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#include <functional>
#include "mvt.hpp"
#include "dirtiles.hpp" // for zxy
struct mvt_tile_seq {
mvt_tile tile;
size_t seq;
};
struct tile_cache {
std::map<zxy, mvt_tile_seq> overzoom_cache;
std::atomic<size_t> seq;
size_t capacity = 1000;
mvt_tile get(zxy parent_tile, std::function<mvt_tile(zxy)> getter) {
mvt_tile source;
auto f = overzoom_cache.find(parent_tile);
if (f == overzoom_cache.end()) {
if (overzoom_cache.size() >= capacity) {
// evict the oldest tile to make room
auto to_erase = overzoom_cache.begin();
for (auto here = overzoom_cache.begin(); here != overzoom_cache.end(); ++here) {
if (here->second.seq < to_erase->second.seq) {
to_erase = here;
}
}
overzoom_cache.erase(to_erase);
}
source = getter(parent_tile);
mvt_tile_seq to_cache;
to_cache.tile = source;
to_cache.seq = seq++;
overzoom_cache.emplace(parent_tile, to_cache);
} else {
f->second.seq = seq++;
source = f->second.tile;
}
return source;
}
};
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