1 files changed, 55 insertions, 0 deletions
diff --git a/src-qt5/desktop-utils/lumina-pdf/lrucache.h b/src-qt5/desktop-utils/lumina-pdf/lrucache.h
new file mode 100644
index 00000000..8c68c1bb
--- /dev/null
+++ b/src-qt5/desktop-utils/lumina-pdf/lrucache.h
@@ -0,0 +1,55 @@
+#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();
+  }
+
+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