[core] Make it possible to limit the size of the SQLite cache

platform/default/sqlite_cache_impl.hpp

@@ -18,23 +18,47 @@ public:
     explicit Impl(const std::string &path = ":memory:");
     ~Impl();
 
+    void setMaximumCacheSize(uint64_t size);
+    void setMaximumCacheEntrySize(uint64_t size);
+
     void get(const Resource&, Callback);
     void put(const Resource& resource, std::shared_ptr<const Response> response);
     void refresh(const Resource& resource, Seconds expires);
 
 private:
+    void initializeDatabase();
+
+    int cachePageSize();
+
+    uint64_t cacheHardSize();
+    uint64_t cacheSoftSize();
+
+    uint64_t softSize = 0;
+    bool softSizeDirty = true;
+
+    bool needsPruning();
+    void pruneEntries();
+
     void createDatabase();
     void createSchema();
 
+    int pageSize = 0;
+
+    uint64_t maximumCacheSize;
+    uint64_t maximumCacheEntrySize;
+
     const std::string path;
     std::unique_ptr<::mapbox::sqlite::Database> db;
     std::unique_ptr<::mapbox::sqlite::Statement> getStmt;
     std::unique_ptr<::mapbox::sqlite::Statement> putStmt;
     std::unique_ptr<::mapbox::sqlite::Statement> refreshStmt;
+    std::unique_ptr<::mapbox::sqlite::Statement> countStmt;
+    std::unique_ptr<::mapbox::sqlite::Statement> freeStmt;
+    std::unique_ptr<::mapbox::sqlite::Statement> pruneStmt;
+    std::unique_ptr<::mapbox::sqlite::Statement> accessedStmt;
     bool schema = false;
 };
 
-
-}
+} // namespace mbgl
 
 #endif