105 lines
3.2 KiB
C++
105 lines
3.2 KiB
C++
/*
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Copyright (c) 2006 Alex Tingle
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifndef GRID_H
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#define GRID_H
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#include "NASAGridSquare.h"
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#include <boost/unordered_map.hpp>
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#include <assert.h>
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/** Interface to the GridSquares. Template parameter determines which kind of
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* raw data is used (NASA, or reduced). GridSquare data is globally cached, so
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* that many queries can be answered without having to constantly mmap & unmmap
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* the data files.
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*
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* Typical usage:
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*
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* Grid<NasaGridSquare> g();
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* cout << g.height(lng,lat) << endl;
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*
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*/
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template<class T>
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class Grid {
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static boost::unordered_map<int,T*> cache;
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static typename boost::unordered_map<int,T*>::size_type cache_size;
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public:
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/** The cache_limit defaults to 360. Adjust it to set the number of
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* grid squares to store in memory. */
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static typename boost::unordered_map<int,T*>::size_type cache_limit;
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Grid(short sea_level_rise_ = 0 ) : sea_level_rise(sea_level_rise_) {
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// Double check that this compiler truncates towards zero.
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assert(-1 == int(float(-1.9)));
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}
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/** Returns the height above sea level for the given lat/lng. */
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short height(float longitude, float latitude) const {
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int lng,lat;
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float lng_fraction,lat_fraction;
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split(longitude,lng,lng_fraction);
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split(latitude ,lat,lat_fraction);
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int k =T::key(lng,lat);
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typename boost::unordered_map<int,T*>::iterator pos =cache.find(k);
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if(pos==cache.end())
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{
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if(cache_size>=cache_limit)
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clear_cache();
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pos = cache.insert(std::make_pair(k,new T(lng,lat))).first;
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if(pos->second->has_data())
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++cache_size;
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}
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return pos->second->height(lng_fraction,lat_fraction);
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}
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/** Returns TRUE if the given lng/lat is underwater. */
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bool underwater(float longitude, float latitude) const
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{
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short h =height(longitude,latitude);
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return( h!=NasaGridSquare::NO_DATA && h<=sea_level_rise );
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}
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private:
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/** Clears the cache of non-null GridSquares. */
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void clear_cache() const {
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cache.clear();
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}
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/** Split a floating point number (num) into integer (i) & fraction (f)
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* components. */
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void split(float num, int& i, float& f) const {
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if(num>=0.0)
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i=int(num);
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else
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i=int(num)-1;
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f=num-float(i);
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}
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short sea_level_rise;
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};
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template<class T> boost::unordered_map<int,T*> Grid<T>::cache;
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template<class T> typename boost::unordered_map<int,T*>::size_type Grid<T>::cache_size =0;
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template<class T> typename boost::unordered_map<int,T*>::size_type Grid<T>::cache_limit=360;
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#endif // GRID_H
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