103 lines
3.3 KiB
C++
103 lines
3.3 KiB
C++
/*****************************************************************************
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*
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* This file is part of Mapnik (c++ mapping toolkit)
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*
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* Copyright (C) 2006 Artem Pavlenko
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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*****************************************************************************/
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//$Id: params.hpp 39 2005-04-10 20:39:53Z pavlenko $
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#ifndef PARAMS_HPP
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#define PARAMS_HPP
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#include <boost/variant.hpp>
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#include <boost/optional.hpp>
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#include <boost/none.hpp>
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#include <boost/lexical_cast.hpp>
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#include <string>
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#include <map>
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namespace mapnik
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{
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typedef boost::variant<int,double,std::string> value_holder;
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typedef std::pair<const std::string, value_holder> parameter;
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typedef std::map<const std::string, value_holder> param_map;
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template <typename T>
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struct value_extractor_visitor : public boost::static_visitor<>
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{
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value_extractor_visitor(boost::optional<T> & var)
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:var_(var) {}
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void operator () (T val) const
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{
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var_ = val;
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}
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template <typename T1>
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void operator () (T1 val) const
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{
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try
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{
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var_ = boost::lexical_cast<T>(val);
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}
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catch (boost::bad_lexical_cast & ) {}
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}
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boost::optional<T> & var_;
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};
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class parameters : public param_map
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{
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template <typename T>
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struct converter
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{
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typedef boost::optional<T> return_type;
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static return_type extract(parameters const& params,
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std::string const& name,
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boost::optional<T> const& default_value)
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{
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boost::optional<T> result(default_value);
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parameters::const_iterator itr = params.find(name);
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if (itr != params.end())
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{
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boost::apply_visitor(value_extractor_visitor<T>(result),itr->second);
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}
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return result;
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}
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};
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public:
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parameters() {}
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template <typename T>
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boost::optional<T> get(std::string const& key) const
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{
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return converter<T>::extract(*this,key, boost::none);
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}
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template <typename T>
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boost::optional<T> get(std::string const& key, T const& default_value) const
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{
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return converter<T>::extract(*this,key,boost::optional<T>(default_value));
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}
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};
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}
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#endif //PARAMS_HPP
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