fixes #1157, #1255: cache parsed tiles in memory

src/mbgl/map/tile_cache.hpp

@@ -0,0 +1,30 @@
+#ifndef MBGL_MAP_TILE_CACHE
+#define MBGL_MAP_TILE_CACHE
+
+#include <mbgl/map/tile_data.hpp>
+
+#include <list>
+#include <unordered_map>
+
+namespace mbgl {
+
+class TileCache {
+public:
+    TileCache(size_t size_ = 0) : size(size_) {}
+
+    void setSize(size_t);
+    size_t getSize() const { return size; };
+    void add(uint64_t key, std::shared_ptr<TileData> data);
+    std::shared_ptr<TileData> get(uint64_t key);
+    bool has(uint64_t key);
+    void clear();
+private:
+    std::unordered_map<uint64_t, std::shared_ptr<TileData>> tiles;
+    std::list<uint64_t> orderedKeys;
+
+    size_t size;
+};
+
+};
+
+#endif