType, typename CallbackType>
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ResultType BasicDispatcher<BaseLhs,BaseRhs,ResultType,CallbackType>
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::Go(BaseLhs& lhs, BaseRhs& rhs)
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{
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typename MapType::key_type k(typeid(lhs),typeid(rhs));
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typename MapType::iterator i = callbackMap_.find(k);
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if (i == callbackMap_.end())
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{
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throw std::runtime_error("Function not found");
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}
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return (i->second)(lhs, rhs);
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}
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////////////////////////////////////////////////////////////////////////////////
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// class template StaticCaster
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// Implementation of the CastingPolicy used by FunctorDispatcher
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////////////////////////////////////////////////////////////////////////////////
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template <class To, class From>
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struct StaticCaster
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{
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static To& Cast(From& obj)
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{
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return static_cast<To&>(obj);
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}
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};
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////////////////////////////////////////////////////////////////////////////////
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// class template DynamicCaster
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// Implementation of the CastingPolicy used by FunctorDispatcher
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////////////////////////////////////////////////////////////////////////////////
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template <class To, class From>
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struct DynamicCaster
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{
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static To& Cast(From& obj)
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{
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return dynamic_cast<To&>(obj);
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}
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};
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////////////////////////////////////////////////////////////////////////////////
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// class template Private::FnDispatcherHelper
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// Implements trampolines and argument swapping used by FnDispatcher
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////////////////////////////////////////////////////////////////////////////////
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namespace Private
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{
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template <class BaseLhs, class BaseRhs,
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class SomeLhs, class SomeRhs,
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typename ResultType,
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class CastLhs, class CastRhs,
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ResultType (*Callback)(SomeLhs&, SomeRhs&)>
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struct FnDispatcherHelper
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{
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static ResultType Trampoline(BaseLhs& lhs, BaseRhs& rhs)
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{
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return Callback(CastLhs::Cast(lhs), CastRhs::Cast(rhs));
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}
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static ResultType TrampolineR(BaseRhs& rhs, BaseLhs& lhs)
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{
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return Trampoline(lhs, rhs);
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}
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};
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}
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////////////////////////////////////////////////////////////////////////////////
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// class template FnDispatcher
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// Implements an automatic logarithmic double dispatcher for functions
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// Features automated conversions
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////////////////////////////////////////////////////////////////////////////////
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template <class BaseLhs, class BaseRhs = BaseLhs,
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typename ResultType = void,
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template <class, class> class CastingPolicy = DynamicCaster,
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template <class, class, class, class>
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class DispatcherBackend = BasicDispatcher>
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class FnDispatcher
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{
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DispatcherBackend<BaseLhs, BaseRhs, ResultType,
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ResultType (*)(BaseLhs&, BaseRhs&)> backEnd_;
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public:
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template <class SomeLhs, class SomeRhs>
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void Add(ResultType (*pFun)(BaseLhs&, BaseRhs&))
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{
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return backEnd_.template Add<SomeLhs, SomeRhs>(pFun);
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}
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template <class SomeLhs, class SomeRhs,
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ResultType (*callback)(SomeLhs&, SomeRhs&)>
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void Add()
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{
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typedef Private::FnDispatcherHelper<
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BaseLhs, BaseRhs,
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SomeLhs, SomeRhs,
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ResultType,
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CastingPolicy<SomeLhs,BaseLhs>,
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CastingPolicy<SomeRhs,BaseRhs>,
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callback> Local;
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Add<SomeLhs, SomeRhs>(&Local::Trampoline);
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}
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template <class SomeLhs, class SomeRhs,
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ResultType (*callback)(SomeLhs&, SomeRhs&),
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bool symmetric>
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void Add(bool = true) // [gcc] dummy bool
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{
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typedef Private::FnDispatcherHelper<
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BaseLhs, BaseRhs,
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SomeLhs, SomeRhs,
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ResultType,
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CastingPolicy<SomeLhs,BaseLhs>,
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CastingPolicy<SomeRhs,BaseRhs>,
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callback> Local;
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Add<SomeLhs, SomeRhs>(&Local::Trampoline);
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if (symmetric)
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{
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Add<SomeRhs, SomeLhs>(&Local::TrampolineR);
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}
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}
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template <class SomeLhs, class SomeRhs>
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void Remove()
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{
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backEnd_.template Remove<SomeLhs, SomeRhs>();
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}
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ResultType Go(BaseLhs& lhs, BaseRhs& rhs)
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{
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return backEnd_.Go(lhs, rhs);
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}
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};
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////////////////////////////////////////////////////////////////////////////////
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// class template FunctorDispatcherAdaptor
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// permits use of FunctorDispatcher under gcc.2.95.2/3
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///////////////////////////////////////////////////////////////////////////////
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namespace Private
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{
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template <class BaseLhs, class BaseRhs,
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class SomeLhs, class SomeRhs,
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typename ResultType,
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class CastLhs, class CastRhs,
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class Fun, bool SwapArgs>
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class FunctorDispatcherHelper
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{
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Fun fun_;
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ResultType Fire(BaseLhs& lhs, BaseRhs& rhs,Int2Type<false>)
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{
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return fun_(CastLhs::Cast(lhs), CastRhs::Cast(rhs));
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}
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ResultType Fire(BaseLhs& rhs, BaseRhs& lhs,Int2Type<true>)
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{
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return fun_(CastLhs::Cast(lhs), CastRhs::Cast(rhs));
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}
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public:
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FunctorDispatcherHelper(const Fun& fun) : fun_(fun) {}
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ResultType operator()(BaseLhs& lhs, BaseRhs& rhs)
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{
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return Fire(lhs,rhs,Int2Type<SwapArgs>());
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}
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};
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}
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////////////////////////////////////////////////////////////////////////////////
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// class template FunctorDispatcher
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// Implements a logarithmic double dispatcher for functors
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// Features automated casting
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////////////////////////////////////////////////////////////////////////////////
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template <class BaseLhs, class BaseRhs = BaseLhs,
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typename ResultType = void,
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template <class, class> class CastingPolicy = DynamicCaster,
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template <class, class, class, class>
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class DispatcherBackend = BasicDispatcher>
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class FunctorDispatcher
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{
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typedef TYPELIST_2(BaseLhs&, BaseRhs&) ArgsList;
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typedef Functor<ResultType, ArgsList, DEFAULT_THREADING> FunctorType;
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DispatcherBackend<BaseLhs, BaseRhs, ResultType, FunctorType> backEnd_;
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public:
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template <class SomeLhs, class SomeRhs, class Fun>
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void Add(const Fun& fun)
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{
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typedef Private::FunctorDispatcherHelper<
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BaseLhs, BaseRhs,
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SomeLhs, SomeRhs,
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ResultType,
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CastingPolicy<SomeLhs, BaseLhs>,
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CastingPolicy<SomeRhs, BaseRhs>,
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Fun, false> Adapter;
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backEnd_.template Add<SomeLhs, SomeRhs>(FunctorType(Adapter(fun)));
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}
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template <class SomeLhs, class SomeRhs, bool symmetric, class Fun>
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void Add(const Fun& fun)
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{
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Add<SomeLhs,SomeRhs>(fun);
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if (symmetric)
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{
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// Note: symmetry only makes sense where BaseLhs==BaseRhs
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typedef Private::FunctorDispatcherHelper<
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BaseLhs, BaseLhs,
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SomeLhs, SomeRhs,
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ResultType,
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CastingPolicy<SomeLhs, BaseLhs>,
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CastingPolicy<SomeRhs, BaseLhs>,
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Fun, true> AdapterR;
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backEnd_.template Add<SomeRhs, SomeLhs>(FunctorType(AdapterR(fun)));
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}
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}
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template <class SomeLhs, class SomeRhs>
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void Remove()
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{
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backEnd_.template Remove<SomeLhs, SomeRhs>();
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}
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ResultType Go(BaseLhs& lhs, BaseRhs& rhs)
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{
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return backEnd_.Go(lhs, rhs);
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}
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};
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} // namespace Loki
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////////////////////////////////////////////////////////////////////////////////
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// Change log:
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// June 20, 2001: ported by Nick Thurn to gcc 2.95.3. Kudos, Nick!!!
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// February 2, 2003: fixed dependent names - credit due to Rani Sharoni
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////////////////////////////////////////////////////////////////////////////////
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#endif
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