diff options
Diffstat (limited to 'trunk/qpid/cpp/src/qpid/amqp_0_10/apply.h')
-rw-r--r-- | trunk/qpid/cpp/src/qpid/amqp_0_10/apply.h | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/trunk/qpid/cpp/src/qpid/amqp_0_10/apply.h b/trunk/qpid/cpp/src/qpid/amqp_0_10/apply.h new file mode 100644 index 0000000000..f32b3482ef --- /dev/null +++ b/trunk/qpid/cpp/src/qpid/amqp_0_10/apply.h @@ -0,0 +1,86 @@ +#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*/ |