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#ifndef QPID_AMQP_0_10_APPLY_H
#define QPID_AMQP_0_10_APPLY_H
/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
#include <boost/optional.hpp>
namespace qpid {
namespace amqp_0_10 {
template <class F, class R=typename F::result_type> struct FunctionAndResult {
F* functor;
boost::optional<R> result;
FunctionAndResult() : functor(0) {}
template <class T> void invoke(T& t) { result=(*functor)(t); }
template <class T> void invoke(const T& t) { result=(*functor)(t); }
R getResult() { return *result; }
};
// void result is special case.
template <class F> struct FunctionAndResult<F, void> {
F* functor;
FunctionAndResult() : functor(0) {}
template <class T> void invoke(T& t) { (*functor)(t); }
void getResult() {}
};
// Metafunction returning correct abstract visitor for Visitable type.
template <class Visitable> struct VisitorType {
typedef typename Visitable::Visitor type;
};
template <class Visitable> struct VisitorType<const Visitable> {
typedef typename Visitable::ConstVisitor type;
};
template <class Visitor, class F>
struct ApplyVisitorBase : public Visitor, public FunctionAndResult<F> {};
// Specialize for each visitor type
template <class Visitable, class F> struct ApplyVisitor;
/** Apply a functor to a visitable object.
* The functor can have operator() overloads for each visitable type
* and/or templated operator().
*/
template <class F, class Visitable>
typename F::result_type apply(F& functor, Visitable& visitable) {
ApplyVisitor<typename VisitorType<Visitable>::type, F> visitor;
visitor.functor=&functor;
visitable.accept(visitor);
return visitor.getResult();
}
template <class F, class Visitable>
typename F::result_type apply(const F& functor, Visitable& visitable) {
ApplyVisitor<typename VisitorType<Visitable>::type, const F> visitor;
visitor.functor=&functor;
visitable.accept(visitor);
return visitor.getResult();
}
template <class R> struct ApplyFunctor { typedef R result_type; };
}} // namespace qpid::amqp_0_10
#endif /*!QPID_AMQP_0_10_APPLY_H*/
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