94 lines
3.2 KiB
C++
94 lines
3.2 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) 2021 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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#include <mapnik/proj_transform_cache.hpp>
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#include <mapnik/proj_transform.hpp>
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MAPNIK_DISABLE_WARNING_PUSH
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#include <mapnik/warning_ignore.hpp>
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#include <boost/functional/hash.hpp>
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#include <boost/unordered_map.hpp>
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#include <boost/utility/string_view.hpp>
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MAPNIK_DISABLE_WARNING_POP
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namespace mapnik {
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namespace proj_transform_cache {
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namespace {
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using key_type = std::pair<std::string, std::string>;
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using compatible_key_type = std::pair<boost::string_view, boost::string_view>;
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struct compatible_hash
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{
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template <typename KeyType>
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std::size_t operator() (KeyType const& key) const
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{
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using hash_type = boost::hash<typename KeyType::first_type>;
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std::size_t seed = hash_type{}(key.first);
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seed ^= hash_type{}(key.second) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
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return seed;
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}
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};
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struct compatible_predicate
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{
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bool operator()(compatible_key_type const& k1,
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compatible_key_type const& k2) const
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{
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return k1 == k2;
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}
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};
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using cache_type = boost::unordered_map<key_type, std::unique_ptr<proj_transform>, compatible_hash>;
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thread_local static cache_type cache_ = {};
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} // namespace
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void init(std::string const& source, std::string const& dest)
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{
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compatible_key_type key = std::make_pair<boost::string_view, boost::string_view>(source, dest);
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auto itr = cache_.find(key, compatible_hash{}, compatible_predicate{});
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if (itr == cache_.end())
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{
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mapnik::projection p0(source, true);
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mapnik::projection p1(dest, true);
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cache_.emplace(std::make_pair(source, dest),
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std::make_unique<proj_transform>(p0, p1));
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}
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}
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proj_transform const* get(std::string const& source, std::string const& dest)
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{
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compatible_key_type key = std::make_pair<boost::string_view, boost::string_view>(source, dest);
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auto itr = cache_.find(key, compatible_hash{}, compatible_predicate{});
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if (itr == cache_.end())
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{
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mapnik::projection srs1(source, true);
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mapnik::projection srs2(dest, true);
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return cache_.emplace(std::make_pair(source, dest),
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std::make_unique<proj_transform>(srs1, srs2)).first->second.get();
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}
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return itr->second.get();
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}
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} // namespace proj_transform_cache
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} // namespace mapnik
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