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#ifndef LUMINA_PDF_LRUCACHE_H
#define LUMINA_PDF_LRUCACHE_H
#include <list>
#include <optional>
#include <tuple>
#include <unordered_map>
namespace LuminaPDF {
template <class Value, class Key = int> class LRUCache {
public:
LRUCache() = default;
~LRUCache() = default;
void setCacheSize(size_t _max) {
max = _max;
hashmap.reserve(max);
return;
}
std::optional<Value> get(const Key k) {
auto itr = hashmap.find(k);
if (itr == hashmap.end()) {
return std::nullopt;
}
Value v = std::get<1>(*std::get<1>(*itr));
values.erase(std::get<1>(*itr));
values.push_front(std::make_tuple(k, v));
hashmap[k] = values.begin();
return v;
}
void push(const Key k, const Value v) {
while (hashmap.size() >= max) {
Key _k = std::get<0>(values.back());
values.pop_back();
hashmap.erase(_k);
}
values.push_front(std::make_tuple(k, v));
hashmap[k] = values.begin();
}
bool contains(const Key k){
auto itr = hashmap.find(k);
return ( itr!=hashmap.end() );
}
private:
size_t max;
std::list<std::tuple<Key, Value>> values;
std::unordered_map<Key, typename std::list<std::tuple<Key, Value>>::iterator>
hashmap;
};
} // namespace LuminaPDF
#endif // LUIMINA_PDF_LRUCACHE_H
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