Result.h

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/***************************************************************************
 *
 * Copyright (C) 2009-2010 Cassio Neri Moreira
 *
 * This file is part of the KeyValue library.
 *
 * The KeyValue library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or (at
 * your option) any later version.
 *
 * The KeyValue library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
 * Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with KeyValue. If not, see <http://www.gnu.org/licenses/>.
 *
 **************************************************************************/

#ifndef KEYVALUE_VALUE_RESULT_H_
#define KEYVALUE_VALUE_RESULT_H_

#include <iosfwd>

#include <boost/variant.hpp>

#include "keyvalue/extern/SharedPtr.h"
#include "keyvalue/value/Value.h"

namespace keyvalue {
namespace value {

typedef shared_ptr<void> ObjectPtr;

class Result {

public:

  typedef boost::variant<ObjectPtr, Value> DataType_;

  Result();

  Result(const DataType_& data);

  template<typename Rhs>
  Result(const Rhs& rhs);

  template<typename Rhs>
  Result&
  operator=(const Rhs& rhs);

  ObjectPtr
  getObjectPtr() const;

  ObjectPtr
  getObjectPtr();

  const Value*
  getValue() const;

  Value*
  getValue();

private:

  DataType_ data_;

}; // class Result

std::ostream&
operator<<(std::ostream& os, const Result& rhs);

template<typename Rhs>
struct Parent;

template<>
struct Parent<Result::DataType_> {
  typedef Result Type_;
};

template<>
struct Parent<ObjectPtr> {
  typedef Result::DataType_ Type_;
};

template<typename T>
struct Parent<shared_ptr<T> > {
  typedef ObjectPtr Type_;
};

template<typename T>
struct Parent<T*> {
  typedef shared_ptr<T> Type_;
};

template<>
struct Parent<Value> {
  typedef Result::DataType_ Type_;
};

/*--------------------------------------------------------------------------
 * Result()
 *------------------------------------------------------------------------*/

template<typename Rhs>
Result::Result(const Rhs& rhs) :
  data_(Result(typename Parent<Rhs>::Type_(rhs)).data_) {
}

/*--------------------------------------------------------------------------
 * operator=()
 *------------------------------------------------------------------------*/

template<typename Rhs>
Result&
Result::operator=(const Rhs& rhs) {
  return *this = typename Parent<Rhs>::Type_(rhs);
}

} // namespace value
} // namespace keyvalue

#endif // KEYVALUE_VALUE_RESULT_H_