diff --git a/src/collocatordb.h b/src/collocatordb.h
index af97419..0eed8d8 100644
--- a/src/collocatordb.h
+++ b/src/collocatordb.h
@@ -12,29 +12,9 @@
 
 #ifdef __cplusplus
 namespace rocksdb {
-    class Collocator {
-    public:
-    uint64_t w2;
-    uint64_t f2;
-    uint64_t raw;
-    double pmi;
-    double npmi;
-    double llr;
-    double lfmd;
-    double md;
-    double left_lfmd;
-    double right_lfmd;
-    double left_npmi;
-    double right_npmi;
-    double dice;
-    double logdice;
-    double ldaf;
-    int window;
-    int af_window;
-  };
-namespace rocksdb {
-    class Collocator {
-    public:
+
+class Collocator {
+public:
     uint32_t w2;
     uint64_t f2;
     uint64_t raw;
@@ -52,41 +32,70 @@
     double ldaf;
     int window;
     int af_window;
-  };
+};
 
-    class CollocatorIterator : public Iterator  {
-    public:
-        CollocatorIterator(const Iterator& it);
-        void SeekToFirst();
-        void SeekToLast();
-        void Seek(const rocksdb::Slice&);
-        void Prev();
-        bool isValid();
-        uint64_t intValue();
-        uint64_t intKey();
-    };
-    
-		extern "C" {
-			class CollocatorDB {
-			public:
-        std::string getWord(uint32_t w1);
-        std::vector<Collocator> get_collocators(uint32_t w1);
-        std::vector<Collocator> get_collocators(uint32_t w1, uint32_t max_w2);
-        void dumpSparseLlr(uint32_t w1, uint32_t min_cooccur);
-        CollocatorDB(const char *db_name, const bool read_only);
-        void inc(const uint32_t w1, const uint32_t w2, const uint8_t dist);
-        void dump(const uint32_t w1, const uint32_t w2, const uint8_t dist);
-        CollocatorIterator* SeekIterator(uint64_t w1, uint64_t w2, int8_t dist);
-			};
-			
-		}
-}
+class CollocatorIterator : public rocksdb::Iterator {
+public:
+    CollocatorIterator(rocksdb::Iterator* base_iterator);
+    void setPrefix(char* prefix);
+    void SeekToFirst() override;
+    void SeekToLast() override;
+    void Seek(const rocksdb::Slice& s) override;
+    void SeekForPrev(const rocksdb::Slice& s) override;
+    void Prev() override;
+    void Next() override;
+    rocksdb::Slice key() const override;
+    rocksdb::Slice value() const override;
+    rocksdb::Status status() const override;
+    bool Valid() const override;
+    bool isValid();
+    uint64_t intValue();
+    uint64_t intKey();
 
-typedef rocksdb::CollocatorDB COLLOCATORDB;
+private:
+    char prefixc[sizeof(uint64_t)];
+    rocksdb::Iterator* base_iterator_;
+};
+
+class CollocatorDB {
+public:
+    CollocatorDB(const char* db_name, bool read_only = false);
+    void readVocab(std::string fname);
+    std::string getWord(uint32_t w1);
+    void inc(const uint32_t w1, const uint32_t w2, const uint8_t dist);
+    void dump(uint32_t w1, uint32_t w2, int8_t dist);
+    std::vector<Collocator> get_collocators(uint32_t w1);
+    std::vector<Collocator> get_collocators(uint32_t w1, uint32_t max_w2);
+    std::vector<Collocator> get_collocation_scores(uint32_t w1, uint32_t w2);
+    std::vector<Collocator> get_collocators(uint32_t w1, uint32_t min_w2, uint32_t max_w2);
+    void dumpSparseLlr(uint32_t w1, uint32_t min_cooccur);
+    std::string collocators2json(uint32_t w1, std::vector<Collocator> collocators);
+    CollocatorIterator* SeekIterator(uint64_t w1, uint64_t w2, int8_t dist);
+
+private:
+    std::shared_ptr<rocksdb::DB> OpenDb(const char* dbname);
+    std::shared_ptr<rocksdb::DB> OpenDbForRead(const char* dbname);
+    void applyCAMeasures(const uint32_t w1, const uint32_t w2, uint64_t* sumWindow, const uint64_t sum, const int usedPositions, int true_window_size, Collocator* result);
+
+    rocksdb::WriteOptions merge_option_;
+    char _one[sizeof(uint64_t)];
+    rocksdb::Slice _one_slice;
+    std::vector<Collocator> _vocab;
+    uint64_t total;
+    uint64_t sentences;
+    float avg_window_size;
+    std::shared_ptr<rocksdb::DB> db_;
+    rocksdb::WriteOptions put_option_;
+    rocksdb::ReadOptions get_option_;
+    rocksdb::WriteOptions delete_option_;
+    uint64_t default_;
+};
+
+} // namespace rocksdb
+
 
 #else
 typedef struct COLLOCATORDB COLLOCATORDB;
-#endif
 
 typedef struct {
   uint32_t w2;
@@ -119,3 +128,4 @@
 extern char *get_word(COLLOCATORDB *db, uint32_t w1);
 extern void read_vocab(COLLOCATORDB *db, char *fname);
 extern char *get_version();
+#endif